DAC Noise Modulation: Chord DAVE vs Topping DX7 Pro+

[amirm]

well he sure did a awesome job making a DAC/Amp that sounds great with planar headphones run from the XLR taps on high gain, that's all I can say about it

An "awesome" job in my book would have called for doing the same at competitive prices, not 10X higher. But sure, it should sound excellent.

 

[lc6]

Goldenboy has been repeatedly asked to comment on whether the Dave is objectively better sounding than the topping and he has avoided all such questions like the plague. It’s fun to watch. He won’t tell people the truth in front of Rob, and he also can’t lie because he knows we are watching. Lol quite entertaining this guy.
Edit, he finally did, unfortunately unproven answer.

Goldenboy (a 23 yo economics grad) also lacks basic engineering knowledge. At about 24:42 into this video
Why you can't trust audio measurements
he claims that the digital full scale in a 16-bit PCM signal is represented by "all ones." Apparently, he does not realize that a sample with all bits of one has an actual value of decimal minus one because PCM samples are signed integers (in two's complement). So, the positive digital full scale is represented by 15 least significant bits (LSBs) of one and the most significant bit (MSB) of zero which amounts to +32767 decimal, and the negative digital full scale sample is 15 LSBs of zero and MSB of one (-32768 decimal).

 

[Peluvius]

well he sure did a awesome job making a DAC/Amp that sounds great with planar headphones run from the XLR taps on high gain, that's all I can say about it

why don't you set it to high gain, plug your Stealths into the back and try not to smile while listening

Not too dissimilar to someone selling $2500 cables which sound the same as $250 cables. Skating very close to the edge in terms of ethical conduct.

 

[AndreaT]

So, modulated or non-modulated noise floor is another non entity in this context. I would suggest these audiophiles to dedicate more time and focus to music listening. Here is one for you (no objective measurement tough!): buy yourself the 2-disc Quartet Edition of “La Dolce Vita” CD: a well done offer of a a film score and superb sounding digital transfer. The recording adds the magic to one of the best soundtracks of Nino Rota. It will cost you much less than any of Chords electronics and it is a great comfort to the soul.

La Dolce Vita (2-CD) - Quartet Records

La Dolce Vita (2-CD) in Quartet Records

quartetrecords.com

 

[dartinbout]

Goldenboy has been repeatedly asked to comment on whether the Dave is objectively better sounding than the topping and he has avoided all such questions like the plague. It’s fun to watch. He won’t tell people the truth in front of Rob, and he also can’t lie because he knows we are watching. Lol quite entertaining this guy.
Edit, he finally did, unfortunately unproven answer.

Me thinks Golden boy is in the review game to buy a house. All of his reviews of late have been multi-multi thousand buckaroos. Just one such sale and the supplier would kick in a down payment. All of this huffery and puffery, in response to Amir's analysis, is just so much hot air. Golden boy should though in the towel, on measurements, and just do subjective reviews. He'll still get his house. He will just have to be satisfied with an above ground pool rather then the sunken.

 

[lazarian]

Me thinks Golden boy is in the review game to buy a house. All of his reviews of late have been multi-multi thousand buckaroos. Just one such sale and the supplier would kick in a down payment. All of this huffery and puffery, in response to Amir's analysis, is just so much hot air. Golden boy should though in the towel, on measurements, and just do subjective reviews. He'll still get his house. He will just have to be satisfied with an above ground pool rather then the sunken.

I assume Golden and the chap from SBAF have tried for months now to get some gotcha measurement that proved for all time how amazing their ears were...

Of course reality is getting in their way, and they're now likely having to work extra hard to pay off the cost of the AP's they have.

 

[amirm]

I assume Golden and the chap from SBAF have tried for months now to get some gotcha measurement that proved for all time how amazing their ears were...

Of course reality is getting in their way, and they're now likely having to work extra hard to pay off the cost of the AP's they have.

Well said. It is like some vegetarians getting 100 pounds of Wagyu steak to try to show why they don't taste good! Complete waste of money on their part.

 

[jeroboam]

Goldenboy (a 23 yo economics grad) also lacks basic engineering knowledge. At about 24:42 into this video
Why you can't trust audio measurements
he claims that the digital full scale in a 16-bit PCM signal is represented by "all ones." Apparently, he does not realize that a sample with all bits of one has an actual value of decimal minus one because PCM samples are signed integers (in two's complement). So, the positive digital full scale is represented by 15 least significant bits (LSBs) of one and the most significant bit (MSB) of zero which amounts to +32767 decimal, and the negative digital full scale sample is 15 LSBs of zero and MSB of one (-32768 decimal).

