Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: marshallguy on August 10, 2023, 07:30:46 pm

Title: Buzzing sound behind the notes
Post by: marshallguy on August 10, 2023, 07:30:46 pm

Hello fellow amp enthusiast,

I found this older trend 2006 on the Amp Garage dealing with the same issue I’m having. His build was derived from a Dumble Overdraft Special. Different amp then mine but same exact problem.

Here’s his response after disappearing for almost a year and someone finally asked if he ever found and fixed the problem……

“I did get that amp to mellow out and it turned into a real sweetie. I wound up making some changes in the power supply resistor string. That tightened up the amp real nice and got rid of the ghost notes.”

Naturally he didn’t say exactly what he did in the B+ resistor string Changed some values?  Link to a Dumble OD not sure if his build was the same.

https://www.schematicheaven.net/dumbleamps/97fullschem.pdf

Can someone with some experience to this chime in? I’ve tried everything else. Maybe which resistor(s) to change in value?

The problem is narrowed down between V4b and the output jack speaker.

Thanks.


Link to some songs recorded with similar amp I built.

https://soundcloud.com/user-259182186/after-the-storm

Title: Re: Buzzing sound behind the notes
Post by: marshallguy on August 14, 2023, 03:37:53 pm

Quote from: marshallguy on August 10, 2023, 07:30:46 pm

Hello fellow amp enthusiast,

I found this older trend 2006 on the Amp Garage dealing with the same issue I’m having. His build was derived from a Dumble Overdraft Special. Different amp then mine but same exact problem.

Here’s his response after disappearing for almost a year and someone finally asked if he ever found and fixed the problem……

“I did get that amp to mellow out and it turned into a real sweetie. I wound up making some changes in the power supply resistor string. That tightened up the amp real nice and got rid of the ghost notes.”

Naturally he didn’t say exactly what he did in the B+ resistor string Changed some values?  Link to a Dumble OD not sure if his build was the same.

https://www.schematicheaven.net/dumbleamps/97fullschem.pdf

Can someone with some experience to this chime in? I’ve tried everything else. Maybe which resistor(s) to change in value?

The problem is narrowed down between V4b and the output jack speaker.

Thanks.


Link to some songs recorded with similar amp I built.

https://soundcloud.com/user-259182186/after-the-storm

TH\his discussion is now closed. Turns out problem is with the speakers, cone cry. :sad2: