[sdiy] Vishay switches - be afraid, be very afraid...

[Peter Grenader]

Heads up here.

I use an analog switch to create the saw on the Model 15.  Up to now I've
been using a Max333 to do this with fantastic results (never had a single
problem in 60 or so units shipped).  For some God unknown reason, I switched
to the Vishay equivalent, the DG333 - which is supposedly pin-functional
compatible to the Maxim part.  It was actually Harry Bisset who tuirned me
on to this.

In short, the Vishay part creates massive amounts of noise all over the damn
circuit.  In the following sample, you'll be hearing the SINE output - and
the noise created by this switch is backing up all over the place - and the
switch again is used in the sawtooth waveshaper.

There are four repeats of a pattern in this sample.  It's the same VCO.  In
thew first two Ive got the DG333 in there.  In the second two it's the
Max333.  The difference is astonishing:

http://www.ear-group.com/sinesample_noise_.mp3

sometimes (up untl this one unit) i've been able to kill the noise by
hanging a small cap to ground on the output of the integrator - but this
ain't fixing this one particular VCO

- P