Some random guitar wiring questions

Dave_Mc

Hi everyone,

I recently (finally!) learnt to solder (badly!), so I've been wiring up some guitars, and I've come across a few things that I'd be interested to know. I've looked them up online and not really found anything concrete about them.

1) I've been trying some treble bleed circuits, and I've come across the Falbo mod (https://www.mylespaul.com/threads/tapered-treble-bleed.82799/#post-1606360)- it basically wires the usual treble bleed circuit (either a capacitor alone, or a capacitor with a resistor in parallel or series) from the middle lug of the volume pot to the unused lug on the tone pot, and it seems to work well- it (supposedly) gradually disconnects the treble bleed as you turn the tone knob down (when the volume is turned down) making it sound more natural if you want to use the volume and tone knobs together. I was just wondering, are there any known downsides to this style of treble bleed?

2) Can you wire the Falbo mod to a push-pull switch to switch it in and out? I know you can do this with a standard treble bleed circuit, but I wasn't sure if you could with the Falbo mod since one of the contacts is to the tone pot. Maybe you can just disconnect the bit connected to the volume pot and the capacitor's not being connected at both ends will mean it's out of the circuit? 

3) When combining humbuckers and single coils (say in an HSS or HSH set), using a 470k resistor from the selector switch single coil hot wire to ground is often suggested to make the single coils "see" 250k pots instead of the standard 500k pots which tend to be fitted (and which sound great with humbuckers). However, it's often mentioned that this makes the in-between sounds darker-sounding, because the pickups "see" all of the resistors and pots in those settings. I held off trying this for a while because of this, however I finally got round to trying it (albeit with only one resistor on the middle single coil as the hot neodymium (!) neck single coil sounds better on 500k), and it sounded great, and the in-between positions still sounded fine. (I also tried it on an HSH guitar, again just the one resistor, and again the in-between settings sounded fine- in fact, probably better than before!).

This got me wondering. It finally hit me that, on a Strat, you have two tone knobs (at least on neck and middle positions) loading down the pickups, whereas on superstrats (at least mine) you usually only have a master tone, so you have fewer pots loading things down. Would this explain why the in-between settings still sounded fine to me? (Or it might just be that split humbuckers, which were combined with the single coil in that setting, sound too bright!)

4) Following on from 1), is the darker in-between setting even worse if you fitted a 470k resistor to the neck single coil, too? I.e. is this a bigger problem on HSS guitars than HSH?

5) One of my HSH guitars actually has no tone pot at all, just a master volume- should I wire a bigger resistor to ground for the middle single coil? 1M, for example? Or would that be too much?

6) Is there any (reasonably easy) way to wire a 470k resistor to ground which would only be active on the humbucker(s) when they're coil-split?

7) I've got a Patrick Eggle New York Pro with a bridge humbucker and neck single coil. It has a 2-way pickup selector that selects the bridge humbucker alone or neck single coil alone, a master volume and then a push-pull tone pot which, when pulled up, splits the bridge humbucker (when the 2-way switch is in the bridge position) and combines the neck single coil with the split bridge humbucker when the 2-way switch is in the other position. It was wired in a way that didn't entirely make sense to me, however when I swapped pickups I just replaced like with like and it worked. This is great, but I kind of wanted to wire a 470k resistor for the single coil, and also a ~5k resistor to do a partial split (as the humbucker is PAF-output and a bit weedy when split), and I was wondering how I would go about this. 

I'll try my best to explain the wiring- worst case scenario I can try to do a diagram of it, but hopefully (when you see my drawing skills!) I won't have to.

The pickup selector switch has 6 contacts laid out much like a push-pull switch- I think this is a DPDT? The bridge pickup hot wire goes to a contact at one corner, the neck pickup hot to the contact at the opposite corner, and a wire from the volume pot input is wired to the two middle contacts. This more or less makes sense to me, and is more or less normal, I think. 

(a) Can I just wire the 470k resistor from the neck pickup hot at the switch to ground to make it "see" a 250k pot?

(b) The partial split resistor is where I'm more worried. There's a wire going from the volume pot input to the top two contacts of the push-pull switch, and then the split wires of the humbucker are wired to one of the contacts in the middle position of the push-pull. There's no connection to ground from any of the push-pull contacts as there usually is, and this is usually (I think) where you wire the partial split resistor. Any ideas? (All the rest of the wiring seems pretty standard, at least to me.)

