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! 
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.
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).
HI..
LATE AS HELL AS USUAL..I ATTACHED A PAGE OF ACTUAL G&L SCHEMATICS..ANY ?? EMAIL ME.
I SEARCHED FOR THE G&L ‘SECRET ‘ DIAGRAMS. GENIUS..BUT WHAT ELSE WOULD I EXPECT FROM A MAN THAT SCREWED 2 PIECES TOGETHER AND CHANGED THE WORLD!!!
I ALSO DID A DOUBLR TAKE AT THE CAP VALUES…
I THOUGHT’ MAN, A STRAT(OR) WITH THE TONE CONTROLS OF A STEREO SYSTEM (AM I SHOWING MY AGE )….PUT IT TOGETHER..WONDERFUL..ALL THE BS. I EAD ALL OVER THE NET..
I AM JUST ABOUT TO WIRE UP MY ‘JAZZ TELE’ BUILD. I HAD 3 HOLES IN THE TOP (HAMER LOOK ) 2 VOL..1 T. OR 2 T..AND 1 VOL.?
DID NOT REALLY LIKE EITHER…
I STUMBLED INTO YOUR PLACE….
S WILL WORK FINE ON A 2 HB GUITAR…….THANKS, ARNIE
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.
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!
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.
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.
Doesn’t the ‘bass’ pot need to be grounded as well?
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:
https://terrydownsmusic.com/Archive/baritone/baritone_wiring_diagram.pdf
https://www.premierguitar.com/Magazine/Issue/2010/Nov/The_Fender_TBX_Tone_Control_Mod_Part_2.aspx
Great idea — thanks! 🙂
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?
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.
will grounding the bass roll off effect he function or tone JH?
There’s no need to ground the bass pot — here the pot simply serves as a variable resistor.
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.
Let us know how it goes! 🙂
Whew, you wouldn’t believe the line up.
Ok, I got the bits, got soldering and it don’t work.
Here’s the diagram. It’s a Burns Marquee that has a push pull to switch on the neck pup to get neck and bridge sounds. With that switch on, it works; otherwise, absolutely nothing. Dead. Do you have any idea what I’ve done?
In the drawing, the pink lines are what I changed from the stock wiring, shown in other colours.
https://www.dropbox.com/s/3g2374kwzo52j3m/Guitar%20%28page%2015%29.png
I figured it out….I had too many wires going from the output side of the switch. They were the ones doing the typical one tone per pickup thing.
And the result?
I loved how my strat (ok, Burns Marquee) sounded, which means it had to be fixed (not being broken….naturally). This circuit sounds simply amazing. I was planning on putting a humbucker in the bridge because I wanted a bit more guts at times, but not now.
If I dial in a beefy gain sound on my amp, and turn up the bass cut, I get a lovely chimey strat tones. Lovely. Just what I usually play with. But wait – I then turn down the bass cut and WOW, it’s like I’m getting more gain, more…MORE! Great for gain swells. It’s like having a gain control on my guitar without changing the volume. So rather than using a preamp to get more gain, I set the amp to that tone, and turn it down with the guitar, giving me loads of headroom.
I’m so excited. I just can’t hide it!
Oh, I’m so glad it worked out. 🙂
You know, I did TONS of alternate wiring experiments last year when I was working with Seymour Duncan. And out of all of them, this is the one that is so amazingly great, I can’t believe more people don’t use it. It’s unbelievably expressive with humbuckers — there’s so much you can do to shape distortion just by dialing out some lows from the guitar. So I’m gratified to hear that it works well on a single-coil guitar! I haven’t tried that yet, but now, I definitely will — maybe on that parts strat I use in the MIDI guitar videos. (And thanks for an idea for a future post!)
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?
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.
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.
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.
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.
Yes — and 500K/500K is a standard value for a concentric pot. 🙂
Dangit, Joe. Even with concentrics, I’m gonna need more knobs.
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.
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) 🙂
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.
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!
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.
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.
Let me know how it goes! 🙂
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?
https://www.guitarnucleus.com/gitschems/ibanezAF120.jpg
Any help is greatly appreciated,
Deyo
This is awesome! I’m a noobs in these things. So, if I want to do that in a Strat with 3 single coils, should I use the same pot rate? or use it with 250k, 500k, 500k?
Hi Sebastian! I’m glad you find the info useful. 🙂
Well, with a three-knob Strat, you’ll have to reconfigure the wiring so that all three pickups are routed through the same volume and tone controls.
I haven’t yet tried this circuit in a Strat, though your email makes me want to do so! My suggestion would be to use the same pot values as in the diagram above and see how it sounds!
Well Joe, I have a Diagram and I can share it with you (:
But it is a little bit “tangled” haha, I’m trying it Today, so if I finish. I tell you if it works
The diagram includes:
DPDT swith for Expand mode, As the comanche guitar from G&L
SPDT swith for diode clipping (Idea taken from one of your posts)
Pots: 250k 500k 500k (I’ll see how it works)
A different kind of 5-way toggle switch that I took from another guitar that uses another kind of wiring.
And possibly I’ll add a Volume kit, to prevent the tone loose when you decrease de volume.
Hope you get interested (:
I just did it in my Squier Double Fat Strat, and I love it. It’s a simple HH guitar, but I’m a metal guy and the ability to clean up the lows is awesome! It brought “fatty” some new life after 14 years of ownership!
I am trying to do the same to an epiphone G-310, and I’m reading through the comments to see if a diagram has been given for what to put where after the volume pots run into the selector switch (I’m still pretty much a noob at this, and am relying on diagrams hardcore). I’ll keep looking, but if one has been posted I’d love to see it.
That sounds so cool — let us know how it goes!
¡Buena suerte! 🙂
Mr.Joe, I need help D:
I did this scheme:
https://imageshack.us/a/img59/1196/ptbwiringscheme.jpg
But something went wrong and the guitar didn’t sounded :cuss: so I keep searching, viewing pictures and googling collecting information and I made another:
https://imageshack.us/a/img337/4406/legacywiringscheme.jpg
I haven’t tried it, because I need a new 5-way toggle switch because I think that the other switch is not working :what: and before starting, Can you give me an advice? 🙂
Thanks in advance
So I tried this out with a dual concentric pot. 500k/500k but couldn’t get it to work. I guess my confusion is on the bass control with the cap on the two outside lugs. The wire on your pictures’ right is it jumped to the center lug or is that line just dark. Anyway I tried both ways and couldn’t get it. I want to see if this has a different effect than the “Modified TBX Tone Control” I tried. Withe the 1meg and 250k in the TBX my guitar got wayyy too bright (ice picks).
Hey,
Cool idea!
I tried it in my les paul, and I think am having an issue…
The bass knob will roll off bass and maaaybe some other frequencies… not sure… but it does it when the capacitor isn’t even installed… and then when I install a capacitor with what I believe to be the recommended rating, I hardly hear a difference in sound to when there was no capacitor…
I’ve wired it just as is in the diagram I believe.
Any insight into this would be greatly appreciated!!
Best,
Geoff
Maybe post a pic of the wiring? There are some smart trouble-shooters here…
Hey man, allright?
Did you used wish kind of 500k pot? Log or lin?
