3-Way Switch on Jazz Bass

thegummy

I feel fairly confident I know the answer to this but just to be sure, hopefully one of our experts can confirm:

If I installed a 3-way switch on a Jazz bass going in to a single volume and tone pot; when in the middle position, would it be exactly the same as a normal Jazz wiring with both volume's up full?

Or would there be a difference, even if slight?

ICBM

There will be a slight difference - a Jazz with both volumes up full has a pickup load of 125K, both 250K pots in parallel. Changing that to 250K will make it a bit brighter.

Actually, because of the way the pots are wired, even a stock Jazz with one pickup turned fully off has a load of 125K on the other one.

Funkfingers

In theory, both pickups selected by the switch should be the same as the original circuit with both volume pots turned up to maximum. 

I would expect the loading effect of a pot per pickup will be greater than when both pickups pass through a single pot.

The real world answer is to try the mod and decide whether its advantages outweigh any disadvantages.

TBH, there are very few occasions when I would use a single J Bass pickup by itself. (PJ pickups would be a different matter. So would one Fender pickup and one Oil City Overkill.)

thegummy

ICBM said:

There will be a slight difference - a Jazz with both volumes up full has a pickup load of 125K, both 250K pots in parallel. Changing that to 250K will make it a bit brighter.

Actually, because of the way the pots are wired, even a stock Jazz with one pickup turned fully off has a load of 125K on the other one.

I thought there was a chance that would be the case.

Unfortunate.

Any workarounds? Do 125k pots exist?

thegummy

Funkfingers said:

In theory, both pickups selected by the switch should be the same as the original circuit with both volume pots turned up to maximum. 

I would expect the loading effect of a pot per pickup will be greater than when both pickups pass through a single pot.

The real world answer is to try the mod and decide whether its advantages outweigh any disadvantages.

TBH, there are very few occasions when I would use a single J Bass pickup by itself. (PJ pickups would be a different matter. So would one Fender pickup and one Oil City Overkill.)

Same here but there's even fewer occasions I'd use either of the volume controls at a value between off and full.

That's why I considered doing it really, so I could turn the volume down with only one knob rather than 2.

Funkfingers

My default setting is bridge PU up full, middle pickup down between a quarter and a third, to get the comb filtering honk. From there, I extract sonic variety by where my picking hand contacts the strings.

ICBM

thegummy said:

Any workarounds? Do 125k pots exist?

100K ones do - you could look for a slightly high-tolerance one, although it's probably not very important since the tolerance is that wide for a good reason.

Or just wire a 220K resistor in parallel with the pot.

thegummy

Thanks a lot, cheers.

ICBM

To be perfectly honest the two separate volumes are worse than useless to me, since you have to turn them both down by the same amount to maintain the both-pickups sound and hum cancellation. I'd be happy with a Jazz with only two sounds - both pickups, either in parallel or in series. The only two sounds I've ever used on one are both pickups up full, and the neck pickup with the tone turned fully off for a fatter sound with fuzz, which would be better as series since it would then be hum-cancelling.

normula1

how about a blend pot? My cheap and shoddy bass came with two vols and master tone and it being a pet hate of mine the first thing I did was to change the second vol to a blend and rewire the remaining as master vol. Works well enough for me, but then again I'm no real bass player..... never even changed the strings on it despite having a spare set that have sat in a box for at least 10 years

thegummy

normula1 said:

how about a blend pot? My cheap and shoddy bass came with two vols and master tone and it being a pet hate of mine the first thing I did was to change the second vol to a blend and rewire the remaining as master vol. Works well enough for me, but then again I'm no real bass player..... never even changed the strings on it despite having a spare set that have sat in a box for at least 10 years

Hmm would a blend pot contribute to the load and sound the same as a default Jazz? @ICBM ?

ICBM

Depends on how it's wired and the pot taper - if it's a true dual-gang balance pot then it should have two half tapers in parallel, so you would actually want a dual 500K to give a combined load of 250K, which would then give you the 125K when added to the volume pot. If it's a simple single-track mixer pot (ends to the pickups, middle to the volume) then it doesn't actually add to the load at all.

Personally I dislike balance pots too, for me they only have three useful settings so you may as well - and more easily - use a switch. I don't find the sounds just either side of centre useful, and they very quickly become not noticeably different from just turning one pickup off. I prefer to set the correct balance using a slightly overwound bridge pickup and adjusting the heights, and leave it at that.

The only reason I would want three knobs on a Jazz at all is just for the traditional look - but I'd rather make the middle one a rotary switch.

normula1

Mine's a dual gang