Wiring schematic...2xvolume/2xtone/No switch

[NancyJohnson]

A few months back I acquired a Spector eight string bass, the active Tone Pump Junior circuit was just horrible, so I took it out and currently have it wired passive with both pickup going to the jack; more of a case of luck rather than judgment, it works fine, but I do have two dead tone pots that I'd like to reincorporate into the circuit.

I'd like to rewire having both pickups having independent tone controls and then combine this signal before it hits the output jack socket.  I've done the usual searches; I suppose this wiring is similar to a Les Paul, but without the switch.  Possible?

[BassBunny]

I think I've got a VVTT circuit on my pc somewhere. I'll have a check later.

It is pretty much s Les Paul circuit without switch but the pots might be different values as the LP has himbuckers.

[prowla]

I'd look at the Rickenbacker schematics and lose the switch.

http://www.rickenbacker.com/pdfs/19501.pdf

(Note that Ric wire the output to the top of the pot and the input to the centre/wiper; this reduces the interplay between the pickups respective controls.)

Edited May 9, 2020 by prowla

[ikay]

Jazz stack-knob VTVT wiring is essentially the same, just use 4 separate pots rather than 2 stacked. If the Spector has humbuckers you might want to make the vol pots 500k instead of 250k. See diagram below. Tone is on top, vol underneath. 

[prowla]

1 minute ago, ikay said:

Jazz stack-knob VTVT wiring is essentially the same, just use 4 separate pots rather than 2 stacked. If the Spector has humbuckers you might want to make the vol pots 500k instead of 250k. See diagram below. Tone is on top, vol underneath. 

What are the series 220k resistors for?

[ikay]

1 hour ago, prowla said:

What are the series 220k resistors for?

I believe they're there to stop the tone controls interacting with each other. If you remove them, the hot wire from each pickup has a clear path to both tone pots. A side effect is that they also attenuate the signal somewhat which isn't ideal. I'll see if I can dig up a schematic for a Ric as an alternative.

[ikay]

Here's the Ric wiring. I've tweaked it to take the switch out of circuit. The 4.7nf cap in the bridge pickup signal path cuts some bass which gives the characteristic Ric clank. Just remove it if you don't want that. Again you might want to change the pots to 500k for your Spector humbuckers. This circuit uses a stereo jack but you could use mono and just connect both hot wires to tip. It has no isolating resistors so there will most likely be some interaction between the neck and bridge pickup controls. Standard Ric wiring though so I guess it works!

[prowla]

1 hour ago, ikay said:

Here's the Ric wiring. I've tweaked it to take the switch out of circuit. The 4.7nf cap in the bridge pickup signal path cuts some bass which gives the characteristic Ric clank. Just remove it if you don't want that. Again you might want to change the pots to 500k for your Spector humbuckers. This circuit uses a stereo jack but you could use mono and just connect both hot wires to tip. It has no isolating resistors so there will most likely be some interaction between the neck and bridge pickup controls. Standard Ric wiring though so I guess it works!

Not all Rics have the treble cap (eg. the one I linked above).

Some of the current 4003 models have it switchable.

For a mono jack, the two hot wires run to the tip.

With the switch removed I guess you'd connect the pickups hot wires and the tone caps to the Vol centre tabs, rather than floating.

Edited May 9, 2020 by prowla

[NancyJohnson]

There's no caps in the cavity, so I've ordered some 0.047, along with some new cloth cable to join everything up.  Gonna be a few days.

Thanks for the schematic.

[NancyJohnson]

The volume pots are marked 500k, the tone pots are smaller in size, but unmarked.  I'll have to find out how to measure them.  

[BassBunny]

The tone pots will presumably be part of the tone pump circuitry so I would ignore them and just use 250k ones.

[NancyJohnson]

8 hours ago, BassBunny said:

The tone pots will presumably be part of the tone pump circuitry so I would ignore them and just use 250k ones.

The Tone Pump is/was a stock add on, the tone pots are just standard/normal potentiometers.

[BassBunny]

2 hours ago, NancyJohnson said:

The Tone Pump is/was a stock add on, the tone pots are just standard/normal potentiometers.

The tone pump is an active tone circuit, ( boost only IIRC ), and the treble/bass pots will be matched to that circuit.

You are going completely passive with 2 x treble bleed pots so they need a value that will do just that. The TP jnr pots may well be OK, but the most popular for what you want to do is 250k.