Header

Objective Reviews & Commentary - An Engineer's Perspective

October 16, 2011

UCA202 DAC Take 2

behringer uca202 testINTRO: The Behringer UCA202 was the first USB DAC I reviewed on this blog back in February. It sells for around $30 and has been around for many years. I’ve revised several of my tests and I was curious to see how it compares, apples-to-apples, with more modern inexpensive USB DACs like the Turtle Beach Micro II. I only tested the line outputs in this review as the original review established the headphone output has some serious problems—most notably a very high output impedance.

BEHRINGER UCA202: The UCA202 is larger than most newer inexpensive USB DACs (many of which are about the size of a USB thumb drive). The UCA202 is about the size of a deck of cards and has a fairly long (1 meter) attached USB cable. Like the Micro II it has an optical digital TOSLINK output. Unlike most newer inexpensive USB DACs, it also has a volume control but it only affects the headphone output. It has RCA line outputs and inputs.

uca202 modesWINDOWS INSTALLATION: The UCA202 installed smoothly in both XP and Windows 7 without needing any drivers. Windows reported it as a “USB Audio CODEC”. Three sample rates are available 32, 44 and 48 Khz all at 16 bits as shown to the right in Windows 7.

SUBJECTIVE SOUND QUALITY: Running the UCA202’s line outputs into my 02 headphone amp the sound quality was good with no obvious problems. There was some hiss audible at high gain settings on the amp but at realistic volume/gain settings it was reasonably quiet. Someday I plan to do an ABX blind comparison between the UCA202 and other DACs using the O2 amp.

MEASUREMENT SUMMARY: The overall results are substantially better than the Micro II and mostly quite good for a $29 DAC. The UCA202’s weak areas are noise and low level linearity (and the poor headphone output). To save space and leave room for more columns in future reviews, I’ve replaced my previous “Excellent”, “Very Good”, etc. ratings with a letter grade from A to F where A is excellent and F is Fail (unacceptable).

Measurement UCA202 TB Micro II FiiO E7
Freq. Resp. 10K +/- 0.1 dB A +/- 1.0 dB B +/- 0.5 dB A
Freq. Resp. 33 ohms N/A +/- 1.8 dB C +/- 0.5 dB A
HP Output Imp 47 Ohms D 0.95 ohms A 0.13 ohms A
Max Output 10K 1.12 Vrms B 1.34 Vrms B 1.87 Vrms B
Max Output 33 Ohms N/A 1.26 V 52 mW B 1.4 V 59 mW B
THD+N 0 dBFS 10K 0.008% A 0.14% C 0.05% B
THD+N 100hz 10K 0.007% A 0.025% B 0.007% A
THD+N 1Khz 10K 0.007% A 0.02% B 0.007% A
THD+N 1Khz 33ohms N/A 0.12% D 0.015% B
THD+N 10Khz 10K 0.009% A 0.11% C 0.007% A
IMD CCIF 10K 0.005% A 0.028% D 0.027% C
IMD SMPTE 10K 0.002% A 0.02% B 0.008% B
Noise A-Wtd -88.8 dBu C -93.8 dBu C -98.7 dBu B
-90 dBFS Linearity 3.8 dB C 0.8 dB A 0.0 dB A
USB Jitter Jtest Very Good B Poor D Very Good B

FIRST CLASS:

  • Low distortion even at high frequencies.
  • Flat frequency response
  • Relatively low jitter
  • RCA Line Outputs
  • RCA Line Inputs can be used for recording

ECONOMY:

  • Poor headphone output
  • Just over 1 volt RMS maximum output (typical of USB powered DACs)
  • Higher than average noise
  • Marginal low level linearity
  • Flimsy plastic construction

BOTTOM LINE: So far the UCA202 is still the best low cost USB DAC I’ve tested if you don’t use it to drive headphones. I’ll be testing other low cost DACs in the coming weeks to see how they compare. The UCA202 isn’t as small as some newer USB DACs but it’s still relatively portable.

