Review and Measurements of CHORD Qutest DAC

[JohnYang1997]

All, skip this unless you are interested in FPGA rabbit holes.



Thanks for the pointer. I found the video you referenced:

It is very interesting but it still only covers the FPGA advantage is general terms. The bias is towards having more taps, which they cite as a product of their fast crystal oscillator (separate component) and the capability of the FPGA, delivering their WTA Filter algorithm. They point out that a normal DAC only operates at a frequency of 6MHz, giving "poor resolution" while their Chord FPGA operates "around 20 times faster" at 104MHz. This is done to reproduce "incredibly small micro-details from the original recording."

Maybe kinda. An FPGA running at 20x the speed of a fixed silicon chip does not indicate being 20 times better or 20 times faster. For example, if the WTA Filter involves any floating point math then a regular chip would potentially be more efficient. A good overview of the relative nature of FPGA advantages/disadvantages is here. This overview is useful because it shows how relative the advantages or disadvantages are depending on what FPGA is being used, how it is being used, and for which purposes.

I am most interested in the first two items right now, but I can't find any detailed information, especially around the how part. If you have information please pass along a link. As mentioned above, I'm curious.

Anyway, let's move away from 'how does the WTA Filter work' and into 'what does the WTA Filter accomplish.' This is the which purpose bit. Chord appear to focus on taps (a sampling rate) because it "solves the question as to why higher sampling rates sound better.” So let's zoom into why more taps are better. As per the link earlier in this paragraph, Chord say it "is well known that 96 kHz (DVD Audio) recordings sound better than 44.1 kHz (CD) recordings [...] What is not well known is that 768 kHz recordings sound better than 384 kHz and that the sound quality limit for sampling lies in the MHz region." They slam mass produced DACs as not being able to provide the same capability.

Hm...their numbers in the video cited above contradict this statement (a normal DAC "operates at a frequency of 6MHz"). But perhaps we should read "the sound quality limit for sampling lies in the MHz region" as "the sound quality limit for sampling lies in the [high] MHz region." Unknown. That information is not presented. But I digress. Just the claim that sound quality limit for sampling lies in the MHz region takes us into a whole new territory beyond the scope of the FPGA per se. Let's just say Chord thinks their WTA filter is useful because it allows lots more sampling. Sometimes this seems to provide good outcomes (Qutest) and sometimes not (Mojo). It does not appear to be a panacea.

In the end, what I can conclude from the Chord information is that their statements ultimately mean "mass-produced DACs do not run our WTA Filter" and "we propose that the WTA Filter is a clear advantage in making better sound" rather than"the use of X FPGA is objectively better because of XYZ factors." There is a subtle difference between these two propositions, and my take from the majority of their material is that they do put some emphasis on the latter. Yet, from the information at-hand, if they had the distribution scale, there is a real possibility that a mass-produced DAC with the WTA Filter would be faster, more effective and less power hungry. This does not mean I am correct. It just means this is where I got with the material I have seen.

Here is another video that explained by himself and is probably a little bit bold in some way. But still, worth watching. I personally only briefly touched a little about fpga in school, so i don't really understand how to make a dac like that.

 

[Music1969]

Hi @shanecoughlan , you can literally ask Rob Watts directly over on Head-Fi forum.

It would save you a lot of time I imagine.

Here is Chord Hugo2 thread:

https://www.head-fi.org/threads/chord-electronics-hugo-2-the-official-thread.831345/

 

[shanecoughlan]

Hi @shanecoughlan , you can literally ask Rob Watts directly over on Head-Fi forum.
It would save you a lot of time I imagine.
Here is Chord Hugo2 thread:
https://www.head-fi.org/threads/chord-electronics-hugo-2-the-official-thread.831345/

Thanks for the pointer!

 

[CTRLM]

I read through this whole thread and didn't see anything on the power supply used?

@amirm : I assume the measurements are with the supplied SMPS and not your SBooster?

