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- Dec 8, 2001
it's basically a break in period before they reach their full potential. sorta like how you need to break in a pair of new shoes before they are comfortable.
*DEAD* Monster Turbine In-Ear Headphones - $58.99 + Free Shipping AMAZON
- Thread in 'General' Thread starter Started by its that dude,
- Start date
- 185
- 10
- Joined
- Nov 20, 2005
this post explains what headphone burn in is
http://www.head-fi.org/fo...44/headphone-burn-in-faq
you could use this site to help with the burn in
http://www.burninwave.com/
http://www.head-fi.org/fo...44/headphone-burn-in-faq
you could use this site to help with the burn in
http://www.burninwave.com/
- 185
- 10
- Joined
- Nov 20, 2005
this post explains what headphone burn in is
http://www.head-fi.org/fo...44/headphone-burn-in-faq
you could use this site to help with the burn in
http://www.burninwave.com/
http://www.head-fi.org/fo...44/headphone-burn-in-faq
you could use this site to help with the burn in
http://www.burninwave.com/
- 21,947
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- Joined
- Jan 12, 2003
Just got mine today, currently breaking them in.
My S4's are well broken in but the main difference I notice is that the bass, although very strong, are not as strong as the S4's, but thats because the S4's are slight exaggerated.
these monster headphones sound a bit more balanced, and it comes with about 6 different sized ear tips which is a good thing, and the casing is nice.
The wire is nothing to right home about, doesn't feel high quality but the S4 wire is def. more flimsy.
But for this price of 58$ with free shipping, this is worth the deal. I would never pay $175 for these since the S4's are about 70-80 max.
In the end, good purchase.
My S4's are well broken in but the main difference I notice is that the bass, although very strong, are not as strong as the S4's, but thats because the S4's are slight exaggerated.
these monster headphones sound a bit more balanced, and it comes with about 6 different sized ear tips which is a good thing, and the casing is nice.
The wire is nothing to right home about, doesn't feel high quality but the S4 wire is def. more flimsy.
But for this price of 58$ with free shipping, this is worth the deal. I would never pay $175 for these since the S4's are about 70-80 max.
In the end, good purchase.
- 21,947
- 1,374
- Joined
- Jan 12, 2003
Just got mine today, currently breaking them in.
My S4's are well broken in but the main difference I notice is that the bass, although very strong, are not as strong as the S4's, but thats because the S4's are slight exaggerated.
these monster headphones sound a bit more balanced, and it comes with about 6 different sized ear tips which is a good thing, and the casing is nice.
The wire is nothing to right home about, doesn't feel high quality but the S4 wire is def. more flimsy.
But for this price of 58$ with free shipping, this is worth the deal. I would never pay $175 for these since the S4's are about 70-80 max.
In the end, good purchase.
My S4's are well broken in but the main difference I notice is that the bass, although very strong, are not as strong as the S4's, but thats because the S4's are slight exaggerated.
these monster headphones sound a bit more balanced, and it comes with about 6 different sized ear tips which is a good thing, and the casing is nice.
The wire is nothing to right home about, doesn't feel high quality but the S4 wire is def. more flimsy.
But for this price of 58$ with free shipping, this is worth the deal. I would never pay $175 for these since the S4's are about 70-80 max.
In the end, good purchase.
- 11,809
- 643
- Joined
- Jan 10, 2010
You need the comply tips mez
I had the s4's and the turbines stomped them out in the bass department. It's night and day with the foam tips.
I had the s4's and the turbines stomped them out in the bass department. It's night and day with the foam tips.
- 11,809
- 643
- Joined
- Jan 10, 2010
You need the comply tips mez
I had the s4's and the turbines stomped them out in the bass department. It's night and day with the foam tips.
I had the s4's and the turbines stomped them out in the bass department. It's night and day with the foam tips.
- 93,978
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- Joined
- Oct 24, 2010
damn im kinda mad i missed out on these, i need something nice for the gym.
- 93,978
- 33,009
- Joined
- Oct 24, 2010
damn im kinda mad i missed out on these, i need something nice for the gym.
- 21,947
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- Jan 12, 2003
Guess I'm going to have to invest in those, so far the default ones fit me best (the others are too small).
I'm sure I will end up liking these more, but for more bang than you buck the S4's are (err were) a better alternative since they are over $100 less and very comparable.
But with this recent deal its a better buy IMO. Sucks the deal died though, and glad I decided to jump on it.
I'm sure I will end up liking these more, but for more bang than you buck the S4's are (err were) a better alternative since they are over $100 less and very comparable.
But with this recent deal its a better buy IMO. Sucks the deal died though, and glad I decided to jump on it.
- 21,947
- 1,374
- Joined
- Jan 12, 2003
Guess I'm going to have to invest in those, so far the default ones fit me best (the others are too small).
I'm sure I will end up liking these more, but for more bang than you buck the S4's are (err were) a better alternative since they are over $100 less and very comparable.
But with this recent deal its a better buy IMO. Sucks the deal died though, and glad I decided to jump on it.
I'm sure I will end up liking these more, but for more bang than you buck the S4's are (err were) a better alternative since they are over $100 less and very comparable.
But with this recent deal its a better buy IMO. Sucks the deal died though, and glad I decided to jump on it.
- 11,809
- 643
- Joined
- Jan 10, 2010
- 11,809
- 643
- Joined
- Jan 10, 2010
- 12,911
- 843
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- May 4, 2005
dont listen to him... just sell me yours
- 12,911
- 843
- Joined
- May 4, 2005
dont listen to him... just sell me yours
- 415
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- Jun 13, 2003
This is slightly off topic, but after listening to these with my ipod and then plugging them into my laptop, there is a noticeable difference in sound quality. I didn't notice anything really special about these headphones at first and that was because I used them to listen to my ipod. It wasn't until I tried these out on my laptop that I decided I wanted to keep these headphones. What are some alternatives to the ipod out there that have better sound quality output?
- 415
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- Jun 13, 2003
This is slightly off topic, but after listening to these with my ipod and then plugging them into my laptop, there is a noticeable difference in sound quality. I didn't notice anything really special about these headphones at first and that was because I used them to listen to my ipod. It wasn't until I tried these out on my laptop that I decided I wanted to keep these headphones. What are some alternatives to the ipod out there that have better sound quality output?
- 11,809
- 643
- Joined
- Jan 10, 2010
It's the ipod
The dac is @%%%*%
Get a portable amp or dac/amp combo
The dac is @%%%*%
Get a portable amp or dac/amp combo
- 11,809
- 643
- Joined
- Jan 10, 2010
It's the ipod
The dac is @%%%*%
Get a portable amp or dac/amp combo
The dac is @%%%*%
Get a portable amp or dac/amp combo
- 9,051
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- Joined
- Jul 6, 2008
even if it was (for me anyways):
"We are not able to ship this item to your default shipping address."
gtfohwtbsg
living in canada ftl
- 9,051
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- Joined
- Jul 6, 2008
even if it was (for me anyways):
"We are not able to ship this item to your default shipping address."
gtfohwtbsg
living in canada ftl
- 21,947
- 1,374
- Joined
- Jan 12, 2003
I only use my iPod since I paid 80$ for my 80gb classic. I just like the simple interface and syncing with iTunes.
What portable amps do you recommend?
- 21,947
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- Jan 12, 2003
I only use my iPod since I paid 80$ for my 80gb classic. I just like the simple interface and syncing with iTunes.
What portable amps do you recommend?
- 11,809
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- Jan 10, 2010
http://www.amazon.com/Nuf...PBO/ref=pd_bxgy_e_text_c
Review
HEADPHONES USED: Westone 3, Klipsch Image X10, Denon C700, Nuforce NE-7M, ATH-ESW10JPN, APS V3 cabled HD600, APS V3 cabled RS-1, APS V3 cabled markl Woodied Denon D2000, and APS V3 cabled Edition 9.
MUSIC USED: Michael Knowles "Bink Audio Test CD", Nils Lofgren "Acoustic Live", Arne Domnerus "Antiphone Blues" and "Jazz at the Pawnshop", Infected Mushroom "B.P. Empire", Tord Gustavsen Trio "Being There", Pat Metheny "Day Trip", Tsuyoshi Yamamoto "Autumn in Seattle" and "Smooth Jazz Festival", B.B. King and Eric Clapton "Riding With the King", Shelby Lynn "Just a Little Lovin'", Nora Jones "Not Too Late", Arvo Part "Tabula Rasa", Jack Johnson "Sleep Through the Static" and "In Between Dreams", Elaine Elias "Something for You", Gary Karr "Super Double-bass", Guinea Pig "Kool Cats", Christopher Hogwood "Handel Messiah", Pink Floyd "DSOT", The Beatles "Love", Beck "Sea Change", Diana Krall "Girl in the Other Room", Coldplay "Viva La Vida", and Skillet "Comatose".
The Nuforce Icon Mobile is a $99 entry level portable USB DAC/Amp, which has more of a flat form factor that is amenable to being stacked under an iPod without adding too much size to the overall package. It is about the same width and depth as the iBasso D2 Boa, but almost half as tall/thick, so you can almost stack two Icon Mobile on top of each other to achieve the thickness of one D2 Boa. When plugged into the Macbook's USB port the DAC shows up as a "C-Media USB Headphone Set". The Nuforce has some unique features including two headphone out jacks which switch on the power when a headphone plug is inserted, with the jack closer the center being a special jack that works with 4-conductor headsets with stereo headphones and a built-in microphone, like the Nuforce NE-7M iPhone IEM (or other iPhone IEM). This allows the NE-7M to be used as a headset with telephony applications, instant messaging and Skype, and probably for gaming as well. I have not been able to test this telephony feature, but the mic did show up in my Mac's Audio MIDI setup application as the left channel only microphone. The analog input is on the same end of the amp as the two outputs (we'll call it the top end), and all three jacks are slightly recessed by about 0.5 mm along one edge of the amp.
