HH wiring with rotary switch

[sedseriyo]

Wotcha all, I've started building my first guitar (for myself), and have run into the issue of finding wiring a little too complicated to get my head around.

What I want to achieve is:

• Two humbuckers - specifically Irongear Blues Engine in neck position and Irongear Dirty Torque in bridge position.
• One tone control and one volume control for each pickup.
• A rotary switch to offer at least the following options
  - Neck only
  - Bridge only
  - Neck and bridge in series
  - Neck in coil split, don't mind which pole
  - Bridge in coil split, don't mind which pole

Giving a total of 5 controls for the two pickups.

A fun addition to the puzzle is that the control cavity only offers enough depth for the style of rotary switch pictured, a 5 position switch with I think 2 poles.

Is this possible or are additional switches going to be required? If so, I would happily add a switchcraft on-on-on DP3T slider switch to the mix.

[newey]

sedseriyo-

Hello and Welcome to G-Nutz2!

What you've got there is a double pole, 5 throw rotary switch, with a single deck. It's abbreviated as DP5T, the "single deck" refers to the fact that both poles are on the same plane, not stacked one atop the other.

I believe it can be made to work for what you want, but it may have a "hanging coil" (or two) when in coil-cut mode. This is not a deal-killer, there is a theoretical chance that the hanging coil might add some noise. Or maybe not, and it may depend on the particular electical environment where you play.

I believe there are single deck rotaries available with 3 poles, and the extra pole could be used to alleviate the issue. But if you've already got this particular switch, I'd say go ahead and use it.

Let me try to work out a diagram for you. It will show only the wiring to the rotary switch; the V and T pots will be wired the same as on any other guitar with a single V and T.

[sedseriyo]

Thanks for the reply Newey. I've not purchased any electronics yet, just working out what space I have available for them all!

[newey]

Don't start wiring just yet, as I'm not 100% sure this is correct, and there may well be a better way to accomplish this. But here's my take on this wiring. Note that I have tried to follow the Irongear wire colors, but have used grey on the diagram for the white wires, so they can be seen.

[sedseriyo]

Thanks so much for having a crack at this. I was hoping to go one volume and one tone control for each pickup, I probably wasn't really clear about that!

Having said that, I quite like the idea of a master tone and master volume. Three controls for quite a few variations seems very neat.

[newey]

You can certainly do individual V and T controls if you want, I misread your original post. These would be wired "across" each pickup, before the rotary switch. The rotary then, instead of outputting to the V and T controls, will just output to the jack.

You can consult any diagram for a Les Paul with 2 X V&T controls for that wiring, your wiring will be identical except that your rotary switch takes the position of the 3-way pickup selector.

[Yogi B]

Jan 19, 2021 12:21:01 GMT -5 newey said:

You can certainly do individual V and T controls if you want, I misread your original post. These would be wired "across" each pickup, before the rotary switch. The rotary then, instead of outputting to the V and T controls, will just output to the jack.

And what about the coil split positions? The tone controls will work mostly as intended: with the series link connected to hot the supposedly non-selected coil will be in series with the relevant tone potentiometer & its cap -- thus when turning the control down, it'll also be blending in parallel the upper mids & treble content (remember it's in series with the tone cap) from that coil out of phase with the selected coil (yes, that'll still have the overall effect of reducing treble, but in a somewhat unusual way).

However the volumes will be completely non-functional, being 'stuck' at 100% -- if we're connecting 'hot' to the series link then the wiper of the volume pot will be left open, and a pot with only lugs 1 & 3 connected is just a fixed resistor.

---

I think individual volumes & tones are possible, but will require different switch wiring and one of the control pairs to be wired 'upside-down'. I'll see if I can draw up a schematic to verify my thinking...

[JohnH]

I also think it can all be done, with the twin V and T controls and the 2P5T switch.

A series chain between two complete pickup, volume (with treble bleed) and tone modules. But as you describe, one of the controls is wired upsidedown. So there is a common connection of both pickups, both volume pot lower halves and both tone controls, at the centre of the series chain. From this one common point, one pole can be selectively shunting one or other entire pickup output, and the other can be shunting a coil from one or other pickup,

[sedseriyo]

Thanks all for weighing in, though I have to admit that I have rather lost the ability to follow what is being discussed!

[newey]

Jan 20, 2021 4:45:56 GMT -5 sedseriyo said:

Thanks all for weighing in, though I have to admit that I have rather lost the ability to follow what is being discussed!

