60s Stack knob Jazz Bass wiring?

[devnulljp]

I snagged a prewired stack knob Jazz Bass control plate a while back like this one with the resistors and caps on the pots.

The standard 62 JB wiring diagram doesn't match this setup though, and the only other one I could find was this one on TB

I wired it into my bass but the tone control on the bridge pickup doesn't seem to work. I've obviously done something wrong when wiring it in, so does anyone have a better wiring diagram?

 

[line6man]

The diagram you posted is the correct one. There is no "better diagram."

FWIW, the parts you have are junk. There is no reason to want carbon composition resistors or PiO capacitors in this day and age, unless you are dead-set on vintage-correctness.

 

[devnulljp]

OK, so it's the right diagram, and you have an opinion over the parts.
It still ain't working. I'll have to recheck the wires.

 

[RobbieK]

Hard to tell from that photo. Looks like there's an earth wire missing, maybe?

But there's a much better way to do VTVT. You'll need different resistors usually around 15K seem to work. And the wiring of the pots is more like standard jazz VVT. I can post a diagram later this evening if you like. Unless of course you need your bass to be as original as possible.

 

[line6man]

But there's a much better way to do VTVT. You'll need different resistors usually around 15K seem to work. And the wiring of the pots is more like standard jazz VVT. I can post a diagram later this evening if you like. Unless of course you need your bass to be as original as possible.

Yeah, that old fashioned VTVT scheme is pretty lame. You can get the same result, isolation-wise, from a much lower resistance, that wont kill so much output. Going with VVT Jazz bass style wiring could definitely allow you to drop the resistance even lower. I'm a bit surprised that 15k is all that it takes, though. That's fantastic.

If you go for the modern scheme, use good componentry! Carbon composition resistors are noisy, and PiO caps will leak or dry out, in time. You will want to use carbon film, or metal film resistors, and preferably a film-based capacitor of some sort.

 

[LoveThatBass]

I like a good Polyester cap. For bass I typically use .047uf (.050uf within the tolerance range). On the pot closest to the output Jack is the #3 wire lug that is bent backward toward the pot's case soldered to the case, The first pot definitely shows it isn't? Can't see evidence that it is. Looking at the back of the pot the lugs are 1, 2, and 3. Also, I know it doesn't show it on the drawing but I personally would connect a wire from the back of the case of the 1st (left hand as looking at your pictorial diagram) pot and connect it to the back of the case in the pot closest to the output jack. This will provide a good ground in the event the nut of the 1st pot got loose so things would not be intermittent during that time.

 

[devnulljp]

Hard to tell from that photo. Looks like there's an earth wire missing, maybe?

But there's a much better way to do VTVT. You'll need different resistors usually around 15K seem to work. And the wiring of the pots is more like standard jazz VVT. I can post a diagram later this evening if you like. Unless of course you need your bass to be as original as possible.

Sounds interesting. I'd love to see the diagram.
TBH, I'm not 100% sold on the stack knob thing, it's more of an experiment as I usually opt for V/B/T. Even my EMG-equipped jazz has a blend pot / master vol / master tone.

 

[RobbieK]

This is how I'd do it. Any resistors around 15K-22K should be fine. With typical pickups, 250K pots, and normal amp loading etc, 10K will give the least volume drop, but the tone pots won't be so isolated. But even with 47K resistors and well isolated tone controls, the volume drop is negligible. Certainly compared to the original. You'll also get a slightly warmer tone with both vols up because you don't get that true parallel coils sound. And if one vol is all the way up, you won't hear as quite much of that typical jazz bass abrupt tonal scoop as the other vol is rolled from 8 to 10.

The original stacked-pot jazz circuit has been discussed at length on this board. It's almost universally misunderstood amongst bassists and techs. I wrote a fairly long post on this maybe 6 months ago. Those 220k resistors are there to isolate the volume controls, not the tone pots. I'm pretty sure this was the first two pickup guitar that didn't have a pickup switch, so needed volume blending. A couple of resistors like this is similar to the way Leo combined the two channels in his twin amps, and how old mixing desks also summed their channels. But when he realized you could hook up the pickups to the wipers and do away with the resistors, the VVT circuit was born. (This is all just my theory of course!) I'm guessing they didn't go with something like my circuit because Leo realized that even with isolated tone pots, it's almost impossible to tell which pickup is having its treble reduced when both are turned up. Or perhaps it was a manufacturing cost reduction that also sealed the deal.