Two-Band “PTB” Tone Control:
Useful, Easy, Cheap & AWESOME!

The PTB Circuit was one of many G&L innovations.

After the frantic soldering fest that was The Pagey Project, I figured it might be time for a nice, simple DIY wiring project. At the suggestion of tonefiend reader JH, I played with variations on the 2-band tone control that appeared in some G&L guitars. And I am over the moon with the results!

This circuit, sometimes called “PTB” (for “passive treble and bass”) combines a standard treble-bleed tone knob with a bass-cut control. The latter has a huge effect on the way distortion pedals and amps respond to the pickups, especially with humbuckers. Cutting some bass makes the pickups sound cleaner, airier, and more dynamic (i.e., less compressed). To my ear, the bass pot is not so much a tone control as a clarity knob.

Check out this brief demo video:

Savvy stompboox builders emphasize the importance of filtering the guitar signal as it enters the effect. And if you’ve built or modded your own fuzz/overdrive effects, you’ve probably discovered how the importance of the input cap’s value. This cap filters out lows. Too large a value, and the tone gets flabby/sloppy. Too small, and it gets thin/shrill.

This tone circuit lets you make similar adjustments from the guitar. And as you can hear in the demo, there’s more to it than just nixing lows. With fewer lows bombarding downstream amps and effects, the signal becomes brighter, cleaner, and livelier. At times you’d swear you were adding highs rather than just removing lows.

This arrangement works great it three-knob guitars, provided you can live with global volume and tone controls for both pickups. Alternately, you could modify it for a four-knob Les Paul so that there are two volume pots and global bass and treble controls.

Here’s the original schematic provided by JH:

I actually prefer how it sounds with three 500K pots — the pots you probably already have in your humbucker guitar. In other words, you can probably mod this circuit without buying anything extra, except maybe some wire and solder.

Here’s a (literally) sketchy wiring diagram I drew up:

Please do like i didn’t the first time I tried this, and note that the bass control capacitor is a .0022uF, not a .022uF like the treble cap. If you’d like a little more treble cut in the fully counterclockwise tone-knob position, try substituting a .033uF or a .047uF for the .022uF.

This circuit also works great paired with single-coil pickups, the way Leo intended. But it seems even more relevant for humbuckers, since low-frequency control is so much more an issue than with brighter single-coils, like classic Fenders or G&L’s signature MFD ceramic-magnet pickups.

This one stays in the guitar! :thumbup:

29 comments to Two-Band “PTB” Tone Control:
Useful, Easy, Cheap & AWESOME!

  • Derick

    I’m totally gonna try this. I have a Hamer Sunburst with a Kent Armstrong High Output in the bridge and a Seymour Duncan SH-5 in the neck. I’ve been able to tame it quite a bit with pole adjustments and pickup height but am still not satisfied. I bet this wiring will help me balance it out! I’ve already re-wired it for 1 volume and 2 tones so this modification should be a snap. 

  • joe

    I think you’ll love it. It’s so simple, but so effective for humbuckers. I can’t believe more people haven’t done this. I can’t believe I’d never even heard of it till JH mentioned it, even though I’m a G&L fan (though I’ve never owned one with the PTB circuit).

  • Bass roll-offs are great for guitar. I’m mainly a bassist, and I see where a lot of guitarist use too much low end. It muddies up the overall tone, and sometimes a thinner guitar sound is better.

     Incidentally, whereas I think G&L was the first company to use this on production guitars, it’s not unique to them. Carvin included pretty much the same circuit in their instruction sheets back in the early 70s. 

    • joe

      Yeah, you’re totally right about guitarists and excessive bass. Sure, it’s gratifying to feel those lows when you’re standing next to the cabinet, but nixing some of them often makes the guitar sound a lot better. Not to mention the bass!

  • Chiller

    So for us n00bs, how would we adapt this for the Les Paul 4-knob setup?  I have an Epi Sheraton that I hardly ever use the tone knobs on, and this mod sounds like a great fit for this guitar.

    • joe

      Hey Chiller! I don’t have time to draw up the wiring diagram this week, though I will soon if no else steps up to the plate first. (Hint, hint.) The tone control part would be exactly the same — the main difference is you’d run the pickups through the volume controls before the pickup selector, and then route the single wire from the selector through the tone controls as seen here.

  • Sam Geese

    Doesn’t the ‘bass’ pot need to be grounded as well?

  • Morti

    Reverend Guitars do a Bass Contour Control in most of their guitars, I wonder how close it is to this.
    If you’re up for another adventure, there’s always the Fender TBX tone control, which uses a dual pot:
    http://terrydownsmusic.com/Archive/baritone/baritone_wiring_diagram.pdf
    http://www.premierguitar.com/Magazine/Issue/2010/Nov/The_Fender_TBX_Tone_Control_Mod_Part_2.aspx

  • Laertes

    I may be asking something stupid and showing my ignorance, but cutting bass can not be done with the EQ? What is the difference between the EQ and this circuit besides one being on the guitar and the other in the amp and thus affecting the stompboxes or not?

