SV: Re: [sdiy] Linear PSU options .. 7815/7915 vs LM317/LM337 vs 723 etc

[Seb Francis]

This is a very good point, but nevertheless many hi-end audio circuits 
do seem to use better than 7xxx PSUs.  Maybe this is kind of over the 
top audiophile engineering, but I'm not so sure.

In my application there isn't anything like a VCO that needs a really 
precise voltage, but there are however hi-end audio components (THAT 
VCAs in the compressor) that need to pass/process the audio with as 
little added noise as possible.  Also, the distortion processor elements 
have very high gain which will probably amplify any power supply noise.

So while I don't want to get over-complicated, if a 317/337 PSU can give 
lower noise than a 7815/7915 PSU with only an extra couple of resistors 
then it seems worth it (maybe I have some traces of audiophile in my 
genes! ;)

Seb

P.S. The only digital bit (a PIC micro for the MIDI interface) has its 
own 78L05 driven power rail.



Paul Perry wrote:

>There's another side to this regulator debate, and that is:
>just how good does the regulated supply need to be?
>When one looks at precision analog circuitry, you often see
>power rails no better than you would get from a LM78xx,
>but wherever a *really* precise voltage source is required, there is a 
>precision source dedicated to just that. And it is right there on the 
>board where it is wanted.
>Which at a stroke solves the problem of noise generated on the 
>power rails by switching transients etc.
>And, speaking of transients...... anyone serious (including some
>members here, I notice) have separate power rails for the digital stuff,
>and for the analog that they try to keep noise free.
>I personally think, the difference between the 78xx and other regs,
>is swamped by these other techniques..... and if you want to go the 
>whole distance, you are going to need to have precision voltage
>diodes & separate analog/digital lines anyway!
>
>paul perry Melbourne Australia
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