Cap-Selecting Mini-Toggle

[killheart7]

Hello all. Been a while since I posted here. You guys gave me a schematic and helped greatly with the master series/parallel mod of my Brian May guitar a few years back. I am eternally grateful, as I use the guitar to great effect in my recordings. The option has been incredibly useful.

My newest project is a Telecaster build, my first ever Tele. I want to include a somewhat unusual mod to test an idea I've been holding onto for a while.

I seldom use but three spots in my tone pot's spectrum on any guitar; wide-open, rolled back slightly, and full-on woman tone. I'd like to try replacing the tone pot entirely with a three-position mini-toggle set to select either of two tone caps or none at all to create those tones instantly.

I've never used three-position DPDT's before, and I'm foggy on their functionality.

I can imagine most of the schematic, but am running into one snag. If I am correct, a DPDT on-on-on will turn on BOTH of the selected capacitors at once in the middle position. Is this right? Will an on-off-on bypass the caps in the middle, or kill the signal entirely?

...Or do I need a different Pole/Throw configuration?

Thanks a lot. I hope everything is well with all of you.

-Justin

P.S. Tried searching for this in past posts, but did not find what I was looking for. Sorry if this is a repeat.

[asmith]

Hi Justin,

---

Your issue

With all due respect, I think what you're asking for here is not what you're trying to achieve.

I seldom use but three spots in my tone pot's spectrum on any guitar; wide-open, rolled back slightly, and full-on woman tone.

Those three options are:
1. Pickup in parallel with ( cap in series with full pot resistance ),
2. Pickup in parallel with ( cap in series with less-than-full pot resistance ),
3. Pickup in parallel with cap.

This isn't the same as using different cap values. If you have a circuit simulation program (I use the free program 5Spice on the commendation of other members here) you can plot out what you have at the moment, with your "pot & cap" arrangement, and compare the frequency spectrum with what you approximate to be your requested "different cap" selection. You'll see the graph outputs are quite different -- giving different tones.

---

Achieving your goal

This is assuming you want to keep the current "resistance + cap" arrangement.

First, check out what the resistance of your tone pot is. Call this value T. When your tone pot is in the "Rolled back slightly" position, measure the resistance travelling through the pot in the circuit. Call this value R.

To maintain the same electronic arrangement as you have now, you could do it using a SPDT "On-Off-On" switch:



a: a resistor equivalent to ( T * R ) / ( T - R ).
b: a resistor equivalent to T.
c: your tone cap.

This gives you:

Switch Position	Result
Up	Rolled back slightly
Middle	Wide open
Down	Woman tone

Alternatively if you want a different switching logic, try this arrangement using a DPDT "On-On-On" switch:



x: a resistor equivalent to T - R.
y: a resistor equivalent to R.
c: your tone cap.

This gives you:

Switch Position	Result
Up	Wide open
Middle	Rolled back slightly
Down	Woman tone

Hope that helps.

[long813]

What asmith is saying, is that changing the capacitor or 'tone-caps' isn't what make those tones you mentioned.

The three positions you talked about,
Wide open
Slightly Rolled
Women Tone

All alter the resistance inside the pot, not the capacitor. A tone-pot is a variable resistor (pot) in series with a capacitor. So, to get those 3 exact sounds, you will need to know the resistance at those 3 points.

When you know these 3 resistances, you can then find resistors to match them and as asmith suggested, wiring them into a switch.

I would how ever, suggest actually measuring the resistance when it's wide open, as there will still be a load. The sound you get with no tone-pot at all may not be the sound you are looking for when you turn your tone pot wide open. Food for thought.

[killheart7]

Much appreciation for the reply, and no respect is due. I know almost nothing about electronics.

Ok so I neglected to mention that I DO want to use a different cap value for the middle tone, as I've been wanting to experiment with some of the "wah-like" effects of smaller value caps that I've read about.

Sorry, I didn't expect anyone to read into the question, so I wasn't as detailed as I could have been. I was just asking about the functionality of the three-way switch.

So assuming that I do want the different responses of two different caps, all I would change is putting the second cap in line past "a" before ground, correct?

Thanks again.

-Justin

[killheart7]

Also, thanks long813. I will almost certainly want to put a small load on the "wide-open" sound, as I'm using pretty bright pickups in this guitar.

-Justin

[long813]

Adding the cap you want after A and before the other tone cap, is the right placement, but not that easy.

Capacitors add inversely when in series. So, when both capacitors are on (in position 1) you won't get C1 + C2 but,

1/Ceq = 1/C1 + 1/C2

Do you have the two capacitor values that you would like to use?

[killheart7]

Ah, yes I see that. I was planning on experimenting, but let's say 6800pF for starters.

[killheart7]

Just noticed I never mentioned the other cap value. I want the typical .047uf for the woman tone, and the 6800pf for the rolled-off tone.

[sumgai]

killer,

Where did you get those figures?

