I just received a pre-production Nuforce uDAC USB desktop DAC amp this weekend and have been really impressed with this tiny device. The main target audience are the same people who would buy a Pico DAC-only to feed a nice desktop amp from their PC or laptop, but who can only afford to pay at a hotaudio price. I have to warn you that some of this will sound like a sales pitch, because I really like the product.





Features:

Discrete USB audio receiver and D/A converter.
Coaxial S/PDIF output (turn off volume control to activate).
Double jitter-reduction mechanism at data level and at oversampling filter stage (They use a PCM2706 as USB receiver and take the I2S data and feed that into a high-end DAC with DSP jitter reduction algorithms - the markings on the DACs are wiped out and the model will hopefully be announced later.)
High voltage 2V analog RCA output (supplied by the DAC chip output).
High-quality analog volume control.
No capacitors in any of the audio signal paths.
No opamps used in the DAC or headphone amplifier.
Low power consumption; USB self-powered, no external power supply required.

Specifications:

Input :

USB Bus Powered.
USB 1.1, 2.0 compatible.
USB DAC native bit rate: 16-bit at 32 - 48kHz

Output:

Analog RCA Output = 2Vrms
Dynamic Range: 110dB
THD+N= -95 dB
S/N Ratio: 98dB

Digital Output: coaxial RCA 75-ohm

Headphone output jack
Power output: 80mW x 2 @ 16-Ohm
THD+N 0.05%
SNR > 98dB

Dimensions: 68x38x21mm

I started off listening to the uDAC right out of the box with my Nuforce NE-7M and really enjoyed it, and then tried my $199 Head-direct RE252 which are a bass-neutral but very rich and detailed earphone, and they sounded even better (and not bass-lite). Then I switched to my flagship custom molded IEMs (JH13Pro, UE11Pro, ES3X).

When I listen to my Ultimate Ears 11Pro custom IEM, most of the time if used with the wrong amplifier I find them to have a little too much bass with slightly recessed mids. But the UE 11pro sound much better with the uDAC than almost all of my portable DAC/amps. The uDAC controls the 11Pro bass very well, yet it is not a bass-lite headphone amp in any way at all. It also helps bring out the midrange clarity and detail very well. The Nuforce uDAC's detail and definition are well above that of the Nuforce Icon Mobile. Although I find the Icon Mobile to be a decent budget DAC/amp, in comparison to the uDAC the Icon Mobile sounds veiled and muffled with my UE 11Pro. The bass is deep and tight, and the mids are rich and vivid, and highs sparkle without a hint of extra sibilance above what is already in the recording (Diana Krall used as sibilance test music).

I compared the uDAC to a $219 iBasso D4 with 200 hours of burn-in. The D4 DAC via USB is slightly better than the D10 DAC via USB, so I stuck with it for this comparison. The D4 can run entirely off 5v USB with no battery needed like the uDAC, and uses a PCM2706 USB receiver and sends I2S to dual Wolfson WM8740 DACs. The D4 adds analog input and 9v battery for use with iPod, while the uDAC is designed to connect your computer to an AMP, home theater via Coax, or headphones. I found that both DAC's performance and micro-detail are similar, but the UE 11Pro midrange sounds a good bit clearer and resolving with the uDAC, while sounding recessed with the D4. Before burn-in I think the D4 paired better with the UE 11Pro than it does at 200 hours. Basically, the UE 11Pro is very difficult to pair with an amp, and usually for a small DAC/amp I need to use my $250 3MOVE or $275 iBasso D10 + $60 in opamps. And the UE 11Pro are best with my maxed Woo WA6 desktop amp or Square Wave XL fed by an Apogee mini-DAC, at which point the sound can be stunning at times. But now I am excited to say that the uDAC is one of the best non full-size amps that I have tried with the UE 11Pro. When I am not listening to the UE 11Pro with the Woo amp, the uDAC will be the first compact DAC/amps I would reach for when using them. Likewise, any IEM in my large collection sounded good out of the uDAC, including my JH Audio 13Pro, Westone ES3X custom IEM, Westone 3 and Livewires.

There is only a very faint background hiss with UE 11Pro custom IEM which is no bother at all, and it seems almost totally silent with JH Audio 13Pro custom IEM, Head-direct RE252 or Nuforce NE-7M earphones. Unfortunately it has more audible background hiss with Westone ES3X, W3 or Livewires when the volume is turned down, which makes using a Westone volume attenuator necessary to to cut the hiss. With the volume attenuator there is minimal impact in the sound quality with the attenuator knob only rolled about 3-4 mm below full volume, and then the ES3X sound very nice with the uDAC as well. This is the same issue I have with the $995 ALO Amphora amp, which has big hiss with Westone IEM but very little with most of the other IEM. Most of the time I would be using my JH 13Pro and UE 11Pro with the uDAC, so hiss is not an issue for me to worry about.

