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Excessive noise


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I'm a newbie to the group and a novice to guitar building. I'm finishing up a p bass project with a humbucker single coil pickup. When I plug in I get a hiss when I touch the strings .  Any advice on solving this problem? Volume and tone Pots, wired with cat5 22 gauge wire. Multi strand to the pickup. Bridge is grounded. Should the 2 pots be grounded together? Thanks in advance.     

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Hello and welcome!

First, what is a humbucker single coil pickup? For what I've learned, a humbucker consists of two single coils that are wound in opposite directions to cancel hum while a single coil is simply a length of wire wound around a magnet which is sensitive to 60Hz hum. The Chinese web shops often seem to put all possible descriptions to their ads without actually understanding what they mean. That said, hum cancelling single coil pickups do exist but they aren't called humbuckers, they are rather called "noiseless" as the construction is different.

I had a somewhat similar issue with a guitar with two single coil P90's. As said, single coils hiss by nature but if the grounding is properly done, touching the strings should damp it down. Mine didn't, yours don't... First I blamed the switch and a different wiring scheme helped a bit but not enough. Finally I took another look to the jack and lo and behold the ground wire went to the tip instead of the sleeve! And you can believe I had triple checked the order of the lugs. Swapping the wires at the jack was a simple task and the extra hum was gone.

As per grounding, everything in the signal chain should be grounded to the sleeve of the jack one way or the other. A common way is to run a wire (even bare metal can be used) from pot top to pot top with one of the tops being a "meeting point" from where the wire to the jack sleeve finally goes. Another good method is to use a metal plate as a common ground at the bottom of the control cavity - the housing and the shaft of the pots are all the same groundable mass, only some of the lugs are connected to "hot".

I took a look to P-bass wiring diagrams and quickly found one without a ground wire going from top to top. There's nothing wrong with that either, the other pot gets grounded through one lug. Utterly simplified the entire signal chain is just a loop from the hot to the ground through various components like pickups, pots and caps, and optionally a switch changing the route. Even in a pot there's an internal path from hot to ground, same goes for pickups.

All that said, check your jack wiring!

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54 minutes ago, davhi888 said:

The pickup I am using does have 2 coils

Silly me, of course that pair is a humbucker. Well, at least most likely. I didn't think about that, I just looked at the single rows of poles,

Yes, that's the diagram I saw without a separate ground wire between the pots.

Let's hope it's something as simple as swapped jack wires!

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if you are getting his when you touch the strings... r u sure you didn't wire your output jack backwards?  double check that.  make sure the neg is going to the ring and the pos going to the tip.  also make sure it isn't making contact with anything.  

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