Phew, that was a lot, thanks a lot in advance for any help you can give me! 

Funkfingers

You don't ask for much, do you?

The Falbo Mod is a treble bypass NOT a treble bleed.

It is now possible to purchase stacked/ganged 250/500k volume pots. Single coils go via the A250 half. Humbuckers and P90s go via the 500.

The Eggle pickup selector switch is a double pole, triple throw on/on/on.

Dave_Mc

Yeah I realised after I wrote it how long it was! I tried to put a pic in of the Falbo mod, and not only did it not work, it posted the thread before I was ready, too! Then I had to quickly scramble to finish writing it before I looked silly... 

Thanks for the help. 

Yeah I know they're treble bypasses, I guess regular treble bleeds are too, but just everyone calls them that.

I've never really tried those dual concentric pots but I was under the impression they were a bit of a pain to turn independently? Certainly they have been on any pedals I've tried them on. Plus you're stymied if you want a push-pull as well...

Is it DPTT? I'm a bit hazy on the naming conventions of them, but it only has 2 positions to switch between, not 3. 

ICBM

There's a lot to answer there .

1. That's not a "Falbo Mod" (whoever he is), that's the standard way volume and tone controls were implemented on most vintage amps with a single tone control. It would be better described as the 'amp tone mod'. It works very well, I have it on one of my guitars.

2. Yes.

3. On HSS guitars you want the resistor engaged in any position where a single coil or split humbucker is used - this is because the lower-impedance pickup dominates a parallel mix (counterintuitively).

4. Only use one resistor. If you use two then both will be combined in the neck/middle position which will give a too-low overall resistance and it will start to sound muddy.

5. You would need a small resistor not larger, but probably not if you like the sound with no tone control anyway.

6. Yes, if the split is done with a separate switch rather than the pickup selector - use the second pole.

7a. Yes.

7b. I can't remember if these guitars split the pickup by bypassing one coil, or selecting where the hot connection is - if it's the latter, you'll need to rewire it to the former first. Personally, given that both pickups are fairly low-impedance and bright, I would just use a 250K volume pot and not worry about the rest.

Does that help?

steamabacus

Dave_Mc said:

I tried to put a pic in of the Falbo mod, and not only did it not work, it posted the thread before I was ready, too! Then I had to quickly scramble to finish writing it before I looked silly... 

[Deftly avoiding addressing the wiring questions...]

Reading the above, it sounds like you have pressed RETURN after pasting the image URL into the Attach Image drop-down. You actually need to press SPACE or alternatively CURSOR RIGHT. Just a weird quirk of the forum software that has caught me out many times.

[Now, back to the guitar wiring ....]

Funkfingers

ICBM said:

Falbo … (whoever he is)

Frank Falbo is a luthier, guitar technologist. Probably best known for creating the P-Rails pickup whilst he worked for Seymour Duncan Inc.

In 2019, Falbo was in dispute with Tosin Abasi over non-delivery, embezzlement and design plagiarism accusations. Some parts of that story have never been properly substantiated. I reserve judgement until I see concrete proof one way or t'other.

Dave_Mc

@ICBM Brilliant, thanks for that great reply. 

1) @Funkfingers described who Falbo is, I think his suggestion for that as a possible "better" treble bleed system predates his work at Duncan, though. But yeah, if it's well known in amps I guess it's unlikely he "invented" it, lol. 

I think in his post about it, he said it only worked if you had the volume connected to the tone from the volume input to the tone middle lug, and the tone cap from the first lug of the tone pot to ground. I have some guitars where the volume is connected from the volume input to the first lug of the tone pot and the tone cap is connected from the middle lug to ground (and the third lug of the tone pot is still free and unused). Will this style of treble bleed still work with the tone pot wired that way?

2) Excellent, thanks!

3) + 4) How would I do that? This is getting well beyond my levels of understanding, lol.

5) Oh ok, I guess I got that backwards. I like the tone of the humbuckers with no tone pot but the single is a bit bright with the 500k pot (that's usually the case even when there is a tone knob, too).

6) Excellent. Is that just one of the middle contacts in a push-pull? And wire the resistor from it to ground?

