Hiss at potentiometer mid position

[mitsof]

I get a hiss at about mid position of the potentiometer.The strange thing is that the hiss is not at the same place everytime.It moves a bit to the left or the right.

How to fix this?

 

[JonSnell Electronic]

Sounds like HF oscillation. Check with your oscilloscope and I would start by reducing the bandwidth to the audio spectrum only.

 

[DF96]

Yes, classic symptom of HF oscillation. To suggest a cure we would need lots more information, such as a circuit diagram.