I've always been under the impression that E.C.'s woman tone was derived from a 0.015µf cap, not the largest-standard value* of 0.047µf..... (Sources upon request, both here and abroad, but I'm asking you for your source(s) first. )

Also, it might be time for a quick review of fractional designators. As in, a micro(µ) is one-millionth of a unit, a nano is one billionth, and a pico is one trillionth. Put another way, we can express it as such:

micro = 10^-6, or 6 places to the right of the decimal point;

nano = 10^-9, or 9 places to the right;

pico = 10^-12, or 12 places to the right.

Given that, your "6800pf" works out to 6.8nf, or 0.0068µf, or about half of the value that I think yields the famous "woman tone". For sure, this value is significantly less than what most single-coil guitars have for their main tone capacitor. Of course, tonal desirability is purely subjective, and no one answer is correct for everybody, but there are "good starting points" that most of us agree upon.

I think you'll want to experiment with several different values for your cap choices. My best advice here would be "don't accept the first thing that sounds pretty good".

HTH



sumgai

* Standard values for most guitars range from 0.022µf to 0.047µf. Other values have been used, though rarely.

[killheart7]

Hi sumgai. I appreciate your input on the subject.

Maybe you know that '68 interview where the interviewer asked Clapton about "woman tone"? He defines it very loosely, saying he uses the bass pickup, or the totally rolled-off bridge pickup, or both pickups totally rolled-off to "1 or 0". I think, from his perspective, it was just the general idea of killing off most of your highs, and I've always run with that definition. Regardless of the specifics, I immensely enjoy turning the tone down all the way with a big-butt fuzz pedal on. I don't even know what cap values are in most of my guitars; mostly just whatever they came with. I appreciate the differences, but they're more subtle than necessary for my goal.

I was going to start with the 0.047µf cap for the woman tone position because, as you mentioned, it's pretty standard. Having never owned a Tele, I'd just like to start from something middle-of-the-road and see where I'd like to take it from there.

As for the 6800pf value, I took it straight from a Tele-playing guitarist's capacitor shootout. It's pure curiosity and experimentation, really. He said that it yields a slightly warmer tone when fully down, which is all I want out of this switch's middle position. If it doesn't work for me, I'll probably buy a grab bag and start experimenting, for sure.

Thanks a bunch for chiming in!

[reTrEaD]

You guys both have it wrong. The woman tone sounds like:

"You bought ANOTHER guitar? Here's a blanket and pillow. You know where the couch is."

Since one of the tones you're looking for is rolling off all the treble, you're on the right track with a 47nf. You might even want to go larger maybe 100nf, with a 4.7k resistor in series with it to reduce the resonant peak.

You mentioned a "wah like tone". Putting a cap directly in parallel with no series resistor does something similar. Nowhere near as pronounced, but the absence of a series resistor causes a small resonant peak with a rolloff above the peak. By experimenting with the cap value you'll probably find a resonant frequency that suits your taste. 6.8nF seems like a reasonable value.

I'm tempted to suggest using a rotary switch so you can compare several different values, particularly during the "testing phase". But finding one that will fit in a Tele cavity might take a bit of effort.

[sumgai]

While I didn't mean to imply any "unreasonableness", I do think that 0.047µf is far too large a value for any pickup, if used on it's own. Thankfully, the ever-inimitable ChrisK has already addressed the topic at hand. As in:

Free Woman Tone

Chris's sources for that combined value were several in number, including the aforementioned article/interview. E.C. was using a slightly modified Strat, having this value cap installed in place of the original (presumably a 0.022µf unit).

Essentially, everything has to work together, there's no one magic solution that will overcome the blight, bring peace to the world, and wow your fellow musicians with The Ultimate Mojo. It could well be that Eric's Strat had a set of "magical"* pickups as well as the modded cap, but we'll never really know, will we?

That said, a quick re-read of the entire thread reveals that you (killheart7) do intend to experiment - good!   May I suggest that you run a pair of wires out of the cavity, to the outside world, where you use some alligator clips to temporarily attach a cap (or two...). Even though you have only two screws holding your control plate down, if you keep on taking the screws out and putting them back in, those holes in the wood will eventually become loose, and then need filling and re-drilling. Might as well avoid that, since it's an easy thing to do.

HTH




sumgai



* Magical, as in, drenched in thousands of hours of sweat or some such....

[reTrEaD]

SG, I think we might be talking about different interviews/articles. killheart7 cited one from '68. That would have been EC's Gibson era. LP, SG, and ES-335.

Anyway, +1* for the alligator clip idea. Run two wires through the now vacant tone pot hole with clips on them. Experiment to your heart's content until you're satisfied with the final choices. Then install the switch and selected caps/resistors.


* Not actually gonna karma you. I know you'll just reset to zero.

[killheart7]

The prize goes to retread. That particular interview shows Clapton talking about his SG:



Very cool guys. Thanks to everyone who helped here, I believe I have plenty to go off of to make my mod work. The alligator clip method is a great idea.

This guitar is in the theoretical stage at this point. I just wanted to have my schematic so I know what parts to order. It may be a matter of months before I can post sound files, depending on the guy building the body, but I will definitely get to it when I can.

Thanks again for the assistance. Without you guys, I might actually have to crack a book.

-Justin