Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: isaac_teller on January 25, 2023, 06:49:28 am

Title: Blackface Vibrochamp tremolo
Post by: isaac_teller on January 25, 2023, 06:49:28 am

Hello. I built a Vibrochamp clone. It sounds just dandy with one fairly minor problem(situation). The tremolo doesn't kick in until the intensity pot(25KA) is at about 80-90% clockwise. Speed knob works fine afterwards. Would a change in pot value correct this? Thank you.

Title: Re: Blackface Vibrochamp tremolo
Post by: Esquirefreak on January 25, 2023, 07:03:53 am

Pot taper matters. RA25K pot will probably get the wobble happening earlier on the dial, rather than the A25K.

Do you have a decent voltage swing on the LFO tube?

/Max

Title: Re: Blackface Vibrochamp tremolo
Post by: isaac_teller on January 25, 2023, 07:14:58 am

I'd have to order a RA25K as I don't have one right now. Could I substitute a 25K linear in the meantime? Or maybe use the circuit for the AA964 tremolo and ground the end that would normally go to the bias supply?

Title: Re: Blackface Vibrochamp tremolo
Post by: sluckey on January 25, 2023, 07:39:06 am

For a temporary fix just swap the wires on the outside lugs of the pot. Intensity will work backwards but should be spread out more evenly over the knob rotation.

Title: Re: Blackface Vibrochamp tremolo
Post by: isaac_teller on January 25, 2023, 07:50:57 am

Thank you!!