7 a) Brilliant.

b) Thanks. I'm not sure- it doesn't seem to split the humbucker in the usual way, by shunting one coil to ground (i.e. one of the contacts of the push-pull wired to ground). I'm not sure if that means it definitely does it the other way you mentioned, though. I don't have the stock pickups in there any more, I put Toneriders in- an alnico II classic in the bridge and alnico II blues in the neck. It's still fairly bright but a fair bit less so than it was (the stock Kent Armstrongs were incredibly bright and shrill, as you suggested). I'm not sure I'm that keen on 250k on a humbucker, if I can get the 470k resistor to work on the single coil, that may do enough.

I've thought of one more question... hopefully this is a fairly easy one. Is there any way to implement either the Falbo mod treble bleed or Gibson-style 50s wiring when you have a different number of volume and tone knobs? Say on a Strat, or on a 2-pickup guitar with individual volumes per pickup but a master tone?

Thanks again for all your help, John, I was hoping you'd see this and reply!

@steamabacus : That's exactly what I did! Thanks for the help, I'll try to remember that in future.

ICBM

Ha .

1. It will only work with two configurations - either with the middle terminal of the tone pot connected directly to the volume pot, or with the tone cap between the volume pot and the middle terminal of the tone pot, and the anticlockwise terminal of the tone pot grounded. (The second of these puts the caps in series, but the tone cap is much larger than the treble pass cap so it acts effectively as a straight connection.) It won't work if the anticlockwise terminal of the tone control is connected to the volume, or if the middle terminal is grounded.

Incidentally the *tone cap* is the "treble bleed", which is why it's always important to call out this mistake .

3/4. The easiest way to do this is to have a separate tone control for the humbucker, and the other for the single coils - then put the resistor in parallel with the single coil tone control. This doesn't allow auto-splitting in the bridge/middle position though. To do that, you need a superswitch.

5. That does sound like you need the resistor in the single-coil positions.

6. Yes - connect the middle terminal to the volume control hot and the resistor between the terminal closest to the pot body and ground. (Or the resistor between hot and middle terminal, and the other one to ground.)

7b. From memory, PE did wire the split switch the other way. This is bad practice really, as it causes more noise in the single coil mode. It's best to fix this first, then the partial split becomes easy.

You can't use the amp treble *pass*  mod on a guitar with two tone controls, no. You can do "50s" Gibson wiring on a Strat though (not sure why you'd want to, but whatever...) - you would need to rewire the switch so both halves aren't linked to the volume control input, and link the tone control side to the volume control output instead.

A 2-pickup guitar with two volumes and one tone inherently has "50s" wiring anyway, since the tone control has to come after the switch.

Dave_Mc

1) Thanks!

And yeah, that's true. There's a bunch of guitar terminology which is "wrong", lol, which makes things a lot more complicated than they need to be...

3/4) Grrr, all my HSS and HSH guitars only have one volume and one tone control (or no tone control!), lol. 

5) Yeah.

6) Thanks!

7b) I was just worried, since I didn't really understand the wiring, that it had to be like that to access all of the pickup selections. I didn't really understand how the neck pickup setting alone became neck + split bridge when the push-pull was pulled up!

Thanks for the info about the Strat.

Actually my 2-pickup guitar had the volumes wired "backwards" (pickup hot to middle lug), so even if that was technically 50s-style, the extra treble loss caused from wiring them backwards must have been over-riding the 50s-treble-retaining properties! I rewired it to "normal", but I also wired in treble bleeds at the same time....

Thanks again for all your help.

ICBM

Dave_Mc said:

3/4) Grrr, all my HSS and HSH guitars only have one volume and one tone control (or no tone control!), lol. 

Ah, in that case it's easy - just use the second side of the switch to add the resistor in positions 1 to 4, ie connected to both the neck and middle terminals on the unused side of the switch. You only need to re-arrange the tone controls if there are two.

Dave_Mc said:

7b) I was just worried, since I didn't really understand the wiring, that it had to be like that to access all of the pickup selections. I didn't really understand how the neck pickup setting alone became neck + split bridge when the push-pull was pulled up!

I can't remember exactly how it's wired, but the second side of the pull-switch turns on the bridge pickup independently of the pickup selector I think.

Dave_Mc said:

Actually my 2-pickup guitar had the volumes wired "backwards" (pickup hot to middle lug), so even if that was technically 50s-style, the extra treble loss caused from wiring them backwards must have been over-riding the 50s-treble-retaining properties!

