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Review and Measurements of Audio-gd R2R11 DAC & Amp

amirm

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and I still don't believe anybody can reliably tell a 320mp3 from the lossless master.
What? I just post a real sample for you of me passing the test. And this was not a carefully picked clip. When I ran it, that content from AIX Record was used as a test of high-res versus CD so I compressed it to 320 kbps and ran the test you saw.

Here is another one I ran taking the content from the very person who made the claim you did (the late Arny Krueger):

foo_abx 1.3.4 report
foobar2000 v1.3.2
2014/07/19 19:45:33

File A: C:\Users\Amir\Music\Arnys Filter Test\keys jangling 16 44.wav
File B: C:\Users\Amir\Music\Arnys Filter Test\keys jangling 16 44_01.mp3

19:45:33 : Test started.
19:46:21 : 01/01 50.0%
19:46:35 : 02/02 25.0%
19:46:49 : 02/03 50.0%
19:47:03 : 03/04 31.3%
19:47:13 : 04/05 18.8%
19:47:27 : 05/06 10.9%
19:47:38 : 06/07 6.3%
19:47:46 : 07/08 3.5%
19:48:01 : 08/09 2.0%
19:48:19 : 09/10 1.1%
19:48:31 : 10/11 0.6%
19:48:45 : 11/12 0.3%
19:48:58 : 12/13 0.2%
19:49:11 : 13/14 0.1%
19:49:28 : 14/15 0.0%
19:49:52 : 15/16 0.0%
19:49:56 : Test finished.

----------
Total: 15/16 (0.0%)

MP3 was never designed to provide transparency. It can get very close and certainly there for untrained listeners. But people with critical listening skills and training like I have, can find the impairments reliably in many clips.
 
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What? I just post a real sample for you of me passing the test. And this was not a carefully picked clip. When I ran it, that content from AIX Record was used as a test of high-res versus CD so I compressed it to 320 kbps and ran the test you saw.

Here is another one I ran taking the content from the very person who made the claim you did (the late Arny Krueger):

foo_abx 1.3.4 report
foobar2000 v1.3.2
2014/07/19 19:45:33

File A: C:\Users\Amir\Music\Arnys Filter Test\keys jangling 16 44.wav
File B: C:\Users\Amir\Music\Arnys Filter Test\keys jangling 16 44_01.mp3

19:45:33 : Test started.
19:46:21 : 01/01 50.0%
19:46:35 : 02/02 25.0%
19:46:49 : 02/03 50.0%
19:47:03 : 03/04 31.3%
19:47:13 : 04/05 18.8%
19:47:27 : 05/06 10.9%
19:47:38 : 06/07 6.3%
19:47:46 : 07/08 3.5%
19:48:01 : 08/09 2.0%
19:48:19 : 09/10 1.1%
19:48:31 : 10/11 0.6%
19:48:45 : 11/12 0.3%
19:48:58 : 12/13 0.2%
19:49:11 : 13/14 0.1%
19:49:28 : 14/15 0.0%
19:49:52 : 15/16 0.0%
19:49:56 : Test finished.

----------
Total: 15/16 (0.0%)

MP3 was never designed to provide transparency. It can get very close and certainly there for untrained listeners. But people with critical listening skills and training like I have, can find the impairments reliably in many clips.
Fair enough, I certainly am unable to disprove your claim (nor do I actually want to). This has not been my experience, but who says my experience is all that so I freely admit that I could be wrong. Thank you for that, but in your experience, do you think that very many people can detect these very small differences? I also make a distinction between practically useful and useful.

If music is for listening, and it required you to have years of honed, critical listening training, and you then had to specifically attend to what you were hearing to detect a difference that in my mind is useful, but in the context of the product, not practically useful. What I mean is that if 95% of all people who listen casually, without training, or even listen critically without training, and they can't hear a difference, that makes the 320mp3 practically useful in that for what it is supposed to do, it actually achieves the intended purpose.

In research into medication there are many times a drug can effect a change, but the change is so small as to have no practical utility and the drug does not get approval as it does not provide enough effect. So my earlier statement was clearly incorrect and I would now say that the vast majority of people who lack years of listening experience combined with some form of detection training; and who are simply listening to music playback for the joy of it will never be able to hear a difference between a 320mp3 and the lossless master. That is a more accurate statement given the evidence at hand.
 

amirm

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Thank you for that, but in your experience, do you think that very many people can detect these very small differences?
Definitely not. They are even challenging for me to do at times despite my training.
 

restorer-john

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Definitely not. They are even challenging for me to do at times despite my training.
But you did that test 4 1/2 years ago. Probably half deaf by now from all those skull rattling headphone amplifier tests..
 

amirm

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But you did that test 4 1/2 years ago. Probably half deaf by now from all those skull rattling headphone amplifier tests..
How true that might be.... :(
 

Hugo9000

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I had written a long rant about MP3 and how it is clearly broken even at 320kbps as it doesn't support true gapless playback.* Anyone who listens to opera, as well as a few pop fans who like the couple dozen or so non-classical albums that transition smoothly between songs/tracks will know what I'm talking about.

