A Schematic inspired by "The Pot"...

[bobbletrox]

From the very first time I saw "The Pot", I've always wondered why it doesn't have a tone knob too.  Why just stop at volume when most guitars have a tone knob aswell?  So anyway, I was bored and drew up this schematic for such a device based on a Telecaster's tone knob (hence "Tonecaster")...and the Kinman Treble Bypass filter.

Then I thought "why stop the gimmicks there?" and added a Black Ice switch and a "Vintage Cable Sim" that I remember seeing somewhere.  Now you can get all your circuits of dubious distinction in the one pedal.  It probably has errors and might not even work...but hey!  I'm tired and bored.  

Here ya go:
Tonecaster Lite
Tonecaster Royale

[Mark Hammer]

That's actually smart.  Seriously.

I had made up some boxes that were based on the Gibson Vari-tone and Craig Anderton's EPFM-II passive tone control.  If you recall, this circuit is essentially an LC notch filter with multiple preset notch foci (I hesitate to call them "frequencies" because the width changes too).  

Anderton uses a pot to ground as a means of adjusting the notch depth.  If you shunt the cap, though, it becomes a variable bass cut circut, and if you shunt the inductor but leave the cap in circuit, it becomes a variable passive treble cut.  Shunt *both* the inductor and cap, leaving only the pot to ground and input resistor, and it becomes a full-spectrum attenuator.

I was impressed that such a "Swiss Army Knife" could be derived from so few components, but your device goes over the top and then some.  Some incorporation of an inductor (and all the possibilities therein) would make this a very powerful, fully passive, "audio first aid kit" for the guitar player.  The sort of thing you could put in a 1590BB with a bunch of slide switches or toggle switches, and take with you everywhere, knowing that one day it would end up being very very handy in a "tone-emergency".

Kudos

[Gringo]

A real KISS gem!!  

As Mark said, a Swiss army knife for guitar.

[Ansil]

hmm still needs a single transistor buffer/booster fro me lol

[Peter Snowberg]

Adding the tone control and black ice style clipper is a great idea. Very versatile!

A couple of suggestions for you:

:arrow:  You can eliminate the 1M resistors because volume pot will already provide that "pull to ground" function.

:arrow: As this volume pot is in addition to the existing one on the guitar, you might want to raise the value to either 500K or 1M to keep the impedance range a bit higher.

:arrow: The vintage cable sim portion of the "royale" version should connect the caps between the signal and ground lines. You can eliminate the bypass switch for that function and just use the 6th rotary switch position as an "off" for that control. As you have it shown now, that rotary switch is a high-pass filter which may be equally useful to some people .

I have a "Curley Cable Simulator" pedal which is very similar in some respects although I've done the attenuator differently, don't have a separate tone control, and no diodes. It's always funny to me how we all seem to think in the same direction.

Great Job! "Swiss Army Knife" is right!

Take care,
-Peter

[lightningfingers]

sounds cool but what does that "vintage cable sim" do?

[Peter Snowberg]

It's reputed that part of the Hendrix tonal mojo was the use of a long curly cable to get rid of some of the really high treble. The longer the cable, the higher the capacitance. These days there is a lot of focus on using low capacitance coax for guitar cords to avoid the loss from this capacitance (especially when dealing with long cords). A "vintage cable sim" just adds some capacitance between the signal and ground lines to emulate this effect.

It can be subtle, but none the less, it's sure there.

Take care,
-Peter

[Mark Hammer]

One of the choices that keeps coming up in the Ampage pickups forum concerns choice of volume pot values.  Generally speaking, single-coil pickups yield a harsher tone when used with volume pot values suitable for HB pickups and HB pickups yield too diffuse a tone when used with pot values suitable for SC pickups.   The choice of pot value is made such that a pleasing tonal balance is achieved by losing or retaining high end via the degree of loading that the pot imposes on the signal path.  

The "cable simulator" is a way of using a higher value volume pot and mimicking the effects of the loading that lower pot values provide.  Sometimes one likes to use a "too high" volume pot value to keep ultra-high end for whatever purposes, and this lets you tame things a bit to offset that.  I might point out that some of the classy high-end phono preamps used to include such features as well, for similar tonal reasons.

[bobbletrox]

thanks for the kudos guys!

I changed the schem thanks to your suggestions, Peter.  Using the 6th rotary switch position to turn off the (now fixed) cable sim certainly makes things more straight forward for the user.

I like the inductor and Varitone ideas too Mark, I'll have to look into them!

*EDIT*  Found and error in the new cable sim...so I'll fix and upload it again later today.

[javacody]

This is a damn fine idea. I bet you could sell this easily.  I'll have to build one after I build the Thunderchief.  

[bobbletrox]

Now it's fixed.

[javacody]

bobbletrox, you should change the name from the tonecaster to the Swiss Army Tonecaster.  

Also, to add to the multipurposeness of this pedal, how about push-push pots for 250k and 500k?

[Mark Hammer]

My wife and I saw an item and picture in the paper this morning concerning a "contemporary" Swiss Army Knife - it had a USB memory stick.

Don't get TOO fancy, now.  :wink:

[jrc4558]

Hey, last year I saw a USB 2.0 interface pressure cooker advertised somewhere on the internet. Now that's something to be avoided!

[Mark Hammer]

"Honey, this tastes simply awful!!  You've made this before and I loved it.  What went wrong?"

"Don't look at me.  It's a software issue."

[Nasse]

:shock: I saw once a band document on TV. The guitarist is a famous about his tone. The band visited several studios and there were shots about the band recording, sound checks and performing. I think the guitar hero plugged his axe into something like this effect. Maybe it had XLR symmetric output for prof gear but I got the illusion that the guitarist carried that box with him.

[will]

Hi,

I believe the Vintage Cable Simulator needs to be moved to the beginning of the Tonecaster Royale. The cable simulator needs to be placed at the beginning of the effects chain. As it should be part of the pickup circuit to get the classic vintage sound. All pickups have a resonant frequency that varies based on the terminating load. As you increase the capacitance you shift the resonance frequency of the pickup to a lower frequency.  The cable acts like a parametric tone control which boosts the highs then cuts then rolls off signal a little above this frequency. The terminating resistance determines the peak of the resonance.  

For a strat single coil pickup:
1000 pF has a resonance at 3.7Khz.
2200 pF has a resonance at 2.2 Khz
3300 pF has a resonance at 1 Khz

So a large value cap would be like increasing a presence control and cutting the highs at the same time.

I would use a large terminating load after the caps like 1 meg resistor to simulate the input impedance of a typical vintage tube amp. Then add a large cap to buffer the Cable Simulator from the other Tonecaster passive effects (i.e. tone, clipping and volume control).

This would then more closely mimic the 60’s guitar sound with the long curly guitar cables.  

See http://goran.tangring.com/index-filer/Pickup-cabletheory.htm for more details.

I also wonder if there will be enough output from the pickups to activate the clipping diodes. You may want to try germanium as they need the least amount of voltage to start clipping. This would work better after some voltage boosting circuit.

Regards,
Will

[javacody]

Will, those clipping diodes should be schottkys. The circuit is based on the black ice clipping circuit (do a search for black ice for discussion on the topic).

I like your ideas about the cable simulator. How large of a cap are we talking about? 10uF?