 


TECH SECTION


TECH INFO: The UCA202 uses the ubiquitous TI PCM2902 integrated USB DAC chip. It’s an old design, but as you’ll see, it easily outperforms the much newer C-Media chip in the similarly priced Turtle Beach Micro II when using the line output. In this case, newer isn't better.

LINE OUT ONLY: I only tested the line outputs as the previous UCA202 review established the 47 ohm headphone output impedance renders it a poor choice for most headphones. Unlike other headphone DACs I’ve tested, you won’t see headphone loads being used in the tests below. All tests were run with a 10K load unless otherwise specified. Please see the original UCA202 review for tests of the headphone output.

FREQUENCY RESPONSE: The frequency response with a 10K load (such as a headphone amp) via the line outputs was substantially better than the TB Micro II. It’s within 0.4 dB from 10 hz to 20 Khz. There are no significant issues here:

UCA202 Frequency Response 10K (blue) vs Micro II (yellow) -3 dBFS -3 dBu 16-44

 

THD+N vs OUTPUT: This test starts at 10 mV where noise dominates the measurement. Despite having higher noise than the Micro II, the UCA202 distortion drops much quicker implying it has much less quantization distortion at low levels. Because the UCA202 is likely to be used at line levels with an external amp the distortion will be around 0.01% or even less at typical levels. It has slightly less maximum output (about 1.1 Vrms) compared to the Micro II but much lower overall distortion. The Redbook standard for digital home gear is 2 V rms. But USB powered DACs usually produce around 1 – 1.5 Vrms:

UCA202 1 Khz THD N vs Output 10K (blue) Micro II (yellow) 16-44

 

THD+N 100 hz 0 dBFS: With the PC volume at maximum, and a 0 dBFS input, the UCA202 produces about 1.1 Vrms at very low distortion. This is excellent performance with all harmonics below the magic –80 dB threshold. Way out of band you can see a spike at the 44 Khz sampling frequency which is fairly normal—especially in low cost DACs. The odd bump in the noise floor above 20 Khz is related to intentional noise shaping in the PCM2902 DAC. It’s an intentional design technique to lower noise within the audio band:

UCA202 Max Output THD N 100 hz 100K THD BW=22 Khz

 

THD+N vs FREQUENCY: Here’s the THD+Noise plotted from 20 hz to 20 Khz into 10K (blue) at 775 mV (0 dBu). The Micro II is shown, for comparison, in yellow. The input is –3 dBFS to prevent any digital overload of the DAC. The UCA202 does much better here staying below the ideal 0.01% threshold until about 11 Khz. This is very good performance for a wideband test:

UCA202 THD vs Freq 10K (blue) Micro II (yellow) ~0 dBu 16-44

 

SMPTE IMD: This an excellent result with essentially no IMD products and everything well below –80 dB. In comparison, the Micro II had 170 times more distortion on this test:UCA202 SMPTE IMD -3 dBFS ~0 dBu 10K 16-44

 

CCIF IMD 44 Khz: The UCA202 does extremely well here for an inexpensive DAC with more than 50 times less distortion than the Micro II at the same level into the same 10K load. More important, all distortion products in the audio band are well below –80 dB. The two spikes around 25 Khz are a little alarming but only your dog might hear them. See the Micro II review CCIF section for both it’s very poor performance on this test and the DAC1’s reference plot. This is excellent for any reasonably priced DAC running at 16/44:

UCA202 CCIF IMD -7 dBFS ~0 dBu 10K Ohms 16-44

 

CCIF IMD 48 Khz: The UCA202 also does well, although slightly worse, at 48 Khz:

UCA202 CCIF IMD -7 dBFS ~0 dBu 10K Ohms 16-48

 

NOISE & LINEARITY: The UCA202 is only average for noise and worse than average for linearity. A –90 dBFS signal is reproduced at –93.8 dB for an error of 3.8 dB. There’s less than 1 dB of error at –80 dBFS so the problem is limited to extremely low levels. Noise referenced to my old 400 mV dBr reference would be 83.1 dB and against full output it’s 91.8 dB both A-Weighted. The good news is the noise will be upstream of the volume control if an external amp like the O2 is used and the PC volume is set to maximum. That means you’ll get around 90 dB of real world S/N ratio which is sufficiently quiet. But if you plan to use the PC’s volume control, the noise and/or linearity might be an issue in some circumstances. The spikes at 2, 3, 4 and 5 Khz are likely quantization distortion of the 1 khz low level signal and are relatively typical. I don’t know what’s responsible for the spike at 30 hz but it’s very inaudible.

