[sdiy] RE: WP20 VCA

[Ray Wilson]

Hi Scott and everyone

I just went and did some breadboarding to see what I was thinking 20 years
ago. The answer... not much. At best the circuit is very non-linear. In
other words if you start with a triangle wave in you get a severely
distorted triangle wave out. While experimenting I had to double the gain
(200K instead of 100K feedback resistor) so that the signal was a little
more above the noise level of the chip. I recommend that you find another
VCA circuit. I have a couple of pretty low parts count VCAs on my site but
the WP20 stuff was the misguided effort of a much younger and not very
electronically savvy man (me). I can't even remember if I had an
oscilloscope back then.

Ray


-----Original Message-----
From: Scott E. [mailto:yahudinyhwh at sbcglobal.net]
Sent: Thursday, September 11, 2003 11:28 AM
To: Ray Wilson
Subject: WP20 VCA


Ray,

I am in agreement with the poster on this list (was it Grant?) who
stated that this is one of the lowest parts count VCA's I've seen. I
have a use for something of this nature (need 8 for one circuit). Can
this module be adapted for 15v? Also, what sort of output protections
must be included in the circuit driving the R200 (pot) to prevent the
P.S. voltage from disrupting the driving circuit?

Ideas?

Thanks and regards, Scott