Tone Pot with Strange Wiring Anomaly question

[ssstonelover]

This is the first and only time I've seen a tone pot wired this way.
The comment for the user was, "I opened the pickguard to see the condition of the wiring because the sound was not satisfactory. This guitar uses 1 humbucker and 2 single coils. It looks like the connection between tone pot 1 & 2 with the capacitor is not correct."

Quite frankly I've never seen anything like this.
It would seem to me that connecting the 2 tone pots in the middle with a common cap would cause interaction with the 2nd pot, causing the cap to see lower Ohms (darkening tone).
Caveat: I don't have this guitar here, so what I am saying is speculation, plus I am more a tech, than an EE. In fact I have never taken any electronics courses, nor have any LCR type knowledge.
I am most curious as to what this unorthodox wiring would do, and what would be any motivation for using or avoiding it.


First image is the wiring in question, the 2nd is common hookup for a SSS wiring harness

[mikecg]

Hello ssstonelover,

As sumgai points out below, reversing the two connections to the terminals of a pot (i.e. wiper lug and end lug) should make no difference to the circuit function. If you can confirm that the lower of the two black wires from the 5 way is indeed connected to the lower lug of the right hand tone pot (not clear from the photo), then, despite the unusual orientation, the dual treble cut circuit should work just as well as that with the more usual component orientation. 
If the owner is still unhappy with his 'non-standard' configuration, you could try shifting the cap, the connection between the two pot wipers (centre lugs), and the black wire from the aforementioned lower lug, to the wiper lug. The result, should then look something like this: 

[sumgai]

Technically speaking, it doesn't matter which terminal of a two-terminal device is connected to where (except in the case of a diode (or a battery!)). Putting the cap on the end terminal instead of the wiper is purely matter of choice. As shown in the image, the controls will act exactly as designed, and as usually accepted by most players, with no interaction between the two (unless both of the controlled pickups are selected at the same time).

Putting the cap on the end terminal was a matter of mass production - one or two workers wired up a bunch of these things all at the same time, and stuck them back into the bin(s). Then when it came time to assemble a guitar, a pot-with-cap was plucked out of the bin, and the time it took to assemble the axe was reduced by this small amount. Looked at another way, it also removed most of the potential errors that usually occur when things are going 90 miles an hour on the factory floor. In this particular case, it looks like the pickup leads went to the outer terminals instead... no big deal.

It's a totally different story when it comes to hand wiring.

HTH






sumgai

[ssstonelover]

sumgai and mikecg,
OK, I'm not going crazy, unorthodox is OK (and certainly I have been creative from time to time) though not especially so on tone pots!
It would seem the core issue is going to be connection integrity, not the wire vs cap path, and that makes perfect sense.
Just time for someone to heat up the solder gun and get continuity and/or better sound by a reflow

On a related "tone pot" issue, and in pursuit of a closely related issue (50s vs 60v vs Modern "Gibson' tone pot wiring) I came across this line of writing which seems a bit strange (and maybe more so based on the discussion we're now having (wires and caps don't care about flipped lug position)

This is from Premier Guitar (Dirk Wacker), a guy who previously made other claims the Nuts have shot down. 
"Electrically, the '60s wiring is completely identical to the modern wiring with the same tone, behavior, and problems. But there is one significant difference: In terms of shielding, the '60s wiring is superior to the modern wiring scheme. When electromagnetic interferences enter a guitar, they will also stray into the tone pot's unused pin and therefore into the middle lug (the wiper) in both wirings. With the wiper connected to ground, as in the '60s wiring, the interferences will stop at this point. But with the tone cap connected to the middle lug, like in the modern wiring, electromagnetic interferences will find their way through the cap and carry on.
So, compared to the modern wiring, the signal-to-noise ratio in the '60s wiring is superior. This is technical knowledge from yesteryear: The wiper of a variable resistor is connected to the low resistance part of the circuit. This knowledge was really important when designing and building tube amps, radios, and televisions, but is almost forgotten today."
I think we all know the illustration....