EDIT 12/1/09 - I received a final production uDAC today and compared it to the pre-production unit that I originally reported on. I am very happy to report that there is NO HISS with my very sensitive Westone IEM, and it sounds even better with a blacker background with the ES3X!

In comparison, the Nuforce Icon desktop is silent in the background with the Westone ES3X, so I tried feeding the Nuforce uDAC into that amp via the RCA outputs. Used as a DAC-only I found that the Icon's sound is noticeably better when using the uDAC as the source instead of the built-in DAC of the Icon. I usually feed the $350 Pico DAC-only into the Nuforce desktop and use that to drive a Stax transformer and electrostatic headphones like HE60 and Stax O2 or Jades, so I don't often use the built-in headphone amp and I was pleased with what I heard. The uDAC, like the Pico DAC-only, takes the Icon to another level.

I've always said the Icon had a decent DAC, and decent headphone amp, with a great sounding speaker amp being the main draw. Electrostatic headphones plugged into a Stax SRD-7 Pro transformer and driven by the Nuforce can sound close to as good as they do from a $500-800 Stax amp, and my HE60 sound better with this rig than the stock HEV70 amp or a Stax SRM-1 Mk2 Pro. The uDAC is a logical upgrade to add to the Icon desktop amp, to get more out of the headphone and speaker amp without doubling the cost of the unit as a whole (like when using a more expensive DAC to upgrade). The uDAC also worked very well feeding my Qinpu A-3 8-watt amp, for driving my HD600 and a Stax SRD-7 Pro transformer box.

I compared the uDAC to the Pico DAC which is one of my favorites, both feeding the Icon or A-3 and switching back and forth, and after volume matching the uDAC was very close in detail and space. There were only small changes in the sound when switching between the two USB DACs, such as a little more open treble with the Pico DAC, or slightly more forward sounding with the uDAC, etc. The mid-fi level of the Icon and A-3 headphone amp may make it harder to hear bigger differences between DACs, so the next step is that I need to use both of these DACs to feed my WA6 with JH13Pro or Eddie Current ZDT amp with the Sennheiser HD800. Then I can switch back and forth between the two DACs for a more detailed comparison (to follow soon).

Not only did I compare the uDAC to the Icon's built-in DAC, but I also compared the uDAC's headphone out to the Icon headphone out, using the uDAC as the source for each; and I believe that I slightly prefer the uDAC headphone out, even though the Icon's headphone amp is a little more powerful for HD600. I also like that I can use the uDAC volume control to adjust the RCA output levels. It makes it much easier to volume match it to other DACs when comparing them, or to lower an amp's output level so the amp could work better with IEM. The iBasso D4's line out is noticeably lower in volume than the Pico DAC-only which has a louder output, and the uDAC can be level matched to either one. I preferred the uDAC's line out to the D4 in that it seemed a little more refined and dynamic sounding, and I'll be the first to say I was happy with the D4 line out prior to this.

The $99 price a no brainer here. It's amazing how things get better and cheaper over time. I am often telling people to buy the $120 SuperPro DAC707 as a budget standalone DAC, but now I can honestly recommend the uDAC over that if they don't need optical inputs. The uDAC USB performance exceeds the USB performance of the SuperPro, although the SuperPro is very nice with optical digital input and can almost match the D10 or Headroom Micro DAC when using a sigma 11 PSU to power the SuperPro. I really think the uDAC via USB is on the level (or very close) with these other DACs when they are using optical out of the Macbook (with 16/44 files).

The dual Wolfson DAC ibasso D4 that I compared to may be $219 and more expensive, but it also includes a battery bay and analog input for portable iPods, while offering USB only power for DAC/amp when you don't want to use up the battery. And the D4 has both a line out and headphone out like the uDAC, although no S/PDIF out. With a 9v battery the D4 can drive a 300 ohm HD600 better than many other portable amps, and just below the 3MOVE and Vivid V1. Yet with only the 5v setting the D4 is only as powerful as the D10 or Predator which is not quite enough, even though they can play louder than the Nuforce Icon Mobile with HD600. When I tried the HD600 with the uDAC I found it could play louder than I would normally listen, with good headroom for music. With HD600 it is not as powerful listening to Infected Mushroom as the 3MOVE or Vivid V1, but it was loud enough that I would quickly become fatigued at those levels if I listened for more than a few minutes - so it doesn't run out of juice too early like other small amps. I would normally listen to the uDAC and HD600 at 2 o'clock, but I can turn it to max at 5 o'clock without clipping, reaching volumes close to the D4 running in 9v mode with a full battery. Some people considering the uDAC might pass it up if it were at a higher price like $149 or $199, to get something like the D4 when the prices get too close, but that would be a mistake to judge the uDAC based on it's low price.

