Opinions on what resistor values I should use in my 3 way tone toggle switch

[toonskeez]

Hi, this is related to the current guitar I've almost finished:

Need some advice/help on wiring this up (5 way import style blade switch)

This post is directly related to this one: https://www.tdpri.com/threads/is-it-possible-to-change-a-pickups-tone-via-a-3-way-mini-toggle-switch-and-no-tone-pot-or-some-other-way-with-no-tone-pot.1107433/ I'm using an import style 5 way blade switch, due to the standard 5 way switch being too...

www.tdpri.com

That other post details the overall wiring in the guitar. This post is specifically related to the 3 way on-off-on mini toggle switch I'll be using as a tone circuit for the middle single coil pickup in that guitar.
Basically the middle pup's tone will have 3 switchable values via the 3 way switch. middle 'off' position will bypass any tone control and therefore be the brightest sound. The other two of the three positions on the switch will be equivalent to ~8 and ~4 respectively out of 10 on a typical tone control.
As far as I've gathered from the helpful folk here on tdpri, I need to use a capacitor and resistor combination wired to the switch to mimic what a typical tone pot would do.
In order to find out what resistor values I would use with the switch, I plugged in my strat, played both neck and bridge pups (the ones that are wired to tone pots on my strat) and chose two sounds I found the most useful for me, which are about 8 and 4, so slightly less that full tone and a hair under half full tone.
I then took off the pickguard and measured with my multimeter (on the two tone pots) what the resistance was for each of these two values (tone at 8 & tone at 4). Cap value for both tone pots was .022
These are the results I got:

Neck pup tone @ 8 = 123 Kohms. Neck pup tone @ 4 = 14 Kohms. (Neck pup tone @ 10 = 260 Kohms)
Bridge pup tone @ 8 = 110 Kohms. Bridge pup tone @ 4 = 13 Kohms. (Bridge pup tone @ 10 = 234 Kohms)

I was surprised at these results. In my inexperienced view, I just presumed that tone at 8 would be much closer to 250 Kohms. Was surprised to see it at just under half of the 250K pot value. And to see the resistance to be just under 15 kohms when tone pot at 4 was a real surprise.
Anyway, I'm sure there's goods scientific reasons for these results, but now I just want to be sure about choosing the correct two resistors for the 3 way toggle (tone) switch.

Do I go by my multimeter results and go with a ~120 Kohms resistor to achieve a tone pot turned up to 8 sound?
and similarly go with a ~15 Kohms resistor to try achieve a sound similar to a tone pot turned up to 4?

 

[Steve Holt]

I can't help you on this one, but I'm along for the ride at this point and eager to see what the end result is!

(chews popcorn)

 

[wabashslim]

Did you disconnect everything from that pot before measuring? If so...you're measuring an audio taper pot. A linear taper would give the results you thought you expected. Go with what the meter says - IF everything else is disconnected.

 

[Swirling Snow]

If you had said, "I figure 80% of 250 should be about right.", I'd be explaining that your tone pot is a "log taper" and the values are unpredictable because inexpensive pots used in guitars generally have only two elements connected to approximate the log curve and where they put the "knee" varies.

If, as Slim notes, you are reading just the pot value, then go with it. This is related to +3dB being "twice the power" but not "twice as loud", just in reverse. That is, halving the value from 10 to 8 is needed because our ears compress loud sounds.

 

[badscrew_projects]

Most today’s log pots will have their resistance at the mid-course equal to 10% of the max value. More or less.

 

[toonskeez]

Did you disconnect everything from that pot before measuring? If so...you're measuring an audio taper pot. A linear taper would give the results you thought you expected. Go with what the meter says - IF everything else is disconnected.

Do you mean, did I un-solder every wire from the pot that I was measuring? if so, no. It's my strat I was measuring off of, which is a separate guitar, all wired up like a typical strat. I didn't have a guitar plugged in, if that's what you mean.

 

[wabashslim]

Do you mean, did I un-solder every wire from the pot that I was measuring? if so, no. It's my strat I was measuring off of, which is a separate guitar, all wired up like a typical strat. I didn't have a guitar plugged in, if that's what you mean.

Yes, you should disconnect the wires from the pot and not have a guitar plugged in, otherwise you'll be measuring those things too, in parallel. Some would say that's not necessary for a tone control since the cap blocks DC but the cap could be leaky or there might be some quirk in the wiring that throws it off, so just do it. And disconnection is imperative for volume controls since the pickups are in parallel.

 

[Bearzooka]

Use trim pots and dial them in until they sound right.

 

[toonskeez]

Ok, so I didn't de-solder the wires from the tone pot in my strat, BUT, what I did do was measure the pots in my current build that are basically mounted in cardboard. The pots aren't wired up yet, so I figured I 'd just measure off of those.
I don't know if having the cap soldered in place affects the resistance readings or not, so I measured with no cap soldered to pot, then with cap soldered to pot.
Of course I only have one 250k pot (I'll be using that for middle pup volume), so I was only able to measure that pot with no cap.
The pots I measured with caps soldered are the two 500k pots I'll be using for both neck and bridge tone controls.
My 250k pot actually measures 270K in value.