Sorry about my english (it’s not my natural language).
And thank you just since now.
Sim, todos os três dos potenciómetros são B500K (linear). 🙂
It should be noted in the article that the sketch provided will give you an opposite rotation for the bass cut. That means 0 = no effect and 10 = full effect. That’s not desirable at all IMHO, because it is opposite from a standard tone pot’s operation. The way a tone pot on a guitar works is engrained in all of our minds. We are used to 10 being no effect and 0 being the full effect of the control. Having it the opposite way is tricky on the mind, especially if the treble cut pot on the same guitar is wired the standard way.
Additionally, the jumper between lugs 1 and 2 is unnecessary. All it does is to create an extra solder joint for the technician, without doing the circuit any good. For sake of efficiency, the input to the bass cut pot (and the input side of the cap) should be connected at lug 2, and lug 3 should be left unconnected. (Assuming you DO want the reversed control as illustrated in the diagram.) I can see why the author might have put that jumper in there. Connecting jumpers is sometimes used to create a backup in case of failure of the wiper, so it might have been done out of habit. However, in this particular use for a pot, wiper failure will result in exactly the same result whether or not that jumper is there. With or without the jumper, the entire signal will be routed through the cap, because the pot will effectively be “stuck” at full resistance. In short, the jumper is a backup that doesn’t back anything up, so why bother using it? It’s like carrying a four-lug spare tire when your car takes five-lug wheels.
In short, sure, this works…but the way G&L wire the bass cut control makes more sense than what is shown here, both from the users P.O.V. and from the designer’s P.O.V.
Nonetheless, thanks for spreading the word about passive bass cut controls. If people only used this type of tone circuit more often, they’d possibly save thousands on aftermarket crap they don’t need.
Keith
Hey Keith — thanks for the info!
Yup, you’re right about pretty much everything. Though I kind of like the way the “reversed” bass pot behaves, or maybe I’ve just gotten used to it. (I still have this wiring in that red Hamer I used in the demo, and it still sounds great to me.) I guess it depends whether you prefer to think of all pots fully clockwise as “maximum signal” or “maximum brightness.”
Got any favorite cool wiring tips or techniques? You obviously know your stuff!
Excuse me Keith but i think you’re wrong about the jumper!
I mean you invert the lugs numbers, don’t you?
Regards
[…] […]
So how exactly do I make this work with two volumes, a master bass cut and master tone control?
Just make sure that the output from both pickups gets routed to the single tone circuit (as opposed to having a separate cap/tone pot for each pickup).
Hi,I’m building a bar Bass from a Fender delux import J bass and would like to upgrade to hi quality controls with this type of tone control and a push pull volume control that allows me to go series or parallel.Do you have any wiring diagrams,info and opinion on this setup and any detailed recommendations on a bridge pick up or parts would be appreciated? My guitar has a soft maple body,hard maple neck,Hi mass bridge(added)and Seymour Duncan designed pickups. I love the sound of both the Fender J bass and the early Ricks so I’m trying to get sort of a Rick sound in addition to the classic J bass if I can. Hey if this works reasonably well I wouldn’t have to carry 2 expensive guitars around and into places they could be stolen or damaged Thanks Dan
Hi Dan — sounds like a cool project!
My source for almost all wiring diagrams is this page at the Seymour Duncan site: https://www.seymourduncan.com/support/wiring-diagrams/
(Scroll down for bass diagrams.)
Let us know how it turns out — I’m curious to hear how far “Rick-ward” you can nudge the tone of the J!
I first found out about this circuit back in 1977 when I bought a Carvin APH-4N humbucker to stick in my ’73 Rick 4001 bass. The pickup came with a sheet of paper with wiring diagrams, and the passive bass control was one of them.
It really is handy to roll off the low end in guitars. You can get all kinds of nice overdrive sounds that way. Too many guitarist use too much low end.. sounds good in the bedroom, but leaves little room for bass and drums. 😉
Sounds so great – especially for a Les Paul, with 2 volumes & master bass/treble like Joe suggested. I hope somebody will post a diagram I want to try this with my epiphone Les Paul. THanks!!!!!
Hi Homesick! If you can read my sloppy handwriting, the diagram in the body of my original post should work great on your Epi!
Hi Joe!! 2 volumes 2 tones converted to 2 volumes & masters bass/treble. is that it? Many thanks.
I’m reckoning that this, in a stomp box, would be outstanding, not only as a tone tweaking tool, but for so many other applications (maintaining tone between two different pickup types, say 2 LPs with passives and actives perhaps, or different tunings)
I think I’m going to have a go knocking this up!
I want to build a varitone stompbox !
Hi Joe! I modified your drawing for use on a Es 335 (2 volumes, master bass/treble), but I’m not entirely sure if it will work.
Could you take a look at it?
Thanks!
Uploaded with ImageShack.us
https://imageshack.us/photo/my-images/23/t8hd.jpg/
HELLO..
AND THANK YOU !!!
I AM STRUGGLING WITH ADAPTING A SEMI-HOLLOW GUITAR ( 2 VOL/ 2 TONES)… TO THE ‘PTB’ SYSTEM…ANOTHER GENIUS ADDITION TO THE WORLD BY MR. FENDER…
I AM STUCK WITH THE 2 VOLUMES, AND HOW TO WIRE THE ‘BLENDED’ SYSTEMS TOGETHER.
I DID SEE YOUR ORIGINAL SCHEMATIC..BUT ONLY 1 VOLUME…
ALSO-LOOKED AT THE ES-335 SCHEMATIC…RICK WAS ASKING IF THIS WOULD WORK. WILL THIS DESIGN WORK?
…I HAVE TROLLING THE ‘NET FOR A DIAGRAM..AND ONLY YOUFOLKS HAD THE ANSWER–OF COURSE .
WHAT CAN YOU TELL ME?
THANK YOU—THIS IS A GREAT SITE…AND SOME ‘ENLIGHTENED’ MUSICIANS WHO HEAR THE BEAUTY& GENIUS OF THE ‘PTB’ SYSTEM…
ARNIE
Being a rewiring, maintenance, and modding noob, I'm recognizing what is what above. But I'm a huge fan of the 0.1uf capacitor on the tone pot (I put one in my Jackson PS-4 with OUTSTANDING results), to help get a hell of a lot of rolloff if needed (I'm thinking of calling it the overkill knob). All I understand at this point is that the higher the cap value, the more treble you roll off. Does it work the other way around (the lower the cap, the more bass you roll off)? I'm unclear on how this mod works, but am EXTREMELY interested in trying it.
“Too large a value, and the tone gets flabby/sloppy. Too small, and it gets thin/shrill.” – I read it more closely, and have my answer. Thanks again!
Joe,
I LOVE this mod too! I often wonder why it hasn’t become more popular also. I think it can be counter-intuitive and alarming to new users who aren’t use to a bit of apparent volume loss. The mod particularly excels in a band situation where you’ve really got to find a small sonic space to inhabit.
The one particular struggle I’ve had is finding a taper that felt right for the bass cut pot. As Leo suggests and I’ll confirm, it really needs to be a reverse audio taper IMO. I started with a 1 Meg linear which was incredibly notched feeling, then tried a 1 meg reverse audio which didn’t really fit the guitar and was quite cheap, but the taper felt right. I’ve finally landed at a reverse audio taper, 3 Meg pot, from the amp parts section at Mojotone. It works very well, much like the PTB G&Ls I’ve played.
