Sanity-check my wiring?

[GregP]

End goal: EMG 89 and 81TW, 2 Volume, mode-switchable ("coil-tappable" but not exactly) via push/pull on the volume knobs.

What I have

- two dual-mode EMGs, an 89 and an 81TW. Their respective wiring is the same.

- two push/pull 25k pots, and a normal 25k pot. I have an appropriate capacitor to use one pot for tone if need be

- the older incarnation of EMG wiring... the pickups themselves have the quick connector end, but the other end (and the pots) are not quick-connect, so I'll need more or less traditional wiring diagrams. For all intents and purposes, the quick-connector is a pickup-changing convenience, not a wiring convenience.

- a Gibson-style 3-way toggle

My desired approach

As mentioned, I would go with 2 independent volumes (NO tone), with each pickup hitting a push/pull-equipped knob for mode-switching ("coil-tapping", but not exactly) duties. HOWEVER, my understanding is that with "typical" wiring, in the middle position, you can't "blend" the way you might think. So you have to use a Jazz Bass-style wiring, which I THINK is the kind of wiring used in one of my samples below.

Sanity Checking needed!

I believe I have hacked together some information, but truth be told it's kind of just trusting that my superficial understanding of things is enough. I don't TRULY understand what happens in a potentiometer and I'm taking EMG's word for it on how to wire up the push/pull.

Speaking of which, for the push/pull, the main diagram I come across is this one:

Is it a proper assumption that the empty lug is what will get wired up to the switch?

There was no one exact diagram (if you find one or know better ones, let me know!) but I did come across this:

Here's where the sanity check comes in! Using this diagram as a jumping-off point, my thinking is that I substitute the white that's coming directly from the pickups to being the output of the push/pull. Then I bypass the tone altogether, sending the switch output directly to the output jack.

Assuming my ability to mentally re-arrange things in 3D space, I believe the diagram also confirms that the "empty" lug from the first diagram is indeed connected to the switch (the orange and blue in the diagram).

So... any takers on a sanity check? Including confirmation that the volumes will not suffer the "in-between" problem of allegedly independent volume knobs? Any opinions on a better setup that uses only 2 knobs? I'm not totally against going master volume plus tone, but that option had me even more confused (and isn't my preference anyhow) when I went looking.

Thanks!

 

[curtisa]

12 minutes ago, GregP said:

Is it a proper assumption that the empty lug is what will get wired up to the switch?

Yes.

 

13 minutes ago, GregP said:

Here's where the sanity check comes in! Using this diagram as a jumping-off point, my thinking is that I substitute the white that's coming directly from the pickups to being the output of the push/pull.

You can consider the first drawing (with the push-pull) as the equivalent "block" of what you should substitute for each volume pot and pickup white wire.

 

14 minutes ago, GregP said:

Then I bypass the tone altogether, sending the switch output directly to the output jack.

Yep.

 

15 minutes ago, GregP said:

I believe the diagram also confirms that the "empty" lug from the first diagram is indeed connected to the switch (the orange and blue in the diagram).

Absolutely.

 

17 minutes ago, GregP said:

I believe the diagram also confirms that the "empty" lug from the first diagram is indeed connected to the switch (the orange and blue in the diagram).

Positively.

 

17 minutes ago, GregP said:

Including confirmation that the volumes will not suffer the "in-between" problem of allegedly independent volume knobs?

Completely

 

18 minutes ago, GregP said:

Any opinions on a better setup that uses only 2 knobs? I'm not totally against going master volume plus tone, but that option had me even more confused (and isn't my preference anyhow) when I went looking

That would necessitate splitting one EMG on a push-pull volume and splitting the other EMG on a push-pull tone, but could still be done if you don't mind using the two "unrelated" pots to do so. However, splitting both EMGs simultaneously on the same push-pull probably won'twork. You need one switching element per EMG.

[GregP]

Man, thanks for your help! I'm going to draft up a completed diagram from the pieced-together info for a final sanity check and for my own reference.

