Anyone measure their tone pots?

[Herr Squid]

Some may have noticed that I've commented before on a very bright-sounding SC 594 that I own. It's particularly noticeable when I compare it to a very close sibling, a DC 594 that has a serial number about 20,000 lower. I think it's a very early one.

The DC sounds warmer to me, particularly when I compare the bridge pickups. After a chance conversation with a friend about tone controls, I thought I'd whip out a multimeter and make some comparisons.

It turns out the doublecut measures about 391 KOhms on the bridge tone control, and the singlecut measures about 467 KOhms. I believe they're supposed to be 500 KOhm pots, so they're running low, and in the case of the doublecut, a lot low (22%).

Can anybody say whether a 76 KOhm difference between those pots would make a noticeable difference in the tone, given that the wood and pickups should be very, very similar between the guitars? I definitely like the sound of the bridge pickup with the lower resistance pot. I think I've heard of people using a parallel fixed resistor to bring the resistance of a pot down, has anyone here tried that?

 

[WEDGE]

Measured mine and they go to ten

 

[Boogie]

Some may have noticed that I've commented before on a very bright-sounding SC 594 that I own. It's particularly noticeable when I compare it to a very close sibling, a DC 594 that has a serial number about 20,000 lower. I think it's a very early one.

The DC sounds warmer to me, particularly when I compare the bridge pickups. After a chance conversation with a friend about tone controls, I thought I'd whip out a multimeter and make some comparisons.

It turns out the doublecut measures about 391 KOhms on the bridge tone control, and the singlecut measures about 467 KOhms. I believe they're supposed to be 500 KOhm pots, so they're running low, and in the case of the doublecut, a lot low (22%).

Can anybody say whether a 76 KOhm difference between those pots would make a noticeable difference in the tone, given that the wood and pickups should be very, very similar between the guitars? I definitely like the sound of the bridge pickup with the lower resistance pot. I think I've heard of people using a parallel fixed resistor to bring the resistance of a pot down, has anyone here tried that?

Makes a difference to me. I measure and mark every one for that reason.

 

[Black Plaid]

A lower resistance would has been cited to make a guitar sound warmer.

If you want to get the same value, add a resistor in parallel, using the following formula to determine the value:

[bunch of removed equations and computation, was getting internal server error when trying to post]

... Or 2402 ohms.

Get somewhere close to that and you should be good enough.

 

[Herr Squid]

Makes a difference to me. I measure and mark every one for that reason.

Oh wow. I wouldn't have guessed that 10s of KOhms would make a difference, but I'll keep my eyes open for that.

 

[Herr Squid]

A lower resistance would has been cited to make a guitar sound warmer.

If you want to get the same value, add a resistor in parallel, using the following formula to determine the value:

[bunch of removed equations and computation, was getting internal server error when trying to post]

... Or 2402 ohms.

Get somewhere close to that and you should be good enough.

I thought I remembered that for parallel resistance, R = 1/(R1 + R2) so I plugged in my numbers for R and R1 and went about trying to solve for R2... My algebra's rustier than I thought, and I got a negative number, so obviously something was wrong. I saw a formula on other pages that I think was R = (R1 * R2)/(R1 + R2) and I figure I should give that one a go...

 

[Black Plaid]

I thought I remembered that for parallel resistance, R = 1/(R1 + R2) so I plugged in my numbers for R and R1 and went about trying to solve for R2... My algebra's rustier than I thought, and I got a negative number, so obviously something was wrong. I saw a formula on other pages that I think was R = (R1 * R2)/(R1 + R2) and I figure I should give that one a go...

I tried to post my original again with changes, but again got the error.

I used Wolfram Alpha to do the algebra:

https://www.wolframalpha.com/input/?i=1/391+=+1/467+++1/X

We find R2 (X in the above) = 182597 / 76

Or 2402 ohms.

 

[Black Plaid]

I tried to post my original again with changes, but again got the error.

I used Wolfram Alpha to do the algebra:

https://www.wolframalpha.com/input/?i=1/391+=+1/467+++1/X

We find R2 (X in the above) = 182597 / 76

Or 2402 ohms.

The formula is

1/TotalResistance = 1/ResitanceOne + 1/ResistanceTwo + ...

 

[shimmilou]

You are all close! It is 1/(1/R1 + 1/R2 + 1/R3....) All reciprocals totaled, then the reciprocal of that.

 

[Alnus Rubra]

Makes a difference to me. I measure and mark every one for that reason.

Lovely work Uncle Boog!

 

[dmatthews]

Makes a difference to me. I measure and mark every one for that reason.

Geekery... I like it!

 

[Black Plaid]

You are all close! It is 1/(1/R1 + 1/R2 + 1/R3....) All reciprocals totaled, then the reciprocal of that.

That will let you figure out what the residence is in an existing circuit, but does not allow you to determine how to get to a particular total given a set of existing inputs.

 

[Herr Squid]

A happy ending to this tale. I strapped a 2 M Ohm resistor across the center lug and ground on the tone control for the bridge pickup, and that pickup sounds waaaay better to my ears. It's still got some brilliance to it, but the offensive icepicky edge to it is gone.

Thanks to Black Plaid and Shimmilou for the equation pointers, and reminding me that Wolfram Alpha exists. Once I figured it out, it sure beat doing the algebra by hand!

Though this thread went down the math hole, I'm still curious: for those who have done this kind of measurement and tweaking before, how much difference can you hear when the pots are some number of K Ohms off spec?

 

[Boogie]

For me and my screwed up ears, it takes a lot...like 100k ohms or more. And if I’m lucky, I’ll turn the tone control into more of a Q control (sounds like a wah running thru it’s range). My best success was on my SE One using a Treble Bleed device. Even with math on my side (I admit to being very much a nerd), it’s a crap-shoot for me. Just when I think “this is positively what it’s going to do” it ends up doing something slightly different. So, for me, it’s all trial-n-error in the end.

Some places have A350k pots for Les Paul applications as a secret weapon, and I think these make a solid difference. Back in the 80s, I’d add a trimmer (small trimming potentiometer...I sold them by the boat load, literally) to a 250k pot so I could dial in the exact resistance I wanted. So with a 250k trimmer, theoretically you could find your favorite value with the twist of a jewelers’ screwdriver.

 

[Herr Squid]

The trimmer pot sounds like genius. So you'd put the tone pot and trimmer pot in series and be able adjust between 250 and 500?

 

[Boogie]

The trimmer pot sounds like genius. So you'd put the tone pot and trimmer pot in series and be able adjust between 250 and 500?

Yep. Usually, I was working on the volume pot but the tone pot would work the same way.

BUT (< big but) now you have 250k ohms, or there abouts, on continuously. Twisting the volume/tone pot isn’t sweeping thru the entire range. If you want to experiment and find what you like, it’s a great tool, but then it gets annoying for live use.

 

[Herr Squid]

Ah! Good point. So I think that tone control arrangement could never turn down more than about halfway-ish. Which honestly might not bother me much since I use that control so seldom.