If I had it to do over, I would likely just try a “lefty” 500K pot, which are all over the place! I was always worried there wouldn’t be enough blockage of the dry signal that way, but it would appear from your video, there is plenty!
Thanks for sharing.
Hi Glenn — well, it won’t surprise you to hear that I couldn’t agree more! 🙂
There are a LOT of circuits that benefit from reverse taper pots. Especially (hint, hint) distortion pedal gain controls. They’re easy to source these days, but that wasn’t always true. Which explains why we encounter so much gear with lousy feeling tapers.
Interesting — I don’t think I’ve ever SEEN a pot over 1M. I’m going to have to poke around Mojotone myself…
Ok, I’d be extremely greatful if you would please show a diagram of some kind showing how to wire this for an SG or Les Paul. I’ve got two guitars that I want to do this to, and am ready to start screaming. :rant: :cuss: :cuckoo: :shake: :what: :noshake:
This site has opened my eyes to a lot, by the way, so thank you very much for all your helpful info!
Hi Joe,
On the original schematic provided by JH, all 3 pots have a “dot” on one of the terminals, can you explain what this is for as I am not familiar with that notation for a pot?
Rod
Hi Rod — can you link me to the diagram in question? I keep getting lost on my own damn site. 😉
I was able to find someone to help me put together a diagram for Les Paul wiring. It’s crude, but from what I understand this should work.
Any feedback on the accuracy of this would be awesome.
SCRATCH THAT DIAGRAM!
Here is how to wire this on a Les Paul style guitar. After scouring the web for a week, I found someone willing to help me find the answer and he drew this diagram for me. I just installed it in an Epiphone G-310 and it works! (I used a 0.1uf capacitor and a 0.001uf capacitor, but I like extremes).
The signal flow goes into the pickups first, then to the selector, and out from there into the two tone pots.
Looking forward to more awesome mods like this. Am contemplating using a cheap bass to add the PTB circuit to (with my extra high and low cap values) on mini toggles, as well as a switchable overdrive and a kill switch. Planning to use it to get synthy tones. Thanks for inspiring me to dig into my guitar and for opening new doors for me! :thumbup:
Oh man — thanks so much for posting this, Brandon. I’m definitely going to try this out! 🙂
No prob! Sold the SG earlier today based on that mod, it was a quick sell. Guy wanted flat wound strings put on the SG too, which made me think of the part of your blog where you mentioned flatwounds. Tried those out before delivering the guitar, and I have to say that they’d take some getting used to. But flat wounds might be the solution for the synth tones I’m looking for out of heavily distorted guitars.
More than stoked that I was able to get it to work, as I’m planning to install the exact same config in my Ibanez GAX 70, which is a cheapo I use for C-Standard tuning.
Having trouble getting this to work. Setup: 12 string acoustic, UST piezo with endpin preamp that booms bass, so I need a bass roll off. I also wanted to move the vol/tone out of the soundhole. Baggs gave me a schematic for 2 (vol/treble) external pots, using 25K pots and .033uF treble cut. Only difference is the volume works as a rheostat bleeding to GND instead of a divider. So I used this diagram to add in the bass roll off (25K, .0033uF) The treble does nothing unless I short out the bass cap and turn the volume way up. Seems to be some impedance magic that I don’t really understand. I tried the volume as shown here (divider), still didn’t help.
I am assuming the controls are on the output of the preamp, but I can’t confirm that.
I expect i’ll want to play with cap values, but I have to get it working first. Right now it’s way too bright.
OK, duh! Figured it out! The existing volume/tone control circuit is actually wires taken off the preamp circuit, which would explain why the volume is also bleed off. So my bass control actually just works as a bleed of through the volume pot, making it just another treble bleed. I’ll have to put this in line between the pick up and pre amp to make it work, I think the 25K pots will still be OK, but not sure what it will do to the rest of the sound. If I learn anything helpful, I’ll post.
Hi Joe,
I’m on a guitar project and i m very interested in your PTB rough schématics.
But i notice that the bass pot is not grounded, i wonder if it’s not better for my project to ground it with a floating mass because my bass pot is far from the volume and treble pots, So the wires are very long. I’m affraid this cause hum!
(In facst the bass pot is located in the pickups selector location on a LP)
Have you any advices about that?
I also notice that the treble pot is grounded on the volume pot, and it makes me wonder if it’s not a issue (hum issue) if the whole cavity is grounded with adhesive copper?
Best regards
Hi David! I don’t experience any hum due to the ungrounded bass pot — but there’s certainly no harm in grounding it. The other ground wires, however, must be connected, no matter how good your internal shielding is. You can even ground all your pots directly to the shielding.
Ok Joe thx for answering So quick!
I will try your wiring as soon as the painting is finished.
But just a last question: the guitar you put this wiring in (the one on the vidéo) is it shielded in the pots cavity or not?
I’m wondering if it’s necessary to shield the pots cavity with humbuckers?!?
Best regards.
like yout page
Hi Joe
I post again because this ground wire between the vol pot & the treble pot cause me matter
I explain. I’m adapting your scketchy diagram using a telecaster control plate which already connects
These two pots together !! I’m talking about ground loop but i’m not an expert.
The fact is that at this point i’m wondering if the pickups selector which is screwed on the same
Control plate should be grounded on the volume pot? Or not?
I will try the 2 possibilities but any advice is welcome ,please help me!
hey joe,
i’ve done this on several guitars now bro,
i love you man!!! thanks!! quite awesome, particularly with anything thru a fuzzface. you can dial in/out the perfect amount of woof..
but i got a problem, and i think someone else may too… especially at stage volumes, i notice when i cut the bass, the hum level goes up substantially in the guitar. it’s doing it in all of ’em, which is leading me to suspect that this pot’s case/shielding may need a jumper to ground.
anyone else have this issue at all? i have the afternoon off, gonna take a peek down in my workshop at my firebird and see if i can suss this out. i’m thinking the ground is floating as i turn up the pot/cut the bass cuz of the cap, hoping a ground strap may help.
also wondering if having the wiper tied to the unused input lug may be doing it.. if i have any luck i’ll report back, but man, i could really dig advice and/or if anyone else has had this issue.
thanks man
peace out
pjp
ok, i figured out what i did wrong…
it was multiples. 😉
used a 22n on the bass pot instead of a 2.2n;
exTREME bass roll off.
so i rewired the whole mess with fresh caps/wire etc, and got it working using Brandon S. Hire’s second layout.
still had a hum problem as i cut the bass tho… nowhere near as badly tho.
so i shielded the control cavity and made sure there was a good ground connection to the shielding and it worked out great.
i guess when ya roll the bass back, it lets a bit more hum be noticeable that would normally be masked by the guitar’s frequencies…. or something.
anyways… onwards and upwards…
thanks guys
peace
jimi
You get more hum because when you roll off the bass you increase the guitar circuits impedance (by the value of the bass pot – 500K if its a 500K pot). That’s compared to maybe 6 to 10K with volume at max and bass at max. The higher impedance means that the control circuit itself (not just the pickups) is much more prone to pick up hum fields. The solution is to shield the control cavity and connect the shield to the output jack ground. I think it is good practice to always shield all the cables and controls in a guitar. It’s not just the pickups that are prone to hum. A lot of guitar companies don’t bother, particularly on the cheaper guitars. They seem to think electric guitarists expect hum.
