Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Nikolaj2121 on May 04, 2024, 03:25:33 pm

Title: 100 hz noise Selmer Treble N'Bass Mk2
Post by: Nikolaj2121 on May 04, 2024, 03:25:33 pm

Hello everyone

I have this Selmer Treble N'Bass Mk2 amp that I am haveing a bit of trouble with. It has a quite noisy 100hz, that is comming through the PI. I have narrowed it down to the PI since when pulling the tube, the noise goes away.

I have also discovered that if I add a capacitor over the negative feedback resistor, then the noise goes away. However this causes the bias on one of the tubes to go to like 45Am, and the other is at 17Am (this can however be fixed be adding a pot to each tube)

But the thing is I would really like to figure out what the source of the noise could be. I have tried a lot of things, and nothing has worked except the capacitor method.

Im open for all Ideas, so please let me know. Also if you need more pictures.

Thanks in regards
Nikolaj

Title: Re: 100 hz noise Selmer Treble N'Bass Mk2
Post by: EL34 on May 04, 2024, 03:38:19 pm

Posted in wrong board........... moving