Fixed Resistor for Knobless Bass?

[fermata]

@RobbieK's video demonstrates that the capacitor plays no roll at all until the tone pot is dialed almost all the way back. He replaces the cap with a piece of wire, and the tone control works fine until close to the end of its rotation, when it suddenly turns into a crude volume control. The only role the cap plays is as a sort of dam that only allows the highs to go to ground. (A secondary effect of the cap is the resonant peak it introduces when it comes into play.) So for most of the tone pot's rotation, it's just the pot's parallel resistance dumping highs to ground.





It's the removal of the pots that makes straight-to-jack wiring brighter, because even at 10, a pot is allowing a bit of the signal (treble) to bleed to ground. (In other words, the presence of the cap is irrelevant to the circuit--and thus the sound--when the tone control isn't turned way down.) When the pickup is wired straight to the jack, hot and ground are completely isolated from each other, so the full signal makes it to the amp and the pickup's resonant peak isn't damped at all, which is why it's generally perceived as rather harsh and brittle sounding. This is assuming a fully passive system, of course.

There's more discussion on the subject in this thread: Capacitors and Tone

And to this thread's larger point, although I do use the volume and tone knobs on my (single pickup) bass, I'm drawn to the idea of a bass with no knobs, partly for aesthetics and partly for an acoustic instrument-like simplicity. Rob Allen has an interesting approach on some of his models: a volume knob accessible to the player and a trim pot for the tone that's accessible from the back that's meant to be more set-and-forget.

 

[walterw]

The easiest way to test is to put a capacitor across the jack socket. You can try the original 0.01 MF everyone first but you could also try other values which raise or lower the cutoff frequency.

Like folks are saying, not the same thing.

wiring in a cap without the pot gives you the sound of the tone knob turned all the way down, a different effect

 

[RobbieK]

I think with an EMG active pickup, even though the passive tone circuit looks the same, with a pot (25k) and cap (100n) in series between hot and earth, it works quite differently than with a passive pickup. The cap forms a low pass filter with the output resistor of the buffer preamp. This would have a fairly constant roll-off point, and the pot sets how much. The output resistor is just inline with the opamp output and means multiple pickups can be summed directly, like on a strat or whatever, with a switch.

 

[iiipopes]

Wait a minute - having a resistor of about 12k to ground would take off more than half the volume and tone. We need to consider the load, not the actual resistance spec of the pickups or pots. The OP said he wanted an emulation of having the circuit with the pickups dimed. In my experience with high impedance pickups, the circuit of an average pickup with standard 250 kohm pots and .047 tone capacitor always measured about 100 to 500 ohm less at the jack with the circuit than the pickup by itself with no load. Take the average: 250 /250 k is a tenth of one percent. I'm thinking that a 25-100 ohm resistor from the hot lead to ground will give about the same volume loading on a low impedance circuit for the volume, then have the full resistance of the recommended tone pot in series with the recommended tone capacitor to ground will emulate the tone dimed, but still in the circuit.