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Do I need clean USB power when using DAC with its own power supply?


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44 minutes ago, kumakuma said:

 

I have never had this experience. I wonder if anyone other than Frank has.

 

In fact, I'm curious what people's experiences are, in general ... I doubt I am the only person who has heard a particular recording sound pleasant on one rig, and quite unpleasant on another - if both setups are supposedly somewhat "accurate", why is this?

 

Troubleshooting system issues is all about reacting to this variance - for years, the now and again visits to the local audio friend have been sessions of tracking what ails the setup, at the time ... strangely, people with TTs have known that SQ changes with adjusting things - but, ahh, that's mechanical; in the magic land of electronics, the special qualities of such items guarantees uniformity of behaviour, no matter what ... 🙃.

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2 hours ago, Archimago said:

I haven't looked at the objective forum thread but all these years of testing and reading comments by people that say a linear power supply makes a difference (or silly USB filters like the JitterBug), I'm left scratching my head.

 

There's  no need for head scratching, its well established in the EE world that switching supplies are common-mode noise aggressors.

 

https://www.eetimes.com/power-tip-47-tame-conducted-common-mode-emissions-in-isolated-switchers-part-1/#

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5 hours ago, Archimago said:

 

I agree @botrytis.

 

I haven't looked at the objective forum thread but all these years of testing and reading comments by people that say a linear power supply makes a difference (or silly USB filters like the JitterBug), I'm left scratching my head.

 

Yes, one should try to keep one's DAC away from a noisy computer to reduce interference especially from busy CPU/GPUs. Yes, USB ports can be noisy. Indeed, we can use battery power to reduce noise.

 

But in the big scheme of things, the differences are really tiny unless one does something silly like put the DAC right on top of the computer case running at 100% load!

 

This week, I published some tests of the Topping D10s which is just a USB DAC with no power supply of its own. I measured it connected to the Raspberry Pi 3 B+ which @audiobomber claims is "very dirty" (which it might well be, who knows), yet the noise floor and resolution including multitone intermodulation testing doesn't show anything unusual/noisy. Likewise, I don't hear any issues - dead quiet when I connected it to my main system in the basement with low ambient noise and great playback resolution.

 

Bottom line is that I see a lot of words by people who complain about noise, yet in all these years, where's the evidence? For those who have "issues" with switch mode power supplies, what exactly are you hearing? Is this something you've measured?

 

Remember years ago Benchmark released their video of linear vs. switching power supply showing that there are times when the switching supply is in fact better. Take heed audiophiles because I think there's just too much nonsense out there with many people talking generalizations that are simply unsubstantiated.

 

I don't have a Jitterbug, but I have the somewhat similar iPurifier2, and it is beneficial with some DAC's. A common setup I've used is the iPurifier to clean the USB signal and the iPower with dual head USB cable to provide a cleaner 5V supply. This has made a significant improvement with several inexpensive DAC's. However the iPurifier2 degraded the sound when used downstream of an sMS-200.

 

The linear power supplies I own all beat the basic iFi iPower SMPS. I have never heard any effect from proximity to the laptop, and I cannot hear any difference in the sound of a DAC whether the laptop is running on battery power, or the SMPS. I also did not notice any difference when I used an iPower on a Raspberry instead of the freebie wall wart. 
 

Digital noise and jitter do not cause hiss or hum, nor do they show up in SNR or frequency response graphs. They show up as high frequency blur and constricted soundstage, and affect PRaT. I bought and returned a Topping D50S, which has damn near perfect measurements. It was the worst DAC I've ever used, worse than cheap dongle DAC's, because it sucked the life out of the music. 

 

I have never claimed that LPS is superior to SMPS. It depends on the implementation. My listening tests with the new iPower X show it to be equal to a similarly priced Zero-Zone LPS, and to the Welborne Labs PS-REG I use on my sMS-200. I've heard a couple of manufacturers say that SMPS is better than LPS for some digital gear. I found this myself when I tried an LPS on my TP-Link switch. It actually degraded the sound of my system. The iPower X was an improvement over the stock wall wart, and the LPS. 

 

People should listen for themselves and decide what works for them. I like to see measurements of audio gear, but unfortunately static measurements of digital gear do not correlate with sound quality.  

Main System: QNAP TS-451+ NAS > Silent Angel Bonn N8 > Sonore opticalModule Deluxe v2 > Corning SMF with Finisar FTLF1318P3BTL SFPs > Uptone EtherREGEN > exaSound PlayPoint and e32 Mk-II DAC > Meitner MTR-101 Plus monoblocks > Bamberg S5-MTM sealed standmount speakers. 

Crown XLi 1500 powering  AV123 Rocket UFW10 stereo subwoofers

Upgraded power on all switches, renderer and DAC. 