[mikecg]

Hello again ssstonelover,


Best not to mention Mr Wacker's 'theories' round here, but if you insist, you could start by reading (re-reading?) this:


guitarnuts2.proboards.com/thread/7680/capacitor-orientation-polarity-outside-direction

[newey]

We sort of touched on this in the other thread above, but prehaps didn't state it very plainly. Essentially, what he claims is that noise will enter the circuit through one lug of a tone pot, which is, what, about 1/2 cm or so long?

Electromagnetic noise can certainly be picked up by the hundreds of feet of wire wound around a pickup frame, acting as a very long antenna, effectively. But I question whether it is realistic to think that a solder lug that short would pick up any frequency of eletrical noise. If this were true, why would it not also be true for an unused lug on a 5-way switch where the commons is connected to the ouput?

[ssstonelover]

Hi mikecg, newey,

Mike, I do remember writing that original query some years ago and the reply too, and the opinion the Nuts here have on his assertions both generally and specifically.
I never ever worried about cap orientation since, especially as I don't build amps, don't use electrolytic caps, etc.

Of course (this time) Mr. Wacker was talking about transposing cap placement and wire placement between 'location 1' and 'location 2' (so overall another assertion was involved).
As Sumgai just said 'Putting the cap on the end terminal instead of the wiper is purely matter of choice'. Given that, Mr. Wacker (again) has no leg to stand on, there is no real difference between Modern and 60's wiring.
I'm really not surprised at all, thanks for confirming my suspicions.

Newey, Yes, Short wires, unused lugs.....yes quite different from a long antenna, and a good point of reference
Upshot: just continue using 'best practices and common sense', decent shielding, rigorous logic, etc, and all will be fine.

[sumgai]

Jun 15, 2024 14:17:48 GMT -5 ssstonelover said:

Upshot: just continue using 'best practices and common sense', decent shielding, rigorous logic, etc, and all will be fine.

This!! This should be every member's tag line, until it finally sinks into the minds of modders everywhere - one simply can't go wrong for living by this standard.

And don't sell yourself short. Like Cindi, you're getting an education by osmosis. Just ask newey how well this method works.

HTH






sumgai

(Note that I've started the ball rolling!)

[newey]

Jun 16, 2024 12:45:07 GMT -5 sumgai said:

Just ask newey how well this method works.

It does indeed. I came here knowing basically nothing about guitar wiring, having redone an old Yamaha as my only previous project. I wired it straight off a basic Strat diagram without having a clue as to why it was wired in the manner that it was- I was just painting by the numbers.

But I had good teachers, sumgai, JohnH, and ChrisK primarily, but also many others along the way. This forum would not exist without that core group sticking around, I just dust the shelves and take out the trash periodically.

[ssstonelover]

newey, sumgai, Yup, you learn from people who are better than you, and I have.
-From asking questions, from poring over diagrams and tracing connections to understand the inner workings, from errors people report and need help with, from screw ups one makes (and the problem solving extrication process), from being inspired by things someone brings to the table (and my God we have those resources too in people and ideas and mentorship) and from our amazing collective library (which can be vexing use as a research tool at times however maybe because it is so big).

It's a schooling, osmosis indeed.

[reTrEaD]

Jun 15, 2024 14:17:48 GMT -5 ssstonelover said:

Upshot: just continue using 'best practices and common sense', decent shielding, rigorous logic, etc, and all will be fine.

We can debate the meaning of "best practices" but to me, it's a balance between simplicity, performance, and reliability. With that in mind, let's look at the two drawings below.

Jun 15, 2024 0:11:04 GMT -5 ssstonelover said:

They both have a slight advantage in simplicity, as there is no need for a wire between the volume pot and the tone pot. The lower drawing has a microscopic advantage over the upper drawing, in terms of performance. While the resistive element of the pot is well shielded, the unused CW lug acts as a tiny antenna allowing very small amount of hum and noise to enter the system. By using the wiper as the ground connection, this hum and noise goes directly to ground rather than coupling to the system via the capacitor.

But neither of these two, are the optimum configuration for the tone network. First we'll discuss the small reason, performance.

