Mid Sweep

If i remember correctly to add a mid sweep to a module you have to replace the slop resistor with the lowest value you'll want and then add a pot in series. The pot is what makes it adjustable.

On the Recto, Black Face, and SL+ schematic i got from Randall R31 in the slop resistor.

i did find out about this, but i was told that there is a possible cause of being electrocuted, but i thought if the pot was grounded (to where i'm not sure) that this danger could be avoided?

nomad100 said:

If i remember correctly to add a mid sweep to a module you have to replace the slop resistor with the lowest value you'll want and then add a pot in series. The pot is what makes it adjustable.

On the Recto, Black Face, and SL+ schematic i got from Randall R31 in the slop resistor.

Click to expand...

Yes, R31 is the slope resistor on those schematics. Yes, a pot in series with the slope resistor makes it adjustable. There's 1 more part though... add a 100n cap in front of the slope resistor/pot. Opinions vary on whether the cap is needed or not, but my personal experience says the cap is absolutely necessary.

With dc on the pot it will make noise as you turn it. Question won't the cap affect the tone?

Adding the 100n cap doesn't significantly affect tone strictly compared to not adding the cap. At least it never has in the dozen or so that I've done.

edit: I can't imagine that there would be any difference, but I meant the dozen or so amps that I've done this 'mod' on... not modules.

your probably right, and it's gotta be better than having B+ on your pot. Have you tried very man cap values? How usable to you find this mod?

100n is all I've tried. That's what was suggested to me... it worked... done deal. I have messed with the range and find that I prefer a 22K slope resistor and 50K-L pot for a smooth sweep of 22K to 72K. Nice (IMO) extended frame of lower than marshall to higher than soldano. Knob centered on 5/noon/12:00/etc puts it exactly at stock soldano. Plenty of adjustment either way from there.

My personal belief is that every part must qualify to earn the right to reside inside my amp. It should have a specific function, make a noticable difference, and actually be used. Bells and whistles are shiny and look cool. They're also potential sources of trouble and tone sucking. Those can go in someone else's amp. This 'mod' is something that deserves to be in my amp.

so there is no threat or harm? where would you ground it too then? I asked Anthony from Salvation Mods and he said there is danger....

there is no more danger once you add the cap than any other control on the amp. The cap blocks the DC voltage! As far as grounding you wouldn't at least not as far as the circuit is concerned. When you mount it to the front of the module the casing will be grounded just like any other pot!

this afternoon i installed a mid sweep pot on my freidman recto...

Just awesome, killer to have!

I used your values but love the 33K setting, which was what it was with just the resistor, but when i plug into different cabs it's going to be awesome, or just for a different sound!

There is an app on Duncan amps website that is a tome stack calculator. You can plug in any valued you want and see the tone curve.