Gain Pot Darkens the Sound

[juan_felt]

Hi,

I built a Mesa Throttle Box, and ir works. The problem I found is that the Gain knob between 50% and 0 darkens the sound very much.
I used this schematic:

Is there any way to avoid this, or to make it less noticeable?

Thanks!

[Mark Hammer]

Delete.  Premature.

[Kipper4]

Do you see the RC filter made up of C2 R13

What happens if you change C2?

[juan_felt]

Do you see the RC filter made up of C2 R13

What happens if you change C2?

When I change that filter I get more bass in the distortion, but doesn't seem to affect the "dark' issue.

Enviado desde mi Nexus 6P mediante Tapatalk

[dschwartz]

Those 1k5/0u22 low pass filters are pretty extreme..you are not loosing high content, you are loosing the higher harmonics generated by IC2D stage. The signal going into that clipping stage is very dark..remove one 0u22 cap and see what happens

[ElectricDruid]

+1 agree with what others have said. If the problem is between 0-50% on the gain pot, it's not really the gain pot that's making the signal dark. The signal is dark *anyway* because of the rest of the circuit, and turning the gain up past 50% probably generates enough high frequency content to mask that effect to some extent.

I'd go through the circuit and reduce/remove some of the lowpass filters. Those 1k5/220n filters that dschwartz mentioned would be an excellent place to start. Replace both 220n's with 22n and see if you like it better (this opens the response up from a roll-off above 480Hz to one above 4.8KHz).

HTH,
Tom

[GGBB]

Just for my own sanity - am I correct in noting that the gain pot is backwards in the schematic? Or is the pedal built that way - which means 0 - 50% clockwise is the gainier part of the control, which doesn't make sense to me since I agree with the other statements about the 1k5/0u22 filters and the generated high harmonic content.

[dschwartz]

+1 agree with what others have said. If the problem is between 0-50% on the gain pot, it's not really the gain pot that's making the signal dark. The signal is dark *anyway* because of the rest of the circuit, and turning the gain up past 50% probably generates enough high frequency content to mask that effect to some extent.

I'd go through the circuit and reduce/remove some of the lowpass filters. Those 1k5/220n filters that dschwartz mentioned would be an excellent place to start. Replace both 220n's with 22n and see if you like it better (this opens the response up from a roll-off above 480Hz to one above 4.8KHz).

HTH,
Tom

480hz.. that's very dull sounding! I'd bet that they are 22n and the schem is wrong

[ElectricDruid]

Just for my own sanity - am I correct in noting that the gain pot is backwards in the schematic?

I think so. I hadn't spotted that, but now you point it out...
The way it's drawn, as you turn the pot "up" the resistance goes down, and so does the gain. It's back-to-front. Still, the minimum gain is 1+100/4.7=21 roughly, so it's still got some gain even then.

Tom