Doubleneck wiring

[billbassman]

I have built a P-bass/ Strat doubleneck on a Warmoth body. Std. controls for each neck, all fitted into a strat control cavity via one 250K pot (strat vol ctl) and 2 500K concentric pots (top are strat tone ctls, bottom are P-bass vol & tone). All terminate at a stereo (TRS) jack. The problem is that the VC's are interactive (e.g., turning down the strat vc slightly actuall INCEASES the P-bass volume!) and neither one increases or decreases the volume smoothly. There is a rapid drop-off that leaves about half of the pots sweep useless. I want to use it mono or split into two amps, a la Rick-o-sound, but this has got me stumped. I own several different doublenecks and none has this problem. Any ideas? Thanks! - Bill

 

[Rickgrxbass]

Do the different necks go to different parts of the jack, ie one goes to the tip and the other the ring?  If that's the case then using a standard mono cable will cause the necks to be wired in series, like a jazz bass, so the volumes will behave in the manner in which you described.  I'd use separate outs, or at least a hard 3-way switch to select the necks.

(edit: fat fingers)

 

[dbw]

Do you really want to have both necks active at the same time?  If you don't, install a DPDT switch between the necks and whack it when you switch.  That way the controls for one neck will be totally decoupled from the other.  The famous SG doubleneck was set up like this.  (If you have the Led Zeppelin DVD you can see Jimmy whack the switch right before he goes into the solo on the 6-string during Stairway.)

So that's one option.

If you want to have both necks on at the same time you'll either have to (1) rewire the volume pots like a Jazz bass, which will change the response of the volume controls, (2) use a stereo jack and cable and build some sort of splitter box to send the outputs from the necks to different amps, or (3) have separate jacks for each neck.

What sort of amplification are you using?  If you have a Bassman or something I'd vote for (2), otherwise I'd say (2) and (3) are equally good.  Option (1) kinda sucks, IMO.

Personally I'd go with the switch... unless you want to do stuff like hit a harmonic on the bass while you play a riff on the guitar.

Can you give us some more info about what you're trying to do?

Also, can we see it?  I don't think I've seen a doubleneck on this forum yet!!  :icon_thumright:

Edit:  Of course instead of a 2-position switch you could use a 3-way switch like Rick suggests.  Then you could occasionally go to the middle position if you wanted to do shenanigans, and you'd only have to deal with the strange volume swells in that position.

 

[tfarny]

Not 100% sure I understand your wiring scheme. Posting a schematic might help us help you. Do both hot outputs terminate at the same point on the jack? If so that would be your problem I believe. You should use a stereo jack and each neck's out needs to go to its own terminal. Then when you use a stereo Y cable you should have 100% separation, if not then maybe a short somewhere. That's my 2c.

Also, do you really want them both on at once? I mean if you've got four arms that would be totally badass (and I wanna see pictures of your band!!!!), but in playing situations, the one you're not playing would just produce annoying noise, wouldn't it?

 

[DiMitriR33]

ok i'm with tfarny, post the diagram! or some good closeup picks of the completed wiring!

for this to work with a stereo jack you must use a common ground at minimum. with the concentric pots it will have a common ground regaurdless. if you used the tip for one neck and the middle ring for the other then a mono cable would short out one neck completely and it's controls wouldn't do anything. a stereo Y-cable is needed for this as are two amps and if done right one neck will work independently on the other. if both necks have hots connected to the tip then turning down one necks volume will short the other neck out and decrease it's volume by nearly the same amount. you can wire the volumes up backwards like a fender bass with two volumes but there will be some tonal change as the volume is rolled off probably more noticabe on the guitar neck. if this is the way you wired it up then the neck not being used is becoming a load, this would not be noticed if the pickups were atached to the same strings as the other pickups would provide power but since it is not attached to the same neck the other pickups look like an inductor coupled to ground giving another path for the electricity and cutting power. also with both volumes at 10 the tone controls will all work as one. in this case you just have too many knobs to be usefull.
using two jacks or a stereo Y-cable and separate standard diagrams or a with two amps is the only sure way to do it.