You're not entitled to your own facts: most DACs do use the 5V from USB and/or thereby share the computer's ground plane. It's very old news that DACs and DDCs depend on clean power for best performance - although, yes, they still work fed with any hideous switch-mode wall-wart junk.
Dual Conduit USB for audio: the future?
- Thread starter ItemAudio
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You're not entitled to your own facts: most DACs do use the 5V from USB and/or thereby share the computer's ground plane. It's very old news that DACs and DDCs depend on clean power for best performance - although, yes, they still work fed with any hideous switch-mode wall-wart junk.
adamdea
You are not a sound quality evaluation device
What exactly are you claiming that a mains powered dac does with the 5V line? I really can't see why you are determined to go into this digression when i was only making the obvious point that the cable on ebay had a completely different function which is to supply more power to devices which use it.
But if you do insist on going down this road I would be delighted to know what (beyond -in some cases-the detection of an upstream device) you are saying that a mains powered dac does with a 5v supply.
I have said that a dac doesn't use the 5v, but if I am wrong about that I would be delighted to know what use the dac has for the 5v, not to mention why my dac has an ac power cable hanging out of the back.
it seems possible that usb receiver chips in mains powered dacs can use the 5 volts from the usb connection. Although it seems quite likely that there is no connection between the earth in the receiver chip and that of the dac itself. Most dacs seem to use bits from various chips. There are some that use the dac in the usb receiver chip.
You raise a good point - if it was more widely known that USB transceivers and components of the async 'master clock' are actually powered directly by the computer, it would be more widely appreciated why controlling the delivery of that 5V rail is so important - and, for instance, why different computers sound so dissimilar.
But try cutting that supply and see if the DAC still works: some do; some don't. Some have quite efficient filtering or regeneration of that incoming 5V; some attempt 'galvanic isolation'; some don't at all. Some well regarded DACs like the Calyx are by default entirely USB-powered. As I always say, the DAC writes the rule book for the transport - including the digital cable. But those that generate a special 5V DC rail specifically for the USB interface are rare: it's much easier not to.
sq225917
Bit of this, bit of that
the reason it's not widely known is that largely, it's not true. only 2nd rate 5hite uses the usb 5v to power parts of the dac. kingrex, Arcam, cheap crap under £100 and overpriced \Chinese 5hite available from your good self.
There's a few serious brands that do the same but they go to great lengths to filter than power input.
There's a few serious brands that do the same but they go to great lengths to filter than power input.
adamdea
You are not a sound quality evaluation device
Yes well the calyx is clearly designed to be powered by the computer. But how many people on this forum don't use a mains powered DAC? And if you don't want a DAC powered by the computer, then don't buy one. It hardly makes sense to buy one and then use a dual usb cable to get your 5v. Even the calyx appears to have a separate DC in.
Fortunately I have checked with the makers of my DAC who assure me that the 5v is not used. Even if it were used to power the USB receiver I'm not sure it would bother me provided that the DAC chip and the output stage were separately powered.
Fortunately I have checked with the makers of my DAC who assure me that the 5v is not used. Even if it were used to power the USB receiver I'm not sure it would bother me provided that the DAC chip and the output stage were separately powered.
I'm trying to help out with a bit of a survey in another thread - perhaps you can chime in with some specific information there. You'll be doing well if you can find one that operates as you suggest for every ten that don't. Let's do that there, shall we?
Again, specifically which 'overpriced \Chinese 5hite available from your good self are you referring to? Ignoring the frankly racist nature of your comment, the only Chinese product I sell over £100 is the Audiolab MDAC you own.
To save you the bother of looking it up, here's a list of DAC manufacturers we represent, with their country of origin:
Aune (Mainland China)
Audiolab (China)
Burson (Australia)
Benchmark (USA)
Calyx (Korea)
Chevron (UK)
Chord (UK)
dCS (UK)
Devilsound/Halide (USA)
Fostex (Japan)
Furutech (Japan)
KingRex (Taiwan)
Metrum (Netherlands)
MSB (USA)
Mytek (USA)
Red Wine (USA)
Resonessence (Canada/UK)
SuperPro (Hong Kong China)
Wadia (USA)
Wyred 4 Sound (USA)
Try again . . . which overpriced Chinese product do you mean?