What we're discussing is the individual V and T controls interacting when you have selected one of the split-coil positions. I misread your original post, so my diagram was based on master V and T pots, which does make life easier.

I had considered wiring one HB "upside down", as Yogi B has suggested, but that is typically done for purposes of hum-cancellation when 2 HBs are both split to one coil at the same time. Since your scheme doesn't have a setting where both HBs are split together, I then thought "why bother?"- but I hadn't considered the tone control issues Yogi B raises.

[newey]

Jan 19, 2021 21:08:30 GMT -5 JohnH said:

A series chain between two complete pickup, volume (with treble bleed) and tone modules. But as you describe, one of the controls is wired upsidedown. So there is a common connection of both pickups, both volume pot lower halves and both tone controls, at the centre of the series chain. From this one common point, one pole can be selectively shunting one or other entire pickup output, and the other can be shunting a coil from one or other pickup,

When I first read Yogi B's thoughts, I thought "Well, what about the Jimmy Page LP wiring? That has individual V and T pots, series HBs, and coil splits, and people use that wiring all the time". But of course one of the HBs is wired "upside down" (or "inside out", as wolf says it).

We have always discussed wiring HBs "upside down" in the context of doing so to select the oppposite coils for hum-cancellation. It had never occurred to me that doing so also affects the operation of the V and T pots as well.

[reTrEaD]

Jan 19, 2021 21:08:30 GMT -5 JohnH said:

I also think it can all be done, with the twin V and T controls and the 2P5T switch.

A series chain between two complete pickup, volume (with treble bleed) and tone modules. But as you describe, one of the controls is wired upsidedown. So there is a common connection of both pickups, both volume pot lower halves and both tone controls, at the centre of the series chain. From this one common point, one pole can be selectively shunting one or other entire pickup output, and the other can be shunting a coil from one or other pickup,

JohnH, I really like where Yogi B is headed with this. While I've never been a fan of shunting, this opens up some possibilities that would otherwise be impossible with a 2P selector.

With our Global series link as the common point of focus, whichever pickup is on the bottom of the stack will have its volume control with the CCW terminal connected to the Global series link and its wiper connected to ground.

Both poles of the selector will be connected to the Global series link. Either one can be used to shunt one entire pickup and associated controls, or one coil of a pickup.

We could have one selection where one coil of each pickup is shunted. That could be hum-canceling and in my estimation a more interesting choice than the bridge pickup only, as a single.

[Yogi B]

Jan 20, 2021 7:19:53 GMT -5 newey said:

When I first read Yogi B's thoughts, I thought "Well, what about the Jimmy Page LP wiring? That has individual V and T pots, series HBs, and coil splits, and people use that wiring all the time".

The JP wiring has a lot more switching 'capacity' than a DP5T -- the coil splits are on separate push-pull switches that are 'closer' the the pickups / 'before' the volume & tone controls.

We have always discussed wiring HBs "upside down" in the context of doing so to select the opposite coils for hum-cancellation. It had never occurred to me that doing so also affects the operation of the V and T pots as well.

Ah, but we're not discussing the wiring of the humbuckers, they stay as they are (for now at least). We're just considering wiring of the volume pot (and potentially the tone pot, though that'd be a change just to make the physical wiring a little easier to follow).

Looking at the following diagram and mentally separating the volume potentiometer into two variable resistors (one between lug 3 & the wiper, and the other between the wiper & lug 1), in the normal wiring we have the lug-3-to-wiper resistor between the pickup and the output and the wiper-to-lug-1 resistor between the output and ground -- in other words the wiper-to-lug-1 resistor is in parallel with the series combination of the pickup and the lug-3-to-wiper resistor.

Thinking of a series combination of a pickup and a resistor we know that the ordering is irrelevant. Instead of the resistor being between the pickup and hot, we could equivalently have the resistor between the pickup and ground -- this is what occurs in the 'upside down' wiring.

An alternative way of 'getting there' would be if we make the distinction between signal ground & shielding ground and keep the two separate (shield ground remaining connected to the sleeve of the output jack), then ultimately we have two signal wires going to the output jack: signal hot & signal ground. If we are diligent and there are no shorts between signal ground & shield ground, then which way we choose to assign these to the output jack can have no effect on the functionality of the controls -- the only change is the overall phase reversal, and we can counteract that by flipping the phase of the pickups. So, in other words, if you take the normal wiring and swap output and ground then also switch the pickup's leads, you'll end up with the 'upside down' wiring.

