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Computer ‘transports’ can they make a difference?

I found him to be very dogmatic in the past, and I find him somewhat less so now!

I've never paid much attention to his summaries but I really appreciate the measurements (bit like Stereophile).
 
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narabdela said:
Sensible stuff, but I'm sure the naysayers will disagree, as per usual.
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Yes - there's some well-produced evidence to add to the library.

When I was building my own audio kit for a short while in the early 1980s it was after hours in a very well equipped lab full of seriously expensive measuring kit. Nowadays much better than that can be achieved with some very inexpensive home equipment.

And yes, I do expect to see uninformed howls of derision from those who don't understand, or who don't want to understand, what the evidence is saying.
 
Purité Audio said:
Archimago strikes again,
http://archimago.blogspot.com/2018/12/measurements-intel-i7-pc-and-raspberry.html#more
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One of the things about these sorts of article is that you have to interpret the results carefully for what they do say and what they don't say.

The USB/DAC measurements I have seen, [1] to [4] below, all measure two systems at once: A USB source plus a DAC. You can say little from the results about either system individually.

[1] For the quoted URL above, what you can say is that for the two USB sources and one DAC, the audio output of all combinations looks to be clear enough of noise across the audio band (to 48 kHz, and one plot to 192 kHz). That could be because (i) the USB sources are very quiet; or (ii) the DAC rejects USB noise very well; or (iii) both of these. You would hope especially for (ii). There are measurements of USB PSU noise in the audio band (https://archimago.blogspot.com/2018/05/measurements-computer-usb-5v-power.html) suggesting (i) is generally not achieved, so (ii) must be true, but you can't say for sure.

[2] For more measurements of one DAC (a Benchmark DAC1) from four SBCs (Single Board Computers) and a laptop see: https://www.audiosciencereview.com/...ic-servers-end-points-are-they-any-good.5707/. All combinations are very clean and noise free except for one case where the author claims there is a ground loop. Even there the noise levels are very low and almost certainly inaudible but the result could be better investigated. There's a great summary:
‘Essentially no significant difference. Well designed DACs should not have a major issue with using SBCs, they work very well. Of course I cannot comment whether any particular DAC you might have will suffer problems, but I very much see this as a DAC design issue and NOT a "noisy computer USB" issue. DAC should be expected to work without issue with a huge variety of USB sources.’​

[3] For further measurements of one laptop (EDIT: it's a laptop, not a SBC as I originally wrote) and several DACs see: https://www.audiosciencereview.com/...battle-of-s-pdif-vs-usb-which-is-better.1943/. The conclusions are:
‘As seen from pure measurement point of view, there was no case where USB was worst than S/PDIF. Indeed the reverse was true in that S/PDIF was noisier in some DACs. So the default assumption that somehow S/PDIF has some advantage over USB is simply false.’ ​

[4] There is one DAC that seems to be too sensitive to USB cables when used with a specified source (Sonore microRendu) but the noise levels are very low: https://www.audiosciencereview.com/...s/do-usb-audio-cables-make-a-difference.1887/. In this case blaming the DAC is most likely to be correct but the effect is almost certainly inaudible.

The number of excellent measurements available certainly rejects the hypothesis that USB is a necessarily noisy interface to a DAC. While not fully proving the key point that DACs reject USB noise to the point of inaudibility the preponderance of evidence is beginning to suggest this conclusion.
 
It's the new thing though, usb filters and linear 5v supplies for she's. It's a huge industry and I've never seen a single measurement showing improved signal fidelity from one of these products. 5 years ago usb was pushed as perfect, now it's sold as barely good enough for audio as the dealers and mags see another product category opening up to fleece us all.
 
The BM DAC2 clearly measures better in the TOSLINK test than in the USB test here: https://www.stereophile.com/content/benchmark-dac2-hgc-da-processorheadphone-amplifier-measurements. More so for the DAC1 here: https://kenrockwell.com/audio/benchmark/dac1-hdr.htm#meas. I advise Benchmark owners (I'm one of them) to use TOSLINK.

But I agree it's a good bet in general that galvanically isolated async USB should measure best, in the absence of specific information.

I'm happy we're now discussing what the differences are and whether they are audible, and not having to bat away people telling us it's impossible for differences to occur.
 
sq225917 said:
It's the new thing though, usb filters and linear 5v supplies for she's. It's a huge industry and I've never seen a single measurement showing improved signal fidelity from one of these products. 5 years ago usb was pushed as perfect, now it's sold as barely good enough for audio as the dealers and mags see another product category opening up to fleece us all.
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Put a USB to TOSLINK converter in between a source and a Benchmark DAC, and you have a measurable improvement ...

So not impossible at all for these things to have a measurable impact. Linkwitz made some comments about the afi+USB device here http://www.linkwitzlab.com/LX521/Supplies.htm.

But till now I believe in general simply a DAC with good jitter rejection and a galvanically isolated input of some description should do well enough, no need for fancy boxes.
 
So if I understand correctly a cheapie RPi digital streamer is as good as any full-blown (aka mega expensive) digital streamer?

Sounds good to me.......I run five of the little darlings :)!
 
suzywong said:
So if I understand correctly a cheapie RPi digital streamer is as good as any full-blown (aka mega expensive) digital streamer?

Sounds good to me.......I run five of the little darlings :)!
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IME yes regarding audio quality. I bought just the one of the critters to experiment with and it sounds perfectly good to me.

I subscribe to the principles that the DAC is the right place to ensure (i) a low enough jitter clock for the converter; and (ii) adequate rejection of any noise on its inputs. If the transport does not change bits (e.g. via digital volume control or sample rate conversion) then it's really a case of "bits is bits" and we need to re-habilitate this derided phrase. And IME bit errors simply do not occur at any appreciable level.

I have acquired a small (still growing) collection of measurements on DACS for the above principles. There are some DACs out there that do show imperfect handling of these issues but almost always the measured imperfections are very low level and likely to be inaudible. But there are also some superb performers out there.

So choose a DAC with sufficient care and my view is that the key things about the transport become the user interface (e.g. library tagging and handling) and the facilities provided (e.g. streaming service integration). Those may be what you might want to pay good money for.
 
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