270k pot resistance values (no cap soldered):
Tone @ 0 = 270K
Tone @ 10 = 0k
Tone @ 4 = 247k
Tone @ 8 = 35k

500k pot resistance values (no cap soldered):
Tone @ 0 = 500K
Tone @ 10 = 0k
Tone @ 4 = 480k
Tone @ 8 = 195k

500k pot resistance values (with cap soldered):
Tone @ 0 = 500K
Tone @ 10 = 0k
Tone @ 4 = 452k
Tone @ 8 = 306k

(Some discrepancies between values could be down to me measuring off just turning the pot to where I deemed '4' and '8' to be)

So, in my head, I'd reason that if I halve the resistance values from the 500k pot, I should get the resistor values I need for my 270k pot , right?
so it would be something like:

Tone @ 4 = ~230K resistor
Tone @ 8 = ~125k resistor

Do these values seem to be in the right ball park?

 

[wabashslim]

You want the highest resistance at 10 and the lowest at 0. You're measuring the wrong terminals.

I'd go with Bearzooka's suggestion to use trimpots. You actually only need 1 to get two settings. Wire each end lug of the trimpot to each end of the switch, then middle pot lug to the cap, other cap end to gnd. Set the pot for the best compromise between the two.

 

[toonskeez]

You want the highest resistance at 10 and the lowest at 0. You're measuring the wrong terminals.

I'd go with Bearzooka's suggestion to use trimpots. You actually only need 1 to get two settings. Wire each end lug of the trimpot to each end of the switch, then middle pot lug to the cap, other cap end to gnd. Set the pot for the best compromise between the two.

Yeah, you're right; I was measuring the wrong two lugs.
I re-measured and got the following resistance readout on the 500k pot:

tone @ 0 = 0K
tone @ 10 = 513K
tone @ 8 = 300K
tone @ 4 = 37K

So halving those I'd say I'll go with the following resistors for my 250K pot:

tone @ 8 = 150K
tone @ 4 = 20K

I'd say I'll just go with the controls I currently have and avoid the trimpot for this build.
Maybe I'll use it in a future build, but I'm happy to just use what I have for now.
I rarely use the middle pickup by itself in a 3 pickup configuration, so 3 set tones for that pup if fine with me.

 

[wabashslim]

Better get a good assortment of resistors (& clipleads), your translation of 500k to 250k might not work out the way you think.

 

[toonskeez]

Better get a good assortment of resistors (& clipleads), your translation of 500k to 250k might not work out the way you think.

Thanks, will do.

 

[wabashslim]

One more consideration - putting the middle pickup on it's own pot means when you turn it up you're going to have the two pots in parallel, cutting their resistance in half and rolling off yet more treble, not counting the tone control. I tried the blend thing once using stacked pots on a Tele and didn't like it, it turned the "quack" into a dull "cluck" and didn't really come into play until the blend pot was up to about 9 anyway, so I just went with the p-p switch pot for the middle.

 

[toonskeez]

One more consideration - putting the middle pickup on it's own pot means when you turn it up you're going to have the two pots in parallel, cutting their resistance in half and rolling off yet more treble, not counting the tone control. I tried the blend thing once using stacked pots on a Tele and didn't like it, it turned the "quack" into a dull "cluck" and didn't really come into play until the blend pot was up to about 9 anyway, so I just went with the p-p switch pot for the middle.

ah yes, that's a good point about the two vol pots cutting the resistance in half for each vol pot. Hadn't considered that.
Well, I just hope it doesn't darken my overall sound too much. Just ordered a load of different value resistors there and some alligator clips, so my plan is to solder everything in place, except the 3 way toggle tone switch, then plug in the guitar and try different resistor values (and cap) with the switch until I find the two extra tones I like, then solder the switch.

 

[Deaf Eddie]

I have tone switches in a few of my guitars. I do not use RESISTORS at all. I use a .022uF for dark, a .0047uf for mellow, and no cap for bright. The caps are connected to the hot output through a 3-way mini-toggle, and their other leg is connected to ground. I find that for me, this scheme leaves a little more midrange and creates a little less mud in the "treble-attenuated" throws.

 

[toonskeez]

I have tone switches in a few of my guitars. I do not use RESISTORS at all. I use a .022uF for dark, a .0047uf for mellow, and no cap for bright. The caps are connected to the hot output through a 3-way mini-toggle, and their other leg is connected to ground. I find that for me, this scheme leaves a little more midrange and creates a little less mud in the "treble-attenuated" throws.

Interesting...
Do you use an ON-ON-ON switch or an ON-OFF-ON switch ?

 

[Deaf Eddie]

You can use either. The on/off/on is easy; the on/on/on takes little thought. The lugs you want the caps on with that switch are at the opposite corners of the switch. It varies from switch brand to brand; use a multimeter to find the lugs that aren't connected to the commons in the first and third throws.

BTW, even if this is connected ONLY to the mid pickup, it will affect the tone of the whole output when the mid pickup is in the circuit, along with any other tone pots connected to the circuit. That's what's so nice about its "off" throw.

 

[badscrew_projects]

I have tone switches in a few of my guitars. I do not use RESISTORS at all. I use a .022uF for dark, a .0047uf for mellow, and no cap for bright. The caps are connected to the hot output through a 3-way mini-toggle, and their other leg is connected to ground. I find that for me, this scheme leaves a little more midrange and creates a little less mud in the "treble-attenuated" throws.

I tried this and there is too much « honk » without any resistors.

 

[TokyoPortrait]

Hi.

I have not read much of this thread, and tried to figure out even less of what is going on, and then got to:

Just ordered a load of different value resistors there and some alligator clips, so...

Which is what I was going to suggest. I don't mess around inside my guitars much, but when I do, I do this. I also put things (essentially) back together and have one end of the wires with clips on the ends coming out from under the semi-attached pick guard, cos it's a lot easier that way to hold / use the guitar as you normally would.

Good luck.

Pax/
Dean