Brownface treble-pot's cap question

[deci belle]

Some of these amps have a .0047 cap and others (like the Showman), have a .003 going to ground (on the volume pot's tab).

I'm not sure if these caps bleed treble or bass frequencies… would someone please tell me what it is called that these caps do and how?

I'm not in a position to swap .0047s for .003 uF caps (waiting for a PT) to hear the difference in tone, but still I don't know why those caps are there or how they do what they do.

[g1]

Caps from the signal path to ground create a path to ground for the AC signal (shunt). The larger the value of the cap, the lower the frequency of the signal allowed to pass through the cap and be shunted to ground.
So these caps would be a bit of a high frequency bleed, the .0047 would bleed off a bit more of the frequency range than the .003

Edit: I was speaking generally about caps to ground, didn't quite clue in that you were speaking of the treble pot, but the principle is the same. The treble pot controls the resistance between the signal and the HF bleed cap. (I think where you said volume pot tab you meant treble pot?)

[Gingertube]

I had to look very carefully at the schematic to convince myself that the cap was in fact labelled 0.003uF and it was'nt just a blured 0.005uF.
http://www.webphix.com/schematic%20h...wman_6g14a.pdf

The value changed from 0.005uF to 0.003uF between the 6G14 and the 6G14A Dual Showman.

This is the bottom cap in the Treble Arm of the Bass + Treble "James" Tone Stack. It would effectively move the Treble Control response a little higher in frequency.

You can see what it does for yourself by using the Tone Stack Simulator from Duncan's Amps Site.
TSC

Cheers,
Ian

[deci belle]

(I think where you said volume pot tab you meant treble pot?)

Hi g-one~ I just meant it grounded on the volume pot's tab that connects to ground …it IS connected to the 350k treble-pot's signal path, but just uses the convenient path to ground via the volume-pot's ground-tab (at least on my amp).

I just finished a blonde twin with the James circuit, Ian— I've been kinda doing some audio-anthropology in the last month: 5F8+6G8 in one head and right now it'a a 6g14a+6G6b in one head.

Thank you for saying…

The value changed from 0.005uF to 0.003uF between the 6G14 and the 6G14A Dual Showman.

This is the bottom cap in the Treble Arm of the Bass + Treble "James" Tone Stack. It would effectively move the Treble Control response a little higher in frequency.