Ribbon Controller Again

[Doug Tymofichuk]

Greetings, all,

I hope everyone had a Very Merry Christmas!

After spending more time with my ribbon controller I found 
that while it functioned great when playing by hand, when 
using drum sticks it would frequently miss the impulses. It 
appears the circuit just isn't fast enough. So, instead of 
attempting to build a faster sample & hold, I modified the 
ribbon controller itself to give a slower response. All 
that was neccesary to accomplish this was to peel off the 
mylar/graphite resistive tape strip, place two layers of 
double sided foam sticky tape down and reapply the 
resistive strip back on over top of the foam tape. This 
way, instead of the drum stick reaching "end of travel" 
just as it makes the electrical contact on the ribbon, the 
stick makes electrical contact and holds it while it pushes 
the ribbon into the foam. This produces long enough 
impulses for the s&h to capture every time now and it 
works great. The ribbon now has much less sensitivity when 
being used by hand, but as I intend to use only sticks on 
it, that's just fine.

I did make a number of modifications to the circuit, see 
attached GIF:

-reduced glide capacitor from .47uF to .22uF as maximum 
glide time was a little too long to be useful.
-increased gain resistor on final C.V. stage from 10K to 
18K for slightly greater output C.V. range.
-isolated the trigger indicator circuit from the actual 
trigger output.
-added a pulse stretcher circuit to allow adjustment of 
minimum trigger pulse duration.
-included the (cheesy) power supply circuit.

Have fun!!
----------------------
Doug Tymofichuk
dougt at cancerboard.ab.ca
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