6v6 Plexi w/ Vox Style Cut control?

[martinman]

I usually run presence around.. well...  zero and it got me thinking about re-purposing the space on the front.  I was thinking of a vox style cut control.  I recently played a Dr. Z maz18 and was quite impressed with what cut did to the amp - it really tames the high end.  The maz18 is an el84 w/ tube rectification, so they're quite different.  Just wondering if anyone has any experience with this mod. 

Ideally, wouldn't want to remove presence, but it's just so under utilized...  I have a lar-mar MV in the 2nd speaker slot in the back, so I really don't have any other room.    Thoughts?

[sluckey]

It's just a series connected 250KA pot and .005µF cap placed across the signal lines feeding into the power tube grids. In your case the cut would be parallel to the Larmar MV pots. Very easy to try and just as easy to remove. It could be useful in the 6V6 Plexi. Gives you one more knob to twiddle.

[martinman]

Thanks Sluckey

I ran across one of your posts on MV -- i think I used it when I installed the Lar-mar.  So, basically, i'm just running (shielded?) signal wires off the .022 PI to the pot ala robs diagram, right?  https://robrobinette.com/Voicing_an_Amp.htm#Vox_Cut_Control

I think i might drill a hole in the back too and preserve the presence.  Never know when you'll need presence!
 

[sluckey]

If I was gonna add a cut pot, I'd put it next to the MV pot to simplify wiring. Probably look kinda like this...

[martinman]

Hey all -- just wanted to check back in and report back.  The mod is in, and ... wow.   This is - to me - a must do mod - especially if you went the lar-mar route; it's for sure a keeper.  I had a 250k & .0047 cap around, so I went with that.  Not much happening from 0-4 on the pot, 5-8 is usable & where the magic is, 9-10 way to dark.  Honestly, i'd probably go with a linear taper pot instead of audio taper - that would smooth out the taper.  The lar/mar is in the 2nd speaker slot in back, so I drilled another hole and move the speaker output to the other side of the impedance selector.  So on the original spec, I'm using both speaker areas for larmar & cut. 

I toyed with the idea of removing presence and adding cut instead, but I don't really think it 'deserves' a spot on the front panel.  I'll likely use it as a set and forget - like lar/mar.