fssshhh noise on crunch channel above half gain

[otto]

I have one problem with my amp. Clean channel is OK. Crunch channel is ok up to half gain (it has maybe more gain than before at the same position of the pot) then there is a big 'fssshhh' turning the pot more. The 'fssshhh' changes frequency continuing rotating, then it disappears when the pot is rolled back to half position, and everything works as before in this position. I have changed the position of tubes and it's the same. Any idea about what to check? The pot sure, then? ... is this a symptom of anything known?

[chipaudette]

What kind of amp is it?

Does it make the noise just when you play or all the time? Does it make the noise with the guitar volume off? Does it make the noise when you unplug your guitar cable from the amp?

Need more info...

Chip

[otto]

it comes with the sound of the guitar

[otto]

Solved, thanks, it was a bad solder