5F6A Bassman Clone - Switchable tone caps?

[nash076]

I had decided to replace the caps in my Bassman clone with PIO K40Y-9's. I did some digging around the net and found out about the discrepancy between the 5F6A schematic and some of the production models (i.e., the 100k slope resistor, the .1uf bass cap, the 25k dc-to-ground presence pot, etc). Given how I was curious about playing with the sound anyway, I decided to make the switch to the production version.

As I was doing so, I opted to make the slope resistor switchable from 56k to 100k, which works just fine. But it also occurred to me to try to make the bass cap switchable too, from .1uf in the production/reissue model to the schematic .022 cap version.

I attempted this using an on/on DPDT switch, with one setting connecting the 56k and .022uf, and the other the 100k and .1uf. I used the middle lugs as commons lines for both (one for the caps, one for the resistors). This configuration did not work; the tone stack was screwed up, with the middle pot shutting off all volume if turned down, and the bass and treble pots doing nothing at all.

I could tell it was doing *something,* because flipping the switch caused the amp to pop. (After that, I only flipped the switch with the standby turned on.) But after troubleshooting my connections, I removed the capacitor side of the switch from the equation and temporarily replaced it with a .022 uf cap. Voila, problem solved. As a result, I removed the caps from the switch and left it for the slope resistors alone.

Now, my question is this: is the idea feasible, but I'm just using the wrong switch configuration? Is using the DPDT with a common connection (the middle lug) making it not work? Would giving the caps their own switch (or potentially using a 4PDT switch) be a viable solution? Is this just not possible to do, or did I screw up somehow?

While I'm good with assembling the electronics, being safe and comprehending some fundamentals and troubleshooting, I'm not trained in engineering, nor am I a deft hand with schematics. (Sadly, I am a Layout Larry.) Any feedback would be appreciated. Thanks!

[Reeltarded]

Instead of swapping caps, add one in parallel that adds up to the value you are looking for with an on-off single pole switch.

Simple and that works.

[martin manning]

Seems like you could put in a 100k slope and a 0.022uF bass cap and arrange the switch to parallel a 120k across the slope and un-parallel a 0.068uF from the bass cap. The switch would only have to lift or reconnect one end of the resistor and cap.

[nash076]

Instead of swapping caps, add one in parallel that adds up to the value you are looking for with an on-off single pole switch.

Simple and that works.

I like this; so, switching caps in parallel won't cause the problem I had before?