Benson preamp "fizz"

[matmonster58]

I just finished a Benson stripboard build, but I have this weird fizz under the sound that I can't figure out.

I have swapped all of the transistors out and have tried different bias voltage for each tranistir but the fizz is still there. Any ideas what is causing this and how I can fix it?

 

[matmonster58]

 

[matmonster58]

Ive proper the circuit and the fizz is occuring somewhere in the third stage.

The gate of transistor three sounds fine

 

[matmonster58]

Whenever I do stripboard builds I always build two. The second copy has the same problem so I can rule out bad components/bad solder joints.

I wired up the second one using a bunch of alligator clips just to check. Obviously it's going to be worse and noisier than the actually wired up copy.

There is an oscillation tied to the gain control that I'm thinking is the culprit. The long wire leads on the second version exacerbates the problem