DAC Noise Modulation: Chord DAVE vs Topping DX7 Pro+

[Lukino]

Of course money. That would be very naive to believe any engineering development is nor about money.

Yes. For me personally, at this time, I already believe in the teamwork and true engineering achievements of AKM, ESS.

 

[PeteL]

Yes. For me personally, at this time, I already believe in the teamwork and true engineering achievements of AKM, ESS.

That’s true, but they only work on improving a tiny little every year, working on very specific scope, with large teams of very vertical expertise. That’s obviously differnt thaan making a DAC from scratch

 

[Sokel]

Yes. For me personally, at this time, I already believe in the teamwork and true engineering achievements of AKM, ESS.

Not that even them avoid claims that refer to audiophoolery.Marketing is unavoidable.

 

[pma]

There will always be certain degree of noise modulation measurable, even with good DACs and ADCs. It is all about the test signal used. Below is the FM modulated tests signal and response of the Topping D10s/E1DA Cosmos ADC combo.

 

[IVX]

with ES9038Q2M which utilizes the same modulator as ES9038Pro, I see the same 3db(maybe less, like 2db?) of the noise modulation 0dbfs vs -140dbfs of input data.
BTW, you'll be surprised how high that modulation reaches in Cirrus Logic inexpensive tiny DACs such as CS43131/198. 0dbfs/-30dbfs makes 10db of the noise floor level difference. I heard the opinion that these DACs have some kind of cheating to deceive AES17 DR test, and they switch the gain dynamically. In other words, DACs are not really -130db(A) but rather -120db(A)+trick.
PS: the result was obtained with no rescaling, hence, 2db is ADC+DAC noise modulation together, and a single ES9038 has nearly no noise modulation at all(as well as ES9822)

 

[Ken Tajalli]

It doesn't matter how old the product is. Technical claims are made that it is the best in the world as late as last year. That simply is not true. You are not the PR person for them to then make arguments about how old it is, etc. Think of being on the side of the consumer, not companies when it comes to such things.

I am posting with a big smile on my face!
I really didn't want to, since it appears you are so passionate about the subject/man and irrigated by my posts elsewhere.
No I am not their PR person, just marvelling at the technology, not just theirs, anybody's.
But on a humerus point (it has been tickling me all night, so here it comes . . )
Do you think I give two ticks about those consumers (and their wallets) who are in a $14K DAC market??
Or they give two ticks about what I say on a forum??
I have said it jokingly to RW, on our sister site! That he should make a Dave2, a four box option, with atomic oven clock outbox, dedicated outbox powersupply and a 2mScaler, all in matching cases and demand $40K!
Why not, others are doing it.

The free delivery option is killing me
V V V

 

[Blumlein 88]

I am posting with a big smile on my face!
I really didn't want to, since it appears you are so passionate about the subject/man and irrigated by my posts elsewhere.
No I am not their PR person, just marvelling at the technology, not just theirs, anybody's.
But on a humerus point (it has been tickling me all night, so here it comes . . )
Do you think I give two ticks about those consumers (and their wallets) who are in a $14K DAC market??
Or they give two ticks about what I say on a forum??
I have said it jokingly to RW, on our sister site! That he should make a Dave2, a four box option, with atomic oven clock outbox, dedicated outbox powersupply and a 2mScaler, all in matching cases and demand $40K!
Why not, others are doing it.

The free delivery option is killing me
V V V
View attachment 229462

I don't think anyone expected to post the results and suddenly Chord has to go out of business or alter their pricing structure. I don't think many now in the market for the Chord care nor those at the other end of the pricing scale. What matters is the truth as best it can be determined and getting the word out. It does make a difference. It does alter things in the future. It does lay bare the various marketing spiels that go beyond marketing and into psycho-babble to be used against the consumer. Slowly some people who considered something like the Chord won't be baffled by the magic story. The idea there is not much behind such product stories will seep into the general consciousness. The idea you can get equivalent performance for a fraction will take hold in some places where without the data nothing could cause any other consideration. Such ideas already have changed things.

“Most people overestimate what they can achieve in a year and underestimate what they can achieve in ten years.”

