Wiring of double-neck basses

Discussion in 'Pickups & Electronics [BG]' started by MrWalker, Feb 3, 2014.


  1. MrWalker

    MrWalker

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    I've got a Clement double neck 5-string fretted/fretless, and I'm not totally happy with the wiring layout currently. Right now, the pickups are wired to the two-way switch, and then everything goes through a Nordstrand 3-band eq. So in other words, flipping the switch swaps necks and retains the same setting for pickups and eq. Which works perfectly for the use Tom had in mind when he designed the bass.

    However, the way I plan on using the bass is for looping, where I'd like to swap and do phrases on each neck, and this means the swap has to be quickly done... I won't have the time to change settings in between the switches.
    In addition, I feel that the settings I use for fretted are different than for fretless... different pickup blend, different eq settings....

    So I'm thinking about how to rewire this from scratch.

    The idea I'm playing with right now is to have two separate circuits for each neck to separate outputs, and then use a foot switch to jump between necks (or actually have both open). This would allow me to have completely individual settings on both sides.

    But it would of course also be convenient to have everything onboard with a switch... So you can just plug everything into your amp and go.

    Any thoughts, idea, experience on this?
     
  2. lz4005

    lz4005

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    Be careful if you wire the necks to separate outputs. There can be grounding issues.

    That being said, I've played a couple of Carvin doublenecks from the 80's that basically used a modified Ric-o-sound wiring setup so you could either send the output of each neck to a separate jack or blend them into one.

    It might be helpful to look at wiring diagrams for single-neck instruments with piezo and magnetic pickup systems that can be split to different outputs or combined for inspiration.
     
  3. MrWalker

    MrWalker

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    That's a good point.. that would be an excellent solution, to be able to do both... Actually, that's pretty ingenious!
    I do have a Epiphone acoustic electric that has this feature... it has the magnetic and piezo pickup, and allows both to go to one mono output, or split it in two outputs....

    Thanks for the advice, that's very helpful!!!
     
  4. MrWalker

    MrWalker

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    Right now I'm thinking of simplifying the entire setup... running Master volume and balance for each neck to a stereo output, and then running each signal through dedicated booster/eq pedals and into a A/B/Y foot switch. That would be really clean and really simple on the wiring, and offer a great deal of flexibility on the sound mix.
     
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  6. line6man

    line6man

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    The easiest thing to do is just use a three-way switch to select outputs.
     
  7. RobbieK

    RobbieK

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    I've wired a few instruments like this. In my old job I wired a twin neck acoustic guitar at one stage.

    I can't imagine you'd need both necks on at the same time, so a three-way switch is no good. I would sum the outputs of each preamp together with a couple of resistors, then have a SPDT switch with earth on the middle lug. This silently switches from one to the other by muting alternate signals.

    I think you should use stacked pots for the preamp tone pots. This way you could have both trebles together, both mids together etc. You could easily adjust both at the same time, or individuals. You could do the same with the volumes. You can easily get stacked 50KB and stacked 25KA pots on ebay.
     
  8. RobbieK

    RobbieK

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    PS: sounds like a pretty wild bass. I think we might need some pics! :)
     
  9. MrWalker

    MrWalker

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    Mobile client won't allow me to upload photos it seems :)

    Can you explain what you mean about summing up the output from the preamps using resistors?

    There are actually a few times I'd consider having both neck outputs open. One for adding ringing notes from one neck, possibly using a spider capo, and the other where you are tapping both necks.

    The only downside with a switch on the bass is the speed of swapping necks. I'm doing some looping tracks and being able to move the hands without having to also flick the switch is required sometimes. So a footswitch has it's advantages. :)

    Thanks for your input, though. Would be interested in hearing about the resistors :)
     
  10. MrWalker

    MrWalker

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    Here's the bass in question:
    [​IMG]
    [​IMG]

    The more I'm thinking about it, the more convinced I'm getting that wiring it passive with dual outputs through a stereo jack and using my A/B/Y foot switch is the best solution. In any case, it's the simplest solution and if I decide to move the switch back on board again, it all builds on the passive wiring I already did with this solution. So I think I'll try it first, and then we'll see from there :)
     
  11. RobbieK

    RobbieK

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    Nice looking axe.

    So five knobs and a switch... Yeah with two 3-band preamps, even with stacked pots, you'll need 6 knobs as you can't have stacked blend controls (well not really easily). If you went to a 2-band pre, you could still fit it all in though... You could also go with two stacked volume controls instead of two blends and a stacked vol. Actually this would probably work quite well.

    Any way, here's how I'd combine the signals.

    [​IMG]

    The top is if you go with an onboard switch. If you use a switch with centre off (on-off-on) you'll have both necks going when the switch is in the middle. For most preamps, the 10K resistors should be fine. If you go with a sadowsky pre or something else that just has fets instead of opamps, I'd probably go with 22K resistors as these don't have as low output Z.

    If you go with a stereo wiring with onboard preamps, you'll need to find a stereo jack with a separate switch to earth the battery -ve as this is normally done through the ring connection on a regular stereo jack. Regular 1/4" phono jacks with switches are easy to find at electronics shops, but if your bass needs a barrel jack, you'll have to go digging. I'd seach ebay for a parker fly jack as these guitars are both active and stereo. The second diagram is how I'd wire a couple of stomp switches in a pedal to switch signals. Obviously you can use DP stomp switched and use led indicators.