All my portable headphones worked fine with the slightly recessed jacks, but my full size APS V3 cabled headphones needed an adapter because the 1/8" Neutrik plugs on my APS cables are too wide and would hit the lip of the case around the jacks. Nuforce has informed me that they are already planning to make changes to the case to allow a wider variety of headphone plugs to fit, and they will make it available to early buyers who have problems - but they are not sure yet if it will be possible to use the wider Neutrik 1/8" plugs used by APS, while I know the smaller Neutrik plugs from Qables.com already fit. On one side there is a USB jack for charging and the USB DAC input, a recessed gain switch that cannot not be accidentally changed, and a rotary volume knob. The volume knob is of fairly decent quality, and in low gain it is easily usable with high sensitivity IEM at very low volumes, with channel imbalance only at the very lowest volumes. The amp is totally silent in high gain with the USB music paused and volume turned all the way up.
To my ears the Nuforce does benefit noticeably from burn-in. When it was right out of the box it struck me as just a little dull and bland when compared to the iBasso D2 boa, and I feared that I would be disappointed with it in the end. I left it running for 6-7 hours and came back to it and the sound was already starting to clean up some. So I left it running via USB with music 24/7 but with a 1 hour break each day, and went back to listen for about an hour each night at 24 hour intervals. By 24-36 hours it was sounding good enough to actually recommend it to others, by 55-60 hours I was posting that it sounded a little forward but was sounding similar to my Meier Headsix which I like more than the D2 Boa. At that time I noted that it was also less edgy than the Vivid V1 but not as powerful. By 80 hours it was becoming more transparent and detailed, and sounded good with all my portable headphones including ATH-ESW10, Westone 3, Image X10, NE-7M and even the Denon C700. By that time I was finding that it is one of those amps that actually makes the C700 smoother and less harsh in the highs, while controlling the bass - one of the things I like about the Headsix and Predator when driving the Denon C700 (sometimes I think the C700 was tuned to sound best right out of the headphone jack of the 5.5G iPod video and 2G Nano). Between 180-200 hours the soundstage had finished opening up. I continued burn-in via USB through 210 hours and then switched to analog input for the remainder of burn-in. I did my once a day listening until it had 230-240 hours on it and felt it seemed to be done changing by 180-200 hours. I did not listen for the last 60-70 hours of burn-in until time to start the review after 300 hours on 12/14.
During burn-in I was able to determine that the Nuforce amp was above the iBasso D2 Boa and Vivid V1 in most areas of performance and sound (but not all areas), but still below the top tier amps like Pico, Predator and D3 Python. I have not reviewed the Practical Devices XM5 yet, but I am fairly sure it will be among the top tier amps based on the limited listening I have done during burn-in. I do not have the 2MOVE or D2 Viper to compare to in this review, but if I did I would guess it would fall below the 2MOVE or rolled-opamp Viper but above the Stock D2 Viper. So, since I had so many headphones to listen with most of my comparisons were with the D2 Boa and V1 to properly discern the ranking. Although I did also do comparisons with the top amps as well, I just did not spend as much time with them.
For the first part of my dedicated listening for the review I decided to start with my full size headphones (HD600, RS-1, D2000, Edition 9) since I had already done a fair bit of listening with my portable headphones and IEM during burn-in, and was already enjoying the amp with them. Typically the Nuforce could be turned up all the way to 100% volume with HD600 without clipping. And, it would play to decent volumes at that setting but not more than mildly or moderately loud - max volume of the Nuforce Icon Mobile was still about 2-3 db below D2 Boa, which could be turned to about 3:30 o'clock before clipping in high gain (max is 4:30). On the other hand, unlike with the HD600, the Nuforce could drive the Grado RS-1 and Denon D2000 at max volume MUCH much louder than I would ever care to listen to music. Typically I could sweep the side scrolling rotary volume knob 4 times to go from from zero volume to 100% volume. With the Nuforce in high gain with anything other than HD600 I would normally listen with the volume rotated up only 1/2 of the way to max. With the volume turned 3/4 of the way up it was quite loud with RS-1 and D2000, and full volume was uncomfortable and likely damaging. With RS-1 there was some clipping starting to creep in as I got very close to max volume at the end of the dial with the RS-1, but it was more of a soft clipping with less dynamics and some fuzzyness to the sound. The clipping was even better/softer with the D2000 at max volume, and with some material it was not even there. I could never explore the upper volume limits with my IEM without worsening my chronic tinnitus, so I didn't try. Suffice it to say the Nuforce will go loud enough with any of my IEM. So, to summarize, the Pico, D3, V1, Micro Stack and XM5 are all more powerful with HD600 than the D2 Boa which slightly edged out the Nuforce, but with any portable earphone or low impedance full size headphone the Nuforce has plenty of power to go around.
With the Nuforce the bass is fairly strong with all the low impedance phones, but with HD600 pushed to high volumes the bass was not quite as good as the D2 Boa, especially as the volumes would get closer to max output. Bass with infected mushroom and HD600 was stronger at normal volumes but not impressive like with the lower impedance phones. It was only a problem with HD600 in which I found the bass pulling back or thinning out when the amp is pushed hard (similar to the Meier Headfive desktop amp when pushed hard with Grados). So like the D2 Boa, the Nuforce was not optimal with high impedance phones, although it still drives the HD600 better than the headphone out of my Macbook. Better portable amps from my review to drive the HD600 better include the Pico and Vivid V1 or D3 Python or XM5 as the most powerful, followed by the Predator and D2 Boa, and then the Nuforce. However, with lower impedance headphones like my portable headphones and RS-1, D2000 and Edition 9, the Nuforce really came into it's element and it became more dynamic and powerful sounding. The D2000 and Edition 9 are very enjoyable with the Nuforce, and the bass is powerful enough to tickle my eardrums and damage my hearing if I wish, passing up the RS-1's bass by a noticeable margin too (unless I switch to flat pads). With test tones on the HD600 the Nuforce sounded strong to 31Hz, and was maybe 3-4db down at 25Hz but then rolled off below that. But I found that the 20-25Hz notes were stronger with the low impedance phones than with the 300 ohm HD600, and the NE-7M actually went deeper than most of my full size headphones (16Hz). The Pico, Predator, D3 Python and XM5 all had more powerful and present or pervasive bass, but you wouldn't know the Nuforce is lacking anything but for the comparison with the top tier amps. It's all relative, as listening to the Nuforce on its own merits did not make me wish for bass boost or anything like that. Bass was fairly well controlled as well, although pushing the amp to it's limits at the highest volumes the IEM, D2000 or Edition 9 the bass was just starting to get a little loose. Only with the HD600 did it start to fade at higher volume levels. The ESW10 bass was lighter and more along the lines of the RS-1 (ESW10 is kinda like a closed RS-1) and just a little more reserved with the Nuforce than with the top tier amps. This is not a bass-thin amp, it's just that some others have more bass punch. But, pair it with the Westone 3, NE-7M with Complys tips, D2000 or Edition 9 and the bass is rocking.
The Mids of the Nuforce tend to be more forward like the Meier Amps (Headsix and 2MOVE) or the Vivid V1. I have always felt that Pat Metheney "Day Trip" is recorded with a little too much energy in the mids with the electric guitar (granted that is the "star of the show"), so switching to the D2 Boa or other amps usually helps pull the guitar back a little. Still, this particular recording was listenable with the Nuforce, although it was much better if I was using the Westone 3, NE-7M, C700, D2000 or RS-1 with bowls than the HD600 or Edition 9 with it. With most music I appreciated the more forward mids of the Nuforce with the D2000, as I feel the D2000 are still slightly recessed in the mids despite the wood cups and earpad mods that I have done which also helped a bit. I haven't been using my RS-1 much lately, as I tend to prefer my stats and my modded D2000, Edition 9, or ESW10 more. The RS-1 did not sound bad with the Nuforce, but with bowl pads I sometimes (not always) felt there was a similar but less prominent upper mid coloration with Grados, like the Vivid V1 amp demonstrated earlier in the review. My other headphones did not have this issue with the mids, and I still preferred bowls with the Grados for their improvement in soundstage through the Nuforce. I would not rule out the Nuforce with Grados as it is still better than the V1 with them, and often better than the D2 Boa as well - where sometimes the D2 Boa's mids felt slightly sucked out with the RS-1 after listening to the RS-1 with the Nuforce for a while and got used to it. I still felt the top tier amps were warmer and richer in the mids than the Nuforce, D2 Boa or V1, and the D2 Boa sounds like an artificial warmth at times, with slightly boosted upper bass and lower mids. But what I liked most about the Nuforce mids was the clarity and very little coloration.
In general I felt that the forward mids of the Nuforce helped improve the audibility of the midrange detail, and music became more engaging than with the D2 Boa (similar to the Headsix and 2MOVE). This was one of the things that attracted me to the 2MOVE that I borrowed a while back. Female vocals like Shelby Lynn, Nora Jones, Elaine Elias and Jane Monheit don't have the bass bleed into the lower mids a little, like with the Boa, so they sound more open and natural most of the time (less boomy or boxy or close mic'd sounding). The D2 Boa with Westone 3 was the worst offender in that regard. Nora Jones's vocals in "Not Too Late" and on Herbie Hancock "The River" are more present and engaging with the Nuforce. With the Boa, Nora Jones and Jane Monheit's vocals do sound better than did Shelby Lynn or Diana Krall on the Boa, but I liked the Nuforce a little better with all of them. On Elaine Elias "Something for You" I got caught up in the music better, and forget that I am doing a review, so it seems little more involving as well. The Boa still acquitted itself well with Elaine Elias during the instrumental jazz parts, but lost the illusion when the vocals would come in.
I did enjoy pianos with the Nuforce, but the Nuforce maybe smoothes out the piano a little more than the other amps, making it more polite. Despite that, it still did a nice job with piano and guitar and vocals in B.B. King and Eric Clapton "Riding With the King". Nils Lofgren "Acoustic Live" was crisp and detailed and airy but not as spacious as the top tier amps listed above. And the Nuforce also seems good with unamplified acoustic guitar as well, like with Jack Johnson and Andy Mckee or Govi. In Tsuyoshi Yamamoto "Smooth Jazz Festival" during "Somewhere Over the Rainbow" the sax is more intimate and engaging with the Nuforce, but the Boa has little stronger bass response from the plucked string bass. However with the D2 Boa the sax sounds thinner in the middle and more upturned at the ends of the frequency spectrum. With Gary Karr "Super double bass" this issue on the D2 Boa also caused the bass fiddle to seem slightly more hollow or lacking than with the Nuforce, especially when listening with the D2000 but also with the HD600 and others. This recessed mids of the D2 Boa was still better than with the stock D2 Viper last time I compared them. These slightly tipped up ends of the frequency spectrum or the recessed mids (however you look at it) make the D2 Boa a little better for low volume listening with the HD600, but very quiet listening was among the few instances where I would grab the D2 Boa over the Nuforce. On the other hand, the Nuforce with D2000 was still better for low volume listening than D2 Boa with HD600.
