Hoffman Plexi 50 mods

[Jhj]

I recently completed a Hoffman 50w Plexi. It works well but needs a bit more “bite”. I added a bright cap to channel 1 (47pf) after trying a 500pf.

What else can be done? Anything with the NFB? Move it to the 4ohm connection, perhaps?

[sluckey]

Hoffman Amplifiers Plexi50 – with Hot Switch Gain Mod

[stratomaster]

Try a 56k for R16 if you're just looking for more high end.

I assume you've tried jumping the channels?  If not, put a jumper wire between pins 2 and 7 on V1.  This will activate both volume controls.  Acts as a gain boost and an eq.  People normally turn up channel 2 for dirt and bite and just turn channel 1 up enough to fill out the low end. 

Failing that, there are entire companies formed based on the modification and perfecting of this circuit. 

I think these two suggestions are a good start. 

[dwinstonwood]

As sluckey said, try using the Hot Switch mod. I wired it always on in the one I built.
And,  what stratomaster described sounds worth trying, too. And, probably less trouble to add!

[edited to remove my PDF that has errors]

[EL34]

Hoffman Amplifiers Plexi50 – with Hot Switch Gain Mod

https://el34world.com/schematics.htm#Mods%20and%20Projects%203

[Jhj]

I had considered the hot switch mod and may still decide on that direction. However, internally connecting the V1 inputs is a great suggestion that I’ll try first.

I’ll report back. Thanks.