Wiring Help -- BTB Pickup, Jazzmaster

[benjaminr]

Hi there!

This is my first post and first project. I have never wired a guitar before, so I was hoping someone could either verify that my proposed schematic will work, or if it won't. If it won't, maybe a few tips would be helpful. Here goes...

I just dreamed up this wiring schematic for a BTB (behind the bridge) pickup set up on a Jazzmaster and was wondering if I could bounce it off a few of you. Disclaimer: I have no idea what I'm doing.

The idea is that when the upper SPST switch is in the 'down' or 'off' position, the rhythm and lead pickups function normally using the master volume and tone controls. In the 'up' or 'on' position, the rhythm and lead pickups still function normally with their own dedicated volume and tone controls, and the BTB pickup is engaged with dedicated volume and tone controls as well. This way, I can either get only the BTB pickup to function by rolling down the lead volume of the normal circuit, or I can blend all three pickups by adjusting each of their respective volumes and tones.

I know that was long-winded, but this is my first attempt at something like this, and based upon my marginal knowledge of switching and circuits, this schematic *appears* like it would work as described above. Lastly, I'm not sure, but I *think* my upper volume and control pots are wired correctly...

EDIT* Just noticed I don't have a ground on that upper volume pot...

Here it is:

 

[David Collins]

Re: Wiring Help -- BTB Pickup, Jazzmaster

As it is you would not be able to get the BTB pickup entirely on it's own, as the standard volume / tone controls are wired for master. Wiring them as independent (coil to center, output to upper lug) would solve this issue, but would introduce others which would not be worth it in my opinion. Wiring the standard volume as independent notably changes the taper of the control as you roll back, and attenuates the high end in a way that can't be recovered with a treble bleed circuit.

You could wire it this way and still roll back the main volumes and bring the BTB/main output ratio to around 80/20 or so before killing the overall volume, which in my opinion would be a better alternative to the impact on the main controls if you were to wire them independent. Or if you do want the ability to use the BTB pickup you may be better off with a SPDT switch so you could select either or both. I may still be inclined to leave the BTB volume wired independent as it is, given that rolling it in or out to varying levels while not affecting overall volume in the "both" position could be greater priority over keeping a consistent tone when fading it out on it's own.

Long answer, but I guess all I'm saying is that I would leave it just as is, but make the upper switch a double throw with center on if you ever anticipate the need to use the BTB pickup in it's own (never played much with these, and not really sure if you'd ever find that as a useful tool).

Edit: I also realized your tone cap a wired to the wrong lug of the upper controls, and the red wire connectiong tone should be to the center lug of the upper volume.

 

[benjaminr]

Re: Wiring Help -- BTB Pickup, Jazzmaster

Long answer, but I guess all I'm saying is that I would leave it just as is, but make the upper switch a double throw with center on if you ever anticipate the need to use the BTB pickup in it's own (never played much with these, and not really sure if you'd ever find that as a useful tool).

Wow, super useful info there--I really appreciate it. I didn't know that the way the pots were wired could be 'master' or 'independent' or that independently wired pots cause severe tone loss.

I'm a bit confused though--I don't think they make SPDT on/on/on, only on/off/on. However, If I were to use SPDT, couldn't I have the up position be the BTB only, the middle be a mute/kill, and the down be normal circuit only THEN have a SPST toggle between the lower volume pot output and the output jack. That way, when that toggle is engaged, I can have both on in the up position. Does this make sense?

SPDT Up, SPST mini toggle off: BTB only
SPDT Up, SPST mini toggle on: Both
SPDT Middle, SPST mini toggle off: Mute
SPDT Middle, SPST mini toggle on: Normal circuit only
SPDT Down, SPST mini toggle off: Normal circuit only
SPDT Down, SPST mini toggle on: ...normal circuit only... two outputs engaged? explosion?

In other words, there's no way to wire (that I can come up with) an SPDT to have the up be BTB only, the down be normal circuit only, and the middle be both.

Thanks again.

EDIT*

Here are two updated versions of the original, SPST, circuit. One for both independently wired (ill-advised), one with the BTB independent and the normal circuit as master.