 

[Thomas savage]

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/

Rob , do you want to come work with me , I will teach you a skill that's needed..

And don't worry is very possible I earn more than you but honestly .

Win win

 

[Thomas savage]

Most folks want better sound just put a extra layer of carpet down in front of listening position.

Job done .

 

[DonR]

It would be an interesting experiment to swap the internals of the Chord with the Topping and see if anyone notices.

 

[fpitas]

In my book, great engineering is being great at solving a real problem, and being able to concretize it.

Always for a price, though. An engineer is a guy that can do something for a dollar than any fool could do for 10.

 

[Ken Tajalli]

Always for a price, though. An engineer is a guy that can do something for a dollar than any fool could do for 10.

If the technology was picked up by uses that required mass production, the priced would have eventually dropped to few dollars.
But it didn't.
So selling just tens of units a year, means much higher production cost, though still not that much!
They can sell the Mojo family in enough numbers to justify its much lower price, but not TT2 or Dave.
Still, in UK a used Dave's value, after say five years, still is in 60 percent of the new.
Not a bad investment.

 

[Trell]

If the technology was picked up by uses that required mass production, the priced would have eventually dropped to few dollars.
But it didn't.
So selling just tens of units a year, means much higher production cost, though still not that much!
They can sell the Mojo family in enough numbers to justify its much lower price, but not TT2 or Dave.
Still, in UK a used Dave's value, after say five years, still is in 60 percent of the new.
Not a bad investment.

I don't think "Not a bad investment" means what you think it means.

A pet-peeve of mine of people calling consumption for "investment" when it clearly isn't.

 

[Ornette]

I don't think "Not a bad investment" means what you think it means.

A pet-peeve of mine of people calling consumption for "investment" when it clearly isn't.

in·vest·ment
/inˈves(t)mənt/
noun

a thing that is worth buying because it may be profitable or useful in the future

(emphasis mine)

 

[Trell]

in·vest·ment
/inˈves(t)mənt/
noun

a thing that is worth buying because it may be profitable or useful in the future

(emphasis mine)

There are many ways to rationalize consumption as an "investment". Perhaps in the weekend I should go to a nice restaurant to "invest" in a nice meal and a couple of glasses of wine. That would be "useful" for me, I'm sure. There are nice pubs around here so I could "invest" in some excellent beer.

 

[Ornette]

There are many ways to rationalize consumption as an "investment". Perhaps in the weekend I should go to a nice restaurant to "invest" in a nice meal and a couple of glasses of wine. That would be "useful" for me, I'm sure. There are nice pubs around here so I could "invest" in some excellent beer.

It's typically used in reference to durable goods. For example, "Due to concerns with Covid exposure, he invested in a home theater setup." You may disagree with accepted English usage, but that doesn't make it incorrect.

 

[fpitas]

There are many ways to rationalize consumption as an "investment". Perhaps in the weekend I should go to a nice restaurant to "invest" in a nice meal and a couple of glasses of wine. That would be "useful" for me, I'm sure. There are nice pubs around here so I could "invest" in some excellent beer.

Yet, if you went to the more expensive pub with the inferior beer, we might think you're a bit daft.

 

[Trell]

Yet, if you went to the more expensive pub with the inferior beer, we might think you're a bit daft.

Hmh, perhaps a double blind beer tasting event should be in order then?

 

[Trell]

It's typically used in reference to durable goods. For example, "Due to concerns with Covid exposure, he invested in a home theater setup." You may disagree with accepted English usage, but that doesn't make it incorrect.

You wrote "a thing [investment] that is worth buying because it may be profitable or useful in the future" is pretty much useless (pun intended) because just about anything you buy is useful to some extent: What is not an investment then? Is shopping for groceries an "investment"? That is surely "useful" as that would help keep me alive.

So, if you want to splurge on audio just call it what it is and enjoy it as consumption. I do for personal use, but if I where to say own a recording studio I could say the outlay was an investment (at least part of it).

 

[Ken Tajalli]

I don't think "Not a bad investment" means what you think it means.

A pet-peeve of mine of people calling consumption for "investment" when it clearly isn't.

It applies to cars, don't it?