PCB for MAT-04 VCA

[gstopp at fibermux.com]

     Okay a little more discussion...
     
     I goofed when I was saying "4V p-p" - what I meant was +/- 4V (duh!) 
     which is of course 8V p-p. So this VCA actually can handle a fairly 
     high input signal for line-level use. However if your PCB design has a 
     cut-down/boost-up function then that may be best for synthesizer use, 
     to prevent the nasty waveform-mangling that happens if the signal is 
     too hot. Hmmmmm that made me think - this might be hacked into a cool 
     timbre modulator by distorting it! Naaaahhh....
     
     Also even though I last reported that cheapo transistors could be used 
     rather than an expensive matched quad (or two matched pairs), this may 
     be true but please note that I have no capability to measure 
     distortion other than by eyeball on a scope, or at best overlapping 
     the input and output traces on the scope to notice any deviation in 
     the waveforms. So - in a synthesizer, where "distortion" may be 
     considered an invalid term (since there is no "input" to "distort" 
     when you synthesize), it may be okay to cut corners a little. But if 
     you keep the matched transistors in this design the specs are probably 
     good enough for a high-end VCA like you'd use for recording consoles.
     
     - Gene
     gstopp at fibermux.com


______________________________ Reply Separator _________________________________
Subject: Re: PCB for MAT-04 VCA
Author:  gstopp at fibermux.com at ccrelayout
Date:    2/24/97 3:56 PM


     Good job Chris.
     
     Well in the time between my last response and now I've tried a few 
     more things. First of all it looks like it's best to keep the input 
     signal at 4V p-p or lower...