replacing vol pot with resistors

[UCSDBoy]

Hi everyone,

I know this may sound odd, but if you'll indulge me:

I know that a tone pot can be replaced with a resistor and a cap in series, and some would say you could do away with the cap entirely if the resistor is around 250k or so. Since a volume is just a voltage divider, I could replace it with two resistors in series, with the hot entering one end, the output hot T'ing off between the resistors, and the other end linked to ground. My question is - if I use a 270k resistor or thereabouts, what resistor do I use for the second one? How does the circuit degenerate when the second resistor is 0 ohms?

Thanks in advance!

C

 

[marcello252]

it depends on what you want to do, I'm not sure if I properly understood.

​​​​​if you make a voltage divider you have to expect a drop in voltage at the junction ( taking the output at R2 with R2 to ground, Vout= Vin * R2 /(R1 + R2 ) ), so how much would you like to tame the output of the pickup?
If you don't want to lower the pickup output, still want the loading effect of the simulated 250K pot just use a plain 270K R from pickup output to ground.
I don't think you can omit the tone cap without hearing the effect of the filter on the treble, but for the lower frequencies the tone resistor is an open circuit, for the upper is a resistor in parallel with the one of the volume cap, the more you lower the tone resistor the lower is the value of the parallel .
So, what are you aiming to?

 

[beaubrummels]

Depends on two things: the goals of this, and what the volume pot was before. I don't understand why you would want to permanently simulate a partly turned down volume control.

 

[UCSDBoy]

So, what are you aiming to?

Just experimenting. I have a small collection of pots that I never used or rescued from previous experiments. Several years ago I bothered to test their actual resistance using a multimeter and marked their actual value on the pot shell using a Sharpie. Recently I tested them again before using them in another project and found all of their values and decreased noticeably from the value I had previously marked.

I also noticed a few fender brand (made by Alpha) push pull pots I just bought measured as low as 220 and 214 instead of 250. That's close to 20% variance - much higher than the 5-10% I was expecting.

In contrast I have 100 ct packages of 270K and 510k resisters and these things are spot-on - a max tolerance of +/- 1%. I like the idea of reliable and dependable components. Don't get me wrong I do know how to use a tone pot but in truth I haven't missed them; everything I need a tone pot for I can get with my EQ pedal. What I miss from a tone pot is the load it puts on the circuit, hence the resistors.

The next logical leap was to ask if I can replace the volume pot with a volume pedal. That got me thinking what would a volume pot + tone pot replaced with resistors would look like on my two pickup guitar. It sounds like it would just be the hot from the switch attached to two 270k resistors in parallel, one with a capacitor attached to it to simulate the volume and tone knob, respectively.

 

[marcello252]

that works for the purpose but they must be in parallel as the last post, non in series as stated on the first one.
I use a lot vol and Tone pot so I see a little excessive to remove both , but if you like it that way it's ok

 

[UCSDBoy]

that works for the purpose but they must be in parallel as the last post, non in series as stated on the first one.
I use a lot vol and Tone pot so I see a little excessive to remove both , but if you like it that way it's ok

Thanks for your help! Yes it's definitely breaking convention.