Treble on the Nuforce is smooth but slightly recessed with a variety of headphones. With my D2000, Westone 3 and ESW10 the Nuforce does not accentuate sibilance that I usually hear in my Diana Krall "Girl in the Other Room" CD, which is my test CD for sibilance since it seems to be mastered with that in there. Switching to the Grado RS-1 I found there was less sibilance through the Nuforce than with my D2 Boa. The slightly laid back treble made the Nuforce amp more forgiving of some music. With the D2000 I actually listened to the entire Diana Krall CD with the Nuforce as I typed my review, without thinking about the sibilance. With Tord Gustavsen Trio's song Karmosin off the "Being There" CD, this is a good test of cymbals as they are lightly and hauntingly tapped during the intro drums and piano, and I did not feel there was a lack of treble as the ring of the cymbals would hang in the air properly with a nice slow decay.
I have rarely bothered to test high frequency extension, but decided to start doing that and tested all of the amps tonight, along with the Nuforce using Michael Knowles "Bink Audio Test CD". With treble test tones on the Nuforce I used the D2000 which for me have better treble extension than my HD600 or most IEM. There I found a problem - with the Nuforce while at 16Khz I was getting a strange harmonic at exactly 4Khz that was louder than the actual 16Khz tone. I've had this problem with another USB DAC amp before, but I cannot recall which one now (might have been the Lyrix or D1). This 4Khz artifact did not happen with the D2 Boa via USB which was still going strong at 16Khz, or with the Nuforce via analog input. With music I was unable to hear any artifacts like with the test tone. For me, 16Khz is the practical limit of my hearing as I can't hear the 20Khz tone unless I crank an amp like the D2 to 3:30 o'clock or 80-90% of max. While I could hear 20Khz with the D2 Boa at full volume, cranking the Nuforce volume at 20Khz was inaudible. Via analog input on the Nuforce the 20Khz test tone was still inaudible to me, although it was still barely audible if I plugged the headphones directly into the Macbook. The only other amps that would allow me hear the 20Khz test tone at high volume was the Pico and Predator, although I could hear it louder with the Pico. I found that in doing this test that the V1, XM5 and D3 were all quite noisy in the background at high volumes past 3 o'clock with the 20Khz test tone, so I could not hear the tone over the noise. The Nuforce had just a tiny bit of noise at max volume hooked up via USB, and the Pico and Predator were silent. The D2 Boa background noise was silent and allowed me to hear the 20Khz tone. After I accidentally hit my ears full volume with a 440Hz piano note, I could not do further testing of the highs until my ears recovered.
The Nuforce combines a forward soundstage with decent air and ambience, although like the 2MOVE it puts the listener in a more intimate position while making the venue seem a little smaller. With the D2 Boa and Arvo Part "Tabula Rasa" the image is a little more spread out and deeper but less precise than with the Nuforce. With Gary Karr "Super Double-bass" the imaging was similarly a little more focused and the bass fiddle more centered with Nuforce (almost like a slight hint of crossfeed), while with the same music on the D2 Boa the bass fiddle sounded a little more spread out and hard to pinpoint. Soundstage is obviously better with the HD600 and D2000 than Westone 3 or ESW10 and RS-1. But even with those headphones, when comparing the Nuforce soundstage to the Pico or D3 and Predator the Nuforce soundstage seems flatter and more 2D, with a wide but not as deep soundstage. Air and ambience with the Nuforce was about the same as my D2 Boa, but with the Boa placing the listener a little farther from the stage than Nuforce or Vivid Audio V1. Switching from the Nuforce to the Pico and D3 (or even Predator) it was clear that the top tier amps are more open and spacious, with more micro-detail and are even more rich sounding and engaging. The difference in sound between the Nuforce and the top three on hand (Predator, Pico and D3) is bigger than it is between Nuforce and D2 Boa or V1, confirming that the D2 Boa and Vivid V1 are it's main competitors in sound and price range. The Predator is in between the forwardness of the Nuforce/V1 and Pico/D3, but still maintains a better soundstage, warmth and richness. The degree of detail of the Nuforce DAC seems to be on par with the DAC in the 2MOVE and Predator, but below that of the Pico and iBasso D2/D3 amps. I have not reviewed the XM5 that is burning-in right now, so I really cannot comment on soundstage or micro-detail yet.
The last area I looked at was the RFI interference problems that have cropped up the past 2 months since I got an iPhone 3G. I found the D3 to be the most susceptible to iPhone BUZZ from 3-4 feet away, followed by the D2 Viper and the D2 Boa from 1-2 feet away, then the Predator/Pico/Nuforce which could be within 6-9" of the iPhone. With an EM blocking card from Quick Bridge Solutions - EM Shield for iPhone I can stack any of the amps under the iPhone except for the D3 Python which still needs to be 6-9" away. The only big problem I have run into is that "static discharge" makes the amp go nuts - so don't shuffle across the carpet and then touch the amp or headphones or laptop or all kinds of nasty noises will emanate from the headphones till you unplug the headphones to switch the amp off.
ADDENDUM: While the Nuforce via USB is slightly brighter and slightly more forward than the 3MOVE with slightly less bass, with analog input it does sound a little brighter and a little more forward and aggressive than with USB input. Keep that in mind when pairing with bright headphones. For example, I can use the Nuforce via USB just fine with Phonak Audeo IEM with black filters, but via analog input and grey filters it can be too bright.
Visit here for more info http://www.head-fi.org/forum/list/105#
@ you guys turning into audiophiles
Review
HEADPHONES USED: Westone 3, Klipsch Image X10, Denon C700, Nuforce NE-7M, ATH-ESW10JPN, APS V3 cabled HD600, APS V3 cabled RS-1, APS V3 cabled markl Woodied Denon D2000, and APS V3 cabled Edition 9.
MUSIC USED: Michael Knowles "Bink Audio Test CD", Nils Lofgren "Acoustic Live", Arne Domnerus "Antiphone Blues" and "Jazz at the Pawnshop", Infected Mushroom "B.P. Empire", Tord Gustavsen Trio "Being There", Pat Metheny "Day Trip", Tsuyoshi Yamamoto "Autumn in Seattle" and "Smooth Jazz Festival", B.B. King and Eric Clapton "Riding With the King", Shelby Lynn "Just a Little Lovin'", Nora Jones "Not Too Late", Arvo Part "Tabula Rasa", Jack Johnson "Sleep Through the Static" and "In Between Dreams", Elaine Elias "Something for You", Gary Karr "Super Double-bass", Guinea Pig "Kool Cats", Christopher Hogwood "Handel Messiah", Pink Floyd "DSOT", The Beatles "Love", Beck "Sea Change", Diana Krall "Girl in the Other Room", Coldplay "Viva La Vida", and Skillet "Comatose".
The Nuforce Icon Mobile is a $99 entry level portable USB DAC/Amp, which has more of a flat form factor that is amenable to being stacked under an iPod without adding too much size to the overall package. It is about the same width and depth as the iBasso D2 Boa, but almost half as tall/thick, so you can almost stack two Icon Mobile on top of each other to achieve the thickness of one D2 Boa. When plugged into the Macbook's USB port the DAC shows up as a "C-Media USB Headphone Set". The Nuforce has some unique features including two headphone out jacks which switch on the power when a headphone plug is inserted, with the jack closer the center being a special jack that works with 4-conductor headsets with stereo headphones and a built-in microphone, like the Nuforce NE-7M iPhone IEM (or other iPhone IEM). This allows the NE-7M to be used as a headset with telephony applications, instant messaging and Skype, and probably for gaming as well. I have not been able to test this telephony feature, but the mic did show up in my Mac's Audio MIDI setup application as the left channel only microphone. The analog input is on the same end of the amp as the two outputs (we'll call it the top end), and all three jacks are slightly recessed by about 0.5 mm along one edge of the amp.
All my portable headphones worked fine with the slightly recessed jacks, but my full size APS V3 cabled headphones needed an adapter because the 1/8" Neutrik plugs on my APS cables are too wide and would hit the lip of the case around the jacks. Nuforce has informed me that they are already planning to make changes to the case to allow a wider variety of headphone plugs to fit, and they will make it available to early buyers who have problems - but they are not sure yet if it will be possible to use the wider Neutrik 1/8" plugs used by APS, while I know the smaller Neutrik plugs from Qables.com already fit. On one side there is a USB jack for charging and the USB DAC input, a recessed gain switch that cannot not be accidentally changed, and a rotary volume knob. The volume knob is of fairly decent quality, and in low gain it is easily usable with high sensitivity IEM at very low volumes, with channel imbalance only at the very lowest volumes. The amp is totally silent in high gain with the USB music paused and volume turned all the way up.
To my ears the Nuforce does benefit noticeably from burn-in. When it was right out of the box it struck me as just a little dull and bland when compared to the iBasso D2 boa, and I feared that I would be disappointed with it in the end. I left it running for 6-7 hours and came back to it and the sound was already starting to clean up some. So I left it running via USB with music 24/7 but with a 1 hour break each day, and went back to listen for about an hour each night at 24 hour intervals. By 24-36 hours it was sounding good enough to actually recommend it to others, by 55-60 hours I was posting that it sounded a little forward but was sounding similar to my Meier Headsix which I like more than the D2 Boa. At that time I noted that it was also less edgy than the Vivid V1 but not as powerful. By 80 hours it was becoming more transparent and detailed, and sounded good with all my portable headphones including ATH-ESW10, Westone 3, Image X10, NE-7M and even the Denon C700. By that time I was finding that it is one of those amps that actually makes the C700 smoother and less harsh in the highs, while controlling the bass - one of the things I like about the Headsix and Predator when driving the Denon C700 (sometimes I think the C700 was tuned to sound best right out of the headphone jack of the 5.5G iPod video and 2G Nano). Between 180-200 hours the soundstage had finished opening up. I continued burn-in via USB through 210 hours and then switched to analog input for the remainder of burn-in. I did my once a day listening until it had 230-240 hours on it and felt it seemed to be done changing by 180-200 hours. I did not listen for the last 60-70 hours of burn-in until time to start the review after 300 hours on 12/14.
