Variatone alike switch (But 1 position only)

[FernandoEsteves]

Hello!
I'm building a guitar with a single humbucker in the bridge, but will have a 3 way ON ON ON switch: position 1 = normal, position 2 = bobbins parallel, position 3 is going to be something alike a variatone, to cut SLIGHTLY the highs to have a little less aggressive tone, eventually.

Found some schematics for variatone. But didn't find an explanation of what values makes what difference, how I should approach it.

Does anyone has experience in this kind of electronic to help me?
Thanks

[Mick Bailey]

The guitar's pickup has a resonant peak that's progressively shifted by the Varitone circuit along with having a notch in the frequency response that also moves. There is some higher frequency roll-off, but the circuit does rather more than a straightforward treble cut does that you would get with a regular tone control.

In it's simplest form you would have a 100K Ohm resistor in series with the pickup and output, and a capacitor + inductor in series to ground on the output side. The inductor is a fixed value and the frequency response is determined by the capacitor value, which is the variable element in the original circuit. The first thing to determine is the inductor type and size and usually in a DIY build it will be the winding of a miniature ferrite-core audio transformer. It then remains to pick a suitable capacitor to achieve the required response. In the original circuit the values range from 0.22uf to 0.001uf, which runs from low to high. So, my starting point in your case would be to begin with a 0.001uf capacitor and see how that works out. You may need to go the next size down in the Varitone range - 0.003uf (nearest standardized size would be 3300pf).

The 10M Ohm resistors in the original circuit become redundant in this application as they are there to prevent pops when switching between capacitors.

One issue that you have is in bypassing the circuit in positions 1 and 2 of your switch, as you need to completely remove the fixed Varitone circuit from your signal path in these positions. Can you post a link to the type of switch you intend to use?

Rather than a Varitone-based circuit you could also consider a simple treble roll-off circuit for position 3 rather than using an inductor.

[FernandoEsteves]

Hey, thanks for the answer!
It's this switch:

[FernandoEsteves]

But ON ON ON, actually

[Mick Bailey]

You don't have enough options with this switch to do what you suggest. You can get parallel/coil split/series, but when thinking it through, to incorporate a single varitone selection there's too much switching needed - you have to break into the output and insert the varitone circuit - it isn't just a single connection that you can connect and disconnect. You have to connect the input of the varitone to the pickup's output, and the output of the varitone to the volume control.

Do you have a wiring diagram that you were thinking of using as a starting point? There may be some other options to incorporate a simple treble roll-off circuit, but I'm struggling to see how that could be achieved with the switch you have.

[Chuck H]

It'll be hard to find an on/on/on with enough poles to do what you want with a single switch. Also, you won't have the varitone option in both series and parallel configurations. But...

You could use pull switch pots. Assuming you'll have a volume and a tone control you could put the series/parallel switch on one pot and the varitone switch on the other. No extra switch on the front of the guitar and you'd have the varitone option in both pickup modes. If you're planning to omit a tone control you could use an 2P2T on/on switch for the pickup mode and put the varitone on the pot switch and you'll still have the varitone option in both pickup modes. Or... Put the pickup mode switch on the volume pot and use a fancier switch (on/off/on toggle or even a rotary switch) for more varitone options.

EDIT: OOOooo... Just thought of another option. If this is to be a rocker guitar (assumed from the single humbucker though I suppose it could be a jazz guitar) you could use a double pole on-off-(on) switch. (on) indicates "momentary" operation. As in non latching. Then you could put the varitone on the on latch, the middle would be off and you could use the momentary for a mute the same way some guys are using pinball machine button switches. Orient the switch so the momentary position is on the down stroke so it feels natural to your picking hand. Now you have some very cool tricks. Series/parallel, varitone selectable for either pickup mode and a mute switch and still with only a volume knob and one switch on the guitar.

[Chuck H]

In it's simplest form you would have a 100K Ohm resistor in series with the pickup and output, and a capacitor + inductor in series to ground on the output side. The inductor is a fixed value and the frequency response is determined by the capacitor value, which is the variable element in the original circuit...

Rather than a Varitone-based circuit you could also consider a simple treble roll-off circuit for position 3 rather than using an inductor.

I think what you described sounds like a mid cut circuit. Most varitone circuits I've seen (including the original Gibson circuit) are just a rotary switch with different cap values (smaller values than a tone control) to ground. Since the pickup is already an inductor reacting to circuit capacitance and forming a resonant peak the added capacitance to ground lowers the frequency of the resonant peak and sounds like a high treble cut/low treble or mid boost. I know you already know this. I just described it for Fernando in case he doesn't.

