Demeter Trembulator without ldr

[anotherjim]

LFO input caps should really be negative ends towards the transistor base, since that's close to 0v.

You may notice the Demeter opto-coupler (it's not an LDR) has its transistor collector & emitter swapped over. That's deliberate, and although technically "wrong" can give better control range. Have you tried that connection with your transistor?

Dragon already awake, but wrong dragon

[Danich_ivanov]

I tried both ways, and when they go negative to transistor the effect dissapears within about 15 seconds, while when they go positive it works totally fine.

Also if you look at the LFO out, you'll see that they connect to + of the 4.7u, so there's only one way to go.

And in order for them to go negative to a transistor, it should go from ic pin 1, and i tried that one first actually, but it didn't sound right, plus there was ticking.

[anotherjim]

You're taking the LFO output from the right place. Pin7 is the "integrator" output and should be a triangle wave. The other output is a square wave, which would be on-off clicky.

Ah, that's the other thing. There is no series resistor to the base to control the current. It's relying on the impedance and leakage of the capacitor(s). Leakage is highest when the capacitors are reversed. To put it another way, a reversed polarity on an electrolytic cap makes it behave as though there is a resistor across it. This is "reverse leakage" and should be avoided because it will over time reverse the polarity of the capacitor.

So, the amp IC1 pin 7 will be a varying voltage around a mid point that's about 1/2 of supply volts. Unless they are rail to rail types, the op-amp output cannot swing all the way to +supply or 0v. The transistor base, when forward biased, is about +0.6v. Therefore the op-amp output will almost always be more positive than the base & that is why the capacitor polarity should be the other way around. When you correct that, you will change the transistor base current and also the effect range - and you may believe you have "broken" it. Try adding a resistor in series between caps and the base.
In fact, you probably don't need any capacitors, just a resistor. The resistor might be high, 470k or so, depends on current gain (hfe) of the transistor. That's another reason to try reversing the collector and emitter, Hfe is much lower that way making it easier for the LFO to turn it off.

[Danich_ivanov]

Alright, i think i see what you're saying, i might try that. Although it works perfectly fine the way the way it is.

[Danich_ivanov]

I tried wrong dragon's suggestion and i have to say that it goes a bit deeper on a depth now, although a single resistor didn't do it, so i've settled down to basically the same setup i have in a schaller tremulator, which is 4,7u plus 1k after it, before the base. Might try the same setup in a schaller to see how it play's out.