During burn-in I was able to determine that the Nuforce amp was above the iBasso D2 Boa and Vivid V1 in most areas of performance and sound (but not all areas), but still below the top tier amps like Pico, Predator and D3 Python. I have not reviewed the Practical Devices XM5 yet, but I am fairly sure it will be among the top tier amps based on the limited listening I have done during burn-in. I do not have the 2MOVE or D2 Viper to compare to in this review, but if I did I would guess it would fall below the 2MOVE or rolled-opamp Viper but above the Stock D2 Viper. So, since I had so many headphones to listen with most of my comparisons were with the D2 Boa and V1 to properly discern the ranking. Although I did also do comparisons with the top amps as well, I just did not spend as much time with them.
For the first part of my dedicated listening for the review I decided to start with my full size headphones (HD600, RS-1, D2000, Edition 9) since I had already done a fair bit of listening with my portable headphones and IEM during burn-in, and was already enjoying the amp with them. Typically the Nuforce could be turned up all the way to 100% volume with HD600 without clipping. And, it would play to decent volumes at that setting but not more than mildly or moderately loud - max volume of the Nuforce Icon Mobile was still about 2-3 db below D2 Boa, which could be turned to about 3:30 o'clock before clipping in high gain (max is 4:30). On the other hand, unlike with the HD600, the Nuforce could drive the Grado RS-1 and Denon D2000 at max volume MUCH much louder than I would ever care to listen to music. Typically I could sweep the side scrolling rotary volume knob 4 times to go from from zero volume to 100% volume. With the Nuforce in high gain with anything other than HD600 I would normally listen with the volume rotated up only 1/2 of the way to max. With the volume turned 3/4 of the way up it was quite loud with RS-1 and D2000, and full volume was uncomfortable and likely damaging. With RS-1 there was some clipping starting to creep in as I got very close to max volume at the end of the dial with the RS-1, but it was more of a soft clipping with less dynamics and some fuzzyness to the sound. The clipping was even better/softer with the D2000 at max volume, and with some material it was not even there. I could never explore the upper volume limits with my IEM without worsening my chronic tinnitus, so I didn't try. Suffice it to say the Nuforce will go loud enough with any of my IEM. So, to summarize, the Pico, D3, V1, Micro Stack and XM5 are all more powerful with HD600 than the D2 Boa which slightly edged out the Nuforce, but with any portable earphone or low impedance full size headphone the Nuforce has plenty of power to go around.
With the Nuforce the bass is fairly strong with all the low impedance phones, but with HD600 pushed to high volumes the bass was not quite as good as the D2 Boa, especially as the volumes would get closer to max output. Bass with infected mushroom and HD600 was stronger at normal volumes but not impressive like with the lower impedance phones. It was only a problem with HD600 in which I found the bass pulling back or thinning out when the amp is pushed hard (similar to the Meier Headfive desktop amp when pushed hard with Grados). So like the D2 Boa, the Nuforce was not optimal with high impedance phones, although it still drives the HD600 better than the headphone out of my Macbook. Better portable amps from my review to drive the HD600 better include the Pico and Vivid V1 or D3 Python or XM5 as the most powerful, followed by the Predator and D2 Boa, and then the Nuforce. However, with lower impedance headphones like my portable headphones and RS-1, D2000 and Edition 9, the Nuforce really came into it's element and it became more dynamic and powerful sounding. The D2000 and Edition 9 are very enjoyable with the Nuforce, and the bass is powerful enough to tickle my eardrums and damage my hearing if I wish, passing up the RS-1's bass by a noticeable margin too (unless I switch to flat pads). With test tones on the HD600 the Nuforce sounded strong to 31Hz, and was maybe 3-4db down at 25Hz but then rolled off below that. But I found that the 20-25Hz notes were stronger with the low impedance phones than with the 300 ohm HD600, and the NE-7M actually went deeper than most of my full size headphones (16Hz). The Pico, Predator, D3 Python and XM5 all had more powerful and present or pervasive bass, but you wouldn't know the Nuforce is lacking anything but for the comparison with the top tier amps. It's all relative, as listening to the Nuforce on its own merits did not make me wish for bass boost or anything like that. Bass was fairly well controlled as well, although pushing the amp to it's limits at the highest volumes the IEM, D2000 or Edition 9 the bass was just starting to get a little loose. Only with the HD600 did it start to fade at higher volume levels. The ESW10 bass was lighter and more along the lines of the RS-1 (ESW10 is kinda like a closed RS-1) and just a little more reserved with the Nuforce than with the top tier amps. This is not a bass-thin amp, it's just that some others have more bass punch. But, pair it with the Westone 3, NE-7M with Complys tips, D2000 or Edition 9 and the bass is rocking.
The Mids of the Nuforce tend to be more forward like the Meier Amps (Headsix and 2MOVE) or the Vivid V1. I have always felt that Pat Metheney "Day Trip" is recorded with a little too much energy in the mids with the electric guitar (granted that is the "star of the show"), so switching to the D2 Boa or other amps usually helps pull the guitar back a little. Still, this particular recording was listenable with the Nuforce, although it was much better if I was using the Westone 3, NE-7M, C700, D2000 or RS-1 with bowls than the HD600 or Edition 9 with it. With most music I appreciated the more forward mids of the Nuforce with the D2000, as I feel the D2000 are still slightly recessed in the mids despite the wood cups and earpad mods that I have done which also helped a bit. I haven't been using my RS-1 much lately, as I tend to prefer my stats and my modded D2000, Edition 9, or ESW10 more. The RS-1 did not sound bad with the Nuforce, but with bowl pads I sometimes (not always) felt there was a similar but less prominent upper mid coloration with Grados, like the Vivid V1 amp demonstrated earlier in the review. My other headphones did not have this issue with the mids, and I still preferred bowls with the Grados for their improvement in soundstage through the Nuforce. I would not rule out the Nuforce with Grados as it is still better than the V1 with them, and often better than the D2 Boa as well - where sometimes the D2 Boa's mids felt slightly sucked out with the RS-1 after listening to the RS-1 with the Nuforce for a while and got used to it. I still felt the top tier amps were warmer and richer in the mids than the Nuforce, D2 Boa or V1, and the D2 Boa sounds like an artificial warmth at times, with slightly boosted upper bass and lower mids. But what I liked most about the Nuforce mids was the clarity and very little coloration.
In general I felt that the forward mids of the Nuforce helped improve the audibility of the midrange detail, and music became more engaging than with the D2 Boa (similar to the Headsix and 2MOVE). This was one of the things that attracted me to the 2MOVE that I borrowed a while back. Female vocals like Shelby Lynn, Nora Jones, Elaine Elias and Jane Monheit don't have the bass bleed into the lower mids a little, like with the Boa, so they sound more open and natural most of the time (less boomy or boxy or close mic'd sounding). The D2 Boa with Westone 3 was the worst offender in that regard. Nora Jones's vocals in "Not Too Late" and on Herbie Hancock "The River" are more present and engaging with the Nuforce. With the Boa, Nora Jones and Jane Monheit's vocals do sound better than did Shelby Lynn or Diana Krall on the Boa, but I liked the Nuforce a little better with all of them. On Elaine Elias "Something for You" I got caught up in the music better, and forget that I am doing a review, so it seems little more involving as well. The Boa still acquitted itself well with Elaine Elias during the instrumental jazz parts, but lost the illusion when the vocals would come in.
I did enjoy pianos with the Nuforce, but the Nuforce maybe smoothes out the piano a little more than the other amps, making it more polite. Despite that, it still did a nice job with piano and guitar and vocals in B.B. King and Eric Clapton "Riding With the King". Nils Lofgren "Acoustic Live" was crisp and detailed and airy but not as spacious as the top tier amps listed above. And the Nuforce also seems good with unamplified acoustic guitar as well, like with Jack Johnson and Andy Mckee or Govi. In Tsuyoshi Yamamoto "Smooth Jazz Festival" during "Somewhere Over the Rainbow" the sax is more intimate and engaging with the Nuforce, but the Boa has little stronger bass response from the plucked string bass. However with the D2 Boa the sax sounds thinner in the middle and more upturned at the ends of the frequency spectrum. With Gary Karr "Super double bass" this issue on the D2 Boa also caused the bass fiddle to seem slightly more hollow or lacking than with the Nuforce, especially when listening with the D2000 but also with the HD600 and others. This recessed mids of the D2 Boa was still better than with the stock D2 Viper last time I compared them. These slightly tipped up ends of the frequency spectrum or the recessed mids (however you look at it) make the D2 Boa a little better for low volume listening with the HD600, but very quiet listening was among the few instances where I would grab the D2 Boa over the Nuforce. On the other hand, the Nuforce with D2000 was still better for low volume listening than D2 Boa with HD600.
Treble on the Nuforce is smooth but slightly recessed with a variety of headphones. With my D2000, Westone 3 and ESW10 the Nuforce does not accentuate sibilance that I usually hear in my Diana Krall "Girl in the Other Room" CD, which is my test CD for sibilance since it seems to be mastered with that in there. Switching to the Grado RS-1 I found there was less sibilance through the Nuforce than with my D2 Boa. The slightly laid back treble made the Nuforce amp more forgiving of some music. With the D2000 I actually listened to the entire Diana Krall CD with the Nuforce as I typed my review, without thinking about the sibilance. With Tord Gustavsen Trio's song Karmosin off the "Being There" CD, this is a good test of cymbals as they are lightly and hauntingly tapped during the intro drums and piano, and I did not feel there was a lack of treble as the ring of the cymbals would hang in the air properly with a nice slow decay.
