Practical Wiring

[alder]

Here is a long treatise on electronics and wiring

Link Removed

... then I had a soldering-fest. I used stock Squier pickups, but with a twist: they are wired in series, rather than the usual parallel. This is how Danelectros are typically wired. Series wiring has some distinct advantages. When two pickups are wired in parallel, each acts as a ( albeit high impedence ) short to ground ( or 'load' ) for the other's output. * The result is not double the output, but actually somewhat less than either pickup alone. The problem gets worse with each pickup you add, which is why Strats do not normally have an 'all three' option. Fortunately, our ears are not linear devices, and smooth out the loss in volume somewhat.

( * This is an oversimplification, but good enough. )

When two pickups are wired in series, the output of one is connected to the ground of the other. The outputs are directly additive, there is no loading effect as with parallel wiring. You get noticeably more output, and usually a much fuller sound. It is possible to 'daisy chain' as many pickups as you want like this, but for practical purposes, three single coils is the limit, more than that becomes boomy and harsh. This is why humbuckers generally do not sound good in series - the two coils in each pickup are already in series, putting the pickups in series puts all four coils in series, it's just overload. On the other hand, humbuckers often sound better in parallel than single-coils, it lightens them up a bit, whereas single coils in parallel can become overly thin - the 'quack' sound that the Strat is so famous for. I'd rather roar than quack, especially on a bass.

The main reason Fender went for parallel wiring is that it makes pickup switching much simpler, and in the beginning ole' Leo barely knew what he was doing, so anything he could get to work with the parts he could get his hands on was going to be good enough. The Strat originally had a three-way switch with no combinations, it wasn't until much later that improvement was added in the factory. Pickup switching with series wiring is much more complicated. Take a look at a Danelectro wiring diagram and try to figure out what is going on with the switch. It is so simple, and yet totally unintuitive. Nathan Daniel was a real electrical engineer, and these things were second nature to him, as was good shielding and grounding, things that are lacking in most guitars to this day.

Pickup switching with series wiring is not so much a matter of selecting the pickup(s) you want, but de-selecting the ones you don't want. You can't do this with an ordinary Strat switch ( another reason why Fender went parallel ) but you can do it with a modern 'super switch'. A super switch is really 4 independent 5-way switches ( or poles ) that move as one, like two ordinary blade switches ganged together. For series switching, you use one pole per pickup, so in this case one pole is unused. For each position on the switch, you remove some pickup(s) from the chain by shorting its output to its own ground, turning it into an inert loop. This preserves the path to ground for the entire chain, while effectively silencing that particular pickup. So for position 1, you would short out the middle and bridge pickups, and only the neck would sound. Etc. Note that you short each pickup to its own ground, not to the main ground.

A caveat about the super switch is that it is physically bigger, wider and deeper than a standard switch, and will only fit into a full-thickness body. You can see the size of it in the photo. Many of the Squier bodies you will find, such as the Bullet line, are too thin to take the switch I used. Even with this full-thickness body, I had to Dremel a shallow pit for the switch to sit in, but that is mainly so that it is not shorted-out by the conductive shielding. I used a double thickness of electrical tape in the bottom just to be sure.

I also installed a push-pull switch to one of the tone knobs which defeats the 'de-selector' for the bridge pickup. ( Confused yet? ) This allows for the forbidden combinations that the 5-way switch won't give you: neck and bridge, and all three. In a parallel world, you would use the switch to do the opposite to get the same effect: it would enable the bridge pickup independently of the blade switch. Everything is topsy-turvy in series land, but its a cool place if you can get you head around it, too bad Leo never did. And then there's Gibsin. Don't get me started ... can't even wire up a volume control right.

So anyway, the end result is that the combination positions, 2&4 and 1&p will actually be bigger than the single positions, and the super-combo 2&p will be even more ( where p stands for the push-pull switch. ) On a bass, that should be pretty cool. Positions 2 & 4 are fully humbucking, with position 2 & p is semi-humbucking, the two end coils overwhelm the middle one, but there is still some reduction in noise. The same is true in parallel wiring.

The middle tone control is also a standard treble roll-off. Now what to do with the other one? How about a bass roll-off? Easy enough, just need a 500k pot and a 0.0022nf capacitor. This is some more topsy-turvy. While a normal tone control works by selectively bleeding off high frequencies to ground through a fairly large capacitor, a bass roll-off is almost the opposite. A bass roll-off works by selectively forcing the output through a very small capacitor, which blocks the low frequencies but passes the high ones. In both cases, the pot is used to control the amount of filtering, whether low or high.

On the piccolo bass, I combined both functions onto a balance pot, which is kind of like two pots that move together in opposite directions. ( Actually, they move in the same direction, but one of them is backwards. There's more to it than that though. ) In that case, you can only access one filter at a time, either high or low. With two separate controls here, you can enable both at once. It will be interesting to find out what that sounds like, maybe sort of compressed, or maybe just strangled, I don't know. Note that even though these guitars have bass and treble controls, they are cut-only. A passive control can only reduce what is already there, it cannot add anything, for that you need a powered circuit and a battery.

