But now even if the potentiometer is at the lowest level some sound from the input is coming off from the speakers, distorted and at constant low volume (not affected by the potentiometer level). Normally (e.g if I bypass the mod) there is some clean sound coming off the speakers bit is nearly inaudible even if you put your ear next to the speaker. Here are the pins I used (photo taken before I did anything) And here is a schematic I found of the speakers
Stray inductive positive feedback and parasitic noise can be a difficult issue to diagnose when we are blind to your layout.
You show two grounds.(left gnd right) and (V+ and Gnd)
It seems the Op Amp (OA) has injected noise but from where?
Do some tests to find out where.
- Short the input signal to local gnd with a sufficient cap if it has DC bias
- the connections at that noise may be insufficiently shielded.
- Change ground for connections to the one between the stereo signal.
- Keep wires short and twisted to reduce stray effects.
- last resort, use an inverting buffer to make the stray feedback inverted
You're using a JFET opamp with a fairly high bandwidth, a very high input impedance, and no decoupling. As others have said, without any pictures of your construction it's hard to pinpoint the problem, but I'd expect you to have problems with parasitic oscillations.
If you do increase the input impedance of your speakers you might also want to check that the rest of the wiring to the speakers it up to the task, and that whatever's driving them can cope with such a high impedance.