I have rarely bothered to test high frequency extension, but decided to start doing that and tested all of the amps tonight, along with the Nuforce using Michael Knowles "Bink Audio Test CD". With treble test tones on the Nuforce I used the D2000 which for me have better treble extension than my HD600 or most IEM. There I found a problem - with the Nuforce while at 16Khz I was getting a strange harmonic at exactly 4Khz that was louder than the actual 16Khz tone. I've had this problem with another USB DAC amp before, but I cannot recall which one now (might have been the Lyrix or D1). This 4Khz artifact did not happen with the D2 Boa via USB which was still going strong at 16Khz, or with the Nuforce via analog input. With music I was unable to hear any artifacts like with the test tone. For me, 16Khz is the practical limit of my hearing as I can't hear the 20Khz tone unless I crank an amp like the D2 to 3:30 o'clock or 80-90% of max. While I could hear 20Khz with the D2 Boa at full volume, cranking the Nuforce volume at 20Khz was inaudible. Via analog input on the Nuforce the 20Khz test tone was still inaudible to me, although it was still barely audible if I plugged the headphones directly into the Macbook. The only other amps that would allow me hear the 20Khz test tone at high volume was the Pico and Predator, although I could hear it louder with the Pico. I found that in doing this test that the V1, XM5 and D3 were all quite noisy in the background at high volumes past 3 o'clock with the 20Khz test tone, so I could not hear the tone over the noise. The Nuforce had just a tiny bit of noise at max volume hooked up via USB, and the Pico and Predator were silent. The D2 Boa background noise was silent and allowed me to hear the 20Khz tone. After I accidentally hit my ears full volume with a 440Hz piano note, I could not do further testing of the highs until my ears recovered.
The Nuforce combines a forward soundstage with decent air and ambience, although like the 2MOVE it puts the listener in a more intimate position while making the venue seem a little smaller. With the D2 Boa and Arvo Part "Tabula Rasa" the image is a little more spread out and deeper but less precise than with the Nuforce. With Gary Karr "Super Double-bass" the imaging was similarly a little more focused and the bass fiddle more centered with Nuforce (almost like a slight hint of crossfeed), while with the same music on the D2 Boa the bass fiddle sounded a little more spread out and hard to pinpoint. Soundstage is obviously better with the HD600 and D2000 than Westone 3 or ESW10 and RS-1. But even with those headphones, when comparing the Nuforce soundstage to the Pico or D3 and Predator the Nuforce soundstage seems flatter and more 2D, with a wide but not as deep soundstage. Air and ambience with the Nuforce was about the same as my D2 Boa, but with the Boa placing the listener a little farther from the stage than Nuforce or Vivid Audio V1. Switching from the Nuforce to the Pico and D3 (or even Predator) it was clear that the top tier amps are more open and spacious, with more micro-detail and are even more rich sounding and engaging. The difference in sound between the Nuforce and the top three on hand (Predator, Pico and D3) is bigger than it is between Nuforce and D2 Boa or V1, confirming that the D2 Boa and Vivid V1 are it's main competitors in sound and price range. The Predator is in between the forwardness of the Nuforce/V1 and Pico/D3, but still maintains a better soundstage, warmth and richness. The degree of detail of the Nuforce DAC seems to be on par with the DAC in the 2MOVE and Predator, but below that of the Pico and iBasso D2/D3 amps. I have not reviewed the XM5 that is burning-in right now, so I really cannot comment on soundstage or micro-detail yet.
The last area I looked at was the RFI interference problems that have cropped up the past 2 months since I got an iPhone 3G. I found the D3 to be the most susceptible to iPhone BUZZ from 3-4 feet away, followed by the D2 Viper and the D2 Boa from 1-2 feet away, then the Predator/Pico/Nuforce which could be within 6-9" of the iPhone. With an EM blocking card from Quick Bridge Solutions - EM Shield for iPhone I can stack any of the amps under the iPhone except for the D3 Python which still needs to be 6-9" away. The only big problem I have run into is that "static discharge" makes the amp go nuts - so don't shuffle across the carpet and then touch the amp or headphones or laptop or all kinds of nasty noises will emanate from the headphones till you unplug the headphones to switch the amp off.
ADDENDUM: While the Nuforce via USB is slightly brighter and slightly more forward than the 3MOVE with slightly less bass, with analog input it does sound a little brighter and a little more forward and aggressive than with USB input. Keep that in mind when pairing with bright headphones. For example, I can use the Nuforce via USB just fine with Phonak Audeo IEM with black filters, but via analog input and grey filters it can be too bright.
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Review
HEADPHONES USED: Westone 3, Klipsch Image X10, Denon C700, Nuforce NE-7M, ATH-ESW10JPN, APS V3 cabled HD600, APS V3 cabled RS-1, APS V3 cabled markl Woodied Denon D2000, and APS V3 cabled Edition 9.
MUSIC USED: Michael Knowles "Bink Audio Test CD", Nils Lofgren "Acoustic Live", Arne Domnerus "Antiphone Blues" and "Jazz at the Pawnshop", Infected Mushroom "B.P. Empire", Tord Gustavsen Trio "Being There", Pat Metheny "Day Trip", Tsuyoshi Yamamoto "Autumn in Seattle" and "Smooth Jazz Festival", B.B. King and Eric Clapton "Riding With the King", Shelby Lynn "Just a Little Lovin'", Nora Jones "Not Too Late", Arvo Part "Tabula Rasa", Jack Johnson "Sleep Through the Static" and "In Between Dreams", Elaine Elias "Something for You", Gary Karr "Super Double-bass", Guinea Pig "Kool Cats", Christopher Hogwood "Handel Messiah", Pink Floyd "DSOT", The Beatles "Love", Beck "Sea Change", Diana Krall "Girl in the Other Room", Coldplay "Viva La Vida", and Skillet "Comatose".
The Nuforce Icon Mobile is a $99 entry level portable USB DAC/Amp, which has more of a flat form factor that is amenable to being stacked under an iPod without adding too much size to the overall package. It is about the same width and depth as the iBasso D2 Boa, but almost half as tall/thick, so you can almost stack two Icon Mobile on top of each other to achieve the thickness of one D2 Boa. When plugged into the Macbook's USB port the DAC shows up as a "C-Media USB Headphone Set". The Nuforce has some unique features including two headphone out jacks which switch on the power when a headphone plug is inserted, with the jack closer the center being a special jack that works with 4-conductor headsets with stereo headphones and a built-in microphone, like the Nuforce NE-7M iPhone IEM (or other iPhone IEM). This allows the NE-7M to be used as a headset with telephony applications, instant messaging and Skype, and probably for gaming as well. I have not been able to test this telephony feature, but the mic did show up in my Mac's Audio MIDI setup application as the left channel only microphone. The analog input is on the same end of the amp as the two outputs (we'll call it the top end), and all three jacks are slightly recessed by about 0.5 mm along one edge of the amp.
All my portable headphones worked fine with the slightly recessed jacks, but my full size APS V3 cabled headphones needed an adapter because the 1/8" Neutrik plugs on my APS cables are too wide and would hit the lip of the case around the jacks. Nuforce has informed me that they are already planning to make changes to the case to allow a wider variety of headphone plugs to fit, and they will make it available to early buyers who have problems - but they are not sure yet if it will be possible to use the wider Neutrik 1/8" plugs used by APS, while I know the smaller Neutrik plugs from Qables.com already fit. On one side there is a USB jack for charging and the USB DAC input, a recessed gain switch that cannot not be accidentally changed, and a rotary volume knob. The volume knob is of fairly decent quality, and in low gain it is easily usable with high sensitivity IEM at very low volumes, with channel imbalance only at the very lowest volumes. The amp is totally silent in high gain with the USB music paused and volume turned all the way up.
To my ears the Nuforce does benefit noticeably from burn-in. When it was right out of the box it struck me as just a little dull and bland when compared to the iBasso D2 boa, and I feared that I would be disappointed with it in the end. I left it running for 6-7 hours and came back to it and the sound was already starting to clean up some. So I left it running via USB with music 24/7 but with a 1 hour break each day, and went back to listen for about an hour each night at 24 hour intervals. By 24-36 hours it was sounding good enough to actually recommend it to others, by 55-60 hours I was posting that it sounded a little forward but was sounding similar to my Meier Headsix which I like more than the D2 Boa. At that time I noted that it was also less edgy than the Vivid V1 but not as powerful. By 80 hours it was becoming more transparent and detailed, and sounded good with all my portable headphones including ATH-ESW10, Westone 3, Image X10, NE-7M and even the Denon C700. By that time I was finding that it is one of those amps that actually makes the C700 smoother and less harsh in the highs, while controlling the bass - one of the things I like about the Headsix and Predator when driving the Denon C700 (sometimes I think the C700 was tuned to sound best right out of the headphone jack of the 5.5G iPod video and 2G Nano). Between 180-200 hours the soundstage had finished opening up. I continued burn-in via USB through 210 hours and then switched to analog input for the remainder of burn-in. I did my once a day listening until it had 230-240 hours on it and felt it seemed to be done changing by 180-200 hours. I did not listen for the last 60-70 hours of burn-in until time to start the review after 300 hours on 12/14.
During burn-in I was able to determine that the Nuforce amp was above the iBasso D2 Boa and Vivid V1 in most areas of performance and sound (but not all areas), but still below the top tier amps like Pico, Predator and D3 Python. I have not reviewed the Practical Devices XM5 yet, but I am fairly sure it will be among the top tier amps based on the limited listening I have done during burn-in. I do not have the 2MOVE or D2 Viper to compare to in this review, but if I did I would guess it would fall below the 2MOVE or rolled-opamp Viper but above the Stock D2 Viper. So, since I had so many headphones to listen with most of my comparisons were with the D2 Boa and V1 to properly discern the ranking. Although I did also do comparisons with the top amps as well, I just did not spend as much time with them.
For the first part of my dedicated listening for the review I decided to start with my full size headphones (HD600, RS-1, D2000, Edition 9) since I had already done a fair bit of listening with my portable headphones and IEM during burn-in, and was already enjoying the amp with them. Typically the Nuforce could be turned up all the way to 100% volume with HD600 without clipping. And, it would play to decent volumes at that setting but not more than mildly or moderately loud - max volume of the Nuforce Icon Mobile was still about 2-3 db below D2 Boa, which could be turned to about 3:30 o'clock before clipping in high gain (max is 4:30). On the other hand, unlike with the HD600, the Nuforce could drive the Grado RS-1 and Denon D2000 at max volume MUCH much louder than I would ever care to listen to music. Typically I could sweep the side scrolling rotary volume knob 4 times to go from from zero volume to 100% volume. With the Nuforce in high gain with anything other than HD600 I would normally listen with the volume rotated up only 1/2 of the way to max. With the volume turned 3/4 of the way up it was quite loud with RS-1 and D2000, and full volume was uncomfortable and likely damaging. With RS-1 there was some clipping starting to creep in as I got very close to max volume at the end of the dial with the RS-1, but it was more of a soft clipping with less dynamics and some fuzzyness to the sound. The clipping was even better/softer with the D2000 at max volume, and with some material it was not even there. I could never explore the upper volume limits with my IEM without worsening my chronic tinnitus, so I didn't try. Suffice it to say the Nuforce will go loud enough with any of my IEM. So, to summarize, the Pico, D3, V1, Micro Stack and XM5 are all more powerful with HD600 than the D2 Boa which slightly edged out the Nuforce, but with any portable earphone or low impedance full size headphone the Nuforce has plenty of power to go around.
