Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: fossilshark on June 22, 2023, 09:33:54 pm

Title: Tone stack mods?
Post by: fossilshark on June 22, 2023, 09:33:54 pm
Hi all, I was just wondering if it would be possible to add a 4th tone knob to this circuit to change the bandwidth the mid knob sweeps. I don't know if that makes sense.

Basically I would like this tone stack to have a bit more versatility in the mid/treble range as turning the knobs above 1 O'clock doesn't have a whole lot of affect.

Does anyone know of a good 4 knob tone stack design for marshally high gain builds?

Any advice is appreciated!
Title: Re: Tone stack mods?
Post by: sluckey on June 22, 2023, 10:32:12 pm
Slope mod is popular.
Title: Re: Tone stack mods?
Post by: pdf64 on June 23, 2023, 04:05:59 am
What taper treble pot are you using?
With a high value slope resistor as per the 100k of the attachment, an audio type may provide a better range of control than linear.
Title: Re: Tone stack mods?
Post by: dwinstonwood on June 23, 2023, 05:23:49 am
I've never tried this, but would it make any sense to put a pot in series with a bright cap around a volume control, instead of the simple Fender-style on/off bright switch? You could experiment with different cap and pot values.
Title: Re: Tone stack mods?
Post by: fossilshark on June 23, 2023, 12:19:07 pm
Slope mod is popular.

This is exactly what I am looking for I think. Thanks again sluckey!
Title: Re: Tone stack mods?
Post by: sluckey on June 23, 2023, 12:31:23 pm
You may want to connect the unused pot lug to the wiper. I would. Don't be frightened by the 100 volts on the pot. You should never hear it. Just always be aware it's the only pot on the front panel with dc voltage so be careful when poking your fingers around inside the amp.

I suggest you search the net for "marshall slope resistor mod" to get an idea just what it can do for you. Anyhow, easy to undo if you don't like it.