Jeez didn't know that!. Still don't - I blame my old maths teacher for not taking enough time with me because I was, and still am, a bit thick in the numbers department

 

[BDWoody]

The awakening

View attachment 229132

Warms the heart.

 

[dartinbout]

Well said. It is like some vegetarians getting 100 pounds of Wagyu steak to try to show why they don't taste good! Complete waste of money on their part.

Their careers as shills are safe. There will always be veils to lift. /s

 

[Music1969]

Warms the heart.

Ha you are a cruel man.

My heart cries for his wasted monies

 

[Geert]

He is not understanding the nature of this analysis. I am trying to replicate both noise floor and distortion in Rob's posted measurement.

Some info on the test protocol by Watts on Head-fi today:

Sep 7, 2022 at 3:08 AM Dave has no measurable noise floor modulation (independently confirmed by GoldenOne). If someone measures it and sees noise floor modulation then they are not doing the test correctly. You can't use the AP defaults to do this test, as that will give the incorrect results. For instance - turning off the signal is done by setting the 1kHz level to -999dB. You must also ensure that nothing changes within the AP, so the input levels must be fixed at say 2.5v for both measurements. If you are using the high performance sine analyser ADC you need to ensure the frequency is fixed too.

 

[strom]

In one of the Chord TT2 review thread, I was asked to comment on noise modulation claims by the product designer Rob Watts. I attempted to recreate his measurements and compare them to Topping DX7 Pro+ which I just reviewed.
View attachment 229006

DAC Noise Modulation
Noise modulation refers to noise floor of the DAC changing with signal. To the extent the signal changes, if the noise floor changes with it, it is said to be "modulated." An ideal DAC would keep its noise floor constant as one has (ideally) nothing to do with the other. In reality activities of the DAC can manifest itself as extra noise, raising that component of the signal.

Chord DAC Claimed Lack of Noise Modulation
Rob Watts claims his DAVE DAC to be completely free of noise modulation and being the only DAC to be so. He backs it with the following measurement:

View attachment 229007

Notations in red are mine. This is the text below the graph:
View attachment 229008

Before getting into the details, the graph shows two overlaid measurements. One is when the DAC is producing a 2.5 volt signal, and the other, when it is producing nothing. From the graph it appears that the noise floor is the same in both measurements, backing what he says.

I wanted to replicate his measurements so that I could test other DACs to see how well they do. As I note above in red, this is made difficult by lack of documentation in the above measurements. The noise floor that you see is the result of both DAC noise and how much FFT has reduced it (called "FFT Gain"). I can make that noise floor as low as I want as long as I keep increasing the number of FFT points. As a result, the comments Rob makes about how low the noise floor is, i.e. -180 dB, is useless. That is NOT the actual noise floor of the DAC. So that claim is wrong although in the context of this comparison, it can be ignored. That is, both the no signal and 2.5 signal measurement are subject to the same FFT gain.

For some odd reason, the output voltage is picked to be 2.5 volt for a DAC that can go up to 6 volts. I suspect this may have been picked because it shows least distortion. So on that front, the claim of low distortion is also misleading especially since 0 dB is NOT set to 2.5 volt. Instead, it is set to 6 volt. In reality then, distortion is NOT -150 dB but something close to -142 dB. But again, in the context of comparing noise floors, we can ignore this.

Noise Modulation Comparison
I took the above graph and applied it to measurements of Topping DX7 Pro+. I played with the FFT samples and measurement bandwidth until I got something similar to DAVE DAC. Something still bothered me though. The measurements I performed of the DAVE DAC did not produce such a clean output. So I stepped back and ran the test against DAVE DAC which I happen to still have (owner is on long vacation). Here are the results for DAVE:
View attachment 229009

We see very different results. Distortion products are much higher (in relative terms) and so is the noise floor. What is more, there is noise modulation although in reverse. Noise floor actually goes up instead of down with no signal! Strange. To measure how much it is changing, I first compensated for FFT gain of 48 dB and then smoothed the two graphs:
View attachment 229010

Smoothing screws up the 1 kHz tone so ignore that as all we care about is the noise floor differential which is 2.8 dB. It is changing from -114 dB to -111 dB. This is barely above best case threshold of hearing. So in an extreme case of 1 kHz tone NOT being audible, and with suitable amount of amplification, one may be able to hear that modulation.

Now let's run the exact same test but simply moving cables from DAVE DAC to Topping DX7 Pro+:
View attachment 229014

We immediately see confirmation of my reviews of both products: Topping DX7 Pro+ despite costing 20 times less, has much lower noise floor. It seems to have more distortion spikes but that is because the noise floor is so low, allowing them to peak through. In absolute levels, it is still superior to DAVE DAC by 6 dB.