UCA202 -90 dB noise linearity ref 0 dBu

 

JITTER: Here’s the spectrum from the dScope’s J-Test for jitter. The two things to look for are the number and level of symmetrical sidebands and the “spread” at the base of the 11025 hz signal. Compare the result below to the Micro II’s Jitter to see how much better the UCA202 does. This is a very respectable result for an inexpensive USB DAC and the frequency accuracy (clock accuracy) is very good as shown by the frequency reading on the left:

UCA202 Jitter 11025 hz J-Test 10K ref ~0 dBu 16-44

 

TECH COMMENTS: Used to drive an amp, powered speakers, or other source with a line input, the TI PCM2902 based UCA202 blows away the Turtle Beach Micro II based on the C-Media CM102. The only weak areas are the noise and linearity below –80 dBFS. But neither of those is likely to be an issue if you leave the PC volume all the way up and use the volume control on the amp/speakers.

50 comments:

  1. Good work NwAvGuy!

    I think you could use a formatting improvement in the Measurements Summary section, aligning the Grade letters with each other.

    That is, in place of (using dots)

    0.006% A
    47 O B

    Add another column to the table so it looks like:

    0.006%..A
    47 O.......B

    ReplyDelete
  2. I like this article. I recently read your original two articles about this little guy.

    One question that's been on my mind is this. Do DACs all render the stereo signal properly or are there sometimes separation issues with the channels?

    ReplyDelete
  3. i have mine running from a:
    pcmcia usb3->isolator->usbhub(li-on battpowered)->uca202

    sounds great. spdif also is suprizingly good

    ReplyDelete
  4. Thanks for the comments. In terms of stereo signals there was an ancient time where, for cost reasons, a single DAC was shared (multiplexed) between the stereo channels which created some problems. But those days, AFAIK, are long gone. So you're left with analog stereo crosstalk after the DAC and possibly channel imbalance as being the main "stereo" issues.

    While it's sort of interesting to compare crosstalk numbers from a theoretical point of view, the reality is any headphone with a normal 3 wire plug is very likely to be the dominant source of crosstalk due to the shared "ground". The crosstalk of everything upstream will nearly always be a non-issue. The exception to this rule are 3 Channel Amplifiers or those with virtual grounds.

    ReplyDelete
  5. Not that you'll hear any crosstalk anyway (-30dB is usually the accepted threshold here) and modern DACs do far far below that so, yeah, stereo crosstalk is a non-issue these days. Anyway, good article. One question: Why would such a DAC, which will no doubt by used by consumers, particularly as it's low cost, with low impedance headphones, have such a high output impedance? It makes no sense. Another example is the smartphone Samsung Galaxy S2 which is even worse at a reported 49 ohm output impedance, which is a complete joke considering what people use smartphones for (and particularly vs. the iPhone 4, it's main competition, which is very impressive at 0.9 ohm output impedance). Why would large reputable companies like Behringer and Samsung have such glaring design flaws in the headphone out......

    ReplyDelete
  6. @Karl, the output impedance issue is complex. Please see my Output Impedance article for more.

    The short answer is a lot of "pro" headphones are typically at least 80 ohms and the makers of pro gear, like the UCA202, are misguided in trying to "balance" the requirements of high impedance voltage hungry headphones with sensitive low impedance headphones. It also saves money. Using a 47+ ohm resistor in the output helps a dirt cheap op amp drive low impedance headphones with less distress.

    There's a historical precedent for higher output impedance for headphone sources but it predates the iPod era. A lot of manufactures haven't really caught on yet. They're still doing old school pre-iPod headphone outputs. It's stupid.