I think the main difference between the sound of the uDAC and the D4 is that the uDAC is a little warmer and forward sounding, and the D4 is a little more neutral and less forward sounding with a little more treble presence. In Diana Krall "Live in Paris" the song "Under my Skin", with the RE252 earphones there is a cymbal in the drum kit that is difficult to hear with the uDAC but is clear on the D4. But this is mainly only an issue with the RE252. After switching quickly from the RE252 to the UE 11Pro IEM, the cymbals became very clear with the uDAC and it sounds so much better. And then quickly switching the UE 11Pro from the uDAC to the D4 makes the sound seem like it's coming out of a cave in comparison. The psychoacoustics are interesting in how the brain adjusts to a particular sound signature, so that a quick swap of earphones or amp can make the differences sound more dramatic.

Normally I would have finished my listening via my WA6 and ZDT (or Amphora) before posting my impressions, but I was excited by the uDAC and how good it sounds for the price. They should be in stock and shipping this week, and I can't think of a better way to spend the $99 than to grab one before they realize their mistake and raise the price.

PS: 1/14/10 UPDATE: For those who haven't read the whole thread, the uDAC does sound good as the DAC source for my WA6, ZDT, Amphora, and EF5 amps as well. It scales up nicely with better amps via the RCA out.

Plus, I tried my new Triple.fi 10 Pro with the uDAC headphone out and it sounds really good, almost as good as my W3, and sounding better than I recall them sounding last time I owned them 2 years ago. The mids are slightly more forward with uDAC/Triple.fi than I'd like, but I could live with it. I'm not having any issues with sibilance with my sibilance test music from Diana Krall Live or Eva Cassidy Live. Bass is strong down to 16Hz, and test tones sound fairly flat out to 16,000 Hz except a slight bump that I hear at 6 Khz. The UE11Pro are still a bit better on the uDAC in most areas (duh!), especially soundstage which is not too forward on the 11Pro. But, with very low resolution Green Day (Shenanigans) 128K MP3 the Triple.fi were actually a little better combined with the high resolution uDAC than the 11Pro or W3 (which revealed the MP3 flaws more readily and sounding a little thinner in the mids and brighter, sharper and edgier).

Thanks HPA - yet again, I cant believe how small this unit is. I thought the Topaz was compact - the size of the Nuforce DAC blows me away. Awesome stuff.

btw, any inside word on this bad boy ? Slightly OT, but you seem to like the Nuforce gear you've reviewed to date:

Nuforce.com | Icon HDP

I noted your reference to the DAC in the other thread on the HDP, but that was over 10 days ago so I felt like now might be a good time to pump you for info

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All I can say is that I will be reviewing it. I am looking forward to it, but I don't have one yet.

Because of the 24/96 USB DAC they didn't need to do optical for computers that have optical out like Macs for listening to native 24/96 hi-res downloads or DVD audio, but it still has coax input for CD and DVD players or for the Wadia iTransport. Optical would have been nice for using with the Apple airport express, but you can't have everything. It does have an analog input to feed it my iMod and portable Vcap dock for when I don't want to tie up the computer with music. So, it has everything I need for my computer desk's DAC except balanced outputs, but I have plenty of desktop sized single ended amps to feed it into (WA6, Amphora, EF2, EF5).

Very good review Larry.

I came to this thread to read your review and ask a question about the uDac compared to the Super DAC Pro 707, because we had a conversation about that DAC at RMAF. But you already covered it in the review. So I don't need to ask. Sometimes you are strangely good at anticipating questions and covering them ahead of time.

Thanks for another wonderful review, Larry. I'd say "keep it up" but it seems you enjoy this hobby too much not to. I greatly appreciate that while you continue to make very expensive purchases and reviewing them, you still give about equal attention to budget products that appeal more to the mainstream head-fier. I can't say, with brevity, how much you have influence my spending plan. I just landed a job, btw. YEA! Time to spend!

