[sdiy] dare I say - decoupling?

[Magnus Danielson]

From: "Paul Schreiber" <synth1 at airmail.net>
Subject: Re: [sdiy] dare I say - decoupling?
Date: Sat, 3 Sep 2005 11:11:04 -0500
Message-ID: <007901c5b0a2$15ab8540$0301a8c0 at bilbo>

> > 
> > I would not be that drastic, it really depends on the circuits dynamic
> > current-dumping behaviour. If you have strong rail-to-rail dynamic current
> > dumping, then doing decoupling rail-to-rail in the neighborhood of such a
> > source is definitly a good idea. 
> 
> 
> In a *synth* circuit?

Yes. The EMS VCS3/Synthi-A is a wonderful example of this unfortunately. The
envelope-generator lamp loads the +12V to -9V rails with enought current to
load the PSU such that you hear the VCOs detune. Of the various variants of
the Mk I design this is noticeable, but it varies. On the Mk II (having a more,
ehum, traditional PSU design) this is not as distinct, but still there.

> Maybe in large industrial stuff :)

Maybe in a synth I own?

My point is that there is no single true way of doing it, but one has to use
the head some, but doing it as you suggested will work fairly well most of the
times. Doing it that way with the main decoupling caps over in the PSU is good,
but on the board(s) one might have to use different strategy to be effective.

Cheers,
Magnus