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Measurement of R2R DAC

andreasmaaan

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The (one) problem with no output filter is that images are now large, adding ultrasonic energy that was not present in the original signal and that you likely do not want to send to your tweeters now. See e.g. https://audiosciencereview.com/forum/index.php?threads/digital-audio-jitter-fundamentals.1922/ for a brief explanation. These images also stress the output buffers and input stages of the rest of the components in the chain, adding distortion and such. I would not want a DAC with no imaging (low-pass) filter at the output. - Don
Would you expect DS DACs to exhibit or be susceptible to transient issues in the passband @DonH56? Or did I understand you correctly that these issues are restricted to the transition band and are a result of the imaging filter?
 

DonH56

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Depends on the filter design, for delta-sigma or conventional converters. And do not overblow "transient issues"; the sort of pulse integrity a radar system needs is not the same as an audio system, particularly for signal at the limit of audibility (or beyond in my case, since my hearing chops off somewhere between 10 and 12 kHz these days). And all those nasty little ringy-looking signals are (a) much higher than the audio band, (b) only present with pretty unrealistic inputs, and (c) completely buried in a real-world signal.

A 1 kHz square wave with fast edges can show (in)stability issues but I would be more concerned with a power amp than a line-level component. And that would generally manifest as peaking in the frequency domain or bumps in the noise floor.

If you are really worried, go change your power cord. :D

IMO! - Don
 

AntonK

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andreasmaaan

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I can see that measurements and blind tests rule on this forum. I like the measurements part a lot, but imo double blind tests are overrated (in audio at least).
I also stumbled upon this article:
https://www.quora.com/Why-do-so-many-audiophiles-reject-blind-testing-of-audio-components
Perhaps the way our brain works when it comes to listening indeed rules out blind tests as a reliable way of getting to audio nirvana? All imho.
The author of the article is confusing blind tests with ABX tests.

The article and the links in it have nothing to do with blind testing, but the writer seems not to understand that blind testing and ABX testing are completely different things

In fact, there is no doubt whatsoever that blind tests (preferably double blind) are not just "better", but are absolutely essential if we want to remove subjects' (possibly unconscious) biases and other confounding variables from the test. This is simply a necessary precondition for any test to have the capacity to yield any valid result whatsoever.

ABX tests on the other hand are a specific type of (of course blind) test in which subjects listen to A, then B, then X (A or B). If subjects are able to reliably determine whether X is A or B, we can conclude that subjects are capable of discerning a difference between A and B. If subjects are unable to reliably do this, we reach the more cautious conclusion that the difference did not seem to be discernible under the test conditions, and that this may indicate an absolute inability to discern the difference (or not).

ABX tests have been criticised for various reasons, and the studies the the author links are among those critical. However, the conclusions the author attributes to those studies are just not there. He hasn't read the studies properly or hasn't understood them.

There are more sophisticated types of blind test than the ABX test, some of which seek to address potential issues with ABX testing.

But it's not even up for debate whether these types of tests should be done blind.
 

March Audio

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I can see that measurements and blind tests rule on this forum. I like the measurements part a lot, but imo double blind tests are overrated (in audio at least).
I also stumbled upon this article:
https://www.quora.com/Why-do-so-many-audiophiles-reject-blind-testing-of-audio-components
Perhaps the way our brain works when it comes to listening indeed rules out blind tests as a reliable way of getting to audio nirvana? All imho.
Audiophiles don't like blind tests because they don't deliver the results they want and tend to invalidate their dogma.
 

March Audio

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Thanks, this clarifies things greatly. I'm of the view that ultrasonic anything (including ringing) is - by definition - inaudible (until proven otherwise). So I'll keep my poison in the ultrasonic time domain rather than the sonic frequency domain.

My main concern here was that perhaps it was being suggested that DS DACs had some inherent disadvantage when it came to transient response in the audible range... But it seems that wasn't what was being said :)
Directly audible no, but There is a possibility that ultrasonic garbage can intermodulate and end up in the audio band. Single sample transient filter response tests don't make sense to me as by definition they are illegal signals. Anything above 1/2 FS should be adequately filtered at the ADC.
 

andreasmaaan

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Directly audible no, but There is a possibility that ultrasonic garbage can intermodulate and end up in the audio band.
Yes definitely in theory at least. But with any decent modern DAC having IM distortion far below audible thresholds and orders of magnitude below that of any transducer, I can't see how this could be a problem in the real world. I'm certainly no expert on digital though - what do you think?
 
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DonH56

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ABX is used so the listener cannot tell what X is. The test could be "sighted" (with the caveat you still don;t know X), blind, or double-blind. Since the listener (and/or one running the test if someone else and using one of the classic ABX boxes) cannot know X it is close enough for me.

I miss Arny... :(
 

gvl

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After some hunting I picked a Denon DVD-5000, it is a vintage CD/DVD player but it has SPDIF inputs so can be used as a DAC. A 40lbs beast with 4xPCM1704 running in differential mode fed by Denon proprietary DSP. Sounds very good to my ears, like goosebumps good, would be interesting to see how it performs technically. Shipping both ways would probably be about the cost of the unit itself, so not worth it. Just putting it on the Amir's radar screen in case one pops up locally, ones with a broken CD transport yet usable as a DAC can be had almost for a song.
 

Sal1950

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After some hunting I picked a Denon DVD-5000, it is a vintage CD/DVD player but it has SPDIF inputs so can be used as a DAC. A 40lbs beast with 4xPCM1704 running in differential mode fed by Denon proprietary DSP. Sounds very good to my ears, like goosebumps good, would be interesting to see how it performs technically. Shipping both ways would probably be about the cost of the unit itself, so not worth it. Just putting it on the Amir's radar screen in case one pops up locally, ones with a broken CD transport yet usable as a DAC can be had almost for a song.
Well thought of due to the B-B PCM 1704 DACs used
If it does fail you can always move it the the exercise room to use for weight training. ;)
 

gvl

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Well thought of due to the B-B PCM 1704 DACs used
If it does fail you can always move it the the exercise room to use for weight training. ;)
Definitely, just need to think of a way to attach a couple of handles securely when the time comes ;)
 

Veri

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watchnerd

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Veri

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Is it still R2R if there is a DSP board?
Well I was confused too, in superbestaudiofriends measurements there is proper digital filter without imaging.
I guess it is upsampled R2R, definitely not NOS. It's still a ladder DAC, just not bitperfect with the DSP ;)
 
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