Identifying pickup wires

VomitHatSteve

Hat STYLE. Not contents.
So I recently came into possession of one of these things - a first act guitar with a built-in speaker. Seems like a good project for hacking open and seeing what I can do with it.

Turns out, they coated everything with white paint - wires and circuit board and all.
I'm thinking that my best bet is to hack something into the middle of the pickup circuit so that I can run other signals into the middle and see what kinda cool noises I can coax out of it.
So I've got one single-coil pickup with two wires going to it, both are black...
One is larger than the other tho. So the question is... which wire is which? Is there a standard for thin is ground, thick is live or something?
If possible, I'd like to ID all of the connections before I hack anything apart.

Also, am I interpreting this right that if I put a 1/4" jack in the middle of the hot wire that I could make a signal on that wire modulate the guitar's signal or vice versa?

Thanks.
 
If I understand it right, the pickup output should be ac, so there's not really a positive/negative. Each wire behaves the same and when you have one pickup you don't need to worry about the polarity.
 
Also, am I interpreting this right that if I put a 1/4" jack in the middle of the hot wire that I could make a signal on that wire modulate the guitar's signal or vice versa?

Thanks.

Yup..What easlern said.
With one single coil pickup it's just like having an speaker or dynamic mic capsule.
Polarity only matters if there's more than one or if there's chassis grounding.

Continuity check from the metal case, or mounting points, of the pickup to the end of each wire.
If one beeps, take that as ground. ;)
If neither beeps, go with whatever.

Also, am I interpreting this right that if I put a 1/4" jack in the middle of the hot wire that I could make a signal on that wire modulate the guitar's signal or vice versa?

Thanks.

I don't know about that.
Have you anything specific in mind? Any specific hardware or effect ideas?

If you want to feed audio in from another source and see what it does, Wire a 1/4" plug in parallel to the pickup, although I think I'd want a switching socket or a toggle to keep the pickup and input as separate options.
Don't really want an input signal feeding to the pickup.

Either that or break both pickup wires and have a two-jack send and return.
Simply pickup out and return in.

Keep instrument-level in mind when feeding any other sources in. If you have line level outputs on external devices you're going to want to attenuate that pretty heavily, I'd think.

If this thing has a built in amplifier you might be able to find a point on the circuit that will accept line level happily.
From the sounds of your description that might not happen, though.
 
Don't really want an input signal feeding to the pickup.
Oh it won't hurt anything. It might not sound very good. If you can find a way to get it in series with the pickup without too terrible much extra noise, it'll act as a lowpass filter and it'll kind of sound like it's coming through the pickup itself. If you put it in parallel, it'll technically make a shelving highpass or a kind of mid scoop, but I'm not sure it would actually have much effect on a lowZ active source.

But what happens to the sound from the strings when we do this? Well, it sure isn't going to be "modulated" in any interesting way. At best it'll be mixed in. I find it difficult to believe you'd hear anything in the series case, but I can see where you might in some situations. In parallel, the pickup will be so heavily loaded by the active output that your actual string sound will lose a lot of treble and probably some overall volume, and then whatever's left will be mixed in.

Either that or break both pickup wires and have a two-jack send and return.
Simply pickup out and return in.
Or a switched TRS "insert" jack. I'm not sure you'd have to "break both wires" here though. (???)

Keep instrument-level in mind when feeding any other sources in. If you have line level outputs on external devices you're going to want to attenuate that pretty heavily, I'd think.
A resistive divider would help to isolate the two sources and avoid some of the negative interactions between the sources that I was talking about above.
 
Good stuff Ashcat. Thanks for that.

Perhaps he doesn't need to break both wires?
I was thinking if he wanted to take the pickup to anther device like a pedal or processor but, to be fair, he didn't really ask about that. :p

If there's a common ground and one side of the pickup is tied to that then no..I suppose he wouldn't.

Interested to see what you do with this, VHS.
 
Thanks for the tips, everyone!

Pickups themselves aren't directional, the circuit they go into is, right?

So it seems like the best way to experiment with this would be... cut either wire and try running various combinations of jacks, pots, etc. in series and/or parallel with it?
There's no possible signal that I could put in that could damage the guitar itself, right? (assuming I keep the volume down so as to not blow the internal speaker.) And the guitar itself couldn't feed back a signal that could damage whatever I plug in?
 
Hi,
Yes, circuit wise the pickup doesn't doesn't need to be wired with a specific orientation but, as I said, if the case or mounting lugs are intended to be grounded and one of the wires is continuous with that, you should observe it.
Level wise, as long as you stay within instrument level I can't see why there'd be a problem.

Even without measuring, you could just record some DI guitar and play it back through a line output. Wire that line output into your circuit as you describe, attenuate it down to zero, then slowly raise it until the speaker is outputting your recording at what seems like a normal level.
If you want to be super safe you could clamp a limiter at whatever level you find but...yeah, I think you'd struggle to do any harm with line level or less.
 
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