Guitar wiring issue? 3-way switch problem?

pikingrin

pikingrin

what is this?
My first time messing with wiring inside of a guitar other than changing out a pickup or two. Wired up a 3-way switch (on/on/on) to a single DiMarzio Air Norton hb. The pickup sounds really good but it feeds back like crazy if there's even the slightest bit of overdrive on the amp. All the soldering was good, used .093 60/40 rosin core and all the joints were shiny so that (maybe) shouldn't be the issue.

There's an audible difference in tonal characteristics when the switch is moved between the 3 positions and I followed DiMarzio's wiring specs to the T as I was making the connections. Would there be anything in the wiring that I can check with a multimeter to double check and make sure that all the connections are correct? Could a faulty connection possibly be causing the feedback? Pickup height maybe? I did my research and checked the pickup height the best that I could with what I have...not sure it's "spot on" though. I'm not too terribly upset with the feedback...yet...but it doesn't seem right. I can plug another git into the same amp and any other HB pups don't produce the same feedback being played the same as the setup that I wired up.
 
Do you really mean feedback or is it actually noise? What does it sound like? Humming, buzzing, squealing? Does it change with the orientation of the guitar? Does it change if you touch the strings, bridge or jack plate?
 
The amps feed back, it's not really a squeal not really a hum...almost like an ebow effect. It happens without even strumming the guitar though, sitting on a stand with the volume knob on the guitar all the way open the amps start feeding back. If you hammer down on a note and hold it until it fades out, the amp feeds back. I'm not completely opposed to it but I'm wondering if it has something to do with my wiring job. Could be pickup height, too; I haven't adjusted it yet and it's a little low (I think).

Outside of that, the only other noise that the guitar makes (without being played) is a slight hum when the switch is in the middle position. That's when it's in coil split mode so that's to be expected.
 
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It's not string feedback? Mute the strings and it happens? Does it change when the guitar moves? Does it go away when you turn the V pot on the guitar down?

I suspect that pickup might be microphonic. There is nothing in the wiring of a passive guitar that can cause actual feedback. A hotter pickup and/or closer to the strings might make it break into string feedback quicker because the string sensing is just louder. I personally count that as a good thing. :)
 
Holy shit, this is the third time I've tried to type this out and have been kicked before it posts...

Room is approximately 10x13, guitar is opposite side of room from highest clean headroom amp I own (clean when you turn the volume to 10). Git sitting in stand, after a few seconds it starts feeding back from amp - no strings have been touched for at least 5 minutes, it's just been sitting in the stand. When I pick it up, feedback stops momentarily as I mute the strings. Without plucking a single string, feedback starts again, to stop if I hammer on to a particular string. If I hold the hammer on it starts spewing feedback in the tone of that note and it changes when I A)move my finger up and down the fretboard on that particular string or B)move the position of the guitar body in relation to the amp. It's turning into sort of a cross between the effect of an Ebow and the sound of a theremin at this point - even through a total clean amp at very reasonable volume.

I have done a bit of research on microphonic pups and it doesn't sound like that's the problem - I could be VERY wrong, depending on the sources (Seymour Duncan forum and a few random pages under that in the google results). Feedback happens even on clean settings and I have tried to speak/sing into the pup and that doesn't register with the amp. Everything I read on microphonic pups said that I could hear my voice through the amp and that it would feed back mainly only when the amp was overdriven. Again, I could be wrong. Would love the correction if that's the case.

I just find it hard to believe that this guitar, in stock form, was complete garbage. Now the body/neck is somehow more resonant when I redid the finish and electronics?!? No way. It's the same wood, slightly different color, less dense finish than originally there (slightly). :wtf:
 
K, so it is string feedback, and it must just be a louder pickup and/or closer to the strings. The wiring itself can't make that happen. Like I said, I wouldn't count this as a problem.