    Samsung seems to get 90+% right only to fail horribly with the last 10%. That's the case with the headphone output on some of their products. At least Apple has found their way and generally lowered the output impedance of their newer products. And the Sansa Clip+ has a near zero ohm output impedance.

    What's required here is for people to vote with their credit cards and not buy products with inferior headphone outputs. If that happens, Samsung and the rest will fix their mistakes quickly.

    ReplyDelete
  7. Good job on this one!
    I was close to be driven insane by all of the conflicting and backwards "reviews" on Head-fi (abet not written with bad intentions). Your blog is very straightforward.

    btw, i picked up a E7 because of your review, mostly to run through usb or from my fuze. Good luck with future reviews!

    ReplyDelete
  8. I have mine for a few months now, and I love it!
    I have absolutely no problems whatsoever, and it sounds great (speakers are Edifier R1600T Plus).

    If only it had low output impedance, it'd definitely be THE best bang for the buck in audio equipment.

    ReplyDelete
  9. Probably there is more potential in this little gadget. I see a JRC4558 on the bottom side (IC6). It requires +-4V at least. And i dont see any decent DC-DC booster there. Maybe IC2 on the top or IC3 on the bottom could be some flying capacitor DCDC, but it would limit the output current to some 20-50mA. Also the circuits lacks a decent anti-aliasing filter (to remove the bump). Anyway, it is good to see, what a ceap circuit is capable of.

    ReplyDelete
  10. Even though theoretically the performance is worse than if the supersonic noise hump weren't there, somehow the noise shaping inspires some confidence. This is maybe an example of a tradeoff made to improve performance rather than a tradeoff made to reduce performance while satisfying an audiophile marketing myth? (go figure, it's a pro audio company)

    It might take a lot more unique page views before the bulk of the purchasing public decides not to support high output impedance headphone outputs. You're getting there. ;)

    To be honest, I think a small portable amp like a FiiO E5 or E6 may be a good companion to many smartphones used with headphones, particularly the slate types. There are only three physical buttons on mine: the power switch and volume up/down. I remapped volume up and down to be Next Track and Play/Pause (granted, that required root access on Android), and I run the output to a Fiio E5 for volume adjustment and presumably a little higher-quality amplification.

    ReplyDelete
  11. @tszaboo, the op amps in the UCA202 operate on filtered USB power (4.5 - 5.0 VDC) and are capacitor coupled. Not surprisingly, there's no DC-DC converter at this price. The op amps still manage over 1.1 Vrms (3.1 Vp-p) with low distortion. The coupling capacitors cause problems for the headphone output, but much less so for the line output with a much higher (10K) load impedance.

    As for anti-aliasing, see the comment after yours. The "bump" is intentional noise shaping and a good thing. The filtering with the PCM2xxx chips is vastly better compared to the C-Media CM1xx chips as can be found in the Turtle Beach Micro II. Just look at the CCIF IMD. The UCA202 blows the Micro II away.

    ReplyDelete
  12. I prefer the previous rating system. It was easier to read. Plus the colour for the lower rating like poor (E) and fair (D) made it even better.

    Excellent = A
    Very Good = B
    Good = C
    Fair = D
    Poor = E
    Fail = F

    ReplyDelete
  13. @Kingpage & Anon, The blog width is fixed globally across all articles and has to be kept reasonable to allow compatibility with netbooks, chromebooks, tablets, etc. The idea behind the letter grades is to allow more columns in one table so more than 3 DACs can be compared. I have a total of 5 DACs and they won't fit in the table if I use the old system or add extra columns for the letter grades.

    ReplyDelete
  14. Thank you for the reviews!

    I think the way you are summarizing your results now is great - If they're aligned, colored, spelled out or represented by grades doesn't make much of a difference in my opinion.

    The hard part is gathering the data - typing it into excel and formatting it is something anyone of us can do on their own, so I think it would be a pity if you wasted any time on that rather than on doing more reviews/articles.