With the Nuforce the bass is fairly strong with all the low impedance phones, but with HD600 pushed to high volumes the bass was not quite as good as the D2 Boa, especially as the volumes would get closer to max output. Bass with infected mushroom and HD600 was stronger at normal volumes but not impressive like with the lower impedance phones. It was only a problem with HD600 in which I found the bass pulling back or thinning out when the amp is pushed hard (similar to the Meier Headfive desktop amp when pushed hard with Grados). So like the D2 Boa, the Nuforce was not optimal with high impedance phones, although it still drives the HD600 better than the headphone out of my Macbook. Better portable amps from my review to drive the HD600 better include the Pico and Vivid V1 or D3 Python or XM5 as the most powerful, followed by the Predator and D2 Boa, and then the Nuforce. However, with lower impedance headphones like my portable headphones and RS-1, D2000 and Edition 9, the Nuforce really came into it's element and it became more dynamic and powerful sounding. The D2000 and Edition 9 are very enjoyable with the Nuforce, and the bass is powerful enough to tickle my eardrums and damage my hearing if I wish, passing up the RS-1's bass by a noticeable margin too (unless I switch to flat pads). With test tones on the HD600 the Nuforce sounded strong to 31Hz, and was maybe 3-4db down at 25Hz but then rolled off below that. But I found that the 20-25Hz notes were stronger with the low impedance phones than with the 300 ohm HD600, and the NE-7M actually went deeper than most of my full size headphones (16Hz). The Pico, Predator, D3 Python and XM5 all had more powerful and present or pervasive bass, but you wouldn't know the Nuforce is lacking anything but for the comparison with the top tier amps. It's all relative, as listening to the Nuforce on its own merits did not make me wish for bass boost or anything like that. Bass was fairly well controlled as well, although pushing the amp to it's limits at the highest volumes the IEM, D2000 or Edition 9 the bass was just starting to get a little loose. Only with the HD600 did it start to fade at higher volume levels. The ESW10 bass was lighter and more along the lines of the RS-1 (ESW10 is kinda like a closed RS-1) and just a little more reserved with the Nuforce than with the top tier amps. This is not a bass-thin amp, it's just that some others have more bass punch. But, pair it with the Westone 3, NE-7M with Complys tips, D2000 or Edition 9 and the bass is rocking.
The Mids of the Nuforce tend to be more forward like the Meier Amps (Headsix and 2MOVE) or the Vivid V1. I have always felt that Pat Metheney "Day Trip" is recorded with a little too much energy in the mids with the electric guitar (granted that is the "star of the show"), so switching to the D2 Boa or other amps usually helps pull the guitar back a little. Still, this particular recording was listenable with the Nuforce, although it was much better if I was using the Westone 3, NE-7M, C700, D2000 or RS-1 with bowls than the HD600 or Edition 9 with it. With most music I appreciated the more forward mids of the Nuforce with the D2000, as I feel the D2000 are still slightly recessed in the mids despite the wood cups and earpad mods that I have done which also helped a bit. I haven't been using my RS-1 much lately, as I tend to prefer my stats and my modded D2000, Edition 9, or ESW10 more. The RS-1 did not sound bad with the Nuforce, but with bowl pads I sometimes (not always) felt there was a similar but less prominent upper mid coloration with Grados, like the Vivid V1 amp demonstrated earlier in the review. My other headphones did not have this issue with the mids, and I still preferred bowls with the Grados for their improvement in soundstage through the Nuforce. I would not rule out the Nuforce with Grados as it is still better than the V1 with them, and often better than the D2 Boa as well - where sometimes the D2 Boa's mids felt slightly sucked out with the RS-1 after listening to the RS-1 with the Nuforce for a while and got used to it. I still felt the top tier amps were warmer and richer in the mids than the Nuforce, D2 Boa or V1, and the D2 Boa sounds like an artificial warmth at times, with slightly boosted upper bass and lower mids. But what I liked most about the Nuforce mids was the clarity and very little coloration.
In general I felt that the forward mids of the Nuforce helped improve the audibility of the midrange detail, and music became more engaging than with the D2 Boa (similar to the Headsix and 2MOVE). This was one of the things that attracted me to the 2MOVE that I borrowed a while back. Female vocals like Shelby Lynn, Nora Jones, Elaine Elias and Jane Monheit don't have the bass bleed into the lower mids a little, like with the Boa, so they sound more open and natural most of the time (less boomy or boxy or close mic'd sounding). The D2 Boa with Westone 3 was the worst offender in that regard. Nora Jones's vocals in "Not Too Late" and on Herbie Hancock "The River" are more present and engaging with the Nuforce. With the Boa, Nora Jones and Jane Monheit's vocals do sound better than did Shelby Lynn or Diana Krall on the Boa, but I liked the Nuforce a little better with all of them. On Elaine Elias "Something for You" I got caught up in the music better, and forget that I am doing a review, so it seems little more involving as well. The Boa still acquitted itself well with Elaine Elias during the instrumental jazz parts, but lost the illusion when the vocals would come in.
I did enjoy pianos with the Nuforce, but the Nuforce maybe smoothes out the piano a little more than the other amps, making it more polite. Despite that, it still did a nice job with piano and guitar and vocals in B.B. King and Eric Clapton "Riding With the King". Nils Lofgren "Acoustic Live" was crisp and detailed and airy but not as spacious as the top tier amps listed above. And the Nuforce also seems good with unamplified acoustic guitar as well, like with Jack Johnson and Andy Mckee or Govi. In Tsuyoshi Yamamoto "Smooth Jazz Festival" during "Somewhere Over the Rainbow" the sax is more intimate and engaging with the Nuforce, but the Boa has little stronger bass response from the plucked string bass. However with the D2 Boa the sax sounds thinner in the middle and more upturned at the ends of the frequency spectrum. With Gary Karr "Super double bass" this issue on the D2 Boa also caused the bass fiddle to seem slightly more hollow or lacking than with the Nuforce, especially when listening with the D2000 but also with the HD600 and others. This recessed mids of the D2 Boa was still better than with the stock D2 Viper last time I compared them. These slightly tipped up ends of the frequency spectrum or the recessed mids (however you look at it) make the D2 Boa a little better for low volume listening with the HD600, but very quiet listening was among the few instances where I would grab the D2 Boa over the Nuforce. On the other hand, the Nuforce with D2000 was still better for low volume listening than D2 Boa with HD600.
Treble on the Nuforce is smooth but slightly recessed with a variety of headphones. With my D2000, Westone 3 and ESW10 the Nuforce does not accentuate sibilance that I usually hear in my Diana Krall "Girl in the Other Room" CD, which is my test CD for sibilance since it seems to be mastered with that in there. Switching to the Grado RS-1 I found there was less sibilance through the Nuforce than with my D2 Boa. The slightly laid back treble made the Nuforce amp more forgiving of some music. With the D2000 I actually listened to the entire Diana Krall CD with the Nuforce as I typed my review, without thinking about the sibilance. With Tord Gustavsen Trio's song Karmosin off the "Being There" CD, this is a good test of cymbals as they are lightly and hauntingly tapped during the intro drums and piano, and I did not feel there was a lack of treble as the ring of the cymbals would hang in the air properly with a nice slow decay.
I have rarely bothered to test high frequency extension, but decided to start doing that and tested all of the amps tonight, along with the Nuforce using Michael Knowles "Bink Audio Test CD". With treble test tones on the Nuforce I used the D2000 which for me have better treble extension than my HD600 or most IEM. There I found a problem - with the Nuforce while at 16Khz I was getting a strange harmonic at exactly 4Khz that was louder than the actual 16Khz tone. I've had this problem with another USB DAC amp before, but I cannot recall which one now (might have been the Lyrix or D1). This 4Khz artifact did not happen with the D2 Boa via USB which was still going strong at 16Khz, or with the Nuforce via analog input. With music I was unable to hear any artifacts like with the test tone. For me, 16Khz is the practical limit of my hearing as I can't hear the 20Khz tone unless I crank an amp like the D2 to 3:30 o'clock or 80-90% of max. While I could hear 20Khz with the D2 Boa at full volume, cranking the Nuforce volume at 20Khz was inaudible. Via analog input on the Nuforce the 20Khz test tone was still inaudible to me, although it was still barely audible if I plugged the headphones directly into the Macbook. The only other amps that would allow me hear the 20Khz test tone at high volume was the Pico and Predator, although I could hear it louder with the Pico. I found that in doing this test that the V1, XM5 and D3 were all quite noisy in the background at high volumes past 3 o'clock with the 20Khz test tone, so I could not hear the tone over the noise. The Nuforce had just a tiny bit of noise at max volume hooked up via USB, and the Pico and Predator were silent. The D2 Boa background noise was silent and allowed me to hear the 20Khz tone. After I accidentally hit my ears full volume with a 440Hz piano note, I could not do further testing of the highs until my ears recovered.
The Nuforce combines a forward soundstage with decent air and ambience, although like the 2MOVE it puts the listener in a more intimate position while making the venue seem a little smaller. With the D2 Boa and Arvo Part "Tabula Rasa" the image is a little more spread out and deeper but less precise than with the Nuforce. With Gary Karr "Super Double-bass" the imaging was similarly a little more focused and the bass fiddle more centered with Nuforce (almost like a slight hint of crossfeed), while with the same music on the D2 Boa the bass fiddle sounded a little more spread out and hard to pinpoint. Soundstage is obviously better with the HD600 and D2000 than Westone 3 or ESW10 and RS-1. But even with those headphones, when comparing the Nuforce soundstage to the Pico or D3 and Predator the Nuforce soundstage seems flatter and more 2D, with a wide but not as deep soundstage. Air and ambience with the Nuforce was about the same as my D2 Boa, but with the Boa placing the listener a little farther from the stage than Nuforce or Vivid Audio V1. Switching from the Nuforce to the Pico and D3 (or even Predator) it was clear that the top tier amps are more open and spacious, with more micro-detail and are even more rich sounding and engaging. The difference in sound between the Nuforce and the top three on hand (Predator, Pico and D3) is bigger than it is between Nuforce and D2 Boa or V1, confirming that the D2 Boa and Vivid V1 are it's main competitors in sound and price range. The Predator is in between the forwardness of the Nuforce/V1 and Pico/D3, but still maintains a better soundstage, warmth and richness. The degree of detail of the Nuforce DAC seems to be on par with the DAC in the 2MOVE and Predator, but below that of the Pico and iBasso D2/D3 amps. I have not reviewed the XM5 that is burning-in right now, so I really cannot comment on soundstage or micro-detail yet.