The possibilities that the normal wiring gives us, and that we commonly take advantage of, are that:

• We can short a tap from the pickup coil directly to ground, without shorting part of the volume control;
• Alternatively, avoiding the shunt we can have a switch pole connected to ground that switches between the pickup's negative and the tap whilst leaving the volume control permanently grounded

However, with the normal wiring we cannot:

• Short a tap from the pickup coil directly to the output, doing so would short the 'upper' portion of the volume control (lug-3-to-wiper);
• Nor can we avoid that shunt via a switch pole connected to the output, as the pickup's positive lead is 'hidden' behind the volume pot, the closest we can get would be switching between the volume control's wiper and the tap, which gives the behaviour noted in my previous post.

With the 'upside down' wiring the two lists of 'can's & 'cannot's are reversed.

Jan 20, 2021 11:05:46 GMT -5 reTrEaD said:

Jan 19, 2021 21:08:30 GMT -5 JohnH said:

I also think it can all be done, with the twin V and T controls and the 2P5T switch.

A series chain between two complete pickup, volume (with treble bleed) and tone modules. But as you describe, one of the controls is wired upsidedown. So there is a common connection of both pickups, both volume pot lower halves and both tone controls, at the centre of the series chain. From this one common point, one pole can be selectively shunting one or other entire pickup output, and the other can be shunting a coil from one or other pickup,

JohnH, I really like where Yogi B is headed with this. While I've never been a fan of shunting, this opens up some possibilities that would otherwise be impossible with a 2P selector.

With our Global series link as the common point of focus, whichever pickup is on the bottom of the stack will have its volume control with the CCW terminal connected to the Global series link and its wiper connected to ground.

Both poles of the selector will be connected to the Global series link. Either one can be used to shunt one entire pickup and associated controls, or one coil of a pickup.

Below is the way I had in mind, rather than having the switch poles on the 'inside' (connected to the inter humbucker series link), they are instead at the 'outside' (connected to hot & ground). The latter gives the option that the pickups/coils can be left hanging, rather than being shunted, if it is so desired. The diagram is a combination of both: the neck pickup is shunted to avoid its coils hanging from hot; whereas the bridge pickup is not shunted, as hanging from ground needn't be avoided. Edit: Scratch that, see reTrEaD's post directly following. Also I've corrected the below schematic to use shunts for both pickups.

The switch positions are as they are in the OP & newey's diagram (N; B; N × B; N split; B split), and the coils are split such that the inner/slug coils (as drawn) are active.

[reTrEaD]

Jan 20, 2021 13:15:44 GMT -5 Yogi B said:

Below is the way I had in mind, rather than having the switch poles on the 'inside' (connected to the inter humbucker series link), they are instead at the 'outside' (connected to hot & ground). The latter gives the option that the pickups/coils can be left hanging, rather than being shunted, if it is so desired. The diagram is a combination of both: the neck pickup is shunted to avoid its coils hanging from hot; whereas the bridge pickup is not shunted, as hanging from ground needn't be avoided.

The switch positions are as they are in the OP & newey's diagram (N; B; N × B; N split; B split), and the coils are split such that the inner/slug coils (as drawn) are active.

This looks to me as if it will produce some unexpected results.

Examine the connections in position 5 (Bridge Only - split to single).

The node where the (-) of the lower Bridge coil and CCW terminals of the Volume and Tone controls are connected, is left hanging. What happens in that position when the Bridge volume is reduced to minimum?

[JohnH]

Just on pickup and coil shunting:

Based on what I recall from Antigua's tests, I think that there's benefit in not shunting a coil to coil-cut a humbucker, because I think we saw a measurable increase in damping affecting the other coils tone, due to the close magnetic coupled relationship between two coils in the same pickup.

But I think that shunting an entire pickup is ok to do tonally, if it facilitates a desired switching outcome. But full disconnection, or just ground connection is best, unless fully shielded, for reasons of noise.

[JohnH]

Here's how I was thinking it might be done:


photo uploader

Its just a train of thought, or more exactly, a thought sketched on a train.

It uses the central common point with a reversed volume I ordered the switch positions to make it easier to see, but the order 1-5 could be rearranged freely

It shunts whole pickups but doesn't shunt separate coils in a single coil mode. Screening is likely to help given hanging parts.