    ReplyDelete
  15. hi, i got the uca222 and it sounds horrible with my shure940 (40ohm). i was thinking buying a different headphone amp and run it trough the uca222. do you think this would work. i was thinking the pro-ject headbox mk ii or similar

    ReplyDelete
  16. I think most of all of Behringer headphone outputs have a 47 ohm impedance, so yeah, using an amp will really help. I haven't tested the Pro-Ject amps so I really have no idea but looking at the circuit board the cheaper one at least seems to have capacitor coupled outputs and the specs are not very impressive. I suspect the FiiO E9 and lots of other less expensive amps out perform it. Even the FiiO E5/E6 is a big improvement on Behringer's headphone output.

    ReplyDelete
  17. @NwAvGuy
    For power: no wonder then, why it has so weak headphone output.
    For noise shaping: First, I understand Delta-sigma modulation. It is much more better to have the noise in the ultrasound frequencies, than elsewhere. But that is no-excuse to just skip the anti-aliasing.
    I don't hear that, that's true. But my headphone can output it. Also high-frequency could cause some psycho-accustical effect, which could cause headache, or uncomfortable listening etc. In not expert on human hearing.
    Also the bump is unnececary work for the opamps.Either they should use more oversapmling (other DAC) or 2-3 stage filtering.

    But i'm glad that the topic came up, You verified, that the texas-DACs are capable chips.

    ReplyDelete
  18. @tszaboo, it's worth noting the ultrasonic noise bump is entirely below -80 dB. So even if you could hear up to 40 Khz you'd still have a hard time hearing it. It's hard to imagine any psycho-acoustic effects from a level so low. Lots of gear has distortion products within the audio band that are much higher in level. The CCIF IMD on the Micro II, for example, exceeds -40 dB. So while the bump might look bad, it's really not an issue. And had I cut the spectrum off at 20 Khz as many do, you wouldn't even know it's there. Any side effects for the op amps would show up in the measurements so that's not a concern either.

    ReplyDelete
  19. I've owned both the Behringer and TurtleBeach, and ultimately kept the Micro II for the smaller form factor. The dongle is surprisingly convenient and easy to tuck away. In terms of headphone out, I actually preferred the MicroII as well, though neither is anything to write home about.

    ~Armaegis

    ReplyDelete
  20. I think the point tszaboo raised is a quite interesting one. Do sounds outside of the audible spectrum have any actual effects on the listening experience?

    I have read on a few sites that they are responsible for the "soundstage" feeling, but I can't remember any of those articles looking credible enough to trust them. Do you know if there has been any real research on this topic? It would also be interesting to know if they can be harmful - e.g. if the regular music in a recording in average stays somewhere at at -15 dBFS (and you set the volume control accordingly), but the inaudible sounds regularly hit 0 dBFS..?

    Also those inaudible sounds are the main difference between MP3s and FLACs (because MP3s cut off the inaudible spectrum) - right?

    I realize these are probably too many questions to answer in a comment, but maybe you could include a section about this in your next headphone article?

    ReplyDelete
  21. @GuiltySpark I will be covering the "out -of-band" topic a bit more in the future--especially when I review the defective eBay DAC I have. It has serious out-of-band problems that can be audible.

    But for the UCA202, find something with an accurate volume control calibrated in dB (like Foobar2000). Play music as loud as you're ever likely to listen, and then reduce the volume 80 dB (if you even can before the volume hits "minus infinity"--i.e. mute) . What you're left with will be virtually nothing. It's hard to conceive of any way something that low in level above 20 Khz could present any sort of problem. We're talking about microvolts of signal that's little different than the broadband noise floor which extends in nearly all gear well beyond 20 Khz.

    ReplyDelete
  22. Could you also test the input when the unit tested has one ?

    ReplyDelete
  23. @Mrqaffe, someday I might do a "pro sound" comparison as I have several USB interfaces that record including the UCA202, E-Mu 0202, 0404, M-Audio, Benchmark ADC1, and a new Roland Quad-Capture. I also have access to interfaces by RME, Motu, PreSonus, and Focusrite but not sure I want to get that carried away.

    The main intent with these articles was to find a playback DAC for use with a headphone amp like the O2. I'm guessing 95% of those who read this blog are mainly concerned with only playback. I'm trying to focus my time on the most relevant content.