So that's some pretty cool wiring on just 3 shafts and a blade switch, which outwardly preserves the Strat aesthetics, while going way beyond the Strat electronics. And all without a battery. If I had another push-pull switch, I might add a simple passive distortion circuit, but I'm all out of them, and enough is enough. You could conceivably put a push-pull on the volume too, but I can't think what I would do with it.

In the picture, you can see the wet shielding paint drying. This is great stuff, expensive, but so much easier than messing around with tape and foil. Just paint it on and connect a ground wire. Takes at least three coats to get a good shield. I painted the entire cavity with one coat, then several more on just the control cavity. The final shield to ground resistance in the control cavity is now well under 200 ohms, probably less with the pickguard installed, as the paint and foil shield also make contact in several spots. I even put a coat of shielding inside the jack cavity, where it is grounded by the cover, although I think that is really just a waste of paint.

A drawback of series wiring is that if two pickups are not a hum-cancelling pair, putting them in series makes them hum even louder, as everything is additive. Two non-cancelling pickups in parallel hum much more quietly, simply because they have much lower output together. This really only applies to the neck-bridge combo on a Strat. Perhaps Leo Fender was deliberately avoiding things he knew would be problems. Danelectro licked the noise problem in a novel, inexpensive, and highly effective way - they completely housed their pickups in shielding - surplus brass ladies' lipstick tubes. These are the only truly quiet true single coils, even now, sixty years later. No need for hum-cancelling pairs, as there simply is no hum. They also enclosed all the electronics in copper foil, and used coaxial wire for the pickup leads, leaving nothing unshielded. Danelectro is my favorite type of guitar, simply for the genius of their unorthodox, inexpensive, yet highly effective designs. I love the tone of old-growth masonite. If I ever decide to upgrade this bass, I will drop three lipsticks into it, then ahhh - quiet.

I find it is a waste to try to shield Fender-style single-coils, it just doesn't work. Once I even painted the inside of a jazz pickup cover and grounded it, it did no good, they're hopeless. But it is still worth it to shield the control cavity, especially the switch, which has all its guts just hanging out in the open. I dispensed with the shielding entirely on some of the other models, but not on this one. I know that elsewhere I've expressed my disdain for humbuckers, but there is no denying that they are much quieter than the single coils I'm using here, so I'm doing anything that might help. To tell the truth, I have never seen more than minimal benefits from even the most thorough shielding, and with three pickups hanging out in the open like old-fashioned AM radio antennas, shielding anything else is kind of pointless, as is obsessing over ground loops and other minutia. It is all drowned out by the chorus of single-coil hum.

One reason Fender uses 250k pots instead of 500k is that the inherent treble-bleed across the lower-valued pots dulls the hum a bit. Rickenbacker compromises with 330k pots, while Gibson uses 500k because with muddy humbuckers they need to hang on to all the treble they can. Danelectro used 1000k ( 1 Meg ) pots, because they have no noise issues to worry about. That is why Danelectros are so jangly, more so than even Rics. Yet, by combining pickups in series, they can also achieve a full, almost humbucker tone. Simply ingenious. Of course, all of this is less important with a bass. But with the two-octave six-string Bass VI capable of going well into the guitar register, it is something to consider here, as it is also on the Piccolo, which is essentially a guitar. One way to de-hum a bass is to wire something like a 100k resistor from output to ground, generally on the lugs of the volume control. This will cost you some treble and a bit of volume, but so what, it's a bass. I've used tiny potentiometers for this purpose, so you can adjust for the best compromise between noise reduction and treble response.

Since this post has bloated into something like a full treatise on guitar electronics, there is some more to say about pots. You may have noticed that they come in two varieties, 'audio' or 'A', and 'linear' or 'B'. A linear pot is just that, the response or resistance of the pot is linearly proportional to the angular displacement of the shaft. In contrast, an audio pot has a variable or curved response that approximates the non-linear response of our own ear to changes in volume - it is more sensitive to lower volumes. Therefore, you should always use an audio pot for a volume control, a linear pot will behave in a way that seems very strange. Our ear has no particular response curve to changes in tone, so for a tone control you can use either one. They will behave somewhat differently, but overall either one will work. You can try both and see which one you prefer, or you can be a dunderhead like me and buy a bag of 'A's and just use them for everything. Balance controls are typically double-A's, opposing on the same shaft.

Pots also come in full size and mini size. That makes little difference, the size of a pot is not indicative of its quality. The commonest shaft style for guitars is 'split coarse-knurled'. Most knobs are made to fit this, and you can also use set-screw type knobs on it. There is also 'split fine-knurled' - if you get these, you'll need to make sure you get matching knobs, the two are not compatible without some hammering, which is inadvisable. Finally, there are vintage-style solid-shaft un-knurled knobs, which are typically only found on high-end Fenders, black-and-white television sets, and other throwbacks. These require set-screw knobs, although I did manage to split the shaft and add crude knurling with a Dremel on a weird switch that was only available that way. Best advice: stick to 'split coarse-knurled' for everything.