Obviously, all of the researchers into the psychoacoustics of lossy encoding were too arrogant in their pop-music-only viewpoint to even attempt to get this right. Let's all speculate on the audibility of thousands of angels dancing on the head of a pin at X-kHz frequency, and whether the demons howling at Y-kHz frequency might mask that, but let's not bother with something so obviously audible and awful as pauses/clicks at track transitions due to a completely broken system...smh (Ogg Vorbis must have been the creation of opera fans or something, as they actually managed to solve this.)

Anyway, I deleted the long rant, and this replacement "short" one is now starting to get long as well, so I guess I'll end it now. lol


*Some pedant might wish to argue that in theory, LAME encoding allows for gapless MP3 with some sort of metadata fix that some players might in theory use correctly, but I have yet to encounter this in any MP3 sold anywhere, so it might be valid for someone ripping his/her own CDs but most current discussions of transparency of lossy files are with regard to services selling streaming and/or downloads of files, NOT with compressing one's own CD collection.
 

Frank Dernie

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I had written a long rant about MP3 and how it is clearly broken even at 320kbps as it doesn't support true gapless playback.
I agree. Anything which doesn't support gapless playback is completely useless as far as I am concerned and not worth bothering with after the first "fail".
 
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This is a review and detailed measurements of Audio-gd R2R11 DAC and headphone amplifier. It is on kind loan from a forum member. It retails for USD $350 plus shipping. From what I can tell, you have to send money via paypal and then the product will be shipped to you as there is no formal online store. Customers in Europe though can purchase it from distributors there. The only price I see is 369,00 € tax included.

I have had many requests to measure this unit and I am very happy to finally get one to review. The unit being an unconventional, discrete "R2R resistor ladder," as opposed to vast majority of DACs we test which are built on integrated DAC ICs (chips). This brings an appeal to many people, considering such DACs as more natural sounding. This has made this DAC and the ones like it from Schiit, etc. very popular.

This is the lower-end of DAC products from Audio-gd and as a result dispenses with displays and such:


Ah, what a joy it is to have simple switches that control functions as opposed to convoluted button presses and cryptic display in their higher-end units.

There is an integrated AC power supply, eliminating the wall power dongle.

Sadly there is no balanced output which I like to see in this price range but I appreciate that this doubles the circuits for the R2R ladder DAC.

I am sure you all are as anxious to see the measurements as I was when I put it on the bench last night so let's get into that.

Measurements
The last two Audio-gd DACs I have tested, unfortunately performed poorly. Would the R2R11 be any different? Here is our dashboard view with RCA outputs:

View attachment 19165

Sadly the answer is no. We have really poor performance yet again. Not only do we have our usual high harmonic distortions but now, have lots of other interference and glitches from mains and other sources. SINAD as a result suffers putting the unit squarely in a class by itself beside other Audio-gd products:

View attachment 19166

Levels in fixed output mode per above were a bit hot at 2.4 volts. Putting the unit in variable mode and reducing the levels though made no noticeable difference.

When I was running my dashboard, I noticed every once in a while the waveform would get distorted and THD would shoot up. I checked and all of my Windows/ASIO buffers were set to large values to avoid buffer underruns but the problem remained. Wanted to confirm it, I ran a continuous measurement, watching THD+N as time went by and got this:
View attachment 19173

As you see, like clockwork, every 25 seconds or so we get a spike in distortion, confirming the problem I saw. There is a clear implementation error here.

To avoid having this impact the measurements, from here on I tested with S/PDIF input which did NOT exhibit this problem.

Audio-gd does not provide any specifications other than signal to noise ratio of 100 so let's see how she does in that department:

View attachment 19167

So about 10 dB shortfall which is pretty significant although similar to performance of Schiit Modi Multibit.

Linearity tests become super important when we are talking about custom/R2R DACs. Ideally, we should see an output that varies in voltage in direct and precise steps to digital inputs. Here is what Audio-gd does in contrast:

View attachment 19169

This is the worse measurements of any DAC. The R2R11 loses linearity very early on (-40 dB) and by just -63 dB loses my threshold of pain of 0.5 dB. By the time you get anywhere close to CD's 96 dB dynamic range the Audio-gd R2R11 is on the next planet in another solar system.

Any more bad stories? Sure, let's look at jitter and noise:

View attachment 19170

The J-test source signal toggles a single bit in 24 bit words to the tune of 250 Hz. This creates a square wave at that frequency which should NOT appear in the output as its level is well below noise. Not here. That square wave is causing pretty major disturbance causing distortion spikes as high as -55 dB!

Embedded in there is also another train of jitter and spurious responses at lower levels which thankfully are inaudible but show dual mechanisms for corruption of audio samples. Lots of power supply noise generates the congested cluster on the left and then around our main tone at 12 kHz.