As we've learned elsewhere the outer foil of the capacitor can be a path where hum and noise can enter the system. Where practical, it makes sense to connect it ground or a low impedance part of the circuit. In an amplifier, we would connect the outer foil to the output of one stage (low impedance) and the inner foil to the input of the next stage (high impedance). But in a tone-cut circuit we actually have a ground to which the foil can be connected. And since the area of the outer foil is significantly greater than a pot lug plus a wire of the same length as the as the cap, this is of greater concern. If we connect the outer foil to the CCW lug of the pot, when the tone is at '10', we have a large resistance between the outer foil and ground and any hum and noise will be coupled via the capacitor to the signal. Not good. Better to connect the capacitor between the wiper and ground, and use a wire to connect the CCW lug of the tone pot to the CW lug of the volume pot. We've sacrificed a small amount of simplicity for a small amount of improvement in performance.

And now for the big reason for connecting the outer foil of the capacitor to ground and the inner foil to the wiper. If the nut securing the tone pot or the volume pot works loose (as they often do), stress and rotation will be applied to whatever is connected between the two. The body of the cap won't flex, so the leads will take the brunt of the abuse and likely fail. A wire will survive more abuse since the flex and rotation will be distributed across the entire length, and even if it does fail, wire costs less than a cap.

Common Sense: An unused pot lug, a short length of wire, and the outer foil, are all potential paths by which hum and noise can enter the system. But none of them are very significant. And far less significant, if the control cavity is shielded. No matter which way the tone pot and tone cap are configured, the differences in performance will be tiny. Don't make mountains out of molehills unless you write for a guitar magazine and haven't a clue. JMO.

[ssstonelover]

reTrEaD

OK, I get that it's bad to have resistors go between pots (breakage due to loose pots), and personally I never go that route.
I get that proper shielding, common sense and best practices, have far more impact on noise reduction than wire or caps being flipping around on terminals or between pots.
But what I do need more elucidation on is: "And now for the big reason for connecting the outer foil of the capacitor to ground and the inner foil to the wiper.".

Background: The caps I use are not labeled for outer and inner foil -- and I don't have an oscilloscope. Furthermore in this thread capacitor-orientation-polarity-outside-direction it was pretty much debunked as having no more than a whisper of influence on guitar noise, though I do see you demurred compared to the others, at least at a theoretical level. You wrote, "I totally understand the concept of grounding the outer foil. It just sensible standard practice. But I really don't think it's all that important in a guitar."

Accordingly I've just ignored foil direction totally: no way to check it (easily) and I was just following what seemed a consensus.
I'm listening to everything you say but that also included you saying, "if the control cavity is shielded. No matter which way the tone pot and tone cap are configured, the differences in performance will be tiny." Thus I'm a bit confused, or maybe what you at heart are really saying is that foil direction is something to think about (theoretically) but fine to ignore in reality (on guitars)?

Another question, and just to be devil's advocate this time, say someone does NOT use shielding or best practices; for those guys will cap foil (outer/inner) orientation impact them, or will it again be masked by their other lousy choices?

Sorry for some many words, I just want to get clear on this. thanks.

[reTrEaD]

Jun 18, 2024 19:26:33 GMT -5 ssstonelover said:

But what I do need more elucidation on is: "And now for the big reason for connecting the outer foil of the capacitor to ground and the inner foil to the wiper.".

If I wasn't clear on the big reason, let me reiterate. Placing the cap between a lug of the tone pot and the case of the tone pot, provides protection from lead breakage in case one of the pots becomes loose.

Regarding the rest of it, we're at a level that falls somewhere between negligible and barely noticeable. Even if we connect the foil the wrong way round, the capacitive reactance is less than 150k ohms at 50Hz and the pot resistance at 10 on a Strat is 250k ohms. So the foil is still "closer to ground" than hot at that setting. And the area of the foil is rather small, although it is considerably larger than a pot lug.

To put this in perspective, we have more than one lug of a pot connected to hot, no matter what we do, plus the lugs of the selector switch, plus the rotating assembly of the selector switch. If you add all those up, the total area is similar or slightly greater than the area of the outer foil of the tone cap. So I wouldn't lose any sleep over connecting the foil 'incorrectly".