Hi Joe,
I was wondering is it possible to do this on a 72 Thinline Reissue? What pot would be suitable for tone control without having to drill an extra hole and add an another pot? Purely for aesthetics.
Thanks in advance.
Ciarán
Ps love your v informative videos and my kids love your expressive facial expressions.
With just two knobs, right? If you don’t want to drill an extra hole, I’d go with a concentric 500K pot like this one:
https://www.allparts.com/EP-4586-000-CTS-500K-500K-Concentric-Audio-Pot_p_1444.html
Use one of your current pots as master volume, and use the concentric as a two-band tone control. Follow the schematic in the Premier Guitar article, which calls for two 500K pots like the ones in the item at the link. Hope that helps — should be awesome!
How would this work with 4 wire humbuckers and a coil splitter?
Hi Joe, is it possible to do this mod to a start?
Yes, it should work fine. Just put the treble-cut and bass-cut elements after the output from your pickup selector. 🙂
So I'm really new to wiring mods, and I like the way this one looks, But is it possible with active pickups?
So color me frustrated.
I understand how a tone capacitor functions with regard to sending signal to ground. The bass rolloff capacitor is not grounded, however, and I’m trying to figure out how it works. I want to mount the small cap onto a mini toggle, and can’t figure out what I need to do to make it work. I imagine I’d need some sort of resistor after the capacitor, but which kind and how would I wire it? Does anyone have any input on this?
I’d love help understanding the basic principle behind how the small cap works to roll off the lows. I get that the big one sends signal to ground, but what happens with the small one to make it work? What makes it work on the lows instead of the highs? I feel that if I understand how it works I could perhaps figure out how to make it work with a switch.
I’ve included a pic of the picguard. You see a volume pot, then a blower switch, a toggle for a 0.1uf capacitor, and then the bottom one is the one I can’t get to work for the bass rolloff. The cap size I’m using is 0.001uf.
For anyone looking, I found this youtube video which helps explain the signal flow. I think I know what I need to do now.
https://www.youtube.com/watch?v=MHEl_m1CjEA
So let us know if you get it working, Brandon! The treble cut cap diverts signal to ground, as you say. The bass-cut cap, however, is inline with the signal, and ground isn’t part of the equation. You don’t even need to ground the bass-cut pot.
Right, and I think I have the outline of what I need to do. Just got back from MicroCenter. Only store in Columbus that sells what I need anymore after Radio Shack went bomb.
Where do you buy your parts online?
I buy most of my guitar-specific stuff from Mammoth or Small Bear, and I usually get generic stuff from Mouser or Digi-Key. But those are just my habits — there are other fine vendors, and I haven’t encountered any I’d urge folks to avoid. (For EU readers: I’ve heard good things about Germany’s Banzai Music.)
After a few days of searching, trial, error, not being able to get it to work, I finally found this page…
Written by Joe Gore… 😉 – suppose I should’ve googled better. I actually was going through this list a few days ago and stopped on page 6. Page 7 is the one that started talking about what I needed to know.
Lesson learned. Don’t be so impatient. LOL!
https://www.premierguitar.com/articles/21112-three-must-try-guitar-wiring-mods?page=8
Anyway, I’ve got it working…kinda. I’m using an On/On switch, not an On/On/On. When I turn on the bass cut switch, I’m getting a hum that goes away when I touch the strings. When I turn off the bass cut it also goes away. Either the capacitor is shot, or I don’t know what…
I’m gonna swap it for a different cap tonight and see if that fixes it. I’ll report back. 😉
Thanks for, yet again, being the provider of the answers I’m looking for!
Patent tone?
What resistance level of pots would you recommend, and why? If it helps, I’ve got a P90 (with a phase switch) on the neck and a humbucker (with a coil-splitter) on the bridge, with seperate tones and master volume/bass.
Also, I wonder if you would take a look at my diagram and spot-check it? I’m a bit new to the game and I may have done the grounding incorrectly.
Loving the education I’m getting just by reading all these posts. I promise I’m not selling any of your ideas!
Hi Evans ‚ glad you’re enjoying the site!
Check out the schematic in the PTB article here, which cover both Fender’s original values and some possible substitutions. For the volume pot, two a 250K, but switch to a 500K is your humbucker is too shrill with the former. Or just get a retro-approved 350K pot if you can (as used on some old Gibsons). Chances are it’ll sound perfectly fine with any of those three.
Does it matter what I use for the tone and bass knobs? I hadn’t thought about retro 350k pots. That would go with my guitar, as it’s kind of a retro model (it’s like a Harmony/Gretsch/Rickenbacker remake). Thanks for your help!
Why the ‘traditional’ pot values were originally chosen and why these values have now passed into the guitarists rule book of ‘because that’s the way it’s done’ is a very interesting question.
Taking a guess I’d say it’s partly because the available values for off the shelf pots are and have been fairly limited, and partly to allow for the various loading effects that occur in a passive electric guitar circuit. Placing a resistive load across an electromagnetic guitar pickup loads the pickup and reduces output level and treble response. The larger the pickups inductance the more sensitive it becomes to loading. A typical Fender single coil might have an inductance of 2.3H. If you wire that direct to a 1Meg guitar amp input using a cable with 470pF capacitance you get a massive 15dB treble peak at 4.35 kHz followed by a steep roll off. Add in the typical 250K volume and tone controls with a 0.022uF tone cap and the control resistances load the pickup, the treble peak drops to +4dB at 3.9kHz (controls at max), again followed by a roll off.
The guitar volume pot also needs to be of a low enough value that the loading of a ‘standard’ 1Meg guitar amp input won’t distort the audio curve of the volume pot too much. Note that Gibson players don’t usually use guitar amps with 2Meg inputs (although some of the early Gibson amps did have higher input impedances) and that some guitar amps, and even more commonly effects pedals, have input impedances of 470K or even lower. Plug yer Gibbo with 500K pots into one of those and you may find your level adjustments seem a bit odd.
Gibson style humbuckers are usually not that far off two Fender single coils wired in series and have an inductance of around 4.4H. So just doubling the value of the pots up to 500K makes sense (and it’s a standard value). However some time in the ’60s Gibson started using 300K linear pots in some of their guitars, presumably because it was felt the blues and rock players of the time wouldn’t buy a bright sounding Les Paul. Why they went with linear pots I don’t know. Perhaps they work better in the 4 knob passive mixing scheme, or it was felt to be a good thing to have very fine control of levels with the volumes up (linear pots tend to present a rather on/off control of volume).
Incidentally – I first saw the treble and bass tone controls on a very handsome trans forest green G&L Strat I picked up on the cheap. If I remember correctly it uses a 1Meg series bass pot, so the usual ‘rules’ don’t apply for the bass pot.
I think I must use this PTB dual tone circuit. great! 🙂
Nice tone control Q and A site! I love reading and seeing all the various things one can do with passive elements.
