I have a double neck Carvin bass/guitar. It has 2 outputs & a 2 way selector to switch between the bass & guitar. The current 2-way switch has 6 terminals on it. It is wired such that on the guitar 1 wire goes to the pickup selector & 1 to the output jack. Same with the bass.
I want to be able to select either the guitar, the bass, or both. They each have volume controls for each pickup, tone control + coil splits.
I'd say what you need is just a single-pole double throw center on switch. This is the switch found on the millions of Gibson Les Paul's and SG's but I wouldn't use the official Gibson switch. It is huge and requires a lot of wood to be removed from the guitar body.
Are you sure about that? There is a DPDT On/On in there now. Guitar On/Bass On. A single pole would only have 3 terminals. 4 terminals are being used right now. 1 wire from each volume control (bass & guitar) and 1 wire to each output jack (bass & guitar).
Don't I need a DPDT On/On/On?
I wire Bass volume to top right terminal, Guitar volume to bottom left terminal. Bass to jack middle right, Guitar to jack middle right.
Thus I am not using the top left or bottom right terminals. Should this not give me what I'm looking for?
Up position - Bass Middle position - Bass + Guitar Down position - Guitar
Bass to jack middle right, Guitar to jack middle right.
I think you mean "guitar to jack, middle left"
I'm a bit unclear on what you intend here, and the Carvin diagram doesn't help matters much, it's more stylized than informative.
As I understand it, you currently have 2 separate output jacks, one for the bass and one for the guitar. Currently a DPDT switch selects either the bass output or the guitar output, but not both at once.
Correct me if I'm wrong, but you want a 3-position switch to allow both outputs to be active at once. Presumably, you want to do this so you can be a-bassin', and just move over to guitarin' without flippin' a switch.
You should consider that, with both outputs active at once, sympathetic vibrations from the bass will likely induce a signal through your guitar pickups, which will also be active in the mid position. And vice versa, if you're on the guitar- although the bass is probably more likely to cause an issue.
I'm not sure the resulting effect is going to be to your liking. I suspect Carvin had a good reason for the either/or setup they used.
But, to answer your question, and assuming I'm right about what you want here, you are correct, you need 2 poles to feed 2 separate output jacks. Wolf's way of using a SPDT center-on would result in the guitar and bass outputs being combined (and going to both jacks at once); I don't think he understood you were talking separate outputs.
Christian from El Ten Eleven modified his Carvin in a similar way. I talked to him about it, but he didn't do it himself so he didn't have specifics.
I put in the DPDT switch, however only one pickup each seem to work on both the bass & guitar and tone control doesn't work. I'm going to diagram out the wire routing that they had. Perhaps that will help.
I put in the DPDT switch, however only one pickup each seem to work on both the bass & guitar and tone control doesn't work.
Inserting the new guitar/bass selector shouldn't have affected any of these things. If your wiring of the new switch were a problem, you'd either get no output at all in one or more positions, or not get the output you wanted at a particular setting. Does the new switch work as intended?
Sounds like you may have joggled a connection (or a couple of connections) loose in the modding process.