The last area I looked at was the RFI interference problems that have cropped up the past 2 months since I got an iPhone 3G. I found the D3 to be the most susceptible to iPhone BUZZ from 3-4 feet away, followed by the D2 Viper and the D2 Boa from 1-2 feet away, then the Predator/Pico/Nuforce which could be within 6-9" of the iPhone. With an EM blocking card from Quick Bridge Solutions - EM Shield for iPhone I can stack any of the amps under the iPhone except for the D3 Python which still needs to be 6-9" away. The only big problem I have run into is that "static discharge" makes the amp go nuts - so don't shuffle across the carpet and then touch the amp or headphones or laptop or all kinds of nasty noises will emanate from the headphones till you unplug the headphones to switch the amp off.
ADDENDUM: While the Nuforce via USB is slightly brighter and slightly more forward than the 3MOVE with slightly less bass, with analog input it does sound a little brighter and a little more forward and aggressive than with USB input. Keep that in mind when pairing with bright headphones. For example, I can use the Nuforce via USB just fine with Phonak Audeo IEM with black filters, but via analog input and grey filters it can be too bright.
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Review
HEADPHONES USED: Westone 3, Klipsch Image X10, Denon C700, Nuforce NE-7M, ATH-ESW10JPN, APS V3 cabled HD600, APS V3 cabled RS-1, APS V3 cabled markl Woodied Denon D2000, and APS V3 cabled Edition 9.
MUSIC USED: Michael Knowles "Bink Audio Test CD", Nils Lofgren "Acoustic Live", Arne Domnerus "Antiphone Blues" and "Jazz at the Pawnshop", Infected Mushroom "B.P. Empire", Tord Gustavsen Trio "Being There", Pat Metheny "Day Trip", Tsuyoshi Yamamoto "Autumn in Seattle" and "Smooth Jazz Festival", B.B. King and Eric Clapton "Riding With the King", Shelby Lynn "Just a Little Lovin'", Nora Jones "Not Too Late", Arvo Part "Tabula Rasa", Jack Johnson "Sleep Through the Static" and "In Between Dreams", Elaine Elias "Something for You", Gary Karr "Super Double-bass", Guinea Pig "Kool Cats", Christopher Hogwood "Handel Messiah", Pink Floyd "DSOT", The Beatles "Love", Beck "Sea Change", Diana Krall "Girl in the Other Room", Coldplay "Viva La Vida", and Skillet "Comatose".
The Nuforce Icon Mobile is a $99 entry level portable USB DAC/Amp, which has more of a flat form factor that is amenable to being stacked under an iPod without adding too much size to the overall package. It is about the same width and depth as the iBasso D2 Boa, but almost half as tall/thick, so you can almost stack two Icon Mobile on top of each other to achieve the thickness of one D2 Boa. When plugged into the Macbook's USB port the DAC shows up as a "C-Media USB Headphone Set". The Nuforce has some unique features including two headphone out jacks which switch on the power when a headphone plug is inserted, with the jack closer the center being a special jack that works with 4-conductor headsets with stereo headphones and a built-in microphone, like the Nuforce NE-7M iPhone IEM (or other iPhone IEM). This allows the NE-7M to be used as a headset with telephony applications, instant messaging and Skype, and probably for gaming as well. I have not been able to test this telephony feature, but the mic did show up in my Mac's Audio MIDI setup application as the left channel only microphone. The analog input is on the same end of the amp as the two outputs (we'll call it the top end), and all three jacks are slightly recessed by about 0.5 mm along one edge of the amp.
All my portable headphones worked fine with the slightly recessed jacks, but my full size APS V3 cabled headphones needed an adapter because the 1/8" Neutrik plugs on my APS cables are too wide and would hit the lip of the case around the jacks. Nuforce has informed me that they are already planning to make changes to the case to allow a wider variety of headphone plugs to fit, and they will make it available to early buyers who have problems - but they are not sure yet if it will be possible to use the wider Neutrik 1/8" plugs used by APS, while I know the smaller Neutrik plugs from Qables.com already fit. On one side there is a USB jack for charging and the USB DAC input, a recessed gain switch that cannot not be accidentally changed, and a rotary volume knob. The volume knob is of fairly decent quality, and in low gain it is easily usable with high sensitivity IEM at very low volumes, with channel imbalance only at the very lowest volumes. The amp is totally silent in high gain with the USB music paused and volume turned all the way up.
To my ears the Nuforce does benefit noticeably from burn-in. When it was right out of the box it struck me as just a little dull and bland when compared to the iBasso D2 boa, and I feared that I would be disappointed with it in the end. I left it running for 6-7 hours and came back to it and the sound was already starting to clean up some. So I left it running via USB with music 24/7 but with a 1 hour break each day, and went back to listen for about an hour each night at 24 hour intervals. By 24-36 hours it was sounding good enough to actually recommend it to others, by 55-60 hours I was posting that it sounded a little forward but was sounding similar to my Meier Headsix which I like more than the D2 Boa. At that time I noted that it was also less edgy than the Vivid V1 but not as powerful. By 80 hours it was becoming more transparent and detailed, and sounded good with all my portable headphones including ATH-ESW10, Westone 3, Image X10, NE-7M and even the Denon C700. By that time I was finding that it is one of those amps that actually makes the C700 smoother and less harsh in the highs, while controlling the bass - one of the things I like about the Headsix and Predator when driving the Denon C700 (sometimes I think the C700 was tuned to sound best right out of the headphone jack of the 5.5G iPod video and 2G Nano). Between 180-200 hours the soundstage had finished opening up. I continued burn-in via USB through 210 hours and then switched to analog input for the remainder of burn-in. I did my once a day listening until it had 230-240 hours on it and felt it seemed to be done changing by 180-200 hours. I did not listen for the last 60-70 hours of burn-in until time to start the review after 300 hours on 12/14.
During burn-in I was able to determine that the Nuforce amp was above the iBasso D2 Boa and Vivid V1 in most areas of performance and sound (but not all areas), but still below the top tier amps like Pico, Predator and D3 Python. I have not reviewed the Practical Devices XM5 yet, but I am fairly sure it will be among the top tier amps based on the limited listening I have done during burn-in. I do not have the 2MOVE or D2 Viper to compare to in this review, but if I did I would guess it would fall below the 2MOVE or rolled-opamp Viper but above the Stock D2 Viper. So, since I had so many headphones to listen with most of my comparisons were with the D2 Boa and V1 to properly discern the ranking. Although I did also do comparisons with the top amps as well, I just did not spend as much time with them.
For the first part of my dedicated listening for the review I decided to start with my full size headphones (HD600, RS-1, D2000, Edition 9) since I had already done a fair bit of listening with my portable headphones and IEM during burn-in, and was already enjoying the amp with them. Typically the Nuforce could be turned up all the way to 100% volume with HD600 without clipping. And, it would play to decent volumes at that setting but not more than mildly or moderately loud - max volume of the Nuforce Icon Mobile was still about 2-3 db below D2 Boa, which could be turned to about 3:30 o'clock before clipping in high gain (max is 4:30). On the other hand, unlike with the HD600, the Nuforce could drive the Grado RS-1 and Denon D2000 at max volume MUCH much louder than I would ever care to listen to music. Typically I could sweep the side scrolling rotary volume knob 4 times to go from from zero volume to 100% volume. With the Nuforce in high gain with anything other than HD600 I would normally listen with the volume rotated up only 1/2 of the way to max. With the volume turned 3/4 of the way up it was quite loud with RS-1 and D2000, and full volume was uncomfortable and likely damaging. With RS-1 there was some clipping starting to creep in as I got very close to max volume at the end of the dial with the RS-1, but it was more of a soft clipping with less dynamics and some fuzzyness to the sound. The clipping was even better/softer with the D2000 at max volume, and with some material it was not even there. I could never explore the upper volume limits with my IEM without worsening my chronic tinnitus, so I didn't try. Suffice it to say the Nuforce will go loud enough with any of my IEM. So, to summarize, the Pico, D3, V1, Micro Stack and XM5 are all more powerful with HD600 than the D2 Boa which slightly edged out the Nuforce, but with any portable earphone or low impedance full size headphone the Nuforce has plenty of power to go around.
With the Nuforce the bass is fairly strong with all the low impedance phones, but with HD600 pushed to high volumes the bass was not quite as good as the D2 Boa, especially as the volumes would get closer to max output. Bass with infected mushroom and HD600 was stronger at normal volumes but not impressive like with the lower impedance phones. It was only a problem with HD600 in which I found the bass pulling back or thinning out when the amp is pushed hard (similar to the Meier Headfive desktop amp when pushed hard with Grados). So like the D2 Boa, the Nuforce was not optimal with high impedance phones, although it still drives the HD600 better than the headphone out of my Macbook. Better portable amps from my review to drive the HD600 better include the Pico and Vivid V1 or D3 Python or XM5 as the most powerful, followed by the Predator and D2 Boa, and then the Nuforce. However, with lower impedance headphones like my portable headphones and RS-1, D2000 and Edition 9, the Nuforce really came into it's element and it became more dynamic and powerful sounding. The D2000 and Edition 9 are very enjoyable with the Nuforce, and the bass is powerful enough to tickle my eardrums and damage my hearing if I wish, passing up the RS-1's bass by a noticeable margin too (unless I switch to flat pads). With test tones on the HD600 the Nuforce sounded strong to 31Hz, and was maybe 3-4db down at 25Hz but then rolled off below that. But I found that the 20-25Hz notes were stronger with the low impedance phones than with the 300 ohm HD600, and the NE-7M actually went deeper than most of my full size headphones (16Hz). The Pico, Predator, D3 Python and XM5 all had more powerful and present or pervasive bass, but you wouldn't know the Nuforce is lacking anything but for the comparison with the top tier amps. It's all relative, as listening to the Nuforce on its own merits did not make me wish for bass boost or anything like that. Bass was fairly well controlled as well, although pushing the amp to it's limits at the highest volumes the IEM, D2000 or Edition 9 the bass was just starting to get a little loose. Only with the HD600 did it start to fade at higher volume levels. The ESW10 bass was lighter and more along the lines of the RS-1 (ESW10 is kinda like a closed RS-1) and just a little more reserved with the Nuforce than with the top tier amps. This is not a bass-thin amp, it's just that some others have more bass punch. But, pair it with the Westone 3, NE-7M with Complys tips, D2000 or Edition 9 and the bass is rocking.
