the TRUTH about "guitar tone caps"

[EBK]

Technically, the researchers were trying to determine the feasibility of using a microwave oven to turn sap into syrup, but we can extend their research into low frequency applications.   

[GibsonGM]

Speaking of low freq applications, hey, this tone mod is wicked cool!!  I had to go thru and re-learn the way it's wired so it took a while...I have a jungle in there.  Beefed up some dodgy areas too.   I'll keep this, I mean - Billy Gibbons to Townshend with a RM, to Zep and Clapton - on a LP - right at your fingertips right from the amp...

My tone pots are probably log - I think this would give more range with linear, so next time I'm parts shopping I'm going to look into that.  But well worthwhile mod..I mean, I barely ever even touched the tones before.   Cool suggestion, Jimi! 

[pinkjimiphoton]

your TOAN is SO TASTY, DEWWWWWWDDDDDD....

that brown soun' do get aroun' <3

[GibsonGM]

You'd think I'd be all over this crap, 50 yrs old, but no, I've always just kept 'em stock.  Playing with this, now I hear a LOT of peoples' tone from the Great Era. 

[pinkjimiphoton]

just wait til ya get used to it. there's really no going back!

[GibsonGM]

Well, that's because the caps...they're yellow... 

[Elijah-Baley]

Their main product seems to be a line of battery powered cables... that do not buffer or amplify... they don't say what it does do except give you very low capacitance.

Its got a battery, but you can use it to power a light bulb because its a "direct connection."

http://zerocapcable.com/?page_id=231

Their claims are actually quite possible, whether it actually delivers or how well it performs I have no idea, but the technique is used in high frequency and low current applications regularly.

All that's needed is a triaxial cable and a buffer - the buffer is not inline, but buffers the signal to drive the "guard"/inner shield. Because there is no voltage difference between the inner conductor and the guard, it eliminates the capacitance that you'd normally see between inner signal conductor and outer grounded shield.
The guard buffer would presumably be ≥10Meg, an order of magnitude more than the traditional 1Meg input impedance of guitar amps so that it ends up an insignificant extra load - it's in parallel, not inline. But the cable capacitance has a larger effect on the resonant peak of a passive pickup than the resistive load of an amp anyway.

So yep, you can get a (near) "zero capacitance cable", of any reasonable length, but triax is expensive, and yes it will need a battery.
The lightbulb demonstation pic is pretty dumb though, agreed.

See Wikipedia for further reading on triax and driven guards.

I'd like to see a schematic or a sketch to make this kind of cable clear even for me, please.

[Phoenix]

I'd like to see a schematic or a sketch to make this kind of cable clear even for me, please.

Sorry for the poor rendering, but hope this helps.

[Elijah-Baley]

Great!
Of course is not so convenient build this thing with my diy method, but just to understand:

Triax cable example: https://shop.sommercable.com/en/Cable/Bulk-Cable-Video/Kamerakabel-SC-Polaris-MKII-600-0313.html

Can this stereo cable can be used as a triax cable? The second inner cable used like the guard shield.
https://shop.sommercable.com/en/Cable/Bulk-Cable-Audio/Mikrofonkabel-Stage-22-Highflex-200-0001.html

SIGNAL CONDUCTOR goes from the tip of the jack to the other tip. It's the input of the buffer.
OUTER SHIELD is the external mesh shielding, the typical ground on the common instrument cable, it connects the two shileds of the jacks. It will be the ground of the buffer, too.
GUARD SHIELD is the middle inner signal of the cable. The output of the buffer goes on it. Is that just it?

How the guard shield have to do with the signal or the ground?

[Phoenix]

Great!
Of course is not so convenient build this thing with my diy method, but just to understand:

Not especially difficult to build, but fairly expensive - triax cable is not normally very flexible, so you'd need to do some shopping around to find something that's pliable enough and can survive a small enough bend radius to be practical for use on stage. If you've ever handled coax, this is even less flexible. Might be fine for use in a studio, but not if you want to move around or coil it up and throw it in the back of a van between shows. Something suitable might not even exist off-the-shelf, and if it does is probably going to be even more expensive. Given that there's little point applying this technique to a short cable with its already low capacitance, making something like a 20'/6m cable at $10USD or more (probably more) per foot, this will quickly become expensive.

Triax cable example: https://shop.sommercable.com/en/Cable/Bulk-Cable-Video/Kamerakabel-SC-Polaris-MKII-600-0313.html

Yep, that'd work electrically, but with a PVC jacket and 11mm outer diameter I'll bet you it's too stiff for practical use.

Can this stereo cable can be used as a triax cable? The second inner cable used like the guard shield.
https://shop.sommercable.com/en/Cable/Bulk-Cable-Audio/Mikrofonkabel-Stage-22-Highflex-200-0001.html

No, unfortunately such easily and cheaply available cable will not work, as the guard shield needs to envelop the signal conductor, simply having a parallel conductor as "guard" does nothing.

SIGNAL CONDUCTOR goes from the tip of the jack to the other tip. It's the input of the buffer.
OUTER SHIELD is the external mesh shielding, the typical ground on the common instrument cable, it connects the two shileds of the jacks. It will be the ground of the buffer, too.
GUARD SHIELD is the middle inner signal of the cable. The output of the buffer goes on it. Is that just it?