The biggest offenders in a Strat are the non-hum-canceling pickups and the plain (unshieded) wires to the pickups. Even if we choose to not improve on the plain wires, a LOT can be done to reduce hum and noise by shielding the cavities where they reside.

Jun 18, 2024 19:26:33 GMT -5 ssstonelover said:

Background: The caps I use are not labeled for outer and inner foil -- and I don't have an oscilloscope.

You have a 50% chance of having the outer foil connected to ground if you just guess. And the world won't come to an end if you're wrong. But you don't really need an oscilloscope. Rather than discerning with your eyes, you can simply use your ears. In the video below, this clever gent is coupling hum and noise to the outer foil of the cap from the 'big ol' bucket of noise' (himself) via his thumb and forefinger, and alternately connecting the outer foil to the tip and shield of a guitar cable connected to an amplifier, and using his ears. We don't need a number, just an ability to discern the difference with our ears.

[ssstonelover]

Jun 23, 2024 16:27:16 GMT -5 reTrEaD said:

1. If I wasn't clear on the big reason, let me reiterate. Placing the cap between a lug of the tone pot and the case of the tone pot, provides protection from lead breakage in case one of the pots becomes loose.

2. Regarding the rest of it, we're at a level that falls somewhere between negligible and barely noticeable. Even if we connect the foil the wrong way round, the capacitive reactance is less than 150k ohms at 50Hz and the pot resistance at 10 on a Strat is 250k ohms. So the foil is still "closer to ground" than hot at that setting. And the area of the foil is rather small, although it is considerably larger than a pot lug.

To put this in perspective, we have more than one lug of a pot connected to hot, no matter what we do, plus the lugs of the selector switch, plus the rotating assembly of the selector switch. If you add all those up, the total area is similar or slightly greater than the area of the outer foil of the tone cap. So I wouldn't lose any sleep over connecting the foil 'incorrectly".

The biggest offenders in a Strat are the non-hum-canceling pickups and the plain (unshielded) wires to the pickups. Even if we choose to not improve on the plain wires, a LOT can be done to reduce hum and noise by shielding the cavities where they reside.

3. You have a 50% chance of having the outer foil connected to ground if you just guess. And the world won't come to an end if you're wrong. But you don't really need an oscilloscope. Rather than discerning with your eyes, you can simply use your ears. In the video below, this clever gent is coupling hum and noise to the outer foil of the cap from the 'big ol' bucket of noise' (himself) via his thumb and forefinger, and alternately connecting the outer foil to the tip and shield of a guitar cable connected to an amplifier, and using his ears. We don't need a number, just an ability to discern the difference with our ears.

You're the man, thanks for the continuing education

1. Crystal clear. Having said that there are still 4 ways to connect caps to the back of the tone pot (excluding the foil orientation, see point 3 below for that). You mentioned 'the CW terminal could act as an antenna I just wanted to tunnel down some more on that (though as you mentioned its a super minor factor) and also you mentioned that the wiper is best suited for attaching the cap for noise shielding, meaning the CCW terminal would be the attachment point to the volume pot (using a strong stranded wire).
Please check this illustration. It would seem the bottom image is the most ideal, the second from the bottom maybe next best, the top one maybe third best, and the second from top would be last (though still better than the drawings from Premier Guitar and for the reasons you have already given). If I got this wrong, let me know that too.


2.  I'm on board with that reality check. I do a ton of SSS type guitars fully shielded, but now I can add foil direction and a more ideal pot hook up methodology to what I already do, thanks!

3. That video is interesting. Reminds me of the screwdriver pickup test to confirm connection and sound for volume and tone pots before closing up the cavity and adding strings.
I don't have any kind of fuzz box. So I tried 2 ways:
a) direct from amp with gain high (and I tried 2 amps)
b) through an Ibanez tube screamer
The tube screamer did nothing, but the amp works for values .0012uF, .0015uF, .0018uF (ok for treble bleed or passive bass cut) but at values .015uF, .022uF and higher (treble tone pot) it did not. I have caps at values between these two ranges and some worked but many did not. Kind of hit-or-miss as it seems the tiniest values are the easiest to detect.