    ReplyDelete
  24. Do you know when the O2 Desktop Mod will be finished ? Will the parts be THAT different ?

    ReplyDelete
  25. I think you could futher improve the articles, if you calculate the ENOB (effective number of bits) for DAC-s. It could be calculated from THD+N and it is a clear comparison between two DAC.
    For example if you have a 24 bit DAC and a "not-so well enineered" analog circuit, if the ENOB is lower than 16-15 we could just use a 16 bit DAC instead, or if a 16 bit DAC has 15.8+ bit ENOB we can tell that it has exceptonally well analog circuit.

    ReplyDelete
  26. It's interesting that a converter with a delta-sigma DAC would have quantization noise that high. Either this thing has some serious correlated jitter problems, or (more likely) the digital filter is operating with 16 bit precision only, like ye olde SAA7378 from the mid-'90s did.

    Lately I was going through some PCM27xx datasheets, and it appears the PCM2702 had a better DAC than later chips (a multibit delta-sigma affair with a better SNR spec). Interesting.

    ReplyDelete
  27. @Anon, I'm still hoping to publish at least the initial info on the desktop version of the O2 with the companion DAC board before winter--i.e. December 22nd.

    ReplyDelete
  28. I would be very interested to see test results of your DAC1 as a baseline. I know Benchmark has their own measurements but since their test setup is likely different from yours it would give a good reference point.

    ReplyDelete
  29. @Anon, there are quite a few DAC1 measurements sprinkled throughout my articles with some direct comparisons. I agree it would be interesting to test it alongside the inexpensive DACs. It's just a matter of time and trying to focus on what's most helpful.

    ReplyDelete
  30. Hey NwAvGuy, I would be interested to know your choices for a desktop DAC short of the Benchmark. Something that slots between the E7+E9 combo and the Benchmark in terms of price, and measures well, even out of USB. I would like to create a stereo (speaker) rig with files played from my computer (44.1/16 FLAC), fed to an integrated (or power amp, if a preamp is also included in the DAC)

    Would the Emotiva XDA-1 (AD1955+OPA2134) fit my bill? Including shipping internationally, it would be the price of a Cambridge DACMagic locally - I am worried about the measurements from USB from Stereophile's Audio Analyzer. You seem to be quite impressed with Emotiva gear, in general.

    Oh, and if it matters, I am using the highly obscure Jungson BD-1 (Morel MW166+MDT29) - the brand OEMs for several well-received brands, including Usher et al.

    ReplyDelete
  31. My favorite "mid price" DAC is the Centrance DAC Mini. The XDA-1 is a bargain but doesn't support 24 bit over USB. Rumor has it they're working on a replacement that does.

    I need to run more tests, but I think 24 bit offers benefits for USB audio where you want to use volume controls on the PC side.

    I'm also working with someone else on a DAC daughter board that will go inside the upcoming desktop version of the O2 amp and support 24/96 over USB. Stay tuned for more on that.

    In general I think we're finally turning the corner towards more DACs that support 24 bit over USB and, if you like to turn the volume down on the PC side, it's probably worth it. Otherwise, even the HRT MS II is a decent DAC.

    ReplyDelete
  32. Thanks for the quick reply! However, the Dacmini is regrettably slightly out of my price range. However, the HRT Music Streamer 2 and it's + variant is, at the expense of the preamp component. That leaves me to look for a cheap & cheerful integrated to pair with.

    I have been looking at another contender that is very interesting: the Furutech GT40 - it is a preamp, headphone amp, USB DAC, phono preamp and ADC all-in-one! Subjectively, it has impressed Stereophile (no full review though). I auditioned it at a local store as a USB DAC, albeit out of cheap Mordaunt-Short Carnival 2 speakers, and found it quite impressive, but still not in the league of a good CD Player, or probably a standalone DAC such as the HRT, after a moderately-long AB comparison.

    What intrigues me though, is that it uses the NJM4556 for the output stage, and 2068 for the gain stage, as I gather, quite similarly to the O2, but probably in a different configuration, and not as powerful. Just highlighting the interesting headphone out to you - I do not have a decent headphone with me to test the HP out.