  • JH

      No it does not get connected to ground Sam. All this really does blend the signal dry and wet
    I tried it yesterday with a LP special copy with p-90s. However I wired it outside of the guitar. I set up 2 jack,s wired the pot in between and used a .0033 cap. I was just wondering what it would sound like. It was ok, definitely usable. I just want to experiment with different values of caps. Im also using a 1meg pot. When I get the time Im going to try out .0022, .0047, and .0068. I have this setup in my strat and love it (1 meg, and .0033). I never thought of trying it in a different guitar.
     
    Here is a pic so you could understand how I wired it outside the guitar. 
     

  • That sounds incredible. The bass roll off sounds so musical. I’d type more glowing phrases but I have to run to the electronics store t…see ya. 

  • Jeff

    Just had a thought, I typically run two humbuckers with the tone full on.  Could I substitute the exiting tone pot and for that bass circuit above which should allow me to roll off some low end?

    • joe

      Yeah, that would totally work if you don’t need a treble cut. Though I’d try nudging the capacitor value up and down a bit till you find your perfect sweet spot.

  • Eric

    Another very awesome post, sir.

    A friend of mine that builds guitars posted a while back about a similar knob for metal players and guys who use extended range instruments(7 and 8 strings and more). It’s a really useful mod and I’m with you I’m not sure why more builders don’t use it. 

    • joe

      Yeah, I can see how it would extremely relevant for metal. Cutting bass doesn’t necessarily mean no low-end impact — it can help focus the lows. It’s my understanding that some metal pickups designed for low-tuned chunking (like the Seymour Duncan Mick Thomson) actually actually do something similar — namely, filter out some of the lowest lows so the low end has more definition overall.

  • Groat post, I have to give this a try.  My neck pickup sounds good clean. But when I turn on the fuzz distortion the neck pick up is no fun any more, too muddy. Seems the bass treble control provides a wider range of options than a treble  roll off for  each pick up.  

  • Peter

    hmmm, so I’m guessing that on a two knob guitar I could use a stacked concentric pot (two knobs in the space of one) and have vol, treb cut, and bass cut.

  • Bear

    Dangit, Joe.  Even with concentrics, I’m gonna need more knobs.

  • Matthew Seniff

    I have a buddy who had a 60′s noname japanese guitar that has the bass and treble controls. I did a bit of circuit sleuthing to figure it out as it didn’t work correctly when he got it. The guitar also had seperate volumes for each of the 3 pickups plus a master volume. I’ve never seen another guitar like it very ugly with a big fat neck and chrome pickguard. It would have won the ugly guitar contest hands down. It even had spiral sound holes in the hollow body. Unfortunately it was burned up in a house fire 20 years ago. 

  • Matthew Seniff

    BTW the reason  it reduces the distortion and compression when you roll off the bass is because most of the energy of sound is in the bass frequencies. This is why we use sub woofers in hifis and PAs once you remove the lows to the subs  you need less power to produce clean mids and highs. 
    For the record tho’ I like to hit my fuzz with all the lows then roll the lows off a bit afterwards with a tight EQ or even a parametric EQ. It gives me a more garbled fuzziness that I dig on single notes and 2note chords with slide (but as an excuse I grew up with psychedelic music of the 60′s and blacklight posters on my walls) :-)

  • Jon

    Funny thing i stumbled across this while looking for how to wire a PTB a day after its posted. i put it in my 2 Pu “jagcaster.” it sounds amazing, i used a 1m volume pot and two 500k for the tones a .01uf on the tone and a .001 on the bass cut, it worked great with my seymorduncan tweakfuzz.
    I think one of the secrets to good single coil tone from fuzz is bass reduction, the ptb bass cut reminds me alot of the highpass filter on a jaguar, which has roughly the same effect on fuzz and distortion. which was what drew me to that for my attempt at a jaguar strat fusion.
    i drew a schematic up in visio if anyone wants it.

  • jeremy

    I’m late to the party, but keen to try this but the guitar in question only has a single volume and tone control. I know there’s the dual-concentric option, but was wondering if maybe a push-pull pot could switch the tone control between bass and treble.
    I know that would miss out on the possibilities of using both at same time, but on the other hand I’ve already got some push-pull pots to hand and I’m cheap. :)
    if indeed it’s possible, could someone maybe draw out an easy-to-follow schematic?
    thanks – I only just found these pages a couple of days ago, but I’ve hardly been anywhere else online since!

    • joe

      I don’t think that would work, or at least, it would only work part way. Yes, you could use the switch portion to select between two destination for the pot, but once you switched it, it would be removed from its former role in the circuit, so you couldn’t have, say, a bit of treble cut and a bit of bass cut — and that’s one of the most fun options in this circuit. But if you’re cool with that limitation, it should work. It may help to check out my “How to Install Onboard Effects” tutorial, which includes a rundown of push/pull wiring.

  • jeremy

    thanks for your reply, Joe. my thinking is that even a limited version is still better than just leaving it as-is. I’ll read up on push-pull wiring and hopefully give it a go soon.

  • Deyo

    Hi, can anybody help me please??!!
    I have an Ibanez hollow body and my neck humbucker is way too bassy, could you please tell me where to insert a capacitor and what are my choices as far as the capacitance value vs. bass reduction. Here’s the schematics I dug out online. Also, what are some good quality capacitors I can buy?
    http://www.guitarnucleus.com/gitschems/ibanezAF120.jpg
    Any help is greatly appreciated,
    Deyo