Am I the only person without a badly grounded G&L bass? I've had 7 and none of them ever hummed in the slightest. Weird.
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I guess you've already checked for a grounding issue?....within the bass itself, somewhere in the chain, or even the power source?
Barring that, I'd maybe send it back to G&L. My MJ-4 is quiet as a mouse, even with a compressor switched on.
Wow! This afternoon I'm comparing the inner wiring against my Tribute M2000 which is dead quiet but seems very similarly circuited. I'm not the only MJ-5 owner on this thread with the same issue, so I'm inclined to think it's not a one-off problem.
Is it my imagination, or are all these hum issues happening only in 5ers? Could it be due to an imbalance in the split coil 5 string pickup? Just an uneducated guess, but the reason 4 string split coil basses don't generally hum is that the coils are arranged with opposite polarity. This sets up a phase cancellation. Grounding issues or electromagnetic interference are, of course, other sources of hum. I've never had a G&L bass that hummed, but then again, I play 4-bangers.
Does a split-coil 5er have true phase cancellation? Seems like 3 versus 2 (as opposed to 2 versus 2) might not be fully humbucking.
??
That sounds like the bridge ground has gone high resistance. I've had to re-make the ground connection on both my L-2000 and L-2500. They are both silent now. See here for details.
Had a read through. I'm inclined to think that isn't the issue with my MJ-5. Just got my ohm meter and recorded the following values:
(i) USA L2000 (unplugged), resistance between jack ground and bridge: 0 ohms
(ii) Tribute M2000 (unplugged), resistance between jack ground and bridge: 320 ohms. Note: this is similar preamp and wiring to the MJ-5.
(iii) USA MJ-5 (unplugged), resistance between jack ground and bridge: 0 ohms
So the bridge ground is really good on the L2000 which is quite quiet, *and* on the MJ-5 which hums badly.
I don't know what to make of the relatively high resistance between chassis and bridge ground on the (quiet) M2000. But because there's a similar wiring architecture between it and the MJ-5, I'm thinking that the difference between the two is an indicator of something. [BTW, the wiring harness in the MJ-5 is very tidy, with wires just long enough for the job. In the Tribute M2000, there's a *lot* of excess wire which has been pulled together and zip-tied. At some point, I'll cut the zip and try to sort out wiring differences between the two, but I do notice one extra black wire coming from the neck pickup cavity in the M2000, over and above the white/green pair coming from the pickup cavities on both basses.]
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If the resistance is more than zero I remake the bridge connection because it is failing. I have no idea what value it can go up to before you start getting problems when you take your hands off the strings. I currently have an old P clone as a project bass and it would be very easy to add range of resistors to find out at what value the problems start.
My guess (and it is only a guess because I don't have your bass on my bench and have never had my hands on an MJ-5) is that your's is suffering from single coil hum.
There are some wiring diagrams for all manner of G&L basses here if they are any use to you.
Hmmm...nothing from the M-series in those diagrams. So the humming MJ-5 has zero resistance and the non-humming M2000 has 320 ohms. If what I'm getting is single coil him, it should be mitigated in center blend with common mode rejection. Makes me wonder if one pickup is not reversed properly, and I'm getting the Rickenbacker hum all the time experience. I would have thought these fancy pickups wouldn't hum like this.
There is the M-2000/M-2500 diagram about half way down
It should possible I would have thought to find the point where the hum cancels out, but as I say I have never had my hands on one so am only guessing.
Jazz pickups are jazz pickups (i.e. single coil) and pick up all magnetic fluctuations including stuff you don't want unless you can match them exactly to make a wide spaced humbucker and cancel out the common mode stuff (interference). I cannot see that the MJ-5 pickups are going to be any different in that respect to any other jazz pickups, they are only a row of magnets (or pole pieces) with a single coil of wire round them.
Out of curiosity, I looked up the MJ-5 specs. The pups are said to be hum-canceling, not single coil. Hmm. Three versus two poles? Starts to sound plausible if the bridge ground is good.
SirMjac28
Patiently Waiting For The Next British Invasion
Just received my L-2000 this morning and all I have is..........drool
It's possible that as nice and neat as the wiring appears there's actually a mistake somewhere. My new SB-1 had a silly wiring error right from the factory.
I clamped down the bridge pretty tight recently, think I broke the connection while trying to secure the bridge?
If the noise goes away when you touch the strings, the bridge ground works. Any possibility that the pickups are wired backwards? If the start end of the coils is connected to + they'll be much noisier.
Check the resistance between the bridge and the ground side of the jack. Should be zero.
Nah it hums when I take my hand away on any setting. I'll pull out the multimeter tomorrow and give an update before I pull out the guts to try taping.
The diagram's very good. I'm going to do a careful comparison tomorrow and see if there's a wiring defect. Thanks!