People unfamiliar with signal processing quip that "single tones are not music." Well, they are because your music can completely represented by the principle tones but ignoring that, we can run a test with 32 tones and see the response there:
View attachment 19171

Ideal response would be those 32 tones with bottoms way low and nothing in between troughs. Of course we don't see anything like that. Instead, we have large amount of distortion products raise the effect noise floor by some 50 dB. Any hope of hearing detail in your music will go out the window and replaced not just by random noise but correlated and uncorrelated distortion products. But we knew that from our earlier tests, did we not?

Even in a test like white noise to see filter response we see odd behavior:
View attachment 19174

For proper reconstruction of audio samples, we must filter everything above half the sample rate which would be 20.05 kHz. In the Audio-gd R2R11 there does not appear to much of any filtering. The math therefore predicts aliasing.

For completeness, here is the square wave response:
View attachment 19178

What do you think intermodulation distortion versus level looks like?

View attachment 19177

Notice the jagged distortion as levels change showing discontinuity errors in the DAC implementation.

Now let's look at the headphone output performance. Output impedance is stated at 2 ohms. I get almost 9 ohms instead!
View attachment 19172

I am scratching my head how they could mis-specify this simple metric. I tested it twice and each time, adding a load to the headphone output substantially lowers its value indicating high source impedance. Now, this is not end of the world but be careful if you use headphones with low but varying output impedance as this could change their frequency response (for good or better subjectively).

Next is power versus distortion at 300 ohm, simulating loads like Sennheiser HD-650 headphones:

View attachment 19175

Out previous measurements of noise and distortion come to haunt us in erratic, high distortion and noise response in both low and high gains. Power is very good at 150 milliwatts although no better than the Topping DX3 Pro shown for reference.

The bad news continues with 33 ohm load:
View attachment 19176

The issues we saw in intermodulation test of course show up in these loads just the same as we vary the input level to plot the power vs distortion.

Listening Tests
I started listening with my Sennheiser HD-650 headphones. My music tracks for headphone testing are designed to test the power limits of the headphone amplifiers and here, the Audio-gd R2R11 did fine. It produced thunderous bass, easily able to push the Sennheiser to produce them well. This explains why many people like this product. If you are coming from an anemic headphone amp or no amp at all, you will be most impressed with this unit.

Similar outcome was waiting for me with Hifiman He-400i. So in casual, isolated listening not much pops out despite the excessive distortions and errors in the output of the Audio-gd R2R11.

I then set up an AB test between Topping DX3 Pro and Audio-gd R2R11. I then matched levels, ganged the two DACs in Roon to play in sync and started to listen. With my busy headphone test tracks performance was actually pretty similar. Importantly, there was NO coloration in response of Audio-gd. I read countless posts online about how these ladder DACs sound different, more pleasing, etc. I could detect none of that across a bunch of tracks. Anyone who thinks otherwise, needs to perform such an AB test to realize differently.

I next ran a set of tests with more isolated instruments. Here there were some subtle differences to my ears. High frequency transients were, forgive my use of audiophile term, muddier in Audio-gd blending more into the rest of the music. Note decays suffered some just the same.

I wanted to run more listening tests this morning but we lost our power and I am typing this under generator power. And at any rate, will be going on a trip later today so need to pack and such.

Conclusions
With now three Audio-gd products tested under our belt, the conclusions are abundantly clear: the company chases audiophile imaginations and lay intuition, producing products that lose the word "fidelity" in high-fidelity. Nowhere this is more clear than in this DAC where every test shows massive deviation from ideal or what the competition delivers.

Please don't say these are musical distortions. There is nothing musical about erratic performance of a DAC and amplifier. Your music was not produced with these devices. Any deviation here is distorting that creation with no intention of musicality in mind. It is like saying the dirtier the dishes in a restaurant, the better the dish would taste. I don't think so.

I took a look inside to make sure the jumpers were as shipped (they were) and you see tons and tons of circuitry as you do in other Audio-gd products. Getting all that to work and manufacture, is not an easy task. That talent and resource though is applied in totally wrong direction. Yes, differentiation is good but not in producing such poorly executed end product. We want transparency in our product, not a random mixture of distortions, all conspiring to reduce fidelity. I hope Audio-gd changes direction and starts to produce well-engineered products rather than a set of buzzwords in spec sheets.

Needless to say, my advice remains to avoid purchasing these Audio-gd products. They are antithesis to what it means to be an "audiophile." That word better have some meaning left it in.

-------------
As always, questions, comments, recommendations, etc. are welcome.

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Another fantastic review @amirm !! The listening impressions really raise some fundamental questions about our measurement of quantitative error v/s perception of noise by our ears. Also, hearing is so subjective due to inability to really doing A/B. As we cannot pause audio like we can a movie and look side by side. Also there is lot of psychology at play. I feel so much better when I listen on Tidal and see that "HIFI" lit up v/s listening on Spotify at 320 kbps psycho-acoustically compressed audio :D. I am not sure how much I will be able to pick up if I do the "A/B" testing.
 
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