Low pass cut-off freq

[studioit]

To calculate the corner freq of a low pass filter on a BF style reverb return circuit - ( I want to put a cap across the signal on the input side of the return tube- probably across the return jack to roll off a touch of the tinnyness) what is the resistance 220 k? or the tank impedance? the 2 paralleled?

thanks,
Ian

[Enzo]

Why do it there? Why not after the recovery tube?

[studioit]

I suppose I could but it's easier logistically to do it there in this application. Also the circuits a bit different on the output side as it's not in a BF reverb.

I'm open to other ideas but I don't have a schematic in a form I can post at the moment.
Don't you people in Mich. Sleep?
Thanks,
Ian

[Enzo]

Yes we do, during the day. Our shop is open musician hours - we come in at 6:30 PM and stay all night.

I'm not saying tacking a cap across the input won't work, but I hate adding things right at the input of something. Doesn't matter what circuit it resembles, the reverb [pan feeds a grid, right? And the plate signal continues onward? Does that plate signal pass through a cap and wind up at a level control eventually? SOmewhere in there your rolloff could fit.

[studioit]

Yes it does .... It goes thru a 4700 pf coupling cap to the wiper of a 100 k pot
which is shunted across the signal. The output of the pot is then mixed back in from there on the other side of a 680k res. It's a cross between a BF and a Blue angel kind of circuit. the 3.3 meg res is in series with the send to the driver tube. Does that make sense?
I'm going to sleep now (even though it's only 2am here in Ca).

Thanks
Ian