I then checked out another video cap direction and at about 11 minutes in he shows his way -- just blasting volume. I could just hardly detect a small difference for a .022uP cap, but it was an improvement over what I'd gotten before.

I'd something to detect foil direction at lower amp volumes and more definitively to make this work faster and more assured. Does a fuzz box help generate the kind of detectable foil noise difference I want to hear, and/or what else will substitute? Thanks.

[reTrEaD]

Jun 23, 2024 23:16:53 GMT -5 ssstonelover said:

Does a fuzz box help generate the kind of detectable foil noise difference I want to hear, and/or what else will substitute?

A fuzz box generates a lot of harmonics from the 60Hz sine wave, making it easier to hear. I reckon a cheap solid state amp with an input gain control could do much the same. That would allow you to crank the gain to maximum, causing clipping of the input signal, and the harmonics would be easily heard without the master volume being so high.

Jun 23, 2024 23:16:53 GMT -5 ssstonelover said:

Before we assess these variations individually, let's look at what they all have in common. We'll call any bare, unshielded wire and any unshielded terminal an antenna.

The wire from the pickup selector is an antenna (a big antenna). The wire going to the output (+) is also a big antenna. The three lugs of the volume control are very small antennae, but the CCW lug is connected directly to ground, so any hum or noise hitting it is not coupled to the output. The other two have some significance, since they're both connected directly to the output when the volume is at 10. The green wire connecting the CW lug of the volume pot is a fairly small antenna. It too is connected directly to the output when the volume is at 10.

First example: The wiper lug, CW lug of the tone pot, and the jumper between the two are all antennae and they are all connected to the output when the volume is at ten. The CCW lug is an antenna but it's connected via a 250k resistance to the output (when the tone is at 10), and has less than 150k of capacitive reactance shunting the hum and noise to ground.

Second example: The wiper lug and CW lug of the tone pot are antennae and they are all connected to the output when the volume and tone are at ten. The CCW lug is an antenna but it's connected via a 250k resistance to the output (when the tone is at 10), and has less than 150k of capacitive reactance shunting the hum and noise to ground. From the "antenna" perspective, this slightly better than the first example because don't have the little jumper also acting as an antenna. (But there is a good reason for having this jumper, which we'll get to later.)

Third example: From the perspective of antennae, this is the best so far. We only have one antenna on the tone pot (the CCW lug) connected to hot. The wiper lug (and CW lug when the tone is at 10) are coupled through 250k of resistance to the output and shunted via less than 150k of capacitive reactance to ground.

Fourth example: Same as the third, but we add the little jumper as an additional antenna, to the wiper lug and CW lug.

Connecting CW to wiper: It's a good idea to connect the wiper and CW lug together on a treble-cut tone pot. If the wiper becomes intermittent when rotated, the worst case is having the full resistance of the tone pot in series with the tone cap, rather than having the tone circuit going completely open-circuit and the tone becoming excessively bright. This makes a potential problem slightly smaller, should it occur.

BOTTOM LINE: We're really splitting hairs when it comes to benefits and drawbacks of these four configurations. I favor the fourth example but I wouldn't lose a minute of sleep if it were wired any of the other three ways.

[ssstonelover]

Jun 24, 2024 23:50:03 GMT -5 reTrEaD said:

BOTTOM LINE: We're really splitting hairs when it comes to benefits and drawbacks of these four configurations. I favor the fourth example but I wouldn't lose a minute of sleep if it were wired any of the other three ways.

I used to be a product manager for various bicycle companies and was responsible for designing and assuring the QC of the new models each year, and had to work with a lot of different suppliers with varying tolerances. Basically I'd figure out what was ideal, to whatever level of precision the math said, then do exactly what you just did: figure out what made a real difference and where to put effort/cost to assure the best real world result, and the needed level of tolerance we could accept to achieve trouble-fee operation (something above minimum to give a comfortable margin of course).

As you've shown here, knowing both theory and the real parts, we then can shoot for creating the right environment for a favorable outcome. Your background of knowing the factors and their interplay and contributions to the whole makes it clear what is important.
It was especially nice to know the 'why' behind the rankings and what drives that. Thanks for all this. No sleep lost, the hairs are too small to split any further LOL.