[Yogi B]

reTrEaD, I've corrected my previous post (which I'm 90% I'd already done last time I was online, but apparently not...).

Jan 20, 2021 16:55:18 GMT -5 JohnH said:

Based on what I recall from Antigua's tests, I think that there's benefit in not shunting a coil to coil-cut a humbucker, because I think we saw a measurable increase in damping affecting the other coils tone, due to the close magnetic coupled relationship between two coils in the same pickup.

I believe you're referring to antigua's Damping caused by the unused coil when splitting a humbucker thread, which agrees with your statement: shunting the unused coil causes damping especially if the pickup has a (brass) cover...

... However ...

Another of antigua's posts (from stratotarts avoiding capacitance from unused portion of coil with a tap thread a few months later), suggest it's also significant whether the coil is shunted-in-place or if it is shunted but otherwise disconnected. Those results show the variant where the coil is shunted, but still connected, as having slightly higher resonant peak than any of the other coil splitting methods.

I was recently (or, back in September according to my files' timestamps) thinking about why this would be true, but came to the conclusion I'd want more data: as there is (at least) eight different ways of splitting a humbucker and although some ought to be electrically identical I could only cautiously narrow those eight down to five -- i.e. still one more that the four tested by antigua.

[reTrEaD]

Jan 21, 2021 16:28:14 GMT -5 JohnH said:

Here's how I was thinking it might be done:

Yours works and Yogi's works but yours is also open to an additional selection ...

[sedseriyo]

Well blimey, thanks all. I feel like I can't let all this effort go to waste, so I'll be giving it a go and will feedback on how it goes.

[JohnH]

I think that it will be a great project if you are sure these are the tones you want. Ive got a couple of suggestions, assuming you'd build from Yogi's:

I would particularly recommend treble bleed circuits, given the series wiring and the ability to blend pickups. I have a similar arrangement on my Gibson. With this, if you don't have them, turning one pickup down when you have both in series, can dull the tone from both. But with TB, mixing works really well. Id suggest 1000pF and 150k in parallel on each volume

You can arrange your combinations in any order, so should consider which should be next to each other to best suit your use.

If you are using a rotary switch, with 5 poles, you can usually also get the same switch with 6 poles at the same size. So you could have one more tone. No point in adding a tone just for the sake of it, and the way these schemes work cant do everything, but you could add say both pickups in series, both cut. Its a good tone and should work well with the system.

[Yogi B]

Jan 22, 2021 1:34:52 GMT -5 reTrEaD said:

Yours (JohnH's) works and Yogi's works but yours is also open to an additional selection ... (B split + N split)

I think mine could be able to do that too, if one were to take to neck tap and attach terminal 5 of the upper switch pole to that (instead of to the pots' wipers / global series link).

Jan 23, 2021 15:30:02 GMT -5 JohnH said:

I would particularly recommend treble bleed circuits, given the series wiring and the ability to blend pickups. I have a similar arrangement on my Gibson. With this, if you don't have them, turning one pickup down when you have both in series, can dull the tone from both. But with TB, mixing works really well. I'd suggest 1000pF and 150k in parallel on each volume

sedseriyo: note that adding a parallel treble bleed will seemingly alter the taper of the pots making them 'less logarithmic' e.g. the 1nF ∥ 150k combination will make a usual 500k 10% log taper pot behave more like a 30% taper. What I'm getting at is: even if you are used to linear taper volume pots without treble-bleeds, you'll probably want to forego them for log pots this time.

(A partial alternative solution that will somewhat help, though doesn't solve the issue as well as TBs, would be to use no-load tone pots with 250k volume pots.)

If you are using a rotary switch, with 5 poles, you can usually also get the same switch with 6 poles at the same size. So you could have one more tone. No point in adding a tone just for the sake of it, and the way these schemes work can't do everything, but you could add say both pickups in series, both cut. It's a good tone and should work well with the system.

On that note, and with the mention in the OP to "happily add a switchcraft on-on-on DP3T slider switch to the mix", it would probably be remiss of me not to mention the idea to have the rotary switch solely responsible for coil shunting, i.e. something like:

• Both full HBs
• Neck split, bridge full
• Neck full, bridge split
• Both split
• Both split to the other coils, maybe?

Then use the slider to select bridge, both, or neck. Technically the slider switch would be redundant -- with series wired volume controls you can turn either of the volumes all the way down to mute just that pickup -- however the switch would still serve as a useful shortcut.