To the question of pot values, they are not specifically locked in stone! Here’s why they pick the values..The pups have. Coil, which also,has inter-winding capacitance creating a self resonant frequency, mire later, and there is a resistance do to the hundered feet of fine wire wound on the coil core. So, all pups are high impedance critters!
Therefore, to add some controls after the pup you want to have pots at least ten times or more than the DC resistance, and the combination of the resistance with the coils inductance, it has reactive impedance. So guitars made before 1975 or so have DC resistance in the 7-9 k ohms, so the “vintage” pups only needed 350 k to not load the pups.
As the desire for mire oomph and use of humbuckers grew the resistance, mire coil windings, and the inductive impedance, is larger. The signal is larger as two coils are in series and the bandwidth of the hum pups is less. Giving a pup with treble cut built into the pup. These require a higher resistance pot, so as to not load down the pup. Hence 500 k pots or larger!.
Now all the capacitors with larger value pits are smaller by the ratio of the pots! Do you scale the caps down by pup new / pup old . I would use am computer model to,get it all perfect. I gave and X sn use SPICE. NEED HELP. Contact me? Skype ? Marc.popek
Hi all, Great site. Does anyone know where to look for the concentric pot and wiring info that would allow changing my G&L Legacy to a two control knob set up? I’m hoping to relocate the volume knob to the center position and combine the two tone knobs into one dual concentric tone control. Sounds like that would take a stacked pot that operates in reverse (left handed) direction with 1M resistance and in right hand direction with 500K resistance. Or can you just use a 500/500 pot and reverse the wiring for the bass control? Thanks much.
In preparation for installing this in my Wildkat and maybe my Les Paul, I tried breadboarding the bass control and found the effect was noticeable but not very strong. After lots of simming I found that the order of the controls in the signal chain is fairly important. The closer to the pickups the bass control is, the more effective it is. Brandon’s diagram in the comments that shows pickups -> volume -> switch -> Treble -> Bass (equivalent to my breadboard experiment) gives the least amount of bass cut, because the bass control is as far as possible from the pickups.
The original schematic (at least according to the article) shows pickups -> Treble -> Bass -> Volume, but this isn’t possible with a standard Les Paul-type of arrangement (2 pickups, 4 pots, 1 switch) because the volume controls have to come before the switch if you want to control the pickup volumes separately, and the tone controls have to come after the switch if you want to be able to select the pickups individually.
Concentric pots can get you there, with Treble and Bass controls for each pickup, and so can a master volume arrangement (which leaves one dummy volume control) but the sims show that you can get a close approximation of the original G&L frequency response from pickups -> Volume -> selector switch -> Bass -> Treble, which makes all of the controls act as expected (independent Volumes, master Treble and master Bass. (This is equivalent to Brandon’s diagram with the order of the Treble and Bass controls swapped.) This way the impedances to ground before and after the bass control are similar to the original schematic, which makes the bass control respond similarly. (Incidentally, if you want even more bass attenuation, put the bass control directly after the pickups.)
Placing Treble before Volume or vice-versa is equivalent to choosing modern LP wiring or 50’s LP wiring, respectively. No matter what order you put the controls in, the bass control is completely removed from the circuit when it’s set at max, so both Brandon’s approach and mine will give you 50’s wiring when Bass is maxed, which is lucky for me because that’s what I prefer.
TL/DR: Swap the order of the Bass and Treble controls on Brandon’s diagram if you want to increase the amount of bass cut available.
Hope someone finds this helpful.
I just did this mod to a 12-string Rickenbacker. The bass cut works brilliantly to bring out the jangle. Thanks again, Joe.
Hi, Colm! Hope you’re doing well. 🙂
Oh, cool! That never even occurred to me — but now that you mention it, it makes perfect sense!
induction, thank you for your tip on swapping the order of the bass and treble controls. I hope to try this out today, God willing. I have a 4 knob tele wired up in a 50’s LP config. My pots are all 500k. How necessary is it to use a 1 MEG pot? I want to know what difference it would make tonally. Also, does that pot need to be a reverse log. pot? I’m also wondering what difference that pot would make in the operation of this circuit.
Using a smaller that 1M means you get less cut. The reverse log gives you a smoother change in control. A linear would be a bit more on / off and a log even more so. However you can use a log wired in reverse, so is becomes anti-log. It just means the control works in reverse.
Hey Terry! How’s it going? Thanks as always for chiming in with useful info.
Hey, I’ve got a question for YOU: Are you aware of any readily understandable resources concerning “pot hacking?” (Insert cannabis joke.) I refer to tricks like the one you mentioned (wiring a logarithmic pot as anti-log), as well as using extra resistors to lessen a pot’s resistance? So, for example, you might assign assign a lower value to half of stacked dual pots, which inevitably share the same value? Like making half of a dual 100K pot behave as a 10K.) A reference chart, if such exists, would be awesome. If it doesn’t, perhaps we can create one?
Hey Joe, there is The secret Life of Potentiometers by the guy I think we all refer back to at some point – R.G. Keen. https://www.geofex.com/article_folders/potsecrets/potscret.htm
(sorry, can’t find the tags to make that an embedded link)
That is a start, but it doesn’t cover everything about pots. For example he mentions the neutral or ‘landing’ zones on either end of a pot track, but he does not highlight that these almost always occupy 5 to 10 % of the track at either end. As a result up to 20%, or more, of a pots rotation does nothing, You can turn from 1 to 2 or from 9 to 10 on a Fender knob and it does nothing. I have proved this to my own satisfaction by measuring the resistance of a fair selection of pots, bolted to a chassis with a large protractor for a scale and long pointer knob on the shaft of the pot for accuracy. I plot my results in a LibreOffice Calc spreadsheet to compare the curves. You can learn a lot about real pot curves by doing this, if you have the patience. It is also great for examining the claims of all the ultra-special voodoo pots sold for the best Wah-Wah pedal response.
I’m still finding out things i did not know about pots. The thing is it can get a bit crazy. I recently tried looking at the best way to select a value and curve / or trick wiring for a really smooth sounding tone control (the guitar magazine reviews used to drive me nuts when the reviewer praised the guitar builder for selecting really smooth tapers for their controls). I used an LTSpice simulation for this. Even though the standard passive guitar circuit only has a handful of components it turns out there is way more going on than you might think.
I’ve just rewired a 335 copy with a bass cut control, so I’m having fun getting used to what it does. I haven’t spent much time with humbuckers as I’ve always worried they wouldn’t be bright enough, so I went with a bass cut using a C1M pot and 2.2n cap and a master tone control using a 15n cap and 500K no-load pot. The bass cut is a lot more useful to me than when I tried coil splitting, plus it feels a bit more elegant and intuitive than messing with push-pull pots. It really does interesting things into a fuzz face too. I think this is a mod which I’ll keep.
I have question… I was going to try this in an SG with split coils, I converted the bridge tone control into a master tone control and I’m using the neck tone pot to make this bass control. The signal path goes from pickup to coil split switch to volume pot to selector switch to output jack. It will be really easy to put the bass control in line between the switch and the output jack. So the question is… Does make much difference if it is after the volume pot instead of in front of it? No matter what I’m going to try this anyway because that neck tone pot will be just sitting there connected to nothing if I don’t.
