250k RAT Distortion Pot

[rthryhorysak]

Will upping the the distortion pot value increase the gain. I know I will need to change the 100pf cap to 40pf to get the same hi freq roll off. Thanks

[electrosonic]

The gain of the pedal is mainly limited by the clipping diodes.

You could change out the diodes for LEDs or replace each diode with two in series to raise the clipping threhold.

This is a pretty good analysis-

http://www.electrosmash.com/proco-rat


Andrew.

[GGBB]

Yes. If you are just trying to replace a bad pot with something you have on hand, you can put a 166k resistor (make it the closest you can find) in parallel with the 250k pot to bring you back down to 100k max, and then not worry about having to change 100pf cap.

[ashcat_lt]

Increasing the value of that pot increases the nominal gain of the opamp stage.  The output of that stage is limited both by the opamp running into the rails and diodes.  It will increase the overall gain through the box for signals that aren't big enough to hit those limits.  It will increase the amount of distortion for signals which are big enough to hit the limits, but I guess you can't really say that the overall gain is increased in that case, because...limit.

Splitting hairs maybe, but the term "gain" is used in a number of different ways.  I tend to use it to mean nominal gain ignoring limits.  Some folks use it to mean distortion, some mean volume, and I suppose some folks use it to mean "loudness".  It will increase nominal gain, distortion, and loudness, but not actual peak volume.

But, it's only a little more than 6db, so not as noticeable as you might think.

[GGBB]

What you probably will notice, however, is that the range of usable settings on the distortion knob shrinks - everything above 7 or so is higher gain than previously available with the 100k. Fine tuning lower settings becomes more difficult, and you may find everything over that 7-ish point to be all the same. I already find my RAT to be all the same above about 8.

[aron]

Yeah mine is like that as well. I replaced the LM308 with an RC4558. I know this changes the sound, but I kind of like it. Will use it tonight for fun.

[aron]

I think I replaced it with a single op amp, but not sure. It actually sounded good last night - really raw with good sustain. Mine doesn't sound like an original Rat anymore.

[ashcat_lt]

I have a 100K pot in mine, but I cut the track at the high end and ran a 186K resistor between lugs 1 and 3 so that just at the top it jumps to almost double gain, but it's really hard to tell cause everything's pretty destroyed at that point anyway.

I used a TL080 with a rather larger compensation cap based on a recommendation from the board.  I have actually had it next to an original ProCo and the PodFarm emulation and I think it sits right in the middle.  It's hard to get the settings the same on any three boxes, of course, but the ProCo is just a little bit raspier or spittier or something.  Nothing I really miss in my own playing, and very subtle.  The PodFarm version really isn't that bad either.  I was kind of surprised at how well it held up in the shootout.  Course now I've coded my actual pedal into a plugin that's actually better than both the PodFarm thing and the pedal it's modeling...

[electrosonic]

Splitting hairs maybe, but the term "gain" is used in a number of different ways.  I tend to use it to mean nominal gain ignoring limits.

That's a fair comment and I agree. I read the original question and guessed (wrongly maybe) that the OP wanted to increase the output volume of the pedal.

Andrew.