Slightly OT, problem removing two clip LED diodes gives HUGE volume boost

[GrantsV]

I have a Marshall MG15CD amplifier and am dabbling with the preamp, which is essentially a distortion stompbox coupled to a poweramp.  As stock, the preamp is all buzz and heavily distorts very low on the gain knob taper.  I noticed its just an IC + two LED diodes doing the clipping so removed the LED's to see if I could reduce the buzz and gain.  It worked!  Now the amp crunches like a nice big Marshall!

However the volume knob is a pain, it goes from silent, to about half the amps decibel power between 0-1 on the vol knob.  Before it would taper nicely up from 0-6 to get that loud!

1) If I jumpered the points where I removed the LED's, what effect would this have on the sound?
2) Should I replace the volume pot to get a better taper?
3) Any other ideas to get control of the volume back but keep my new distortion sound!

All the best,
Colin

[~arph]

1) Dead silent
2) Not sure, but I don't think so
3) No, if you put a resistor (say 100k) to ground in place of the LEDs the pedal will not push the amp as hard as it does now and your new distortion sound is gone.

Probably you need to reduce the power amp gain a bit, to make up for the higher input, but this is really just a guess.

[Caferacernoc]

I actually think putting a 100k resistor in place of one of the LED's might work. Can't hurt to try.

[earthtonesaudio]

I would put a resistor close to (but not higher than) the volume pot's value between lug 3 of the volume pot and whatever it's connected to.

So if you have a 100k volume pot with lug 3 going to ground, I'd put a 68k resistor between lug 3 and ground.  That would help move the taper around.


...I think it would work between lug 1 and the rest of the circuit also, but I'm not sure.  As for the other things to try, it depends a lot on the type of circuit.  Clippers to ground is one way, clippers in the feedback loop is another.

[WGTP]

Might try 4 LED's instead of 2.