    If you go with a stereo passive wiring, then this switching won't work as is. You would go back to a conventional AB box. Obviously if you mount the two preamps in the floor pedal box, then my switching will work fine.

    It's your call of course, but personally, I'd still run two preamps and a switch onboard. Perhaps you could move the switch to between the bridges or something so you can flip it with your hand on the way from one set of strings to the other. This would probably involve a router and a little round rear cover plate or something, but would make more ergonomic sense and keep your instrument self contained.
     
  12. Stealth

    Stealth Supporting Member

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    I would run two preamps (one per neck) and then run a modified Ric-o-sound wiring:

    [​IMG]

    This uses two Switchcraft 13E switches with isolated break circuits. If you insert a single cable into either jack, both preamps go to the same output. If you insert two cables, each preamp gets its own output. So later on if you wanted to go stereo but still have the ability to footswitch between one neck, the other or both, you have it.
     
  13. MrWalker

    MrWalker

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    Awesome inputs here, gentlemen!!
    @Stealth: So the last wiring scheme doesn't really include a switch then? If you insert one cable, both necks are open?

    @RobbieK: yes, it would be nice to have a fully self contained bass, of course! Thanks for valuable input!!
     
  14. RobbieK

    RobbieK

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    I do a lot of these custom wiring jobs and really enjoy helping guys find their sound. Keep us informed and let us know how it turns out...
     
  15. Stealth

    Stealth Supporting Member

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    Exactly.

    Suppose you only insert a cable into the top jack where the blue one goes to the tip and the red goes to the isolated switch. Now, the jack will disconnect the red from the blue - but, since the other jack doesn't have anything connected, the red and blue are still connected and so both necks' outputs go to the top jack.

    Now, if you insert a second jack into the bottom one as well, suddenly you've completely separated the two signals and you'll give each neck its own output.

    I had the idea for the longest time, but didn't draw it like this until line6man, the resident wiring guru, explained it in detail.
     
  16. tjclem

    tjclem

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  17. RobbieK

    RobbieK

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    Stealth's diagram is fine if your bass is passive, but if you put two preamps onboard, you'll need to use those 10K resistors to sum the signals to avoid the Z load of the signals on each other.
     
  18. Stealth

    Stealth Supporting Member

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    You're absolutely right. I made that with passive pickups and controls in mind. The resistors should go in series with each signal line, just before the "split".

    Which incidentally reminds me, using 47K or 100K resistors would make it work well in a passive circuit, because they'd work as isolating resistors, ensuring the passive tone controls don't interact.
     
  19. MrWalker

    MrWalker

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    Thanks, RobbieK and Stealth for extremely useful posts! I'm learning lots here now!

    So to sum it up...

    RobbieK's first sketch would give me a mono output with completely separate settings (pickup mix and preamp settings), with a 3-way switch giving A/B/Both capabilities. However, the switch would be on the bass itself, not an option for a foot switch.

    RobbieK's second sketch would give a stereo output into a required foot switch which would provide the switching. The bass would be "useless" without the foot switch, in reality, so it's a two-piece solution where both parts would be required.

    Stealth's solution involves two jacks, so if plugging one jack into any of the outputs, will produce the combined output from both necks, whereas putting two jacks in will separate the signals and allow for floor switching. In this case, muting a neck would be through closing the volumes for the neck that isn't supposed to "chime in".

    Have I understood correctly?

    All three are interesting options.
    In addition I have my original thought, passive volume controls running through a stereo jack and going through pedal eqs and a pedal foot switch. It would also require the pedals to be included whenever the bass is used.

    Pondering about this... Currently all bets are still open.

    I suppose the ideal solution would obviously be RobbieK's first option with a twist... when the switch is in the centre position, it would run both signals to a stereo jack... if a mono jack was inserted, it would be the sum of the outputs. If a stereo jack was inserted, necks would go on separate channels to a regular A/B/Y switch...

    Is this last option possible at all?
     
  20. RobbieK

    RobbieK

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    Yeah I see what you mean, but stereo jacks don't really work that way. You'll need a switch to set the stereo operation. But I would put it on a separate switch, like a Parker Fly. They have a little red push button mounted on the underside that sets the guitar in stereo mode. If memory serves, this simply disconnects the piezo from the mix, and hard wires it to the ring connector. I think if you are using the neck swap switch all the time as you play and loop etc, then you are better off with an extra switch that disables the other switch and sends one signal to the ring connector.

    I forgot to mention in my last post, that you may want to get your tech to wire the neck swap switch with a solderless connector of some sort then wire a few spare toggle switches ready to throw in. These toggles are typically only rated for 10000 operations, which sounds a lot, but if you practise and gig a lot, you may need to replace it every year or two, and possibly at a gig.
     
  21. MrWalker

    MrWalker

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    I see :)
    Excellent input again!
    I think we have a winner on this! If it's possible to get it wired up is another thing... I don't really have a tech, but I have a soldering iron... so might do a little research and see what it leads to. :)

    Thanks again a million times for your valuable input!
     

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