One of my favorite kinds of pot combines a mini rotary pot with a double-pole push-pull switch. You can substitute one of these for any ordinary pot, and add a switch to your circuit with no extra hole. The up or down position of the knob serves as an indicator for the switch. There are many things you can do with this: series/parallel switching for two pickups, auxiliary pickup selector as above, internal series/parallel switching for a single humbucker or 'coil tap' for a pair of humbuckers, phase inversion for a single pickup, simple passive distortion using diodes a la 'Black Ice', select between different tone capacitors, and one of my favorites, dead-battery bypass / manual shutdown for active electronics. Now there's a whole other subject.

You can also replace a pot with a rotary switch, with no outward change to the guitar. Rotary switches come in all sorts of flavors, some of them equal or greater in switching power to the 'super switch' above. I have described several uses in previous posts, as well as everything in the preceding paragraph. There are as many more uses as your imagination.

In the photo, you can also see some practical improvements I've made to the body wiring. I enlarged the hole between the control cavity and the jack cavity, and then ran the bridge and shielding ground wires directly to the jack. That leaves just the hot and ground from the pickguard to the jack, which are twisted together neatly and long enough to lay the pickguard aside to work on it without disconnecting it. If you do need to disconnect it, you only need to break 2 solder joints at the volume pot, the body grounds never need to be disturbed. You could even go a step further and install a disconnect, but I have found that if you simply leave the leads long enough, it is not needed.

You can see the pickup wires are twisted together as well. Twisting pairs of wires together like this can help with noise rejection if it is done just right. That's why network wiring is 'twisted pair'. But twisting the wires together like this with my fingers probably does nothing, although I don't think it does any harm. It just makes for a neater installation. The amount of noise that several inches of pickup lead is going to pick up is inconsequential compared to the amount of noise the pickup itself will pick up.

A guitar pickup is actually a highly efficient radio antenna, even though it is used as a magnetic sensor, technically a tiny electrical generator. The radio frequency (RF) noise piggybacks on top of the desired signal generated by the strings moving in the field of the magnets. It is actually easy to block RF noise without impeding the magnetic sensing function, yet almost no one does it. Some humbuckers have partial metal covers that they don't really need, as a humbucker deals with RF noise through something called 'common mode rejection' - the two coils sense the RF noise in opposite phase, so it cancels when they are combined, while the desired signal is unaffected. This phenomenon was well known and understood long before Gibsin tried to patent it.

The Telecaster neck pickup is partially shielded, which is therefore only partially effective. As I mentioned earlier, this record you are now playing is another example of The Completion Backward Principle ... oops, sorry ... lipstick pickups are fully shielded and quiet, but most pickups have little or no protection. Just goes to show, the entire guitar industry is mired in nostalgia and stupidity. And judging by how slavishly I try to preserve the Stratocaster oeuvre, maybe so am I.

So, that's a lot of blah blah blah, but I think most people have no idea about series wiring, or wiring in general, so perhaps someone will find my explanations useful. I would finally like to note that I didn't invent any of this. "If I have seen a little further, it is by standing on the shoulders of Giants." - Sir Isaac Newton

 

[walterw]

Here is a long treatise on electronics and wiring.

and it's full of good stuff, except that you do want linear volumes for bass, and you always want audio tones.

(audio volumes are for compressed and overdriven guitars, on a clean bass sound you get that annoying dropoff between 10 and 8.)

you want audio tones either way, linear tones act like on-off switches at 0.

also, what's "wrong" with gibson volume controls?

 

[alder]

also, what's "wrong" with gibson volume controls?

'Gibson Disease'

If you have two pickups and two volume controls, then each volume should control one pickup, as done correctly on a jazz bass or a Ric. But with classic Gibsin wiring, the volume controls are crossed into each other in such a way that either one turns down everything. They only separate by the pickup switch. Yes, you can make an argument for that, but at the end of the day it is just wrong, defeats the purpose of having separate volume controls for the pickups.

I remember the first time I ran across this, and thought 'What idiot wired this up wrong?' I reversed a few wires on the pots and then everything worked right. That was on an old Westbury, a surprisingly high quality import from Matsumoko that I wish I still had. It was only much later that I discovered it is done deliberately, and that there is even a name for it: 'Gibson Disease'.

Actually, if you want separate volume controls, then use a master volume and a balance control, it's not hard or expensive, and it is much more flexible. And no one does it.

Likewise, their separate tone controls are a fraud, as either one turns down everything, and there is no way to wire it so that doesn't happen, so you might as well just have one tone control. That's not just Gibsin. On a Strat, you have two tone controls selectable by a switch, which is kind of silly, but at least it does something. And both tone controls cleverly use the same capacitor, for a savings of like, once cent, because Leo was that cheap.

Gibsin's wiring mistakes are so enshrined and copied in the industry that most people don't even realize they are flaws. Like using two different scale lengths on the same neck, another Gibsin invention, because apparently they are not good with math and rulers. So what if it goes out of tune above the octave? It's a Les Paul !!!