So the single varitone option should only require adding a cap to ground (simple switching) and not adding anything in series with the hot lead (more complicated switching).

[FernandoEsteves]

Thanks for the answer. It won't be a variatone, it was just an example of how it will work. It will be just a position that cuts a little of the treble to have a little sweetier tone for melodic parts...

Yes, it's a thrash metal guitar =)

[Chuck H]

Well ok. But we'll need to see the intended circuit to figure out what's necessary for the switching. Like I mentioned above, I don't think you'll find an on-on-on switch to do what you want. You'd need at least three poles depending on your high cut circuit and most on-on-on switches are wired as on-both-on which may not serve for the pickup mode switching. I haven't checked on that yet.

If you can't post pics or diagrams yet please describe the guitar circuit for us. Will it have a volume and tone control? Just a volume and the one switch? Volume, tone and the switch? What is involved for the high cut circuit you want to use? We have nothing to work with right now and we may need to know all this to figure out a switching arrangement you'll be ok with.

[FernandoEsteves]

The switch looks exactly like that one I posted, but i's ON ON ON, I thought it was 3 position different, but seems it's like a Les Paul switch?

1 Humbucker + 1 Volume and that is it. Passive pickup

PS: I need to say I know nothing about guitar wiring, that is why I came here

[Chuck H]

Well we're here to help (for our own reasons ) Unfortunately I was unable to find a way to make a on-both-on switch work for this application. I did propose some alternative switching in post #6. If it's not too clumsy having a pull switch on the volume control I really like the idea I posted in the edit. That is, pickup mode switches with the volume pull pot and the switch actuates the sweet circuit. And alternately can be used by depressing it's momentary operation as a mute/cutoff switch. If you've ever heard a metal player use this effect you know it's really cool. There are some good, sturdy switches available that will do this but they're a little pricey. In the $30-$40 dollar range. There are cheaper switches that will do it too if you just wanted to try it out. But if I were hammering on a switch for a cut off effect, the way I play a guitar I'd buy up if I could afford it.

[Mick Bailey]

I think what you described sounds like a mid cut circuit. Most varitone circuits I've seen (including the original Gibson circuit) are just a rotary switch with different cap values (smaller values than a tone control) to ground. Since the pickup is already an inductor reacting to circuit capacitance and forming a resonant peak the added capacitance to ground lowers the frequency of the resonant peak and sounds like a high treble cut/low treble or mid boost. I know you already know this. I just described it for Fernando in case he doesn't.

So the single varitone option should only require adding a cap to ground (simple switching) and not adding anything in series with the hot lead (more complicated switching).

Here's the original Varitone schematic. The stereo version is just doubled-up. I've not come across a Gibson Varitone equipped guitar without the inductor - the shifting mid scoop and resonant peak is part of the distinctive sound. A simple cap to ground, or cap + resistor, or switching in a parallel resistor to the tone pot was also what I was thinking about as an alternative approach with simplified switching.

[bbsailor]

Here's the original Varitone schematic. The stereo version is just doubled-up. I've not come across a Gibson Varitone equipped guitar without the inductor - the shifting mid scoop and resonant peak is part of the distinctive sound. A simple cap to ground, or cap + resistor, or switching in a parallel resistor to the tone pot was also what I was thinking about as an alternative approach with simplified switching.

Mick,

Here is my wiring idea that creates a variable Varitone like effect. I used a push pull volume pot to switch dual pickups on but out of phase. I wired individual volume controls for each pickup and then when the dual pickup mode was out of phase, a slight change of one pickup volume gave me a variable Varitone like effect.

Give it a try.

Joseph J. Rogowski

[Chuck H]

I remember seeing the inductor in the old Gibsons. At any rate I do think the version you propose would be best for getting the "sweeter" tone that Fernando wants. IIRC guys wiring up this circuit were using a small audio transformer made by Xicon for the inductor. Though I can't remember which one or how it's taps were wired. It wasn't that long ago it was discussed here so I think a little searching might reveal the details. That'll be later when I have more time.

[Chuck H]

I think it was this transformer with the primary CT and all the secondary leads snipped off. Just using the primary ends to wire it as an inductor.

https://www.mouser.com/ProductDetail...6mAo%2FPHkg%3D