Yep, got that pretty much right. The diagram was simplified for clarity. There's three LAYERS. Signal in the middle, guard shield completely surrounds the signal conductor, just like a regular shielded cable. But then there's the third outer shield, that again completely surrounds the guard, a "shield for the shield".
With the buffer following the signal and putting a copy of that onto the guard shield, there's no voltage difference between the signal and guard, so there's nothing to cause the accumulation of opposite charges on the two conductors, with nothing to charge, there's no capacitance. The guard shield shields the signal conductor from the outer shield, which is at ground. The capacitive burden is now shifted from the passive pickup to the buffer.
The buffer shares the ground provided by the outer shield.

How the guard shield have to do with the signal or the ground?

Not sure exactly what you're asking here, but the guard just has a buffered copy of the signal on it. The buffer shares the ground provided by the outer shield.


Note that I can only think of one real good use-case for such an elaborate setup. Most use cases would be better and cheaper served by a battery powered buffer in the guitar, a wireless system, or a buffer built in to the guitar or guitar-end jack of a TRS cable with power supply located back on your pedalboard.
The only advantage this elaborate setup offers is that it preserves the interaction between passive guitar controls and load, so if you're a fuzz player who needs a super long cable that erodes your bypassed tone (and you USE that bypassed tone/other high impedance effects with the fuzz bypassed), and you ALSO use the guitar volume control to "clean-up" the fuzz, then this does offer that advantage over conventional buffered options.

Edit: TYPO

[GibsonGM]

The thing reminds me of a pentode.

[pinkjimiphoton]

Speaking of low freq applications, hey, this tone mod is wicked cool!!  I had to go thru and re-learn the way it's wired so it took a while...I have a jungle in there.  Beefed up some dodgy areas too.   I'll keep this, I mean - Billy Gibbons to Townshend with a RM, to Zep and Clapton - on a LP - right at your fingertips right from the amp...

My tone pots are probably log - I think this would give more range with linear, so next time I'm parts shopping I'm going to look into that.  But well worthwhile mod..I mean, I barely ever even touched the tones before.   Cool suggestion, Jimi! 

dunno how i missed this bro lol.... was wondering how ya made out!
glad you liked it!

log for tone controls is fine. don't try reverse log. it will make you frustrated!!!!!!!!!!! trust me on this!!
linear or log works well for this particular mod. the key is only using one side of the bass cut pot. you can use whichever side sounds best to you for taper, one side will be more linear than the other... but if you use both sides, half the revolution of the pot may occur with very little effect.

[GibsonGM]

No reverse log, no nooo, lol!   Just thought of getting B tapers.    My log pots have it bunched up right now, so only useable from 8 to 10 and no 'fine tuning'.  So maybe I'll move the input wire over and see if the 'not log half' does better!  Tho I like it as "10" = full bass with decrease going down in numbers.  But hey, it sounds wicked cool!  Esp. on the neck PU, of course.  That mud is gone; normally I have to use an EQ for that.   

Growing up we were far from a music store or books on the tricks - we were limited to mainly coil cut, out of phase switches and that crap. Everything was 'what guitar'  'what amp is he using'. What effects pedal.  Does he wrap his strings OVER the tailpiece? lol  I didn't even hear much about amp mod tricks/guitar circuit stuff playing in Boston in the early 90s! You'd think everyone would've been all chatty about those things...nope.   Lots of blues players at that time, and most of them were kind of purists.  "My tone caps are TROPICAL FISH from two '69 TELEs..." guys.  To be fair, we were coming outta the digital 80s, lucky anyone even still played anymore, ha ha! 

Now that I've played with this, I'm sure many 'recording artists' were doing very much the same on classic albums. You hear so many funky tones, and can't find a way to get at them; this probably explains some of that!  I always assumed they were using EQs and stuff, but you know, once the FULL signal hits other equipment it's all mixed together and hard to make something like an EQ 'unmix'  or enhance it.   

[pinkjimiphoton]

yeah, changing the eq before the amp makes a huge diff. a lot of what ya hear is done in post production, i think, not many peeps use this trick. but with this trick, a fuzzface really comes to life... and to my ear, i hear most of the tones of the classic rock era right there at the ol' fingertips.

[GibsonGM]

For sure you don't hear much lo-tech 'inventiveness' in modern (mass produced) stuff - haven't in a long, long time.  At the console, yes, and with effects, but not on the axe.  Live is different.  Gotta go underground to find the players who still have the touch, IMO.

I came to electronics late in the game for stage use other than repairs...don't play out much anymore. When I was doing the band routine, not a lot of time to learn and tweak...and what is GREAT on recordings (what I'm into now) often won't translate in a live environment, as I know you well know (drop the mids too far...bye bye guitarist! lol)   Combining this stuff with the right measure of dirt boxes and EQ...man, we're ALL jimi now!   ha ha  kind of...

[idy]

like tone haiku

The capacitive burden is now shifted from the passive pickup to the buffer.

The capacitive
burden is now shifted from
pickup to buffer.

[pinkjimiphoton]

like tone haiku

The capacitive burden is now shifted from the passive pickup to the buffer.

The capacitive
burden is now shifted from
pickup to buffer.

lol
dude, sigworthy! 

[mozz]

On the "someday project list" to simulate up to approx. 40 ft. of cheap guitar cable,(1200pf) you can find your sweet spot.

[GibsonGM]

Can I get a few of those in nanofarad values?