Bypassing tone pots: DPDT required?

Jagdmusik · #1 09-10-2006, 04:45 PM

I'm looking to equip a passive bass with a tone-bypass switch, and for reasons I won't get into, I'd like to only use a single pole to do so. Is it possible to do this while completely nullifying the tone control's effects?

It seems to me that COMPLETELY removing the tone pot from the circuit requires TWO poles on a switch: the first being the hot lead from the pickup (for simplicity here I'll ignore volume/blend pots), and the second being the hot lead coming out of the tone pot. With tone bypassed, then, the former would be connected directly to the output jack, while the latter would be totally disconnected.

However, it also seems to me that the second pole should be unnecessary, because just switching the hot from the pickup should cause the signal to go around the tone pot instead of through it. The tone pot would still be connected to the circuit at the output jack, but with the hot from the pickup also connected to the output, the signal would no longer need to go through the tone pot to reach the ground. Since electricity follows the path of least resistance, that implies to me that the tone pot would thus have no effect.

However, I'm definitely not an electrical engineer (I've just pieced things together from a lot of websurfing), and I often find that the way I expect things to work is mysteriously not quite the way they actually do. Could someone confirm for me that my single-pole solution would in fact result in NO tone coloration from the tone pot or cap?

luknfur · #2 09-10-2006, 05:44 PM

FWIW:

Depends on how you've got it wired. If you've only got a single lead running from the volume pot to tone then you should be able to throw a single pole switch in between to run through the tone in one position and skip it and complete the circuit in the other position.

A9X · #3 09-10-2006, 05:59 PM

An SPST will do. Just wire it in series with the top of the tone pot. When the switch contacts are closed the pot/cap network is in circuit, and with the contacts open, it's not.

Jagdmusik · #4 09-30-2006, 07:02 PM

Thanks for your replies. At first I wasn't understanding why just one pole would work, but then after some more net research I realized that I hadn't actually been understanding how the tone pots really worked. It was like I thought there was something magical about the capacitor being connected to the circuit in any way.

Sorry for the n00b question.