 

[VintageFlanker]

I read through this whole thread and didn't see anything on the power supply used?

@amirm : I assume the measurements are with the supplied SMPS and not your SBooster?

Should it be otherwise?

 

[CTRLM]

No but amirm has used the SBooster in other tests before, I just wanted to to make sure he used the stock supply (or other) here.

 

[amirm]

@amirm : I assume the measurements are with the supplied SMPS and not your SBooster?

I state it if I use other supplies and did not in this case.

 

[amirm]

Here is another video that explained by himself and is probably a little bit bold in some way. But still, worth watching. I personally only briefly touched a little about fpga in school, so i don't really understand how to make a dac like that.

The FPGA is not performing the DAC function.

In simple terms, the Chord DACs first upsample the audio to much higher rate so that they don't need as many bits to convert to analog. The FPGA performs this function as would any other upsampling DAC. Where it differs from other DACs is that its reconstruction filter uses far more audio samples to perform its filtering than off-the-shelf filters do. Rob Watts says this improves fidelity but that is a hand wave. What is implemented in mass market DAC chips is already at point of diminishing returns. Going 1000 times more taps (audio samples) doesn't amount to much improvement. The asymptop has already been reached.

FPGAs are inefficient to use by the way compared to hard silicon such as what is in a DAC chip. The main benefit of FPGA is that it can be programmed over and over again whereas a custom IC cannot. The price for that is higher cost and higher power consumption. An ASIC can be produced from an FPGA to get those benefits but it will have NRE up front costs north of a million dollars plus that much in engineering design cost (and tools). So it is not done in the scale that Chord sells these DACs.

As an analog, think of a car with 100 exhaust pipes instead of two. That is what Chord says will produce more horsepower. For measurements though, they show 0.01% more horsepower and can't show anyone actually feeling the improvement. They incur the expense, heat, etc. but the benefit simply is not there.

 

[shanecoughlan]

Going 1000 times more taps (audio samples) doesn't amount to much improvement.

I found it fascinating that in his expository dialogue Mr Watts was suggesting that these samples would provide an improvement despite what logical analysis would show. People could “hear” the difference. We return to the golden ear myth. It’s one thing to say “some people might have cognition above 20kHz” and another to say “magic Dan can identify a DAC across a crowded room” (assertion in another forum that best remains nameless). No matter how young and wonderful ears are, they are not going much above 20kHz, hence decisions like 44.1kHz on CD (Nyquist rate, perfect fidelity at 22.05kHz) and Apple tapping out their excellent DACs at 48kHz.

We return to “nope” and “sure do it if you want it”, but the numbers are not there. Which is fine. I have a bunch of 24 bit 192kHz files just because...fun.

Come to think of it, the numbers are not there link should probably be mandatory reading, so people chill out and realize further fidelity is just because they want to get close to studio mixing rates, not because it is useful for playback.

Which is fine! Fun! See above.

 

[amirm]

I found it fascinating that in his expository dialogue Mr Watts was suggesting that these samples would provide an improvement despite what logical analysis would show. People could “hear” the difference.

I asked him at the end of one of his talks if he had done his listening tests blind. He said no that blind listening tests confuses one or some such thing. This, after talking at length on how to do proper listening tests yet having this simple control was not in his vocabulary.

 

[shanecoughlan]

I asked him at the end of one of his talks if he had done his listening tests blind. He said no that blind listening tests confuses one or some such thing. This, after talking at length on how to do proper listening tests yet having this simple control was not in his vocabulary.

Indeed. Double blind testing preferred. Anti-science benefits no one. And it’s totally fine if people want to deviate from logical analysis. Just preface with “this is totally subjective but I like X.”

I had a great discussion with a gentleman on Head-Fi about tube amps. It was refreshing to hear that he liked the tube amps he had heard but he was under no illusions that tube amps provided more accurate sound or that euphonic distortion was a universal constant. He just liked the warm sound (distorted sound) he perceived from the devices he heard.