A lot of Gibsin's woodwork is pretty awful too, which is why their headstocks break off with alarming regularity. They are designed as though they know absolutely nothing about wood. Much of their finish work is second-rate, and their selection of 'tone woods' is based mostly on whatever they can get cheap and then charge top dollar for. Mahogany is for boat decks and furniture, not guitar necks, it is too brittle. I won't even go into their design aesthetics, and ergonomics is a mystery to them. They should just drop out of the bass business entirely.

But most unforgivable is that they will never admit a mistake or correct it, they just keep chugging along like everything they do is perfect, and the necks keep breaking and the electronics are still wrong, and the intonation is still off. Crap guitars, at ridiculous prices, I wouldn't own one. If you want a nice Les Paul, buy an Epiphone or a clone.

If an engineer does something wrong, other engineers will fix it. If a luthier does something wrong, other luthiers will copy it. What a ridiculous business.

 

[alder]

and it's full of good stuff, except that you do want linear volumes for bass, and you always want audio tones.

(audio volumes are for compressed and overdriven guitars, on a clean bass sound you get that annoying dropoff between 10 and 8.)

you want audio tones either way, linear tones act like on-off switches at 0.

I never considered that audio volume controls could be a hold-over from guitars, and that linear might work better on a bass. You may very well be right, but that means every bass ever made is wrong, which is entirely possible in this business.

Actually, I don't think there is that much difference between a guitar and bass. First of all, a bass merges with a guitar at the octave, and shares a good deal of overlap with it at the high end. And second, every note is not just a single frequency, but a base tone, plus all of its even higher harmonics, in decreasing amounts. This is what makes different instruments sound different, as each accentuates or diminishes different harmonics. This is also what makes different pickup locations sound different, as different harmonics are more or less prevalent at different locations along the string. So the higher frequencies play a very important role even on the lowest notes of a bass, and you really can't ignore them. A bass has much more in common with a guitar than you think.

That said, you could still be right. Perhaps what you are really pointing out is that there is no right. Now I am going to have to try a linear control just to see. But finally, the whole point is really moot, who ever turns down their own volume anyway, when the drummer and guitarist are already too loud? I sometimes wonder why basses and guitars even have volume knobs. And likewise, whose favorite tone is the mush you get from a standard tone control? An instrument with no knobs and a foot pedal for the volume would be a lot more functional. Well, knobs are fun to play with, even if they don't get used for real very much.

At Shea Stadium, the screaming was so loud that the Beatles couldn't even hear themselves, let alone anyone else. Shouldn't that be the goal of all aspiring rock stars? That makes all these discussions of 'tone' kind of silly, don't you think? Nowadays, most 'rock stars' would be much better if you couldn't actually hear them.

"Wagner's music is better than it sounds" -- Mark Twain, re-quoting humorist Edgar Wilson "Bill" Nye

 

[walterw]

wow, a lot to unpack here:

1. gibson volumes do not control "everything", check that again. they absolutely adjust just the one pickup, all the way down until just before "0", at which point they do indeed kill the whole signal. anywhere above that they're shading between the two pickups just fine.

you could "fix" that by wiring them "backwards" so that one volume can be shut off with the switch in the middle and leave the other pickup on, but you pay a big price in the tone and sweep of the pot, which is why gibson doesn't do that.

2. sure, the tones affect everything when both pickups are on, but the idea there is to allow for switching between pickups with the tones preset, like between a bright bridge and a dark neck à la '60s clapton. going to one tone forces the tone to be "after" the volumes, where it behaves differently when you turn it down. (guitar geeks call it "50s wiring".)

+1 on a master volume/blend for bass, i prefer that myself as well. hell, i modded my gibson guitars for one volume/2 tones, almost more like a strat.


3. yeah, i've heard about gibson's scale calculation weirdness too.


4. mahogany is a terrific wood for guitar necks, that's just silly. it's not as durable as maple sure, but it's more stable and sounds great. (not a big fan of it for bass necks though).

mahogany gibson headstocks are indeed annoyingly fragile, but i've found a pretty good workaround: don't drop it


5. plenty of modern basses do use linear volumes. that vintage ones didn't probably was a holdover from guitars, and maybe due to the fact that lower impedance pots like fender's normal 250k audio have a smoother sweep than say 500k audios, making them "close enough".

the difference is not really about "bass" vs "guitar", it's about the amp; compressed and crunchy amp tones respond best to audio volumes, while totally clean tones respond most evenly with linear volumes.

old-school clean jazz guitar players are gonna want linear volumes to adjust the loudness into their ss polytone amps, while bass players who run fuzz pedals all the time into their old 50 watt bassman tube heads will probably want audio volumes.

6. instruments have these controls because people do use them and because the pickups are usually voiced to sound right with the controls in mind; removing them entirely can mean an overly brittle, harsh tone. plenty of real bass players work the tone knob to get varying shades of "old school", while any guitar player worth a damn is working the volume knob all the time to shade from clean to crunchy and create energy and dynamics.

 

[alder]

wow, a lot to unpack here:

2. sure, the tones affect everything when both pickups are on, but the idea there is to allow for switching between pickups with the tones preset, like between a bright bridge and a dark neck à la '60s clapton. going to one tone forces the tone to be "after" the volumes, where it behaves differently when you turn it down. (guitar geeks call it "50s wiring".)

