teach me a bit about adding envelope control rather than a pot, please?

[Rob Strand]

maybe this will be ok
previous version only went from common mid-point to extremes
I've never mucked with bipolar devices wired as VCRs

It's worth giving it a try. The pots will help tweaking it.  Might have to tinker with the 22k's and 100k's to get 10k resistance range. 

The other day I pondered over it and I got caught up on keeping the circuit simple and trying to make the range of resistance stay between a small value and 10k.

FYI, I tend not to use emitter resistors for transistor VCRs since it increases feed-through (base current through RE).   You can also flip E and E to double the resistance and reduce the DC on the control pin.

[pinkjimiphoton]

jc, you rock man!
thanks, will look it over once i'm semi conscio... long show yesterday, i did a bonus accoustic set for 'em, man i am bushed. and stuffed. and hung over. good times.

i love that acid rain

[pinkjimiphoton]

maybe this will be ok
previous version only went from common mid-point to extremes
I've never mucked with bipolar devices wired as VCRs

It's worth giving it a try. The pots will help tweaking it.  Might have to tinker with the 22k's and 100k's to get 10k resistance range. 

The other day I pondered over it and I got caught up on keeping the circuit simple and trying to make the range of resistance stay between a small value and 10k.

FYI, I tend not to use emitter resistors for transistor VCRs since it increases feed-through (base current through RE).   You can also flip E and E to double the resistance and reduce the DC on the control pin.

the best actual sweep for this circuit is actually about 20k on either side to ground. may try it with a 50k pot. but first gonna try jc's idea.

[pinkjimiphoton]

Pink, just a rough idea ...



of course, you'll want to set the bias for Q1 higher and Q2 lower

I'm curious if this does anything useful
~jcm

JC

we all know i'm a moron at this point but.... how/where do i integrate this with the original circuit? i think i understand how it would operate... but not sure how to interface?

thanks bro
p.

[Eb7+9]

thx for asking Jim,

You'll want to remove the sweep pot in the original circuit
and tie in the collector of new Q1/Q2 (where it says NO-DC)
to where the two ends of the prior sweep pot went in the circuit

Of course, there is an option as to which goes where ...

Now, once you have the "range" trimpots set right,
in one arrangement the sweep will start from set high-frequency
at idle and sweep low in response to signal envelope

... in the reverse arrangement, you'll have a low starting point and
opposite/upwardly response to envelope

Assuming the combined system works well enough
you might want to insert a DPDT switch in your final build
to make sweep directions selectable ...

This is what the up/dn switch in the Mutron-3 does

good luck
~jcm

[pinkjimiphoton]

brilliant as always, bro!!
i thought that was it, but wanted to ask.
i have to start some laundry and make a grocery run, but as soon as i get back, i am dungeon bound.
if all goes well, i'm gonna put one of these in the next care package to Steve Hunter in spain!
he really dug the last batch... put an ibanez em5 clone in there, a buncha fuzzes and overdrives, and one of rick holt's causalitys.

this ones gonna include an uglyface with lfo too lol

i'll post how it goes tonite hopefully!
again, thanks brother... and thanks for all you do/have done for the communiity for all these years!!!