    ReplyDelete
  33. @Anon, if you need a phono stage the GT40 might be interesting, but at $525 it's getting close in price to the CEntrance DACmini. It's a nice confirmation that a well reviewed high-end product uses the same op amps I chose for the O2. But I still have a lot more faith in the CEntrance DACs. I also suspect the next Emotiva DAC will also have far more features than the GT40 for less money. Finally, if all goes as planned, the ODA (desktop O2) with the DAC option should cost significantly less even in assembled form.

    ReplyDelete
  34. Hello nwavguy,

    Great blog, have enjoyed reading every post. Being an electrical engineer getting into "audiophile" gear, it has helped me a lot.

    A suggestion: could you do a subjective experiment to see if the improvement provided by a USB DAC vs onboard sound is comparable to the improvement provided by lossless audio vs mp3/320kbps?

    This is just to see if using lossless will provide a comparable improvement in quality as opposed to buying an external DAC, for n00b audiophiles like me.

    An example is here: http://www.reddit.com/r/audiophile/comments/lmuil/an_experiment_for_those_with_a_usb_dac_and_a_pc/

    Thanks

    ReplyDelete
  35. @Anon, you're welcome and glad you like the blog. The internal vs external DAC issue is a bit more complicated than just using Foobar2000 to blind ABX compare two audio files using different compression.

    In order to prevent biased results, you have to feed the same digital signal to both DACs in reasonably perfect sync and level matched to 0.1 dB. As long as the person even suspects which is which due to time differences, level differences, or other clues, such a comparison is of limited value for all the reasons I mention in my Subjective vs Objective article.

    Even advanced players like Foobar will not send the same audio stream to two different audio devices simultaneously. One solution is to launch two instances of the player with each configured to feed a different audio device and try and get the music in sync but that's challenging. Even if you get the two players in sync you can't pause or repeat a track or segment without losing the synch.

    You have to level match the signals in the analog domain outside the PC. If you try to use the digital controls in the player software they may be too coarse and you're no longer feeding identical bit accurate signals to both DACs.

    Finally, you need to use external switching hardware that can accommodate everything and ideally supports ABX blind switching. That's also not trivial to do in a way where the listener doesn't know which is which.

    I have the means to conduct such a comparison but it's not trivial to set up. And ideally you want more than one or two sets of ears listening to the result.

    ReplyDelete
  36. One request on the DAC...

    Given that many of us are building the current O2 design (thanks for that) - please can you make the DAC you're working on usable in a stand alone enclosure (no need to build the O2 desktop just to get the DAC).

    Thanks for all the hard work on all fronts.

    ReplyDelete
  37. @Anon, that's the plan. The 24/96 USB DAC will also work standalone from USB power in its own standard BEX enclosure.

    ReplyDelete
  38. Hi! That's great news! Thought the early adopters will be left in the lurch after reading about your plans to include a daughter board DAC with the ODA.

    On another note, I have ordered "your favorite mid-price DAC". Impressive credential at this mid-price. Also, Michael Goodman might drop you their highly acclaimed DACport variant -LX for objective evaluation after I wrote him about you - a rising rock star.

    Cheers,
    Julian

    ReplyDelete
    Replies
    1. Hi NwAvGuy,

      Did this ever happen? I would very much appreciate one of your great reviews on the LX, and specially in comparison to the now released ODAC.

      Cheers!

      Delete
  39. On one hand: I'm dissappointed that there have been no new blog entries in a while...

    On the other hand: I console myself with the notion that instead of writing blog entries, you're working on the new Desktop Amp and DAC.

    I'm looking forward to the Desktop O2 and DAC design and schematics more than the upcoming blog entries; and that's saying something, because I *really* enjoy the blog entries.

    Keep up the fantastic work!