"I preferred the uDAC's line out to the D4 in that it seemed a little more refined and dynamic sounding, and I'll be the first to say I was happy with the D4 line out prior to this."

Does this mean you prefer the uDAC's DAC component to the D4's DAC?

We first found out about Larry after we saw his posting on head-fi.org for NE-7M and were very impressed with his knowledge. Larry is very thorough and fair with his review so we have since started sending him new products from pilot production.

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We have debated about the uDAC pricing internally. Yes, we do realize that we priced it too low considering the performance. But we already have many other products in this family (Comparison Guide and there has to be some relation between the products pricing. Icon Amp + uDAC should be slightly higher than Icon.

uDAC didn't started out with this level of performance in mind. But as we developed other high-end products, we figure out circuits and parts that could be used for uDAC and before we know it, uDAC got better than we have hoped for.

Most importantly, we want uDAC to be used by many people, especially those with cheap $300 netbook.

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Thanks Jason - I think I speak for many here when I say that we do appreciate VFM products in a sphere often dominated by the 'it costs more, therefore it has to be better' hype. Most of us realise that we get what we pay for, and that there is no such thing as a genuinely free lunch, but its refreshing to see a DAC so competitively priced. No-one expects Berkeley parts in a product at that price, but HPAs review would seem to indicate that you have produced something that is better than the sum of its parts. I look forward to the 'killer amp' being rolled out very soon

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It's very close - both are similar in performance to the Pico DAC-only, with small differences in presentation between the three. If I had to rank them I would say the uDAC as a "DAC line-out feeding a bigger amp" is a little better than the D4 as a DAC line-out feeding a bigger amp - which is what I said in the quote above.

The D4 is still an excellent DAC, and my preference is more about the way the music affects me when I listen through this gear - the D4 is technically very proficient and detailed and spacious, but the uDAC was a little more musical and engaging at times. The uDAC gave me more of the feeling that I was listening to one of my bigger rigs.

It gets harder when I try to decide whether I prefer the Pico DAC-only or the uDAC as a line-out DAC (not considering the headphone out). It seems the uDAC is better suited to pairing with my ALO Amphora than the Pico is, but the Pico DAC is more suited to my Head-direct EF5. Both were equally suited to pairing with the HiFiMan EF2, Qinpu A-3, Nuforce Icon (desktop model), and WA6.

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$300 netbooks are the wave of the future! I keep meaning to get one and install OSX 10.6 on it with about 100GB of music.

When I bought the NE-7M, I got them only because of the 20% off pre-order, which I heard about because I had bought an Icon previously (that I still use to drive Stax electrostatic headphones via a speaker output transformer). I bought the Icon after I read the impressive 6moons review, and I was excited about the Icon and posted my thoughts in a couple of threads as well. I didn't really expect much from the NE-7M, so they were a pleasant surprise, and anytime I am excited about a product I like to write about it and share it. To me, there is just as much beauty to be found in the "best bang for the buck" as there is in the "best you can buy" category. That's why I can enjoy a burger as much as I can a steak.

I had been considering getting a set of NE-8M from NuForce for use with my iPhone 3Gs, but after seeing this review, ended up purchasing a black uDAC as well.

You guys aren't kidding about being sorry about your wallet if you spend too much time on these forums =(

Wow, comparable to the Pico? At a 3rd of the price? Nice! For a proud member of the Budget-Fi world, this is heaven sent. I have been scouring these forums and ebay for a usb dac for under $100 that would give me SQ well above its price range. I think the perfect unit has finally been made. And it looks great, to boot. Can't wait for some Christmas cash to get one. And thanks to Headphoneaddict for yet another stellar breakdown.

'sorry about your wallet' is ironic when you stumble on something like this DAC : its more applicable to DACs like these:

Isabellina DAC, 1500 USD
Products > Isabellina - Red Wine Audio

MBL 1611-F DAC, 24,750 USD
mbl 1611 F - MBL of America

Whatever advantages each of these has over the uDAC technically, I think its fair to say that your wallet could be a whole lot sorrier

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Well, like jasonl said, "uDAC didn't start out with this level of performance in mind. But as we developed other high-end products, we figure out circuits and parts that could be used for uDAC and before we know it, uDAC got better than we have hoped for."

It sounds like they ended up wish a large amount of high-end inventory and DACs at a bulk unit price, and spread the wealth around to the little guys.

So now all we need is a NuforceIconMobile+ to integrate the better uDAC circuitry with a battery and line in.