Another grid-to-ground tone robbing cap? (A1270)

JJman

Member
Messages
994
I just spotted a grid to ground .002 (2000pf) cap on the reverb return jack of my '71SFDR. Looking at the schematics it looks like this was added with the A1270 and was not on the previous AB868 or AA/AB763. I removed the ones on the output tubes a long time ago with no problems.

Anyone ever remove this one? Is it another tone robber, only relating to the reverb sound? I'm thinking that brighter reverb might be a good thing on this amp. But maybe .002 is already above the relevant audible frequency in this location? Anyone know the frequency at which this one begins to do it's thing? Maybe I should replace it with a smaller value so it still prevents the boogie man from entering? :messedup

Of course I will experiment but maybe this has already been done.
 

JJman

Member
Messages
994
I noticed a lot of microphony around the cap and it's connections. Removing it solved the microphony and did not brighten the reverb. I put a new .001u(1000pf) cap back there and no problems.
 

itkindaworks

Member
Messages
3,247
I believe the reverb was changed a little on silverfaces(to allow mostly highs through?). This is what I've heard.
 

Fuchsaudio

Member
Messages
7,920
That cap is there to control the resonance of the reverb return circuit. Replacing it, is wiser than removing it. It can also prevent possible oscillations from occurring.
 




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