 

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3 hours ago, fas42 said:

 

In fact, I'm curious what people's experiences are, in general ... I doubt I am the only person who has heard a particular recording sound pleasant on one rig, and quite unpleasant on another - if both setups are supposedly somewhat "accurate", why is this?

 

 

Is that what you meant?

 

It sounded like you were talking about the same recording on the same "rig" sometimes sounding good and sometimes sounding bad.

Sometimes it's like someone took a knife, baby
Edgy and dull and cut a six inch valley
Through the middle of my skull

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10 minutes ago, Archimago said:

 

How do you know that these are issues affecting modern USB DACs?

 

 

Since its not an issue of the DAC, rather the power supply, it affects not just USB DACs and not just 'modern' DACs. S/PDIF fed DACs can have common-mode noise susceptibility too.

 

12 minutes ago, Archimago said:

Engineers who make DACs these days are also aware of potential noise so will address them in the designs whether common mode or otherwise. So unless we can demonstrate an issue with the DAC output using the stock power supply that came with the device, no need being concerned, right?

 

 

Do you have evidence of engineers awareness of potential noise issues? I think Schiit engineers may be aware (that's just a guess though) but are engineers in general? No, it isn't just about 'the DAC output' because typically that gets measured normal-mode.

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18 minutes ago, Archimago said:

 

Sure, but the audio signal is characterized by the electrical output from the DAC to your amplifier. What do you think is wrong with the output signal to suggest power supply related issues are present (whether it's USB or S/PDIF)? Do you have a specific example of this issue?

 

That is the usual way of defining the audio signal I agree. But amps interconnected with DACs via single-ended cabling don't have very good common-mode rejection (CMR) in many cases. Nothing need be wrong with the output signal when common-mode noise resides on both conductors (which is the very definition of common-mode) yet the amp typically gets influenced by it and it doesn't benefit the SQ. An AP won't see CM noise because its designed to have very good CMR. No I don't have an example to share right now, but I'll keep my eyes peeled. 

 

26 minutes ago, Archimago said:

Well, over the years I have spoken to a few DAC "audiophile industry" designers. People you would know if I named them but that's not really relevant here since I don't think they generally want to participate on consumer forums ;-). And I have seen some of the internal testing documents (that cannot be released of course). Let's just say that noise level testing is a very important parameter for everyone and it's done on multiple levels from the power supply output noise to of course balanced and unbalanced outputs.

 

If there is a noise issue that can be addressed, I cannot imagine that they would not fix it. (To be clear, the DACs these guys I've spoken to make are not cheap!)

 

So when I hear that aftermarket companies are making power supplies or noise filters that somehow improve performance, I'd certainly like to see what the deficiencies are and then how the products have fixed the issues.

 

I recall from reading his posts here and on AudioCircle that Charlie Hansen (Ayre) was aware of the CM noise issue. Which is presumably why he went to the lengths he did to introduce isolation between source and DAC. But he said even that didn't render his DACs completely immune to source noise.

 

'Nose level testing' does not sound to me like the same thing as CMR. I'd be very interested if you had evidence of companies doing measurements of CMR on their single-ended inputs. Its quite common on balanced inputs but then the test signal is only applied to the signal conductors (pins 2 and 3 on an XLR) and not between pin1 and mains earth. Not every manufacturer I've opened boxes of is aware of 'the pin1 problem' but I do admit awareness of it is gradually seeping out. Bruno's doing a sterling job in that regard I think.

 

As regards the aftermarket offerings - you and me both.

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9 hours ago, Archimago said:

Engineers who make DACs these days are also aware of potential noise so will address them in the designs whether common mode or otherwise. So unless we can demonstrate an issue with the DAC output using the stock power supply that came with the device, no need being concerned, right?

 

You are very naive in thinking that engineers successfully adress these issues. I don't know who you have been talking to, but there are plenty of manufacturers who will admit that DACs remain sensitive to noise and very few who claim to have successfully addressed this. 

 

Your logic demonstrates a fundamental misunderstanding of these issues. 

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4 hours ago, hopkins said:

When it comes to PRaT, and most other attributes, it is simply a consequence of accuracy (what else could it be?). 

I read some, but it's just another anti-audiophile diatribe. Salvatore has been a troll for decades.

 

If I were looking for a measurement to correlate with PRaT, the first place I would look is transient performance. How closely does the DUT follow transient swings, i.e. attack sustain decay release? 

Main System: QNAP TS-451+ NAS > Silent Angel Bonn N8 > Sonore opticalModule Deluxe v2 > Corning SMF with Finisar FTLF1318P3BTL SFPs > Uptone EtherREGEN > exaSound PlayPoint and e32 Mk-II DAC > Meitner MTR-101 Plus monoblocks > Bamberg S5-MTM sealed standmount speakers. 

