FW: [Malvern] Re: [OT] PC PSUs & turntables

[Guy Inchbald]

On Fri, 9 Feb 2007 18:50:27, Ian Pascoe <ianpascoe at btinternet.com> 
wrote:
>The only reason, going back on topic, I elluded to hi-fi was that it was
>generally agreed that if you provided components within the same housing
>their own regulated power supply, you can add minimal degredation to the
>signal throughout it's path.
>
>As has been said earlier in the trail, that is needed because of the low
>data rates involved compared with normal PCs.

Not so much needed as possible.


>So if you have a blob (technical term) on an audio system that corrupts 2
>data bytes, but could have been avoided with individual power supply, and
>you move to a PC, the blob lasts for the same time span, but affects more
>data as the stream is faster.

"Glitch" is the technical term you are looking for. Yes, the capacity to 
corrupt data is greater in a PC because there is more data to corrupt.


>I suppose in essence that the PC PSU already has multiple power supplies
>within it, but what I was trying to get at is if the supplies were more
>automonus an external RF / HF interference couldn't cascade throughout the
>entire PC.
>
>Or have I totally mis-understood the construction of PSUs as they are now?

Up to a point, yes you could isolate the various sources of RFI (RF 
interference) by putting them in separate, screened and filtered 
enclosures. But the whole point about a PC is that very broadband 
signals up to UHF frequencies can go most everywhere without hindrance. 
So most connections between those enclosures would be able to carry 
interference along with the signals, rather defeating the point of 
having separate enclosures.

PCs rely on being digital devices which switch over a finite voltage 
range - as long as the internal interference is at a low enough level it 
will not trigger a bit transition and so will not corrupt any data.

So a little bit of noise on the PSU output lines will not hurt anybody. 
Why spend money reducing it unnecessarily?

This is not a good design philosophy for analogue audio! High-quality PC 
soundcard design is a black art, indeed.

-- 
Cheers,
Guy