Backwards isn't 50s, it's just wrong . (Unless it's a Jazz Bass or a Rickenbacker, and then it's necessary but still wrong!)

Dave_Mc said:

I rewired it to "normal", but I also wired in treble passes at the same time...

Dave_Mc

ICBM said:

Dave_Mc said:

3/4) Grrr, all my HSS and HSH guitars only have one volume and one tone control (or no tone control!), lol. 

(a) Ah, in that case it's easy - just use the second side of the switch to add the resistor in positions 1 to 4, ie connected to both the neck and middle terminals on the unused side of the switch. You only need to re-arrange the tone controls if there are two.

Dave_Mc said:

7b) I was just worried, since I didn't really understand the wiring, that it had to be like that to access all of the pickup selections. I didn't really understand how the neck pickup setting alone became neck + split bridge when the push-pull was pulled up!

(b) I can't remember exactly how it's wired, but the second side of the pull-switch turns on the bridge pickup independently of the pickup selector I think.

Dave_Mc said:

Actually my 2-pickup guitar had the volumes wired "backwards" (pickup hot to middle lug), so even if that was technically 50s-style, the extra treble loss caused from wiring them backwards must have been over-riding the 50s-treble-retaining properties!

(c) Backwards isn't 50s, it's just wrong . (Unless it's a Jazz Bass or a Rickenbacker, and then it's necessary but still wrong!)

Dave_Mc said:

I rewired it to "normal", but I also wired in treble passes at the same time...

(d)

(a) Even better! Just so I'm clear about this, does that mean I would wire one end of the resistor to ground, and then wire two wires to the other end of the resistor, one of them going to the neck and the other going to the middle terminals on the unused side of the pickup selector switch?

(Sorry for being so dopey, if you think I'm bad now you should see how bad I was when I was just starting to solder about 6 months ago!  )

(b) That may be it. Or the split half of the humbucker, at least (I assume).

(c) Sorry, I phrased that a bit poorly! I know backwards isn't 50s-style, what I should have said was "If having a master tone with two volumes is technically 50s-style anyway, that didn't seem to help much with the treble loss (when rolling down the volume) incurred by having the volumes wired backwards".  The backwards wiring (lose lots of treble when rolling back guitar volume) seemed to be trumping 50s style (retain treble when rolling back guitar volume). That's certainly what happened when I tried wiring in treble pass caps when it was still wired backwards- it didn't seem to make any difference at all! However, I was using a fairly low value of 180pF, maybe a bigger value would have helped a little more.

I can't stand backwards wiring either (apart from, as you said, in the couple of places where it's strictly necessary). You lose all your treble when you roll back (standard wiring is bad enough for that, backwards is far worse!), treble bleeds passes don't even seem to help much, and all for what? So you can roll the volume back on the middle position to get one pickup alone? It doesn't seem worth it to me. (I've heard some people say it lets you balance pickups better in the middle position using the volume controls, but I didn't notice much difference, plus the flaw in that is that you lose so much treble that even if they are better balanced, they sound rubbish!)

(d) 

ICBM

a) - Yes, although one wire going to both terminals is easier . If the resistor is long enough it should reach by itself.

c) - Yes, agreed. I can’t see the point at all either, if there’s also a switch. I should actually get around to rewiring my Rickenbackers...

Dave_Mc

a) Oh so you can just wire it to connect to both terminals with the one wire (or even just the resistor itself)? Even better!

That leads me on to another question I was going to ask- you can wire the ground end of the resistor to any ground, can't you? Because of the length of the resistor (like you mentioned), I had just been wiring it to the ground of the selector switch, since that seemed more convenient, rather than to the back of a pot. (The selector switch was grounded through that same point to the pots ok.)

(c) Yeah. I'm wondering if that's why selector switches exist in the first place? Presumably on a Jazz bass (or any passive bass with two pickups, but I guess the Jazz was the first), losing the treble isn't such a big deal, but on a guitar it's pretty annoying.

ICBM

Yes, you can use any ground point provided it is definitely grounded. I prefer soldered connections rather than relying on contact to shielding foil, but that usually does work fine too.

Dave_Mc

Briliant, thanks! Yeah they're definitely grounded and soldered- I only tried it so far on guitars without a scratchplate.

Thanks again for all your help   EDIT: Wisdoms awarded all-round, I forgot to do that until now