Gosh, I don’t THINK that should matter, but I haven’t tried myself. Maybe give it a go and see (and tell me how it works out)?
I have my 335 copy wired in a similar layout; individual pickup volumes before the selector switch, then master tone and bass cut between the switch and output jack. It all works as expected, no problems doing it that way.
Thanks, Martin. Good to hear! 🙂
I finally got my SG back together about a week ago and I’m a little underwhelmed with how it turned out. I guess it could have something to do with where I have it in the signal path (although I don’t see how). I can hear a slight reduction of lower frequencies but you really have to listen for it. To my ear it sounds almost like rolling off the bass on the amp from 11 o’clock to 10 o’clock, which is a pretty cool thing to be able to do but Its still nothing like the effect seen in your video. I’m going to do further experimentation in an Epiphone G310 with it between the pickup and volume pot then move it to where I have it in the SG and see if it makes a difference. I’ll also try different pots (a pot not functioning properly could explain the weak effect) and different value caps (.001, .0033 & .0047). I’m going to have fun with it.
Hi Kevin,
The bass control is a simple single stage capacitor and resistor filter. For bass cut the capacitor needs to be a relatively small value so it passes more of the signal as frequency rises. For bass cut the important resistor is the resistor that goaes to signal ground, not the rotary control wired in parallel. In Joes original circuit he shows the capacitor connected to a 250K volume control (as is typical for guitars with single coil pickups). So the two components determining the bass roll off are the capacitor C2 0.0022uF and VR2 250K. When the bass control VR1 is at zero resistance the capacitor is shorted out, has no effect so there is no bass roll off. At the other extreme VR1 is large enough compared to VR2 that the capacitor has an effect and blocks the bass.
If you put the bass pot and capacitor elsewhere in the circuit it is no longer driving the 250K value and the amount of bass roll off will be different. If for example you put them on the other side of the volume control between the volume wiper and the output jack then, when you plug in to an amplifier, the capacitor will be connected to 1Meg (the input impedance of most amplifiers) not to 250K and you will get less bass cut. In that situation you might think of perhaps putting maybe a 270K across the output jack to get the bass cut effect you want. Except then you are increasing the overall loading on the pickups and will lose a little treble.
Um yeah, this is embarrassing but I didn’t wire it correctly. I’ve rewired dozens of guitars and was so confident that I had it right I must have looked at it ten times and not even noticed. I had the output on the center lug and the input on the jumpered lug, don’t know what I was thinking. I’m actually surprised it made any change in the tone at all, I guess a small part of the signal was getting shunted through the capacitor when the pot was wide open? I would like to mention that even though in theory you don’t need to ground the case of the pot its not a bad idea, there was some serious buzz until I grounded it. Now that I have it set up correctly I love the huge variation of sounds you can get when combined with the tone control. This is hands down the most useful mod I’ve ever done to an electric guitar. Still want to try this with different capacitors and 1meg pots and a resistor or two. I have a few guitars that are really ‘dark’ with neck pickups that I can only describe as muddy, I think a variation of this mod could clear that right up. Thanks Joe!
Terry,
That is some really useful information, I’m definitely going to see what a resistor will do. I’ve seen several variations of this mod, one said to have maximum bass cut potential uses 1meg pots and a 1meg resistor across the output jack. It should be really easy to experiment with a resistor value that will be right for my set up. I’m thinking since I used 500k pots a 470K resistor would be a good place to start. Thanks
Hi Kevin,
I don’t know if this has already been mentioned but the -3dB roll off point for the capacitor / resistor combo is f = 1/(2PiRC) where C is the bass cut cap and R is the output volume (assuming you follow Joe’s original diagram).
So for a 0.0022uF and a 250K pot the signal will be -3dB at around 289Hz – below that the signal will diminish by -6dB per octave. In practice the 1Meg in parallel pushes the roll off frequency up to around 347Hz but that simple formula will give you some idea of where your roll off frequency is. With 500K volume pot (and a 1Meg) the roll off point is 191Hz. You might expect it to be one half of 347Hz but you would need to use a 2Meg bass control to get it to scale exactly, which is not a standard value.
Hi Terry!
In the formula, did you use capacitance in uF, and the resistance in “k”?
Thanks
Hah! for the first time in history, I’m going to jump in and answer a tech question BEFORE Terry. Hopefully he’ll step in to correct me is I get this wrong. 🙂
You are correct! Capacitance is measured in farads (F). Putting a mu symbol (µ) in front of the F means microfarad, or a millionth of a farad. Since there’s not always a µ symbol on hand, folks often substitute a u. (Fun fact: On a Mac keyboard, type, opt+m for µ.)
Resistance is measured in ohms, depicted by the omega symbol (Ω). So “1k ohms” or “1kΩ”) means a thousand ohms. Note that American and European conventions differ when using a decimal point. In the US, you’d probably see 2.7k for 2,700 ohms, whereas a European would probably type 2k7. (On a Mac, opt+z = Ω. There are PC equivalents, obviously—I just don’t know them.)
I’ve been looking at this circuit for a while now for a pair of Alchemist P90s that I purchased last year. They’re P90s in an HB chrome case and, given that P90s to my ear sorta’ sound mid way between a single coil and an HB, I’m thinking that a bass filter might be a good match for them.
Any idea of how well this would work with a P90? As well, what sort of values for caps and pots would work with a P90 in this circuit?
Thanks and best in the new year,
Mike in Winnipeg
I haven’t tried that brand of pickups, Mike, but I generally agree with your “midway between” idea. P-90s also have a touch more … not quite distortion, but a character sometimes described as “furry” or “rough.” The bass cut should work nicely on them, but bear in mind that the mod’s effects are most dramatic when playing with distortion. For strictly clean playing, the result might be underwhelming. Good luck, and let me know how it goes. 🙂
Ooops, the Alchemist P90 come from Iron Gear in the UK(forgot to mention that!).
I did a re-build of a Squier SE about a year ago using Iron Gears’ “Pig Iron” single coils, along with A+B CTS 250K pots, .047uf Sprague cap, and some other stuff and I have to say that I was really impressed with the way that the Pig Iron single coils woke up woke up an otherwise mundane Strat copy. I’m Not a professional so I don’t really know the words to describe what the SE sounds like but if you’ve heard hand held Christmas bells when they peel, that’s the sort of crystal tone and sustain that the Pig Irons produce. It’s not something that would appeal to everyone but I like it.
As for the P90s, I’ve had a yen to build a hard tail for a long time now and I wanted to try something different. The problem I had is that most of the two coil circuits out there seem to be designed for a Tele with very little for dual P90s: that’s why I thought I’d give you a shout. You figure that the values mentioned above for caps and pots would work with P90s?
Hello, I’m trying to add this to an HSH ibanez guitar and I was wondering if this would be the correct wiring.
Also, I’m curious as to why there’s a jumper on the bass pot, I’ve seen other diagrams for this and some have it, and others don’t, and some connect one of the capacitor ends to the middle connection on the pot, I’m kinda confused about all that.
Rotary controls have three terminals – one terminal for each end end of the resistive track (often referred to as the clockwise and counter-clockwise terminals) and one which is the variable, moving terminal known as the wiper. You will also see these terminals numbered as 1,2 and 3 for CCW, wiper and Cw.