Yup, that's the argument in favor of two tones, and even two volumes, and it makes sense if you play that way. Fender went even further with the Jazzmaster, and built two completely different wiring schemes into one guitar. Hardly anyone uses any of this. I would much rather have a single set of sensible controls than a bunch of redundant ones that I seldom if ever use.

You're right about the action of a 'diseased' guitar, I didn't remember it quite right because I haven't had one in a very long time, I fix them straight away. But from Harmony to Rickenbacker, no one else builds a guitar that way unless they are deliberately copying Gibson. And not all Gibsons have the disease. On another note, I am amazed how many old guitars and amps left the factory wired up wrong, and stayed that way. What are you supposed to do when you find one of those, leave it because it's a classic, or fix it?

The whole reason logarithmic audio taper pots were invented was for use as audio volume controls to match the characteristics of human sound perception, which is logarithmic. An audio and linear pot are both the same at 0 and 100%, where they spend most of their lives anyway, and in between they are not that much different, so you can use either one for a volume control, or a tone control, and get away with it, and come up with arguments to support whatever you are doing. The fact remains, audio pots were invented for audio volume control, frequency perception is not the same as volume perception, and it's a free world, do what you want. But just because some guy sixty years ago put one or the other in a guitar because that's all he had doesn't make it right forever more. Oh wait, it does if he was a luthier. Idiocy.

Don't drop it is good advice that should be printed on every guitar. But there are plenty of stories of people taking out Gibbies that were lovingly stored in their case in the closet for ten years, and finding that they spontaneously self-destructed just from the string tension. Don't tell me that you shouldn't store it under tension, that's nonsense, if the string tension alone can break it, then it is NOT STRONG ENOUGH. This stupidity carries over even into Epiphone, which I am glad for, as I have a nice Fenderbird that started out as a Thunderbird without a headstock. But why does a design that was defective sixty years ago have to still be reproduced today? Why can't they use a volute or a scarf joint, or at least change the angle to something sensible. I'm trying hard to think of something that Fender did egregiously wrong and never fixed, but I just can't. But for a company that is truly frozen in time, forget Gibson - Rickenbacker.

I think it is great to have informed discourse like this.

 

[walterw]

You're right about the action of a 'diseased' guitar, I didn't remember it quite right because I haven't had one in a very long time, I fix them straight away.

and how do you "fix" gibson wiring? (like i said, i change my own to single volume/two tones.)

An audio and linear pot are both the same at 0 and 100%, where they spend most of their lives anyway, and in between they are not that much different, so you can use either one for a volume control, or a tone control...

sorry man, this is wrong on its face; the differences are obvious, and the right pot works way better than the wrong pot in its particular circuit.

there are plenty of stories of people taking out Gibbies that were lovingly stored in their case in the closet for ten years, and finding that they spontaneously self-destructed just from the string tension.

i literally don't believe those stories, they don't break unless they get broken. (which isn't to say that a good hard drop while in its case isn't enough to break one.)

But for a company that is truly frozen in time, forget Gibson - Rickenbacker.

ha! got that right.

 

[alder]

I pulled the active electronics out of a guitar I built where I found they really didn't do much, and rebuilt it with passive controls. While I was at it, I did a little experimenting with the treble control, the usually-only tone control on a guitar. I found that "A" or "B" pots really didn't make much difference to me. However, 250k or 500k made a huge difference. The 500k pots behaved like an on/off switch - nothing until you get almost all the way down, then everything. The 250k pots have a much more graduated response. Then I built a series balance control, which turned out to be as unintuitive as it could be and took a while to get right. The A500k volume pot sounds fine to me. I also used a B500k pot for a bass control, I don't think a 250 would work very well. I didn't experiment with either because I got sick of soldering - some other day. The active electronics will go in some future bass, where they are a lot more useful.

"Diseased" volume controls are wired kind of mirror image to what you'd expect, the ins and outs are reversed, with the ground in the normal place. The volume controls still work, but it couples them together. Some people like it that way, I don't, and I know how to solder. I just pull it apart and put it back together like a Fender. It's just as easy to do the opposite, I wonder what a "diseased" Ric would sound like. Probably just the same, but the controls would work funny.

Gibson's way puts the output as far from ground as it can be, as opposed to the input, like a Fender, or what I'd call normal. It's been said that there is some subtle difference in high-end response, which might also depend on the type of pot. I can't say I've ever listened that close. In fact, it may very well be imaginary, like so much else in the business.

My guess is Gibson always wired up single volume controls like that, where it's not an issue. When they came out with double controls, they just kept on wiring them the same way, and it became canon. Fender certainly saw fit to do it differently on the Jazz, and Ric on their entire line, and just about every other manufacturer. Except for some Gibson clones, you really don't find it elsewhere. You don't even find it on all Gibsons.

Sorry, but as an engineer, when I look at just about any Gibson guitar, I see an example of how to do just about everything wrong. I'm sure that statement will bring Gibson's flying monkeys down on me. I knew a guy who's new SG split right up the middle of the body. Gibson wouldn't make good on it, said he abused it, which he did not. It was clearly unseasoned wood that warped and pulled the body seam open. Ever see a Fender do that? I'll never shell out for a piece of Gibson junk. Many of the clones on the market are better than the originals, and a lot cheaper.

