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Message

STC rant ...LONG and OT

2000-12-03 by thomas white

Hi all,

just thinking about a new project at home and wanted to ask around about it. 
Has anyone built a Paia provided Electronics Projects For Musicians (EPFM) 
Super Tone Control Before?

This is a Craig Anderton design from the late 70's based around a quad 
op-amp in a design that is actually a filter (12dB I think) Anyway, I have 
an old one of these from my EPFM days complete with rosin-core solder still 
on the board, YIKES! It makes a cool textured filter sound, but has no CV 
inputs...stock anyway. I was reading the project notes for this and 
discovered that it can be modified with 2 resistors and caps changed to work 
with 10v peak to peak voltages. Perfect with MOTM. My next problem in 
adapting it was the CV inputs.

So I got my old Super Tone Control (STC) out of its Frac-Rak and started 
with the voltage testing. I found that the frequency with no CV inout jack 
was reading 0-5v response. I figure I can patch a cv right in place of this 
pot and whammo, I will have at least a dirty CV input of sorts. Wait 
though... upon further reading, I discovered that you can also get the 
envelope follower kit from the EPFM book and hard wire it up to the STC. 
This of course allows the filter to be controlled by the audio signal at the 
input. I read the description of the schematic and the input circuitry 
converts the audio to 0-5v DC as expected to control the frequency of the 
STC. I should be able to feed a CV into the EF socket as well and use it a 
CV input for the frequency. I will also be able to control the sensitivity 
and sweep range of this CV due to the controls on the EF.

Another mod I want to make is to have individual outputs for the three 
filter responses. This filter has High, Band and Lowpass sections with an 
attenutaor for each one feeding a summing mixer for the output. I want to 
split each signal out to a duplicate circuit of the output on the STC to 
buffer and amplify each filter response. Now the STC will have a Mix out 
with attenuators for each response and individual outs for other uses.

Unfortunately the STC filter does NOT self-oscillate. :~( Sad time, but 
there is a resonance boost switch in the circuit that gives an almost 
shell-resonance type effect to your sounds. I always use this to my benefit 
with my old STC to make percussion samples.

I plan to mount this thing into a 3-space MOTM panel with full pot upgrade 
and components replacement for the long run in as many places as possible. 
Where do you get the shielded wire Paul? Part-number? I want the exact same 
if you can dig it. I know this is knid of off topic, but you guys are the 
first guys I have to ask in this situation. Thanks to Paul for the MOTM 
format inspiration and teaching me to use better components (My old Paia 
stuff iscratchy all over at 2 years old...Yikes)

Thomas White

PS. I guess the stuff from Paia runs about $60 total for the basic component 
kits or you can get pcb alone. Ciao'
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