These controls can be wired in several ways. The most common are as a potentiometer as in a volume control, with the CCW terminal grounded, or as a variable resistor as in a tone control, with the connections between the wiper and CCW.
Wired as a potentiometer all three terminals are connected so that the track resistance from the clockwise (CW) terminal to the wiper and the track resistance form the wiper to the counter clockwise (CCW) divides the voltage across the track (between CW and CCW). The divided output is taken between the wiper and one of the other terminals, usually the CCW which is connected to circuit ground.
Wired as a variable resistor only two terminals are used and the resistance varies between the wiper and one of the track ends. You will often see a link between the wiper and the ‘unused’ track end. This is simply a ‘safety’ link. Without it, if the wiper stops making contact with the track the variable resistor will go open circuit. With the link, if the wiper looses contact, the full track resistance is still connected into the circuit.
Alright, so it’s just like a safety measure. Thanks.
Joe, when you have a moment, could you help me make sure I get this PTB circuit right for a three-pickup guitar with three volume controls? Yep, I’ve got a fifth hole in my Les Paul and was thinking Varitone at first, but your article and demo has convinced me that three independent volumes and the global PTB is the way to go. Much appreciation for the original article and any help you can offer.
It should be pretty easy: Just put the bass-cut knob as the last thing before the output jack. 🙂
(With Dunce Cap firmly on head) In your “sketchy” drawing, one lead of the bass cut pot goes to the tone pot and the other goes to the volume pot. I have my volumes before the LP three-way switch, so should the lead going to the volume pot connect to the output of the three-way switch instead?
If you wire it that way it will do something. Just not the same thing it would do if you have it before the volume controls. The thing about passive guitar electronics is that all the components interact with each other, sometimes in rather unexpected ways. The principle of placing a ‘small’ value capacitor in series with the signal from the pickups to cut bass relies on there being a resistance to ground. The signal entering the small cap is then divided down by the ratio of that caps impedance to that resistor. With the bass cut cap placed before the volume that resistor is the track resistance of the volume control. Placing the bass cut cap on the other side of the volumes makes that resistance the input of the amp or pedal you plug in to. Now when you consider that pedal inputs can vary from several megohms down to a few hundred K (less for a Fuzz Face) you can find your bass control operates differently depending on what you plug in to. If you plug in to a pedal or amp with a 1 Meg input then with the same value of bass cut cap you get less cut than if you are running it into 250K volume.
Even with a bass cut cap before the volume what you plug in to can have an effect on the amount of cut, its just the the fixed track resistance of the volume tends to stabilize what you get.
With a dual volume set up you could use a dual gang pot for your bass control and place it before the volumes. Then you could even fool around with different values of bas cut cap for each pickup.
Hi! Noob alert, sorry.
Given my guitar has two humbuckers, one volume & one tone pot. I want a third pot for the bass cut option. Is the connection of the bass pot (with cap on it) to vol.& trbl. pot most likely the ONLY work to be done here? Or is a lot of re-wiring between the original components necessary ere the bass pot functions as desired?
Excuse my idiocy, this is the first time I try to understand guitar electrics.
With just one volume and tone on a two humbucker guitar not a great deal of re-wiring is required.
Just disconnect the output from the pickup selector switch from the volume and treble tone control. Connect that pickup switch output to the counter clockwise end and wiper of the bass pot. Connect the clockwise end of the bass pot to the top of the volume pot. The bass cut cap goes ‘across’ the bass pot as shown in the schematics.
Thank you! But the treble pot stays connected to the volume pot as was before, right?
ALWAYS trust Terry’s tech advice over mine. Really.
I sure do trust in what Terry says. I just don’t know where the treble tone pot goes now. I sum up: 1. Disconnect switch from volume AND treble 2. Solder selector to bass pot 3. Solder bass pot on top of volume. Question: Where is the treble pot now?
Sorry again, I’m not only a noob but also not English-speaking. (Now excuse also the unintended double post)
I sure do trust in what Terry says. I just don’t know where the treble tone pot goes now. I sum up: 1. Disconnect switch from volume AND treble 2. Solder selector to bass pot 3. Solder bass pot on top of volume. Question: Where is the treble pot now?
Sorry again, I’m not only a noob but also not English-speaking.
Well the treble stays where it was. Treble pot in series with the treble cap, across the volume.
Oh wait a moment, I have just looked at the original diagram that Joe posted (it is after all a long way above all these comments). That shows the treble control and cap on the other side of the bass control to the volume. I don’t think it makes any difference whether the treble control is before or after the bass control.
I’ll have to construct a simulation and double check.
Well that’s interesting. I ran simulations of the PTB circuit with the treble pot and cap to the left of the bass cut (as shown at the top of this post) and with the treble pot and cap to the right.
It turns out that placing the treble pot and cap to the right of the bass cut is a superior configuration. It provides about 3db more bass cut at 100Hz and a little more treble peak. And if you make your treble control 250K instead of 500K you lose just a little treble, but get even more even more bass cut.
And BTW Joe’s pencil drawing shows the Bass cut control as cutting bass as you rotate the control clockwise. I think I would wire it reversed so both the treble and bass controls cut as you roll them anti-clockwise.
Thanks a lot for your help and your interesting findings!
My guitar has the tone pot wired in parallel with the volume pot so that cut out treble is bled to ground. That’s why I was confused, I guess.
Now I would go this route: 3-way switch out –> Bass pot left lug, cap soldered acordingly, and from bass pot right lug to –> Treble pot left lug, from same left lug to –> Volume pot left lug and from volume pot right lug to –> Tip of output jack. All groundings remain as they were before.
Massive apologies to everyone. I goofed, the treble network MUST be before the bass as shown in the schematic at the top of this post. In my simulations I neglected to check what happened with the bass flat and the treble cut with the treble network AFTER the bass – it doesn’t work!
The image in the previous post is the response with a typical Strat pickup and an instrument cable with 470pf capacitance into a 1Meg amp input. Sorry its so blurred. The axes are 5dB per step vertical and 10Hz to 10kHz horizontal. The image with this post is bass cut.
And this, treble cut.
And this one is both cut.
Thanks so much Terry for all your effort. However, my main problem (new to electronics) was/is this: My tone pot is connected exactly as shown in the scheme I attached(quoted from guitarelectronics.com). It’s wire does not even directly touch the Volume pot’s lug but goes off from the PU selector out shortly before the volume put. So, volume and tone are in parallel, did I get this right?
But I think I see now. Disconnect PU switch’s out completely from volume and tone, new single wire from selector to connect with tone, from there to bass pot as shown above, and to volume.
Seems like the picture was not attached. The scheme is here:
https://cdn3.bigcommerce.com/s-fxdzp2uudp/products/2416/images/5091/wd2hh3t11_00__73696.1470694370.1280.1280.jpg?c=2
If your treble control is connected to the pickup selector switch then leave it there. Insert the bass control and its capacitor between the switch and volume. Although your final sentence seems to describe things correctly. Good luck!
