Blend Pot for Bass/Treble Cut (Tone Pot)

[thehallofshields]

Okay, so I've been amplifying all sorts of instruments, and to save space, I'd like to be able to be able to cut treble and bass with the same knob. This would be nice for instruments that can sound muddy. My understanding of tone controls is not excellent, so it seems to me, that something simple like this should work.



So Center would be a Cap with no Resistance to Ground (I Think that is a problem)
Turning to the left would Cut Treble and turning right would flip the RC Filter and Cut Bass. I'm certain this idea needs some work, could anyone else offer some ideas on how to make use of blend pots for tone controls??

[J M Fahey]

You've invented a tone control that does absolutely nothing.
Imagine you are using a 2 x 1 MegOhm linear pot.
Both sections are in series with the capacitor.
oN "0" the top one is shorted, the bottom one is 1M, total resistance in series with the cap=1M
On "10" the opposite is true, total resistance in series with the cap=1M
On "5", top is 500K; bottom too, total resistance in series with the cap=1M.

[thehallofshields]

Thanks. It seemed flawed, but I had a mental block to seeing how. I see now that however I wire this, it will fail.

I probably need a mini dual-concentric pot to get bass-cut and treble-cut control in a single knob space huh?

I guess I'll be going with a plain-old-fashioned treble-cutting pot. What a shame...

[Albert Kreuzer]

You could go for a Big Muff type control. Single pot, two resistors and two caps. One side cuts treble, other side cuts bass.
Look up "Big Muff" or "tilt control", or better yet, get Duncan's tone stack calculator at www.duncanamps.com/TSC for a neat Spice simulation.

[MWJB]

"I'd like to be able to be able to cut treble and bass with the same knob" Fender have had this for years, it's called a middle knob.

I don't understand the need to do this via a single knob (unless chassis size prevents more pots & knobs), another alternative could be a hard wired Fender tone stack, with fixed, preset treble & bass settings, just a 25KL or 50KA middle pot?

Gibson's GA 90 had a combined treble & bass pot, turning one up turned the other down - you could have a look & see whether you could get them to both cut when turned CCW?

[thehallofshields]

Is this what I'm looking for:
CRAIG'S GIUTAR TECH RESOURCE - Tone Controls



Unlike a normal dual-ganged pot, blend pots have 0 resistance at the center-detente -right?