And let such clarity be our guiding light so others do not waste money or time.

Edit: was "Double blind testing or nothing" but it stuck with me as too absolute.

 

[blueninjasix]

Measurements-wise this really should be the same

Irrespective of the measurements, this was EXACTLY my experience of comparing USB to OPTICAL on the Qutest. It has been suggested that the extra perceived brightness of USB is a result of RFI.

 

[geoffgjones]

I have, in the last few weeks, taken delivery of a Qutest. I have also listened to many DACs included the much over vaunted Shitt series. The Qutest blew them away easily. So what is the magic, you have been asking? Perhaps the air in the UK? I really think it must be the programming within the FPGA, and as they clearly are not giving anything away there, then it may be a long time before we know the answer. I know I would like to know! It is clearly a master class in audio design, so I am just going to enjoy the ride, and so should you.

 

[VintageFlanker]

I have, in the last few weeks, taken delivery of a Qutest. I have also listened to many DACs included the much over vaunted Shitt series. The Qutest blew them away easily. So what is the magic, you have been asking? Perhaps the air in the UK? I really think it must be the programming within the FPGA, and as they clearly are not giving anything away there, then it may be a long time before we know the answer. I know I would like to know! It is clearly a master class in audio design, so I am just going to enjoy the ride, and so should you.

Welcome...

This should worth more than anything I may answer : ASR Manifesto

 

[Shoaibexpert]

I saw the review now a bit late off course. But I noticed that DACs like say the SMSL M500 which I happen to own are showing better stats than this expensive Qutest in all categories Amir threw at it. Is it safe to assume that my chinese ~$300 DAC sounds better, more natural and neutral than this ~$1900 DAC? I don't have any Demo places where I live so has anyone listened to them to form an opinion? I am asking coz I'm thinking of upgrading to the Qutest. Thanks

 

[VintageFlanker]

Is it safe to assume that my chinese ~$300 DAC sounds better, more natural and neutral than this ~$1900 DAC?

Not a chance. Both are competently designed and engineered gears and should sound equally transparent.

I would bet quite a few money that no-one would pick up one or the other in a DBT, level matched.

 

[majingotan]

Nope. If anything they will audibly sound exactly the same

 

[Shoaibexpert]

Not a chance. Both are competently designed and engineered gears and should sound equally transparent.

I would bet quite a few money that no-one would pick up one or the other in a DBT, level matched.

Thanks. Have you had a chance to listen to some highly rated cheap Chinese DACs on ASR and compare to a $1500+ DAC...just confirm the variance in sound quality? I cant here...the best I've heard is the one I own...the M500!

 

[maxxevv]

Not a chance. Both are competently designed and engineered gears and should sound equally transparent.

I would bet quite a few money that no-one would pick up one or the other in a DBT, level matched.

Nope. If anything they will audibly sound exactly the same

Agreed. Usually, the end output amplifier (be it power amp/ Hp amp ) will create a bigger difference (if any). Purely as DAC's go, if there differences, its usually very subtle, and in very specific areas only if properly volume matched and double-blind tested. Unless of course 1 of the 2 is badly broken or that its output values has already touched saturation/clipping during the test.

If the THD+N as well as IMD performances are very close, there is absolutely no reason there should be "obvious" differences.

Minor to the point of negligible it would be at best.

 

[Shoaibexpert]

Agreed. Usually, the end output amplifier (be it power amp/ Hp amp ) will create a bigger difference (if any). Purely as DAC's go, if there differences, its usually very subtle, and in very specific areas only if properly volume matched and double-blind tested. Unless of course 1 of the 2 is badly broken or that its output values has already touched saturation/clipping during the test.

If the THD+N as well as IMD performances are very close, there is absolutely no reason there should be "obvious" differences.

Minor to the point of negligible it would be at best.

Thanks. So the differences in output analogue stage between DACs create no differences in audio output or how rich or thin it sounds? Everywhere I read, I've got experts swear by Chord DACs so I was wondering...