Terry,
First of all, thanks to you for all your effort and to Joe for countless inspiration for all tonefiends in this world. Now, I would gladly pay you to draw a schematic that includes a three-way Les Paul switch, three volumes (one for each pickup, the middle being connected to the output of the three-way switch a la typical Gibson Les Paul three pickup guitars), but also includes Joe’s PTB before the volumes as you recommended in your earlier post. I think many would benefit from seeing this. If you have PayPal or another way to pay, let me know. I readily admit I am not knowledgeable enough to work this out myself. Help me, Obi-Wan Terry, you’re my only hope! 🙂
I’m not sure it is even possible to configure the arrangement you describe in such a way that all the controls work as expected. You have to consider that, as far as I know, the PTB circuit was conceived for a Strat style guitar (by G&L) with three pickups switched into a single volume, single treble and single bass control. All the controls come after the pickup selection.
Also as far as I know, the Gibson 3 humbucker guitars have volume and tone controls for the neck and for the bridge and the switch flips between the neck, middle plus bridge or bridge. The middle pickup is not selectable on its own and has no dedicated controls. And note that the neck and bridge pickups have their own treble tone controls, before the switching.
The problem with putting tone controls after volumes is that the effect of the tone controls then changes with different volume settings (as in the ‘magic vintage’ wiring of the tone control in Gibson Les Pauls). I may play around with a simulation and see if something can be done.
Thanks for the quick response. Let me put my dilemma another way. I’ve got five holes in my Les Paul, the four normal ones and then a fifth one positioned approximately where you’d find the Varitone on a ES-345. It’s a three pickup guitar. It has great pickups; a Harmonic Design pure P90 in the neck, a Lindy Fralin hum-cancelling P90 in the middle, and a DiMarzio DP154 DLX Plus humbucker in the bridge. It is currently unwired. I’m open to any tonefiend suggestion to make this a legitimately usable and toneful instrument.
OK well here are a couple of suggestions – Wired as normal for a 3 humbucker Gibson with the addition of a phase reversal switch for one of the pickups. The middle pickup is probably the poorest candidate for phase reversal. Or wired as normal and fit only the neck pickup with the bass cut control.
Truly, thank you for the time and expertise. I will read and re-read everything (remember: dunce cap here), it should all work out thanks to you and to Joe.
GW
I got a G&L S-500 Tribute this year and the bass rolloff is really an interesting and useful feature. I mostly play clean and using my Katana 100W 1×12 in the man cavelet and the Yamaha THR10C I keep in the living room, I can get sort of flubby distortion sounds on the low strings playing clean which the bass knob helps to clear right up. Not that I’m the arbiter of anything musical but it’s a really useful feature that should be on all guitars.
Years ago I did the ‘tight control’ from this site:
https://www.metalguitarist.org/forum/guitar-tech-electronics-and-diy/773-tight-control-simple-passive-bass-cut.html
I was instantly hooked on having a bass cut; so much more clarity and if you use a looping pedal it sounds so much better once you have a couple parts stacked up!
This may have been answered and I missed it but, would there be any drawbacks to putting a 500K Dual Concentric pot for each tone instead of having 1 tone dedicated for bass and the other dedicated for treble? I have a LP type control configuration but don’t require long pots. Am I missing something or would this give me total sculpt-a-bil-i-ty of the neck and bridge humbuckers separately?
Would a 500K DC pot be the best to use for this setup or get a TBX and wire it the ‘mod’ way?
Thanks man, I’m gonna have to try this. Does the pot being used for the bass cut add load on the pickups, like the tone and volume do? Or does it not, because it’s not grounded?
I take pleasure in, lead to I discovered exactly
what I was having a look for. You’ve ended my four day long hunt!
God Bless you man. Have a great day. Bye
Rather late to the party.
After implementing these low-cut pots (I have them on all my guitars now) I realized that I never used the low-cut and tone control at the same time.
The sound simply becomes too weedy.
So I figured that I could make a low-cut/tone control with a single knob, using a blend-potentiometer (see attached image).
In the centre-position low-cut and tone are both off.
On “10” the tone control is engaged (and low-cut still off).
On “0” the low-cut is engaged (and tone control is off).
You could wire it to work the other way around, but you can’t solder the middle lug to the pot’s housing anymore.
Ahh… I need to attach a JPG instead of a PNG.
So here’s the image.
Hi Bas — that sounds like a very cool idea! But the attached image never came through. If you still have the diagram, you can email it to me at joe@tonefiend.com, and I’ll add it manually. Sorry about that!
Between this two band PTB and your cap-fade tone control, which do you like better?
I’m wiring a guitar with a multi cap selector. After seeing these to mods, I am reconsidering. These seem like they would be easier to put together and maintain.
If I want to really drive myself crazy, I could add a multi cap option to one these mod 🙂 That would probably end up giving me lots of different way to make the same tones.
Thanks!
If there were no logistical concerns, I like the multi-cap option because there’s a stronger contrast between the resonant peaks of each cap. But either work as a distortion/“tightening” control.
Thanks! I ended up going with a bass and treble cut for each pickup, with three possible tone caps for each. It wasn’t that hard! I have it working in a prototype layout. I need to add a few more switches before it’s complete.
Terry Relph-Knight, on February 21, 2018 at 10:22 AM wrote:
> Well that’s interesting. I ran simulations of the PTB circuit
What did you use to simulate the circuit? I looked for a while so I can try out guitar wiring ideas before firing up the soldering iron, But I could find any that had the switches that I needed, like a DP4T or a DPDT 3 position on-on-on, or a way to make one. Thanks!
Joe – On the bass cut control, you have the center lug jumpered to the right lug and the cap across the left and right lug. Does it matter which lug the right side of the cap is soldered to? Can I put it on the center lug, or does it HAVE to go to the right lug?
I thought I had it working, but no matter what I do, no matter what cap I use, I only get a very sight effect, even with distortion. At first, I tried wiring the cap and the treble left lug just to the center bass lug and skip the right lug altogether. When that didn’t work, I use an alligator clip to jumper the center and right lugs, but I did not move the wires, with no change.
Also, I know none of the tabs should go to ground, but does it matter is the pot housing is grounded?
Thanks so much!
Re My question 12/12/21:
I figured some things out. 1) Grounding the pot housing does not negatively affect the operation of the bass cut control. It may decrease hum. 2) I had it mis-wired. Some where along the way, I confused lugs 1 and 3, looking at them from the front or back of the pot. Not the first time. I ended up labeling them to avoid this in the future. So I did get it working. I also found that at least one connection was bad, causing the control to do nothing. 3) I can’t tell the difference between wiring the right lug, then jumpering to the center lug vs. just wiring to the center lug. I guess it might be a matter degree. I’m proto-typing and so can’t really put it through it’s paces yet.
so Joe, please let me know if/why I should wire it as in your diagram. Note: The diagram on the right is like Joe’s except that the blue wire on Bn lug 2 is on lug 3 in his diagram. I don’t think that make a difference. The diagram on the left is my alternative. Are they functionally the same?
Thanks!
Image…
Sorry. Can’t seem to upload a JEPG. Here is the link.
Sorry again. Here a Google Drive link..
https://drive.google.com/file/d/1HOpmX4mmFGK11Zzg44pkGSkGYVg3Wyo-/view?usp=sharing.