Yes, you're quite right! And the CV Squier Mustang also has the two split sections of the older style Mustang small pickup w/o any J and so has no hum whatsoever..
Question tho: What about the newer Fender PJ Mustangs (that I'm becoming interested in)? Since they also have a split P pickup (full P size tho) over a J one, wouldn't that mean they also suffer from HUM??? ~And taking this a bit further, wouldn't all PJ basses also have hum then too??
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Those are valid questions, all of them.
I thought that we covered this upthread, but it might have been in another thread.
Anyway, the original USA design is different for the two sizes of split pickup.
The Mustang split pickup, though it came later than the Precision pickup, is of a simpler design.
We have two identical halves, wired out of phase externally to cancel hum, and since each string only activates one or the other half of the pickup, the phase does not of the signal matter.
But if we try to add another pickup, half of the split pickup will be out of phase with it, so for the Am Performer, Fender lazily solved this by wiring everything in phase, so there became hum from the split pickup.
The design of the Precision pickup tackled the situation in a more complex manner.
Each half of the split pickup is NOT constructed the same as the other, and you need one of each half to make a whole pickup.
In the two halves, the wire is wrapped in the opposite direction on one half, and the magnets are facing the opposite direction, but the pickup halves are wired externally in phase.
This results in hum cancellation, but the signal from each half remains IN phase with the other, so if we add an extra pickup as in a typical PJ bass, the signals are all in phase.
However, since a standard J pickup is a single coil, it will notice hum when soloed, if there is any in the room, regardless of what other pickups are on the instrument.
I should add, that info has been posted on TB, that on Japanese Fender Mustang basses, and on Squiers, if there is a small Mustang split pickup, it seems to have been designed like a P pickup, instead of the Mustang way.
Not sure about the JMJ in this regard.
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