Working on something like that - please see the other thread.
How the DAC designer chooses to power chipsets in the immediate vicinity of the USB transceiver - and whether the DAC is therefore 'USB power-independent' - isn't the whole story, as I hinted earlier. XMOS chipsets, for instance, prefer to see a 'live' USB socket, even if the chipset isn't powered via USB.
See here: http://www.psaudio.com/vanilla/discussion/5062/does-pwd-require-the-5v-in-the-usb-cable-/p1
Empirical Audio's Short Block USB, the new iFi, the old Aqvox - all attempt to address similar issues.
As a question apart from to the +5V rail, severing the ground connection (for instance, when using a battery) can also actually increase common-mode differential noise.
I suspect that controlling the electrical properties of the USB interface is more than half the battle, and the majority of the explanation for why USB transports differ. Not to forget mechanical issues on the data side, of course . . .
How the DAC designer chooses to power chipsets in the immediate vicinity of the USB transceiver - and whether the DAC is therefore 'USB power-independent' - isn't the whole story, as I hinted earlier. XMOS chipsets, for instance, prefer to see a 'live' USB socket, even if the chipset isn't powered via USB.
See here: http://www.psaudio.com/vanilla/discussion/5062/does-pwd-require-the-5v-in-the-usb-cable-/p1
Empirical Audio's Short Block USB, the new iFi, the old Aqvox - all attempt to address similar issues.
As a question apart from to the +5V rail, severing the ground connection (for instance, when using a battery) can also actually increase common-mode differential noise.
I suspect that controlling the electrical properties of the USB interface is more than half the battle, and the majority of the explanation for why USB transports differ. Not to forget mechanical issues on the data side, of course . . .
Citation please....
adamdea
You are not a sound quality evaluation device
I'm very familiar with that thread, and all of its contradictions. The pwd uses xmos, but apparently works with the 5v disconnected. I was previously under the impression that it used it to detect the presence of the device upstream. Oh well.
Either way no reason to care about the 5v source.
Meanwhile on absolute sound
http://www.theabsolutesound.com/articles/bryston-bda-2-digital-to-analog-converter/?page=2
"Alas, as with every other DAC that I have auditioned including the aforementioned dCS and Esoteric products the BDA-2 can sound substantially better when driven by a SPDIF or AES/EBU source than via USB."
Is it true. Is it false? is it just more crap about the sound of things that probably sound the same? Yes.
Teddy Ray
pfm Member
yep
all this stuff is disregarded by real audio engineers who work with sound every single day.
it is a non-issue.
Higher quality! Says who?....oh sorry you are trying to sell somefink!
By 'higher quality' I mean better built. If you invested £5 buying each from eBay - then took them apart - you'd see the Microtok is worth the extra 45p. You can imagine how rich we get selling a handful of these a month . . . almost enough to give a tramp a cup of coffee.
It used to be, yes. Not so much now: you might want to check the articles and posts of engineers like Barry Diamente. Also, you're confusing recording with playback.
We find the main detractors of digital audio hardware are those working in software-related IT, and those who just haven't thought about it. Almost everyone we meet who works with telecoms and IT hardware gets it straight away. And increasingly, musicians and engineers working at the sharp end.
Not contradictions at all! Just not as simple as 'noughts and ones'.
Your point about USB vs SPDIF is apples v oranges. However, it tends to support my point: the reason many journalists don't rate USB is that they haven't allowed the USB DAC to perform properly by using a proper USB transport and cable.
When SPDIF sounds better than USB, it's nothing to do with the inherent properties of those protocols: there are way too many variables to permit comparison.
As we've said ad nauseam (see 'Cheap DAC, Expensive Transport thread), if you boss a DAC with a very good SPDIF transport, it stands a chance of being the optimal source; USB performance is limited first and most inviolably by the DAC's design, then (fixably) by the computer.