 

[walterw]

Gibson's way puts the output as far from ground as it can be, as opposed to the input, like a Fender, or what I'd call normal.

uh, no.

aside from the jazz bass, fender and gibson have always wired the volume pots the same way (which is to say the right way) with the input as the far lug and the output as the center lug.

the jazz is "backwards" (with the pickups going to the center lugs) because it has to be to get individual pickup selection with no switch, and you pay a price in the tone and sweep to get there.

that's another reason among many that i greatly prefer master vol/blend pot/tone for jazz basses, to get all the options without the drawbacks; the volume and tone can both get wired the right way for better control and better sound throughout the sweep.

 

[alder]

uh, no.

aside from the jazz bass, fender and gibson have always wired the volume pots the same way (which is to say the right way) with the input as the far lug and the output as the center lug.

the jazz is "backwards" (with the pickups going to the center lugs) because it has to be to get individual pickup selection with no switch, and you pay a price in the tone and sweep to get there.

that's another reason among many that i greatly prefer master vol/blend pot/tone for jazz basses, to get all the options without the drawbacks; the volume and tone can both get wired the right way for better control and better sound throughout the sweep.

I agree with you about the balance control, but I like to put a push/pull on the tone knob, and add a series/parallel switch. There's no way you can wire that with a balance control, you'd need a switch/pot that doesn't exist. I think a triple-pole will do it, or maybe it takes a quad, I don't remember. Ever heard a Jazz in series mode? Very un-wimpy. On the other hand, I once did the same to a Precision, so you could get the coils in parallel. Sucked. I like to put coil options on Musicman pickups as well. You'd be surprised all the different tones you can get out of one pickup. 4-wire humbuckers are fun to play with. I built a Strat bass with three of them that has 15 different pickup modes. Who needs a tone control with that? I put series/parallel options in all my 2-pickup basses with JJ or PJ pickups. I think the variations you get that way are much better than simply crushing out the treble with a 'tone' knob, which really ought to be called a 'kill tone' knob.

 

[alder]

One of the fun things about building electric guitars is wiring them up. Factory wiring tends to be simple, minimizing the amount of fussy hand work required. Many manufacturers keep strictly to 'classic' designs, seldom if ever changing anything. These designs are generally simplistic, often crude or even stupid, and sometimes outright flawed. There is no need for you to do this. I don't. Here are some of the things I have done over the years. I don't claim to have invented any of this, although some of these schematics I have never seen anywhere else, and had to derive them myself.

These are my pencil drawings from over the years. Many of them are not just circuit diagrams, but actual physical representations of the wiring that you can much more easily work from. Most are drawn from actual working hardware. Many of them may look quite simple, but are actually totally unintuitive and not at all easy to derive ( or I am a bonehead. ) Starting out with the basics:

These are your standard volume and tone controls, and one more tone control that is not so standard, but very useful. The volume control also shows an optional 'treble bleed' circuit that preserves high frequencies at low volumes. You can get into a big argument over what type of pot - linear or audio taper - to use for what application, so the diagrams don't list any. I find that the resistance of the pot has a much greater effect than the actual taper.

For volume pots, 250k is generally used with single coils, like Fender, while 500k are generally used with humbuckers, like Gibson. A 250k volume control has an inherent treble bleed that somewhat mitigates single-coil noise. The same treble bleed on humbuckers would make them muddy. Talking about basses, a small loss of treble is likely to go unnoticed. Rickenbacker splits the difference with 330k pots on their hot single-coils, while Danelectro uses 100k volume pots with 1 Meg tone pots. Many of these conventions were established decades ago for reasons that no long matter and perhaps never did, so don't feel you need to adhere to anything.

For the treble control, a 250k pot gives a much smoother and more graduated response than a 500k pot, which can act almost like an on/off switch. The bass control requires a 500k or greater pot. I have a large stock of audio pots and tend to use them for everything, and the results suit me fine. All I can say is experiment for yourself, and see if it even matters to you.

For a low-impedance version of the treble control, use a 50k pot with a 0.5uf capacitor. Yes, I said 0.5uf, also commonly known as an amplifier 'death cap'. Anything up to 1.0uf would probably work, as would a 100k pot, but 50k/0.5 seems to be the sweet spot. This can be used as a passive tone control downstream of a preamp, as in a piezo setup.

Here is that volume treble bleed again, along with an alternative. I should also mention that wiring a 150k resistor across the output-ground lugs of a volume control can be used as a hum reducer, at a cost of some treble and volume. Using a variable resistor, such as a tiny potentiometer, will allow you to tune such a circuit to your preferences.

Here are some uses for a balance pot with a center detente. In all of these cases, a 500k pot is assumed, although it is only strictly required for the last one. The first diagram is a typical balance control for two pickups in parallel.

The second diagram is also a balance control for two pickups, but this time in series. This gives a completely different response from parallel wiring, louder and fuller, but also has an odd characteristic where the output drops slightly midway to either side, then picks up again as that pickup maximizes, sort of a 'W' shaped curve.

