Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Colas LeGrippa on February 21, 2014, 08:00:48 pm
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Hi, just finished a simple s/e ( single ended, not special edition ) guitar amplifier with used parts laying around in my drawers and closet. This shit gave me one extra afternoon of work, cause it had parasitic oscillation and I had to try different things to get rid of that, which happened after five hours of headaches. I HAD NOT FOLLOWED MY OWN DESIGN. Everything was fine, I just had forgotten to hook up a bypass cap to the cathode resistor of the (only one) output tube. I didn't know a bypass cap at this particular place was so important. I knew though it increased gain having one. Same issue or almost last week with a Fender deluxe reverb amplifier. A bad cathode on a preamp tube was causing oscillation ( hi pitch squeal when reverb pot was turned past 4, with no reverb tank plugged in ). I'll pay more attention (even if I aint got too much money ) to the cathodes, next time I experiment with oscillation. Hoping this experience helps you, one of these days !
Have a nice w-e
Colas