Crown XLi 1500 powering  AV123 Rocket UFW10 stereo subwoofers

Upgraded power on all switches, renderer and DAC. 

 

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1 hour ago, audiobomber said:

I read some, but it's just another anti-audiophile diatribe. Salvatore has been a troll for decades.

 

If I were looking for a measurement to correlate with PRaT, the first place I would look is transient performance. How closely does the DUT follow transient swings, i.e. attack sustain decay release? 

 

 

An anti-audiophile diatribe coming from an audiophile? Your non-sensical explanation that follows makes you sound more like a troll than anyone else. Transient response, attack sustain decay release are meaningless concepts in digital audio - these are just terms you  use to  express the impressions you get when a track is accurately reproduced and gives you a sense of PRaT.

 

In digital audio, things are very simple: either a recording is accurately reproduced by a DAC or it isn't. If it is, then everything else,  including PRaT, soundstage, ect.. follows. 

 

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17 hours ago, kumakuma said:

 

Is that what you meant?

 

It sounded like you were talking about the same recording on the same "rig" sometimes sounding good and sometimes sounding bad.

 

The same system can sound different, just as much as different rigs typically sound different from each other - understanding why it occurs for a single setup, where none of the basics are altered, is how to improve understanding of what matters.

 

16 hours ago, Archimago said:

 

Unless you test this somehow, how do you know if the "supposed" accuracy is indeed the case?

 

Trouble is, accuracy is a complex thing, when talking of the hearing sense - the normal objective stuff is trivially easy, if you have the right measuring gear; but most agree it gives little idea of what it's like to live with ...

 

16 hours ago, Archimago said:

Besides, when it comes to "setups", usually we're dealing with variations in speakers, rooms, maybe amps. Much less likely that small fluctuations in the USB DAC (noise or other distortion) are the main issues.

 

No. The closer the system is to achieving high transparency to the recording, the less important are speakers, room, etc; and the more important is the absence of noise and similar issues - the crossover to convincing illusion status only occurs when the latter is sufficiently sorted.

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16 hours ago, Archimago said:

Besides, when it comes to "setups", usually we're dealing with variations in speakers, rooms, maybe amps. Much less likely that small fluctuations in the USB DAC (noise or other distortion) are the main issues

 

Why is it so much easier for people to accept that a high quality turntable can significantly improve a system over a bad turntable, but not accept that the quality of a DAC could not have the same impact? 

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23 minutes ago, hopkins said:

In digital audio, things are very simple: either a recording is accurately reproduced by a DAC or it isn't. If it is, then everything else,  including PRaT, soundstage, ect.. follows. 

 

 

Except, I would replace the word "DAC" with "system" - most setups fail to live to expectations because the overall chain is not accurate; for example, the DAC may be "perfect" in isolation, but its power supply current draw waveform is enough to disturb the accuracy of the amplifier - it is never enough to isolate the performance of a single component as being key; it's always going to be how well the combination of all parts functions.

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2 hours ago, audiobomber said:

I read some, but it's just another anti-audiophile diatribe. Salvatore has been a troll for decades.

 

If I were looking for a measurement to correlate with PRaT, the first place I would look is transient performance. How closely does the DUT follow transient swings, i.e. attack sustain decay release? 

Prat is just a made up term, it has no meaning.  

 

Just ask people to explain it and see how far you get.  If you take the actual meaning of the words then it makes little sense.

 

If someone is concerned about pace, rhythm and timing, don't ever play an LP record with its inherent speed fluctuations which are massive compared to digital audio.

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On 7/7/2021 at 9:20 AM, visigt said:

Can I simply block the "dirtu power"simply by blocking the power connection in the USB plug?

 

Whenever you have an electrical signal connecting  two equipment, noise can find a way from one to the other. The fact that the 5v wire is disconnected between your source and DAC does not effectively isolate the two (the data wires are also electrical signals...) . The best way to isolate the DAC from the source is to use an optical connection, but that introduces different problems.

 

If you want to follow the advice of those who believe that DAC engineers know how to deal with noise, then by all means don't bother with any of this and simply try to enjoy your system as is. 

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1 minute ago, kumakuma said:

 

Never had this problem and the flawed recordings that I own sound equally flawed on every system I've every heard them on.

 

Since day one, over 35 years ago, of having capable playback I have had the problem of recordings sounding acceptable, or unacceptable, depending upon the 'tune' of the system ... people listen to playback with different mindsets; unless one is in the same room with the other person, hearing what's going on, then communication on the matter is always going to be difficult.

 

As an example of a recording that was very much on the edge, I have a standard CD version of Carole King's Tapestry - I played that album of the order of a 100 times back then; because it immediately told me the status - when below par, it set my teeth on edge; it was, unpleasant. By contrast, current actives sail through this very same recording with ease ...

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