[GregP]

Something like this, then:

 

[GregP]

Had a small follow-up question. If you'll recall, I had another thread in which I was considering adding a separate piezo preamp into the mix. Forgetting about blends and switches and stuff and imagining I'm tying it directly to the output jack as a first experiment:

Assuming the piezo preamp has red for hot and black for ground, to share the same battery it should be a simple matter of adding its red wire to the same spot as the EMG reds, and its black wire to the same spot as the EMG blacks, yes?

[curtisa]

Assuming the split-EMG diagram you originally provided is correct, I can't see anything wrong with your wiring diagram. Only suggestion is to consider grounding the two cases of the volume pots, otherwise you may find you get buzz if you reach for a volume pot knob and you aren't simultaneously touching the strings. Also not shown on your diagram is a ground wire to the bridge, although I note that EMG suggest that it isn't necessary for their pickups.

 

16 hours ago, GregP said:

Assuming the piezo preamp has red for hot and black for ground, to share the same battery it should be a simple matter of adding its red wire to the same spot as the EMG reds, and its black wire to the same spot as the EMG blacks, yes?

Yes, although a bridge ground may be necessary for the piezo for buzz reduction (as per above). Also bear in mind that the 18V mod may not be compatible with whatever piezo you end up using.

[GregP]

Thanks again Curtisa. I mentally noted the casing and bridge grounds but I haven't come across diagrams that show them so I figured it was a "given". That said, I think I'll add them in for completion. ;-)

Piezo preams don't generally need the bridge ground; their most common application is in acoustic bridges. And one of the joys of piezo pickups is that they're not terribly susceptible to 60-cycle hum or EMI.  Not sure if I'm going to use a bridge piezo element yet. I have 3 circular piezo elements tied together that I'm going to affix to various locations in hopes of picking up some vibrations. Might add a bridge, though, and do all 4.

Definitely agreed that the piezo preamp might not play well with the 18v mod. After researching a "real" solution and finding the price tag too high, I decided to give this experiment a try more or less on a whim. The preamp is a $9 endpin jobbie from China, so my hopes aren't super high. The entire guitar is meant to be a frankenstein weirdo thing anyhow, so I didn't want to bother going top shelf. The plan is to affix the piezos but use alligator clips for a proof-of-concept. If the 18V either doesn't work in general or damages the piezo preamp unit, I will consider it a failed experiment. No huge loss. I just like to mess around. ;-)

Thanks again for the eyes and the suggestions!

 

[GregP]

So, the wiring diagram is confirmed working!

It turns out that the previous owner of the electronics had the ground lug already wired to the casing, so I went ahead and just connected it the casings to each other and then to ground. If I use copper foil for shielding the cavity, I might desolder the redundant wires, but it wouldn't be killing anyone to leave it, either.

Had a moment of panic last night-- after my last wire was soldered, I brought the harness to an amp, then used a guitar and put the pickups near the strings to see if it all worked. It did not. Fiddled, flipped switches, and nothing. Became worried that I had bum pots or (worse yet!) pickups, but it was late so I went to bed.

Got around to it tonight. Busted out the continuity checking mode on the meter, and started looking for shorts. It didn't take long to discover that my output jack had a short in it. I (stupidly? Is there actually a best practice for this?) soldered the jack with the lugs pointing up, and probably used a bit more solder than I really needed. Some must have flowed down and around and created an invisible short.

Thankfully, I had a spare stereo jack. Didn't have to try to salvage the shorted one.

Soldered more carefully this time (and with the lugs pointing down), plugged it in, and I was off to the races! Tested the volume knobs and the mode switching, and it all seems to be working. I did NOT install the 18v mod yet (don't have a 2-way switch on-hand) but I can't imagine there will be any difficulties there.

Here's an updated diagram with the optional grounding noted, and showing ground symbols instead of the literal representation of the star. Not sure if anyone will ever have any use for it, but you never know!

EMG 89, EMG TW, 2 volume, no tone:

[curtisa]

Good job that man.