Bright caps values to emulate tone control 3/4 way up?

[RobBozic]

Hi,

I've ditched the tone control on my 5E3, and want to put some bright caps over the volume controls which are set up as a mixer (brownface deluxe). Anyway what value cap would emulate a tone control sap half way up and 3/4 way up? Is it half and 3/4 of the 500pf cap?

Thanks in advance
Rob

[soundguruman]

Anything from 50 pf - 500pf is usually used.
Silver mica caps are useful, because they tend to pick up less filament AC Buzz.
Volume control with 40-60% tap is sometimes used, to smooth out the curve in frequency response.

Usually the best result is obtained by experimenting w/ different caps, playing guitar, and adjusting it to taste.
A lot of more modern amps are using 50 pf, as opposed to the older style 250-500.
Using 50, the highs are smoother, and the effect is less harsh, in many amps...it does sound better.

[Tom Phillips]

Rob,

The bright cap circuit produces a different frequency response effect at a higher frequency band than the tone control. In addition, the amplitude of the bright capacitor's effect is dependent upon the setting of the volume control. The higher the volume control is set the less the bight cap brightens the tone. By the time the volume is full up a bright cap has no effect no mater what its value. Because of this, there really is no bright cap value that will emulate a given setting of the ditched tone control. Especially if you still intend to change the setting of the volume control. The way your ears respond to different sound pressure levels comes into play too. That changes the perceived tone vs. change in volume setting. You can experiment with bright cap values anyway of course and maybe you will discover a value you like but the overall tone will be different than it was with the original tone control setup.

Tom

[J M Fahey]

True.
*If* what you mean is that you can't use that pot because of lack of space or something, yet you like the sound "on 3/4" , before pulling it set it to your preferred value by ear , turn amp off and read both halves resistance, then replace them with fixed resistors.
Say ... 750K + 250K or whatever you find.
And then pull the pot and use that hole for whatever you want.

Using a single bright cap of any value is not the same, by a long distance.

[RobBozic]

Gents, thanks for your help.

I've put 250pf on both volumes and like the way it sounds at the moment.

I was intending to install a VVR where the tone control is, however, I might install it where the standby switch is, and then put the tone control back in.

Rob