    ReplyDelete
  40. Hi, I'm really enjoying your blog and have ordered a ready made O2 from Epiphany Acoustics. My request for the O2 desktop would be variable output to control active speakers and a speaker defeat when headphones are plugged in so I can switch quickly between headphones and speakers.
    Cheers
    Mike

    ReplyDelete
  41. Would there be many downsides to hooking up a Fiio E5 to the UCA202 via RCA to 3.5mm conversion for a USB DAC + amp on the cheap for low impedance phones? It would use 2 USB ports, but I can't think of anything too bad happening besides that.

    ReplyDelete
  42. I've suggested the E5 and UCA202 combo several times. Although if you don't yet have the UCA202 you might want to wait for the rest of my USB "thumb DAC" reviews due out shortly. Two of them rival the UCA202 and even beat it in a few areas and they're much more portable. I'll also be reviewing the FiiO E6 which is supposedly better than the E5.

    ReplyDelete
  43. Could you tell us the names of that two?

    ReplyDelete
  44. I just received my UCA202 and am amazed at the sound quality. It even edges out my Audinst HUD-MX1, which of course has more features, but was also $180. I've been looking at $300+ DACs but now have no interest. I might well lay out a lot of lettuce and find nothing that much better. I've spent a lot DACs not worth keeping. And this proves my theory that it should not be that friggin' impossible to build a simple cheap DAC that is also transparent.

    Can't wait for your upcoming thumb DAC reviews. Anything you find that beats the UCA202 will get my money. Here's hoping the Hifiman Express HM-101 is on your test bench . . .

    ReplyDelete
  45. Hello, I enjoy your articles very much, not many people take the time to review inexpensive equipment in such detailed and professional way. I've always liked the idea that you can find a diamond among inexpensive gear, as happened with Sonic Impact T-Amp, which was a cheap portable digital amp that was compared to amplifiers costing thousands more. I think the same could happen in the DAC world and I wouldn't doubt it could happen after one of your reviews.

    I was wondering if you had the chance of trying the Behringer FCA202 which is a 24bit/96khz Firewire audio interface that sells for under $90. I got mine used for about $40. I would love to hear your opinion on this one.

    Cheers
    Christian

    ReplyDelete
  46. Boy would it be nice if this thing sounded as good as it measured.

    Something about it I can't stand, compared to my audio interface (the drivers stopped working on Mac so I had to get the UCA-202 and had high expectations based on your review).

    It's just not there. The clean undistorted sound I remember is gone. Stereo imaging isn't nearly as good as before even. Is it possible I just got a bad one?

    ReplyDelete
  47. @Anon, I'm not sure why you're not happy with the sound unless you're using the lousy headphone output (you didn't say). If you look at the original UCA202 review you'll find the comments are mostly the opposite of yours for those using the line output. If there's something wrong with yours I would expect it to be more obvious but it's hard to say for sure. Very high jitter, for example, might degrade stereo imaging.

    But I also should mention "audio memory" (i.e. of your old interface) is notoriously inaccurate. See: Subjective vs Objective

    ReplyDelete
  48. From you original review the low level linearity was really good. If I read the old graph correctly, the output level was -90.41dB on -90dB input signal which would be 0.41dB for low level linearity. Why does this review have a much worse result?

    I've only just started reading your very informative blog, so if I misinterpreted your results, I'm sorry...

    ReplyDelete
  49. @Anon, good catch. The original UCA202 article was in the early days of this blog and I've improved several of my measurements since then based on feedback from others and to bring them more in line with other reviews. In the case of the UCA202 it didn't do as well on the improved version of the test. The difference is related to how the measurement is made--in this case how the noise is rejected from the measurement. The newer result is more accurate.

    ReplyDelete

PLEASE NOTE! If you see "LOAD MORE..." OR "LOADING..." just above this paragraph, you need to click that link to load the newest comments. It may take several seconds. When all the comments are displayed the Load More/Loading link disappears.

COMMENT APPROVAL: Comments may take anywhere from a few minutes to a few days to be approved. You might want to save a copy (highlight Ctrl-C) of your comments before submitting in case something goes wrong. The approval process is necessary to prevent obscenity, etc. Please keep comments on topic. Comments promoting commercial interests will not be approved and may be reported as SPAM.