Edit - I didn't see the thing about the refinish. IDK if the slightly lighter finish itself would do it, but I'd imagine you took the whole thing apart when you did it, right? If you put it back together in such a way that the neck and/or bridge make better contact or are more solidly attached, that could make a difference.
 
ashcat_lt said:
Edit - I didn't see the thing about the refinish. IDK if the slightly lighter finish itself would do it, but I'd imagine you took the whole thing apart when you did it, right? If you put it back together in such a way that the neck and/or bridge make better contact or are more solidly attached, that could make a difference.
Click to expand...
Homing in on this point right here real quick... The guitar had a super thick finish on it, at least 3-4 mils (if not more), that took a belt sander to remove. This was neck and body, both. Go to your local shop and see if they've got an Epi LP spec II... Ridiculous amount of finish that doesn't come off with paint stripper. The neck pocket had a few pieces of fiber tape, which I assumed were there for some weird reason but, during my reconstruction, they mysteriously disappeared. Neck angle is still good but now, with my few layers of spar urethane - not even sure if that's a decent finish but I had it handy and it's gonna stay a beater - not even a mil thick at the most, there may be additional points of contact that weren't there before. I took it all the way apart and all the way down to bare wood before I did anything.

Like I've mentioned, this feedback issue isn't something that's irritating - it's confusing how such a cheap POS could turn into that with the cheapest "upgrades" I could do to this thing. It's going to be a matter of adjusting my playing style a little for this particular git to make sure the feedback stays in check (unless I want to use it for something), and I wanted to make sure it wasn't a problem with something I had done.

It's crazy; next to an American strat with a bolt on neck and TX special singles or a LP Studio with dual HBs (not coil split) this little LP acts nothing like either...

And, for what it's worth, I have to spread rep around before I can give you any more Ash...thanks for all your responses - I was hoping you'd have a go at this as you have, IIRC, some gits with those mini switches and I wasn't sure if they made any differences in the overall sounds.
 
Maybe one other thing that I haven't mentioned but may be a potential issue...maybe. As previously stated, I have never done much more on guitar electronics except a pickup change or 10. Never changed pots, never changed caps. I bought a prewired kit that included the pots and the cap all wired up. 500k pots with a .022uf cap in there. The thing that makes me a little curious is that in all of the wiring diagrams I looked at, it appeared that the tone cap goes from one leg of the tone pot to ground on the body of the same pot. The prewired kit I got, Emerson custom for an LP Junior, the capacitor is wired between the tone and volume pots. Is that right? It defies every single wiring diagram I have seen, even SD and DiMarzio shows the cap wired strictly to the tone pot...and it appears to be going from one leg of the tone pot through one leg on the volume pot and then grounded to the body of one or both. I have no clue about how these components work together, outside of the differences in pickups (again), so layman's terms are appreciated - tech speak is more than welcome though.
 
The short answer (cause I'm going to bed) is that it doesn't matter which end of the pot the cap is on.

Edit cause I'm back up and don't want to double post -
The somewhat longer answer is that a standard T control on a guitar is a variable resistor (not technically a potentiometer, but rather a rheostat even though it's the same physical part) in series with a capacitor. That series structure is wired parallel to the pickup(s) - between "hot" and "ground". You will always use the wiper of the pot and its counterclockwise lug. Sometimes the other lug will be tied to the wiper (it really is best practice) but doesn't have to be. When two (or more) components are in series, their order doesn't matter as long as there's nothing connected at their junction. Some folks say it's because in AC the electrons go back and forth, but it's true for DC circuits too. The current had to flow through both components either way, so it just doesn't matter.

If you were to listen to the junction between the pot and the cap, it would make a difference which came first, but you won't, so it doesn't.

While we're on it: in a guitar, the cap actually has very little to do with the filter action of the T control until you've turned that knob most of the way down. Most of the filter action comes from the inductance of the coil against the resistance of the pot. The cap comes in toward the bottom of the rotation to limit how low that filter sweeps (and keep it from going silent at 0) but ends up adding a bit of resonance at lower settings as it interacts with the inductance. So if you never turn the T pot down, the cap value really hardly matters, and it could almost be omitted. I always say to choose the cap value for your 0 tone, and pot size for your 10 tone.
 
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What you have done is increase the sustain on the guitar. That's a good thing.

You really shouldn't be able to leave the guitar on a stand with the volume open in the same room with the amp. Even though, I would have to assume, your amp is up pretty loud in order for it to get out of control when you are playing.
 
Ash, that gives me a good point to start researching a bit more. Thanks for all of the info!

Farview, the amp that I did my last test on was turned up about halfway. It was turned up about halfway, 5 out of 10. It was loud but not louder than bedroom volume but not loud enough to rattle the windows. For grins, I also tried my little fender Mustang I down in the living room. Volume stands at 3, low gain (bassman model, gain control at 2) and it does the same thing. I'm not sure how, but I guess I did increase the sustain.

Overall, I dig it so far. Still learning how to control it but it's a pretty cool little git now.
 
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