Hello guys

- How do I get a '-infinity to 1' gain regulation out of a signal?-

I'm building a little synth (noisemaker) project.
I've got 2 oscillators , one of which is a sine-wave and the other a square wave.

Both oscillators will be fed into a simple Op-amp adder circuit.

I want to be able to regulate the feed of both oscillators with 1 stereo pot so I can get the waves in their pure form and their combinations aswell by adjusting that pot . The question is:
When I want a pure sine wave for example , how do I get the square wave osc to shut up? I guess there would have to be some sort of complete attenuation , a gain of - Infinity or something no?
I've tried doing it with an op amp but it goes unstable at a gain of -3.
I tried using a potential divider to simply bring the voltage down and then feeding it into the op amp adder , and still no luck
I've also tried a similar method with a T-network that I read about , still crap.
I can get the signal down to a few mV with a potential divider and measure it with my oscilloscope , but when I connect it to an op amp amplifier then it just goes unstable . I guess that the resistances come in parallel or something and it upsets the op amp.

My signal is about 300mV and I can't bring it to lower than about 90mV.

-->>> So how do I get a -infinity to 1 gain regulation out of a signal? <<-----

Thanks in advance for any help

 

I can get the signal down to a few mV with a potential divider and measure it with my oscilloscope , but when I connect it to an op amp amplifier then it just goes unstable . I guess that the resistances come in parallel or something and it upsets the op amp.

My signal is about 300mV and I can't bring it to lower than about 90mV.

-->>> So how do I get a -infinity to 1 gain regulation out of a signal? <<-----

Thanks in advance for any help

Try AC coupling to the opamp via a small capacitor. Say, 10uF.

 

Post the op amp circuit that doesn't work. It should.

 

Here is the problematic part of the circuit.

 

Try AC coupling to the opamp via a small capacitor. Say, 10uF.

Hmm yes why Didn't I think of that . I'll try it out today , thanks

 

It's also a good idea to AC couple audio signals through pots. Because, If DC is allowed across pots, they may produce noise when rotated.

 

It's also a good idea to AC couple audio signals through pots. Because, If DC is allowed across pots, they may produce noise when rotated.

Thanks for the insight