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

Tim Parkhurst tim.parkhurst at gmail.com
Tue Jan 10 02:12:18 CET 2006


On 1/9/06, Seb Francis <seb at burnit.co.uk> wrote:
>
> 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
> >
> >
> >
> >
>
>
The ARP Odyssey has a pretty good dual tracking supply built around the
723...
http://www.physicsenterprises.andrews.edu/diy_archive/manuals/arp/odyssey/ody_40.gif

Tim (trying to type with a cat on my lap) Servo
--
"Imagination is more important than knowledge." - Albert Einstein
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