Reducing ohms on 1 meg pot by increments of 25, 50,100 HOW?

[KLINKDETROIT]

I know its possible to connect resistors or a resistor to your volume or tone pot to reduce its ohm readin. I have a BBQ pickup from Rio grande. I bought a couple of 1 meg pots from Torres as the BBQ needs the higher headroom or openness from the 1 meg but not 1 megs worth. My figures of multiplying the pickups k reading of 13.5 x 40 = 540 ohm pot is what I need. All the so called 500k pots I find are more like 450 or 480 on my ohm meter.

I want to take the 1 meg pot and reduce its ohmage to experiment on what tone I like. I have a feeling it will be around 650 but thats just a guess. I also find that the tone pot while all the way up is also a factor.

If I get a 650k pot or resistored to 650k then what value tone pot is the best with a .047 cap?

I also need the resistor values and instructions for my neck pickup. It is the texas and rates around 8.9 so 8.9x40= 356k pot Is that what I should use? Should I stick with a minimum of 500k on the volume even on a pickup like the texas?

I am confused. Any info is greatly appreciated. Thanks in advance.

 

[Artie]

Re: Reducing ohms on 1 meg pot by increments of 25, 50,100 HOW?

Here's the formula, which isn't as complicated as it looks since most calculators have the 1/x key:

The second formula is what you want, which yeilds 1.174 meg to get 540k. Trouble is, thats not a standard value resistor.

1.86 meg would get you 650k.

However, the better thing to do might be to use the technique that I outline here, in the vault:

https://forum.seymourduncan.com/showthread.php?t=27328

Wire up your 1 meg pot as shown. I'd probably use a 100k resistor with that. Dial it up and down until you find the "tone" you like, then carefully pull the pot out without turning the knob, and measure its value. Then use the formula to determine which resistor you need to place across it.

 

[KLINKDETROIT]

Re: Reducing ohms on 1 meg pot by increments of 25, 50,100 HOW?

I am afraid you are much smarter than I. I will ask a buddy to decipher your formula. Any idiot proof diagrams?

 

[Artie]

Re: Reducing ohms on 1 meg pot by increments of 25, 50,100 HOW?

I'll make you up a "table of values" tonight.

 

[Artie]

Re: Reducing ohms on 1 meg pot by increments of 25, 50,100 HOW?

Using standard resistors, you'ld get the following:

1.1M = 523k
1.2M = 545k
1.3M = 565k
1.5M = 600k
1.6M = 615k
1.8M = 643k
2.2M = 687k
3.3M = 767k

 

[KLINKDETROIT]

Re: Reducing ohms on 1 meg pot by increments of 25, 50,100 HOW?

You freakin rule man thanks a bunch

 

[theodie]

Re: Reducing ohms on 1 meg pot by increments of 25, 50,100 HOW?

This should be in the Vault!!!!!

Vault material!!!!!!!

 

[KLINKDETROIT]

Re: Reducing ohms on 1 meg pot by increments of 25, 50,100 HOW?

Anyone have a diagram of how the wires hook up to the volume pot with the resistor in place? I also run a 500k tone pot connected with a .047 cap. Thanks

 

[aleclee]

Re: Reducing ohms on 1 meg pot by increments of 25, 50,100 HOW?

Given the not-so-tight tolerances on a lot of resistors, I'd suggest that you get a trim pot, run it in parallel with the 1M volume pot, and adjust it 'til it sound good.

 

[KLINKDETROIT]

Re: Reducing ohms on 1 meg pot by increments of 25, 50,100 HOW?

I think I will be ok with around 640k but not sure where the resistor hooks up to what lug etc.

 

[Artie]

Re: Reducing ohms on 1 meg pot by increments of 25, 50,100 HOW?

I think I will be ok with around 640k but not sure where the resistor hooks up to what lug etc.

The resistor connects to the two "outside" lugs of the volume pot. Then make all other connections as if the resistor wasn't there. That is . . . like normal.

 

[KLINKDETROIT]

Re: Reducing ohms on 1 meg pot by increments of 25, 50,100 HOW?

Thanks. Is this different from the 50s way where the center and ground lugs are used?