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Do USB Audio Cables Make A Difference?

I'm not sure what's different about a linear or a switched supply for a DAC. They both charge of a capacitor, which is the ultimate arbiter of stability on the fine grain, neither a switched or a linear can react so fast.

Yes, capacitors (but in the case of digital circuits it is mostly the smaller bypass capacitors that deal with the HF noise, not the power supply stabilizer caps. A switched supply tends to react much faster to the heavily transient power demands of digital circuits.
 
I agree that switchers react much faster: but the noise doesn't affect the digital part, but the analog part of the DAC, and the buffer or headphone amplifier.. in the Apple the digital current demands would I suspect, be consistent and small.

So perhaps the noise limit is constrained by the impedance of the supply, to prevent noise created by the digital side leaking onto the analog. But even there, it's unlikely to be 5V so will be isolated by it's own regulator.

Either way I can't see any downside to a small linear supply to the DAC: better in every way than the current 'end of USB cable chain' arrangement I think ;)
 
My standard is to not use USB power, never mind LPS or SMPS...although at least LPS means one less damn wall plug thing, if it's built into the DAC.

My router started giving shit last night, today I had to fiddle with the wire for about 10 minutes before I got it to work. I always thought it was getting stressed there. Now I have to buy a new router, ASAP...if I crack this thing open, I might end up with it not working at all. And my soldering iron is not here anyway.
 
Ironically the buzzing PSU was an official Pi PSU, and was also double isolated I think - no earth pin connection to the output.

That's exactly what causes groundloops. The switching noise common mode (leakage) currents still make it through.
 
Brilliant, thanks. Reading this saved my $$.
 
That's exactly what causes groundloops. The switching noise common mode (leakage) currents still make it through.

I was unable to find any 'loop' though - this was the puzzle. Replacing the PSU with a different one fixed the issue.
The solid (mains) ground was in the amp, the Pi grounded from that (Via the RCAs/DAC wire shield, the PSU grounded from the Pi.

Anyway, it will be interesting to see if a quiet supply for the DAC makes an audible difference, I'm waiting for the USB extension lead to turn up so I can have a go at making my PSU :)
 
Either way I can't see any downside to a small linear supply to the DAC: better in every way than the current 'end of USB cable chain' arrangement I think ;)

According to what I rencently tested, this may depend of the DAC. If its PSU is well built (filter on the input, and/or switching regulators inside), no need of an expensive low noise PSU to feed it. The downside may be the money, for not much or no benefits.
 
an expensive low noise PSU

Expensive? Well, yes, they can be expensive, true :)
But mine, will be about £10 :)

A USB A panel mount extension, fitted into a box, socket on the box, flylead to the data source.
A 5.5/2.5mm power plug in the side, powered by any handy wall-wart linear supply.
Inside, a couple of caps and a 7805 to power the socket...
... Just some careful surgery to the wire, to access ground and intercept the power wire :)

The only flaw to this wonder plan is the lack of a box, I'm trying to look for one! :)
 
Post pics when you do. :>
Black/grey plastic "project box"? - as in radio/electronics shop. .....Bantek pen case?...
...You get "wall-warts" that are Linear?
 
Plastic is not the best, or a big enough, plus a heatsink for the 7805, it will heat up inside...

Or an alu box, the 7805 screewed on it, maybe isolated.
 

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Post pics when you do. :>
Will do!
I want a box that a) I already have, and b) looks good, or at least reasonable! :).

I have an old linear wall wart for 9V that I'll use. Age is the key :), most of the new ones are switched. Switched wall warts can be Ok, but the switching noise is often good in the design, and lost when the makers cheap-out and omit some basic parts.
As a general rule, quiet switchers ones are fine, but noisy ones can never be silenced...

But yes, old and heavy :).
Else I think miniature potted transformers are available for projects, and with an IEC socket are not too much hassle.
 
plus a heatsink for the 7805, it will heat up inside.
I'll not bother with that :)
It'll drop about 9-5 = 4V and draw about 20mA tops, so dissipate 80mW, and it has internal thermal protection :)
Because of the low power, a lazy / sloppy approach works perfectly here :D
 
It'll drop about 9-5 = 4V and draw about 20mA tops, so dissipate 80mW, and it has internal thermal protection :)

You should be safe. My DAC needs 330mA :)

I had bad experiences with thermal protections, ended in definitive shutdown :)
 
You don't even need an IEC socket, just a grommet.

With decent wire /cable.
\\ Shxt, I need to order a router tonight. Before I do surgery on this thing. I'm pretty sure the wire's broken about 5mm from the..rubber thing.
 
With decent wire /cable.

The better it is built, the longest it will work without any issue.

@CuteStudio You may add any piece of metal as heatsink, for 80mW. It will last for years and whatever room temp will be. You may also add an LC filter after the 7805, L being pulled out where you find one. You will get clean for cheap.
 

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The photo of the little board looks nice, an LC filter too?
A small mod - to allow the data through, and it would be ideal !
 
so, a dac should sound the same out of a rapberri pi or out of a powerfull desktop?
Have we tested this?
 
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