The last diagram shows the previous two tone controls combined onto one knob. Turn it back for a normal treble control, or forward for a bass control. You can't get both at once, just one or the other, but that is less of an issue than you'd think, as using both controls at once can easily strangle everything. This control can be used to replace a stock treble control with no outward changes to the guitar, adding the bass control.

This is another version of the series balance control. You'll notice that the two are wired completely differently, yet both work the same. This one is more intuitive, it functions basically the same as a Danelectro pickup switch, shorting either pickup's output to its own ground. I think I like this one better.

Here is a 4-way blade switch used as a series/parallel selector for two pickups, as is often done on a Telecaster. The difference is that mine places both combinations in the middle, with the singles at the ends. I find this much more natural for a bass.

Here is a 5-way 'super switch' wired for 3 pickups in series. This is something you never see, which is a shame, it sounds awesome. Gone is the thin quack of the combination positions, replaced by a much bigger tone that actually exceeds the single selections. Also shown is a push-pull pot wired to make the bridge pickup 'always-on', allowing for the two forbidden combinations.

If anyone knows of a way to achieve this using a regular blade switch, I would love to see it. I don't believe there is such a way, and this has the advantage of not needing any other switches but the one blade, with the push-pull shown being entirely optional, but a nice addition.

This is a selectable on-board passive distortion circuit using clipping diodes wired to ground. All solid-state 'artificial' distortion circuits, no matter how expensive, have something like this at their core. Instead of requiring power, this circuit uses the output of the pickups themselves, and therefore should work better with higher output pickups. It uses a 2-pole 4-position rotary switch to select various combinations of diodes for different degrees of distortion, or none. You could also select one of the diode combinations and wire it to a push-pull switch for a single level of distortion, or even wire it to a separate 'volume' control to control the resistance to ground and therefore the amount of distortion. The diodes cost pennies. I have yet to actually try this one, but when I get back to building six-strings, I definitely want to.

Each 'pole' of a switch is actually a separate switch. A 3-pole switch is actually 3 separate switches on one shaft that move together. The diagram shows a 3-pole 4-position rotary switch instead of a 2-pole 4-position, which is instructive: you can always use a bigger switch and just 'waste' the extra capacity. Why would you want to do this? Switches can be used for may different applications, and there is often little difference in price between different models. Stocking the 3-pole switch gives me more flexibility in what I can do later, even if, as in this case, I waste part of it.


Here are two complete wiring diagrams of something completely different from typical guitar wiring:

This is the standard wiring of a 2-pickup Danelectro. Talk about unintuitive, what on earth is that switch doing? Remember, that is an on-off-on switch like you'd find at the hardware store, not an off-on-off switch as is typically found in a guitar. An on-off-on switch makes a contact to either side, and is fully off in the center. An off-on-off switch breaks a contact on either side, and is fully on in the center. I love Danelectros for defying all conventions of 'luthiery' and being great instruments in spite of that, or perhaps because of that.

Note that the volume and tone controls are individual for each pickup, and upstream of the switch. The key here is the series wiring. You don't have to use the individual concentric controls typically found on Danelectros.

Here is the same Danelectro wiring simplified to the bare minimum, with single downstream volume and tone as is typical in most guitars.

This is the ingenious wiring of a Danelectro single pickup guitar. The switch selects between no tone control, treble control, or bass control, and the whole circuit is so effective that you don't even miss a second pickup. The switch has no apparent effect if the tone control is zeroed.

 

[jcanderson]

. Ever heard a Jazz in series mode? Very un-wimpy. On the other hand, I once did the same to a Precision, so you could get the coils in parallel. Sucked.

I'm very much enjoying this discussion on wiring. Some notes:

1. If pickups sound wimpy when combined in series or parallel, try reversing the phase of one of them. I'm finishing up a build using an SCBP-3 and a G&L Humbucker. When I first connected them in parallel (with the humbucker's 2 coils already in series), I did what I thought made sense, i.e. black wire of one to black wire of the other, etc. The combo sucked. Then I reversed the phase of the SCBP-3. Big difference!

2. When wiring up a typical "tone" control with an audio (log) taper potentiometer, make sure you use the correct outside terminal of the pot. You want the terminal that, if measuring resistance from it to the center terminal of the pot, has the lower resistance when the pot has been rotated halfway. Why? The effect of the cap is most noticeable when series R is small, and this terminal will keep series resistance low over a wider angle range than if you used the other outside terminal (which I've found makes the tone control seem more on/off, with very little noticeable difference between the extremes).

3. You can make a balance control with a single pot. Feed the pickups into the two end terminals and take the combined audio from the center terminal. It isn't as good as the dual-pot implementation because there will always be some small amount of bleed-thru from the other pickup when the control is rotated to one extreme or the other. But to minimize this, make the pot large (e.g 500k), as the larger the pot resistance, the better the isolation. (Also, the lower the impedance of the pickups, the better the isolation). Oh, and the pot should be linear, not log, taper.

