Tremulus Lune Gain Stage question --- mainly C3

[brokenstarguitar]

My question is about C3, the 330pf cap between lug 1 and 2 of the gain pot. In actuality, what does this do? What the reason for this? I noticed it isnt in any version where the "Gain" pot is interior. Any help would be appreciated! Thanks as usual guys!

I attached the schematic im going off of.

[rankot]

It is filtering out high frequencies.

[Elijah-Baley]

Exactly now rankot said.
Higher value cut off more treble.

[GibsonGM]

Or, we could look at it 'functionally' and say that it is bypassing the opamp...passing high frequencies from input right to the output.  Lower frequencies will be boosted, but the highs will not.  They are still there at the same level as they were at the opamp input, but just did not get the boost...it is a small difference in semantics, but one day it may be important to know...

[brokenstarguitar]

I also thought it was a treble bleed but wanted some reassurance. Thanks a bunch guys!

[ElectricDruid]

Or, we could look at it 'functionally' and say that it is bypassing the opamp...passing high frequencies from input right to the output.  Lower frequencies will be boosted, but the highs will not.  They are still there at the same level as they were at the opamp input, but just did not get the boost...it is a small difference in semantics, but one day it may be important to know...

Another way to express the same thing would be to say that it "limits the gain bandwidth". After all, we don't want to be amplifying ultrasonics, and the op-amp might be able to do that unless we specifically tell it not to.