Mmb-4 parallel/single/series switch

[Graham]

Hi, I've made the Stingray style bass and I've recently upgraded it by wiring in a switch that allows me to switch the pickups from parallel wiring, to bridge single coil, to series wiring. I used this wiring diagram: https://guitarelectronics.com/1-humb...outh-parallel/

It works in that I get three different tones. However, when I go to the single coil mode (centre switch) and tap on the pickup poles with a piece of metal I hear a loud noise from the bridge-side magnets, but also a faint noise from the neck-side magnets too. Shouldn't the neck-side magnets be completely silent if this is single coil? Have I messed something up in the wiring do you think? Incidentally, when I do go to the 'single coil' mode, there is no humming, so I'm still getting the clean humbucker sound, and it sounds thinner and more trebly than the other tones but with same volume as the parallel mode (series is loudest and most bassy). Is this the way it should be or should I rewire? Thanks for your help.

[fender3x]

It sounds like it is doing just what it should be. Loud click from one side, faint click from the other means you are in single coil mode. Thinner, more trebly *is* the single coil sound.

How much hum you get from a single coil has a lot to do with the environment. I find that when the compressor kicks in on the refrigerator in my studio (you might call it my "garage") I hear a hum. If you shielded, that also helps avoid hum. My experience has been that, while single coils are sometimes quiet, this is not reliable. At other times/places they will probably be noisy.

Series should be loudest, the fattest and darkest. Parallel should be a little thinner, with a bit more highs. Single coil should sound like parallel, but quieter and a bit better highs. If that's what you got--congrats! ;-)

[Simon Barden]

As above.

The faint click in single coil mode is because the metal (screwdriver, rod etc), is moving through the magnetic fields created by the pickup magnets and generating a small voltage, in the same way a string does. But it’s not vibrating like a string, so the actual sound produced is of a sub-sonic nature. Until the metal stops moving, at which point the generated voltage suddenly stops. It’s this sudden cut-off in the voltage which creates a large number of harmonics for a very short period (it’s effectively like the falling edge of a square wave) and a lot of the harmonics are at audio frequencies, hence the click. If you’ve ever used a DAW, you should know how any sudden start or end to a waveform through bad editing will produce an obvious audio click.

It’s a lot louder for the active coil as the metal movement is centred on that coil, but it will still sense the movement of the metal when fairly close by as well, just with less output. There is also an element of transmitted vibration as well. Tapping the pickup, even with some wood, will make a soft click. The vibrations move the coil windings slightly in the magnets fields, which generates a small sound. Same principle as microphonic pickups, but physical vibrations from direct contact are large compared to those transferred by sound waves, so even wax-potted pickups will make some noise.

[Graham]

Thanks for your replies and explanations guys, really appreciate it. I found the wiring difficult and really didn't want to go back in there, so you've put my mind at ease!

[fender3x]

I found the wiring difficult and really didn't want to go back...

You should feel pretty good that you wired this properly on the first go.

[Graham]

Thanks. It was one long and arduous go I guess. I'm not great at soldering (this was my first build) so it was difficult trying to get 2 wires soldered onto the small lugs of the switch. I just religiously adhered to that wiring diagram I put a link to on my 1st message. I'm really pleased with the outcome though and I'm glad it worked. There's so many wiring diagrams out there that are inconsistent with each other and sometimes unclear. I always wanted a stingray bass but they're pretty expensive so this is a substitute I'm happy with now!