 

[alder]

I'm very much enjoying this discussion on wiring. Some notes:

1. If pickups sound wimpy when combined in series or parallel, try reversing the phase of one of them. I'm finishing up a build using an SCBP-3 and a G&L Humbucker. When I first connected them in parallel (with the humbucker's 2 coils already in series), I did what I thought made sense, i.e. black wire of one to black wire of the other, etc. The combo sucked. Then I reversed the phase of the SCBP-3. Big difference!

2. When wiring up a typical "tone" control with an audio (log) taper potentiometer, make sure you use the correct outside terminal of the pot. You want the terminal that, if measuring resistance from it to the center terminal of the pot, has the lower resistance when the pot has been rotated halfway. Why? The effect of the cap is most noticeable when series R is small, and this terminal will keep series resistance low over a wider angle range than if you used the other outside terminal (which I've found makes the tone control seem more on/off, with very little noticeable difference between the extremes).

3. You can make a balance control with a single pot. Feed the pickups into the two end terminals and take the combined audio from the center terminal. It isn't as good as the dual-pot implementation because there will always be some small amount of bleed-thru from the other pickup when the control is rotated to one extreme or the other. But to minimize this, make the pot large (e.g 500k), as the larger the pot resistance, the better the isolation. (Also, the lower the impedance of the pickups, the better the isolation). Oh, and the pot should be linear, not log, taper.

1. Out of phase is really really wimpy. I'm just talking about ordinary singles-coils-in-parallel wimpy, which is often referred to as 'quack' on a guitar, but on a bass it is just wimpy. The Jazz bass may be one of the two pillars of bass tone, but it is the wimpy pillar. I need to post the diagram for jazz bass with a series/parallel switch.

2. Good point. I drew it the way I've seen 90% of them wired, but I think you're right.

3. That would incur a resistance of 1/2 pot value to either side when centered. That's bound to have a significant effect on volume. A centered balance pot has zero resistance.

 

[walterw]

tons of good stuff!

A centered balance pot has zero resistance.

as long as it's the "M/N" type yes, other types leave resistance in the center.

 

[jcanderson]

3. That would incur a resistance of 1/2 pot value to either side when centered. That's bound to have a significant effect on volume. A centered balance pot has zero resistance.

Yeah, one would think so. But doing the calculations (using the Principle of Superposition and Ohm's Law), assuming an amplifier input impedance of 1Meg ohms and each pickup modeled as a voltage source with series resistance of 10K ohms (a simplified model, to be sure), the blending method that I describe, using a 500K pot set to its center point, is only 1 dB down from dual M/N taper pots set to their center point (0 ohms).

And if the blending pot is instead 250K, rather than 500K, then the difference in output is only 0.5 dB under the same conditions. Pretty much mouse nuts small, in my opinion.

On the other hand, best case off-channel rejection, rather than being infinite with the dual blend pot, is -34 dB with a 500K pot and -28 dB with a 250K pot.

And there's another potential issue -- if the passive tone control follows a single-pot blend control, there will be interaction between the blend pot's resistance and the tone cap.

(Anyone, feel free to check my calcs. I'd be happy to post them, too.)

 

[alder]

(Anyone, feel free to check my calcs. I'd be happy to post them, too.)

Yes, I'd like to see, not that I doubt you

one thing I wouldn't like about your way is there is no certain center, you place the knob as carefully as you can and then center it

I like the feel of that click when you hit dead center on a balance control

What do you think of the combined bass/treble control?

 

[jcanderson]

Yes, I'd like to see, not that I doubt you

Here is the calculation showing the delta in gain between a single 500K pot and a dual M/N pot, when both are at their center positions, to be -1 dB. The amplifier input impedance is shown as Ramp.

My apologies for my penmanship -- it has never been my strong suit. But I hope I've gotten the idea across. And anyone -- please feel free to correct any mistakes I've made!

- Jeff

 

[jcanderson]

In the previous post I was trying to get the important parts of the derivation onto a single sheet of paper. Just in case it isn't clear how to calculate the quantity "[Ramp || (Rn + Rb)]" shown in the previous post, it can be easily calculated using this formula (which is just calculating resistances in parallel, which is what "||" means):

[Ramp || (Rn + Rb)] = 1 / [(1/Ramp) + (1/(Rn+Rb)) ]

So, for example, if you use a calculator and plug these values...

Ramp = 1Meg
Rn = 250K
Rb = 10K

...into the right-hand side of the equation above, the answer calculates to be 206K.

 

[jcanderson]

What do you think of the combined bass/treble control?

Hi Alder,

I forgot to answer this question. Your combined bass/treble control looks fine to me. Very similar to what G&L does with two separate pots, although they use different resistance values (which I don't think will be significant, but there will be some difference).

 

[jcanderson]

Realized overnight that there's a slight error in one of my calculations.

In the M/N dual-pot example, there are also two 500K resistors (the other legs of the two pots, tied to ground) that are in parallel with the amplifier input resistance.

This means that the overall voltage gain of the dual-pot circuit is 0.488, not 0.497, and therefore the delta in gain between the dual and single pot topologies is -0.86 dB, not -1.06 dB.

(Pretty much an insignificant change to the overall result, but thought I'd include it for completeness).