It does show noise floor modulation and this time, as expected noise floor goes up with signal. Smoothing and compensating for FFT gain we get:

View attachment 229016

The average noise modulation is 4.2 dB which is just slightly more than DAVE DAC. However, in this case, the modulation is occurring at -130 dB to -127 dB. With threshold of hearing at -115 dB, no way this is remotely audible no matter what contrived test we create for it. It is a completely non-issue and the reason I don't measure it.

Note: these tests are pushing limits of physics and instrumentation. Distortion measurements at -150 dB and lower is just crazy! It is unknown how accurate the AP is in this regard. Ditto for its own noise floor/modulation. When I first started to test the DAVE dac it had small train of pulses which disappeared after warming up. So some variation is to be expected in such tests.

Conclusions
This investigation of noise modulation shows that not only does the DAVE DAC perform worse than shown, but it also suffers from some noise modulation. While this noise modulation is slightly (0.5 dB) less than Topping DX7 Pro+, it happens at the threshold of hearing which may make it audible in pathological situations. Topping DX7 Pro+'s noise floor and modulation thereof is so far below audible threshold that it simply is not an audible concern in any contrived situation.

Maybe company's claim that it is the best there is was due to understanding of DAC performance years back (Rob Watts' post is from 2015 although renewed in 2021). This is certainly not true today where a $699 Topping DX7 Pro+ easily outperforms the DAVE DAC on both distortion and noise performance.

Company needs to provide comparative measurements to other current DACs before continuing to make such objective performance claims. And certainly not push points that are not the strength of its DAC, i.e. noise performance.

Bottom line, noise modulation is not a performance metric to worry about in well implemented DACs.

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

It was bound to happen: the panthers have unionized and now demanding raises through collective bargaining. They are threatening a walk-out leaving me with no panthers for product reviews. In other words, they have me by the neck. So, please donate generously to keep them modeling for us using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/

I would love it if Topping made an electrostatic energizer. I currently have the Stax SR 009 earspeakers driven by the Stax SRM 323S energizer, connected with standard USB cables to the Topping D90SE DAC.

 

[lc6]

Jeez didn't know that!. Still don't - I blame my old maths teacher for not taking enough time with me because I was, and still am, a bit thick in the numbers department

Goldenboy and others routinely show graphs of sine-like signals that have positive and negative values and are being sampled. So it follows that the sign and magnitude of these signal values is somehow encoded in the samples. In theory, there are multiple ways to do it. For example, as in Goldenboy's theory, you could have the lowest negative value (i.e. negative digital full scale, or DFS) encoded as all 16 bits of zero, no signal as 15 LSBs of zero and MSB of one, and the highest positive value (i.e. positive DFS) as all 16 bits of one. But that would complicate math. Consider an addition of two signals, e.g. when mixing audio sources. Adding two no-signal samples (i.e. each with 15 LSBs of zero and MSB of one) would result in all zeros (since the addition of two MSBs of one results in an MSB of zero plus the 17th carry bit of one that is discarded) , which equals the negative DFS. The two's complement avoids this problem and has only one natural representation of no signal, i.e. all 16 bits of zero.

 

[AaronJ]

The repeated purposeful misspelling of Golden Sound (aka Cameron) as Goldenboy by multiple posters is very childish and distracts from the good conversation.

 

[the_brunx]

The repeated purposeful misspelling of Golden Sound (aka Cameron) as Goldenboy by multiple posters is very childish and distracts from the good conversation.

Is it not GoldenOne?

 

[Arnas]

Goldenboy has been repeatedly asked to comment on whether the Dave is objectively better sounding than the topping and he has avoided all such questions like the plague. It’s fun to watch. He won’t tell people the truth in front of Rob, and he also can’t lie because he knows we are watching. Lol quite entertaining this guy.
Edit, he finally did, unfortunately unproven answer.

He have no choice though... He wants to be in ''snob club'' thus he have to say more expensive is better! How can you be elitist with a dac that dont cost atleast 6k?
They have this expensive is better! Bias and they cant see it how it is.

 

[Jimbob54]

The repeated purposeful misspelling of Golden Sound (aka Cameron) as Goldenboy by multiple posters is very childish and distracts from the good conversation.

Can we call him Goldenballs instead?

 

[the_brunx]

With all his Golden names, This must be similar to how one would imagine he looks like in real life:

 

[dartinbout]

Is it not GoldenOne?

Is it not GoldenOne?

May I suggest Golden Cow? After enduring many of his reviews, his pontificating tone has earned him these sobriquets.