The Mids of the Nuforce tend to be more forward like the Meier Amps (Headsix and 2MOVE) or the Vivid V1. I have always felt that Pat Metheney "Day Trip" is recorded with a little too much energy in the mids with the electric guitar (granted that is the "star of the show"), so switching to the D2 Boa or other amps usually helps pull the guitar back a little. Still, this particular recording was listenable with the Nuforce, although it was much better if I was using the Westone 3, NE-7M, C700, D2000 or RS-1 with bowls than the HD600 or Edition 9 with it. With most music I appreciated the more forward mids of the Nuforce with the D2000, as I feel the D2000 are still slightly recessed in the mids despite the wood cups and earpad mods that I have done which also helped a bit. I haven't been using my RS-1 much lately, as I tend to prefer my stats and my modded D2000, Edition 9, or ESW10 more. The RS-1 did not sound bad with the Nuforce, but with bowl pads I sometimes (not always) felt there was a similar but less prominent upper mid coloration with Grados, like the Vivid V1 amp demonstrated earlier in the review. My other headphones did not have this issue with the mids, and I still preferred bowls with the Grados for their improvement in soundstage through the Nuforce. I would not rule out the Nuforce with Grados as it is still better than the V1 with them, and often better than the D2 Boa as well - where sometimes the D2 Boa's mids felt slightly sucked out with the RS-1 after listening to the RS-1 with the Nuforce for a while and got used to it. I still felt the top tier amps were warmer and richer in the mids than the Nuforce, D2 Boa or V1, and the D2 Boa sounds like an artificial warmth at times, with slightly boosted upper bass and lower mids. But what I liked most about the Nuforce mids was the clarity and very little coloration.
In general I felt that the forward mids of the Nuforce helped improve the audibility of the midrange detail, and music became more engaging than with the D2 Boa (similar to the Headsix and 2MOVE). This was one of the things that attracted me to the 2MOVE that I borrowed a while back. Female vocals like Shelby Lynn, Nora Jones, Elaine Elias and Jane Monheit don't have the bass bleed into the lower mids a little, like with the Boa, so they sound more open and natural most of the time (less boomy or boxy or close mic'd sounding). The D2 Boa with Westone 3 was the worst offender in that regard. Nora Jones's vocals in "Not Too Late" and on Herbie Hancock "The River" are more present and engaging with the Nuforce. With the Boa, Nora Jones and Jane Monheit's vocals do sound better than did Shelby Lynn or Diana Krall on the Boa, but I liked the Nuforce a little better with all of them. On Elaine Elias "Something for You" I got caught up in the music better, and forget that I am doing a review, so it seems little more involving as well. The Boa still acquitted itself well with Elaine Elias during the instrumental jazz parts, but lost the illusion when the vocals would come in.
I did enjoy pianos with the Nuforce, but the Nuforce maybe smoothes out the piano a little more than the other amps, making it more polite. Despite that, it still did a nice job with piano and guitar and vocals in B.B. King and Eric Clapton "Riding With the King". Nils Lofgren "Acoustic Live" was crisp and detailed and airy but not as spacious as the top tier amps listed above. And the Nuforce also seems good with unamplified acoustic guitar as well, like with Jack Johnson and Andy Mckee or Govi. In Tsuyoshi Yamamoto "Smooth Jazz Festival" during "Somewhere Over the Rainbow" the sax is more intimate and engaging with the Nuforce, but the Boa has little stronger bass response from the plucked string bass. However with the D2 Boa the sax sounds thinner in the middle and more upturned at the ends of the frequency spectrum. With Gary Karr "Super double bass" this issue on the D2 Boa also caused the bass fiddle to seem slightly more hollow or lacking than with the Nuforce, especially when listening with the D2000 but also with the HD600 and others. This recessed mids of the D2 Boa was still better than with the stock D2 Viper last time I compared them. These slightly tipped up ends of the frequency spectrum or the recessed mids (however you look at it) make the D2 Boa a little better for low volume listening with the HD600, but very quiet listening was among the few instances where I would grab the D2 Boa over the Nuforce. On the other hand, the Nuforce with D2000 was still better for low volume listening than D2 Boa with HD600.
Treble on the Nuforce is smooth but slightly recessed with a variety of headphones. With my D2000, Westone 3 and ESW10 the Nuforce does not accentuate sibilance that I usually hear in my Diana Krall "Girl in the Other Room" CD, which is my test CD for sibilance since it seems to be mastered with that in there. Switching to the Grado RS-1 I found there was less sibilance through the Nuforce than with my D2 Boa. The slightly laid back treble made the Nuforce amp more forgiving of some music. With the D2000 I actually listened to the entire Diana Krall CD with the Nuforce as I typed my review, without thinking about the sibilance. With Tord Gustavsen Trio's song Karmosin off the "Being There" CD, this is a good test of cymbals as they are lightly and hauntingly tapped during the intro drums and piano, and I did not feel there was a lack of treble as the ring of the cymbals would hang in the air properly with a nice slow decay.
I have rarely bothered to test high frequency extension, but decided to start doing that and tested all of the amps tonight, along with the Nuforce using Michael Knowles "Bink Audio Test CD". With treble test tones on the Nuforce I used the D2000 which for me have better treble extension than my HD600 or most IEM. There I found a problem - with the Nuforce while at 16Khz I was getting a strange harmonic at exactly 4Khz that was louder than the actual 16Khz tone. I've had this problem with another USB DAC amp before, but I cannot recall which one now (might have been the Lyrix or D1). This 4Khz artifact did not happen with the D2 Boa via USB which was still going strong at 16Khz, or with the Nuforce via analog input. With music I was unable to hear any artifacts like with the test tone. For me, 16Khz is the practical limit of my hearing as I can't hear the 20Khz tone unless I crank an amp like the D2 to 3:30 o'clock or 80-90% of max. While I could hear 20Khz with the D2 Boa at full volume, cranking the Nuforce volume at 20Khz was inaudible. Via analog input on the Nuforce the 20Khz test tone was still inaudible to me, although it was still barely audible if I plugged the headphones directly into the Macbook. The only other amps that would allow me hear the 20Khz test tone at high volume was the Pico and Predator, although I could hear it louder with the Pico. I found that in doing this test that the V1, XM5 and D3 were all quite noisy in the background at high volumes past 3 o'clock with the 20Khz test tone, so I could not hear the tone over the noise. The Nuforce had just a tiny bit of noise at max volume hooked up via USB, and the Pico and Predator were silent. The D2 Boa background noise was silent and allowed me to hear the 20Khz tone. After I accidentally hit my ears full volume with a 440Hz piano note, I could not do further testing of the highs until my ears recovered.
The Nuforce combines a forward soundstage with decent air and ambience, although like the 2MOVE it puts the listener in a more intimate position while making the venue seem a little smaller. With the D2 Boa and Arvo Part "Tabula Rasa" the image is a little more spread out and deeper but less precise than with the Nuforce. With Gary Karr "Super Double-bass" the imaging was similarly a little more focused and the bass fiddle more centered with Nuforce (almost like a slight hint of crossfeed), while with the same music on the D2 Boa the bass fiddle sounded a little more spread out and hard to pinpoint. Soundstage is obviously better with the HD600 and D2000 than Westone 3 or ESW10 and RS-1. But even with those headphones, when comparing the Nuforce soundstage to the Pico or D3 and Predator the Nuforce soundstage seems flatter and more 2D, with a wide but not as deep soundstage. Air and ambience with the Nuforce was about the same as my D2 Boa, but with the Boa placing the listener a little farther from the stage than Nuforce or Vivid Audio V1. Switching from the Nuforce to the Pico and D3 (or even Predator) it was clear that the top tier amps are more open and spacious, with more micro-detail and are even more rich sounding and engaging. The difference in sound between the Nuforce and the top three on hand (Predator, Pico and D3) is bigger than it is between Nuforce and D2 Boa or V1, confirming that the D2 Boa and Vivid V1 are it's main competitors in sound and price range. The Predator is in between the forwardness of the Nuforce/V1 and Pico/D3, but still maintains a better soundstage, warmth and richness. The degree of detail of the Nuforce DAC seems to be on par with the DAC in the 2MOVE and Predator, but below that of the Pico and iBasso D2/D3 amps. I have not reviewed the XM5 that is burning-in right now, so I really cannot comment on soundstage or micro-detail yet.
The last area I looked at was the RFI interference problems that have cropped up the past 2 months since I got an iPhone 3G. I found the D3 to be the most susceptible to iPhone BUZZ from 3-4 feet away, followed by the D2 Viper and the D2 Boa from 1-2 feet away, then the Predator/Pico/Nuforce which could be within 6-9" of the iPhone. With an EM blocking card from Quick Bridge Solutions - EM Shield for iPhone I can stack any of the amps under the iPhone except for the D3 Python which still needs to be 6-9" away. The only big problem I have run into is that "static discharge" makes the amp go nuts - so don't shuffle across the carpet and then touch the amp or headphones or laptop or all kinds of nasty noises will emanate from the headphones till you unplug the headphones to switch the amp off.
ADDENDUM: While the Nuforce via USB is slightly brighter and slightly more forward than the 3MOVE with slightly less bass, with analog input it does sound a little brighter and a little more forward and aggressive than with USB input. Keep that in mind when pairing with bright headphones. For example, I can use the Nuforce via USB just fine with Phonak Audeo IEM with black filters, but via analog input and grey filters it can be too bright.
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