Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: jewishjay on January 14, 2022, 05:11:56 pm

Title: Some experienced eyes on this?
Post by: jewishjay on January 14, 2022, 05:11:56 pm: I'm building a Brownface inspired harmonic tremolo amp. It's running and I love the tremolo sound, but I'm still tweeking.
Here's the voltages I read with a DMM right now. See anything of concern?

1. The bright switch is much too ice picky. Would I try a larger or smaller bright cap?

2. the NFB seems to have no effect, I think I want to lower the R. But I'm not even sure if I should use the 4 or 8 ohm tap. Is there some math I could learn?
Title: Re: Some experienced eyes on this?
Post by: sluckey on January 14, 2022, 05:43:06 pm: Experiment with the bright cap until you like it.

Use 56K and 4.7K in the NFB circuit. Look at some 6G?? schematics.
Title: Re: Some experienced eyes on this?
Post by: ac427v on January 14, 2022, 06:46:39 pm: 512 volts on the plates of the output tubes is beyond my experience.
Title: Re: Some experienced eyes on this?
Post by: echuta13 on January 14, 2022, 07:30:55 pm: Maybe try a 100pF or no bright cap.
Title: Re: Some experienced eyes on this?
Post by: BrainDeadAmps on January 14, 2022, 11:05:11 pm: Looking at several 6gx circuits, most have a split plate load resistor on v1B. how is the tremolo with the volume cranked?
Title: Re: Some experienced eyes on this?
Post by: ghostinthescope on January 15, 2022, 08:47:31 pm: Like Sluckey said the negative feedback shunt resistor probably wants to be 4.7k. I’d keep the 100k as is, since thats what the 6gx circuits use. I recently built an amp with this same harmonic tremolo circuit as well as a bias vary trem and reverb. I definitely did a lot of head scratching and tweaking to get it working well.