Thoughts on replacing slope resistor with a pot.

[JD0x0]

Anyone have thoughts on replacing the slope resistor on my OTS, or any other amp for that matter, to a 250K pot.

It seems like a simple mod that should be standard on all amps. It's so simple yet it does so much. The amp would be tunable from a "flat," bass heavy tone, to a more trebly scooped tone and everything in between is possible by the turn of a knob. not to mention it affects the other tone controls for more flexability.

My question is how come no one seems to be doing this? I mean in theory it would turn a normal blackface fender into a "poor mans marshall" by turning the pot to a lower value which would increase midrange and bass.

Just one of my crazy amp mod ideas

[Bob-I]

A friend of mine did that on one of this Plexi style amps. He used a 47K slope resistor and a 100K pot. He said that going to 0 on the slope pot cause all kinda of problems including oscillation.

[JD0x0]

A friend of mine did that on one of this Plexi style amps. He used a 47K slope resistor and a 100K pot. He said that going to 0 on the slope pot cause all kinda of problems including oscillation.

So im assuming as long as it stays above "0" or very low settings it okay?

[dave g]

I have seen this done before a few places. I think all the old Heritage amps had this standard.

Yeah, you don't want the slope resistor going to 0. Put a 22k in series with the pot.

[ayan]

Anyone have thoughts on replacing the slope resistor on my OTS, or any other amp for that matter, to a 250K pot.

It seems like a simple mod that should be standard on all amps. It's so simple yet it does so much. The amp would be tunable from a "flat," bass heavy tone, to a more trebly scooped tone and everything in between is possible by the turn of a knob. not to mention it affects the other tone controls for more flexability.

My question is how come no one seems to be doing this? I mean in theory it would turn a normal blackface fender into a "poor mans marshall" by turning the pot to a lower value which would increase midrange and bass.

Just one of my crazy amp mod ideas

Be careful. Unless you put a coupling cap after the preceding stage, you will have one hot pot there.

Gil

[odourboy]

Be careful. Unless you put a coupling cap after the preceding stage, you will have one hot pot there.

Gil

Sounds scary but 24mm Alpha linear pots are rated at 500V and PEC pots even higher.

[ayan]

Be careful. Unless you put a coupling cap after the preceding stage, you will have one hot pot there.

Gil

Sounds scary but 24mm Alpha linear pots are rated at 500V and PEC pots even higher.

I appreciate that. Still, I would be careful about turning the metal shaft when one of the lugs is hot.

G.

[j-po]

So what if the pot shorts to ground? B voltage through the plate resistor to ground. Nothing dangerous about that. Of course if it were to short to an ungrounded pot shaft you might be in trouble.

[odourboy]

Not much different than a toggle switch with 450V of standby or 120VAC just under that metal shaft if you think about it. (I try not to think about it! )

[j-po]

Not much different than a toggle switch with 450V of standby or 120VAC just under that metal shaft if you think about it. (I try not to think about it! )

With the exception of that plate resistor limiting current.

[ukulele]

We is no corrupt in government of Soviet Finland. It is being legal to bribe politician. Country very niiice.

[Bob-I]

Be careful. Unless you put a coupling cap after the preceding stage, you will have one hot pot there.

Gil

Oops, I didn't think of that. Beyond a hot pot, you'll also be changing the plate loading. I'd say the coupling cap is a necessity.

[dave g]

Oops, I didn't think of that. Beyond a hot pot, you'll also be changing the plate loading. I'd say the coupling cap is a necessity.

A coupling cap isn't going to prevent the loading, that's not how it works...there is no DC path to ground at the input of the tonestack anyway.

[briane]

for a personal amp its a fine idea. If its going on the road, in general less knobs is better. More knobs, more things for a tech to fiddle with, more things to go wrong.

One also has to wonder about the quality of the resistive material if you put a pot in there. Will you be getting RN65 smoothness and quitetude? We can surmise the answer is no.

[butwhatif]

pots go bad over time, esp w hi voltage on them. even a new pot leaks dc