CK switch on first stage

[Fred G.]

I have an unused DPDT slider bright switch on the Normal channel of a Fender Bandmaster which I'd like to use to switch between cathode cap values. I'd like to be able to do this "pop-free" and without having to shut off the amp.

I know this is very do-able, but I don't remember the specifics - there needs to be a resistor to ground somewhere to accomplish this, right?

Thanks,

Fred G.

[famp69wv@yahoo.com]

CK switch

Fred

I generally wire it with the boosting cap negative lead to one side of the switch & a 10K resistor from there to the center pin (& from there to ground). That usually takes care of the popping.

[Enzo]

Yep. The resistor value is not critical, any high resistance works. It provides a charging current path for the cap, and that leeps it charged up. If it is not charged, the charging current rush is what makes a pop.

[Fred G.]

The single resistor to ground fron the center lug would be shared by both caps, then?

[famp69wv@yahoo.com]

Not exactly what I was getting at

Fred

I'm sorry I wasn't a little more clear. I assumed you'd want to have some thing on the order of .1, .68, or up to 5uf across the CK to ground already. Then take the larger capacitor, say 25uf from the tube's cathode to the switch so you'd have a mid/bass boost fuction. This would give you two distinct sounds as you are, no doubt, aware.

If you want two caps on the switch you'd need two separate resistors going from the negative side of each to the center lug (& from there to ground) of the switch to eliminate the charging current in-rush pop from occurring.

Used with a fixed value as in paragraph one above I suppose you'd have three distinct sounds in that set up. IMHO this type arrangement doesn't give you much bang for the buck though because any change seems to be too incremental or subtle on the 'medium' setting (low side of the switch). YMMV

[Fred G.]

Thanks, Philip!

It is very clear now - what you describe is more straightforward and simpler than what I was thinking of doing, it just hadn't occurred to me. I want to switch between a .68 or 1.0 and maybe a 10.0 or so, value as yet TBD.

Thanks!

[Enzo]

Each cap needs its own resistor. The switch really just shorts across the resistor. The value of the resisitor is high enough that the cap has little effect when it is in circuit, but it still remains charged. When the switch shorts across the resistor, then teh cap fully participates, and was already fully charged.

[Chris / CMW amps]

here's a way:

wire the cathode-resistor in parallel with the smallest cb-cap.
than connect the larger cap to the cathode and between the other connection and ground a 10k-100k resistor, than a switch between the other connection and ground