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Options for Connecting Multiple Basses to One Amp

Discussion in 'Miscellaneous [BG]' started by JazzBassvb, Jun 16, 2005.


  1. JazzBassvb

    JazzBassvb

    Aug 5, 2003
    Hi all,

    I just got another bass and I'm wondering what are some options for running two basses into one amp at a time.

    I think that's kinda what A/B boxes are for, but I'm not totally sure.

    Is this something I can build? I can solder and whatnot.

    I thought about just having two inputs and one output. The inputs would have a switch in the middle to connect one or the other to the output and send the signal.

    Is this correct and if so, I'm wondering what sort of switch (DPDT, etc.) I need?

    Thanks for any advice!
    JB
     
  2. All you need is an SPDT switch. The center tap goes to the output jack. Each one of the the outer taps goes to the corresponding input jack.

    Since the signal doesn't care, this A/B box can also be used with one input, selecting either of two outputs.

    For a slightly fancier setup, use a DPDT switch. One half will be wired the same as the SPDT switch. The other half can be used to control some LED's to indicate which side is switched on. The center tap on that half will be the + coming from a 9 volt battery. The two side taps will go out to the LED (don't forget a dropping resistor, 390 to 470 ohms). Use a 3 conductor jack for the input, the - off the 9v battery will go to the "ring" contact on the jack, the cathodes off the LED go to the "ground" on the jack. This switches the power off when you unplug the box.

    edit: Regarding the signal path: all you need to switch is the + signal, the grounds from all jacks are connected together. That's why a SPDT is OK if you don't use the LED's.
     
  3. Bryan R. Tyler

    Bryan R. Tyler TalkBass: Usurping My Practice Time Since 2002 Staff Member Administrator Gold Supporting Member

    May 3, 2002
    Connecticut
    Yeah, an A/B box with two inputs rather than the standard two outputs will work fine. I can't find the link, but I know I've seen one before on how to build your own A/B box- if you're handy I'm sure it's not complicated. I'm electronically inept so I bought a Loooper for my two in A/B.
     
  4. JazzBassvb

    JazzBassvb

    Aug 5, 2003

    Sweet! The LED was something I was thinking of using as well. I've used some LEDs that had a built in resistor, so I'll use those again.

    Ok, next couple of questions:

    What sort of wire should I use for this? Speaker wire is ok or stuff from cables?

    In theory, will I have to worry about 'pop' when switching from one bass to another if the volume on them is down?

    If you don't mind, I'll try and draw up a schematic and if I have anymore questions, I'll post.

    Thanks very, very much!
    JB
     
  5. JazzBassvb

    JazzBassvb

    Aug 5, 2003
    Thank you Bryan! If you come across something, please post. I have to get my terms correct and review different switches and stuff, since I've only used SPST before.

    JB
     
  6. I just used some 22 ga single conductor wire sitting around the shop. I don't plan to use my A/B box with speakers so the 22 ga is just fine. Since this is in a metal box, if the box is grounded, this acts as a shield just fine, so there's no need to run shielded wire inside the metal box.

    Mine doesn't pop, generally, but if I remember I still turn the volume down (using pedal on my effects board) before switching.
     
  7. Bryan R. Tyler

    Bryan R. Tyler TalkBass: Usurping My Practice Time Since 2002 Staff Member Administrator Gold Supporting Member

    May 3, 2002
    Connecticut
  8. JazzBassvb

    JazzBassvb

    Aug 5, 2003
    nashvillebill,

    Great! That sounds good.

    Thanks,
    JB
     
  9. JazzBassvb

    JazzBassvb

    Aug 5, 2003
  10. JazzBassvb

    JazzBassvb

    Aug 5, 2003
    Ok,

    I'm a idiot.

    I thought that our cables had two different strands, but I was mistaken. I was confused with the stereo input jacks that are needed on active pickups to turn off the battery when not in use. The cables are only single. That makes it much easier.

    I did have a question about grounding it. You mentioned about it being a metal box and grounding it. That's what I would like to do, but not sure how.

    I have a drawing in mind and I will post one when I get it drawn just to make sure it's right. I hope NashvilleBill or anyone who knows anything about this stuff will confirm it is correct or what I need to fix.

    Oh, and nevermind on me using SPST switches, they were actually SPDT, so I do have some experience using them.

    Thanks,
    JB
     
  11. JazzBassvb

    JazzBassvb

    Aug 5, 2003
    Something else to ask,

    Just browsing the Radio Shack online catalog, they have the 1/4" panel jacks with a open or closed circuit. I want the open circuit, correct?

    Thanks,
    JB
     
  12. JazzBassvb

    JazzBassvb

    Aug 5, 2003
    Ok,

    Is this correct?

    View is looking at it from the top with the box on the floor.

    Thanks,
    JB
     

    Attached Files:

  13. Sorry, my internet connection's been out....

    The schematic is correct, go for it! I don't think it shows any dropping resistors inline with the LEDs but you said you've got the LEDs with the built-in resistor, so that doesn't matter...
     
  14. JazzBassvb

    JazzBassvb

    Aug 5, 2003
    Sweet deal! I'll let you know how it comes out.

    It may be a week or two before I do it, but I'm going to do it.

    JB
     
  15. Oh, by the way, I'd use the open circuit jacks, not closed. In case you or somebody else plugs this into speaker-level signals, I wouldn't want the jack to short closed if nothing's plugged in.

    Great job on the schematic, too!

    If I remember correctly, either Antique Electronic www.tubesandmore.com or Angela Electronics www.angela.com had the DPDT switch in a metal foot-pedal version. (I had one already, so I didn't need to buy one). Another option was a round DPDT rocker switch from Radio Shack.

    Good luck!
     
  16. JazzBassvb

    JazzBassvb

    Aug 5, 2003
    Thanks for the additional notes, Nashvillebill.

    I appreciate the kind words on the schematic too. Gotta love MS Paint! :D

    I appreciate the source for the foot-pedal versions of the switch. That's what I would prefer to use if possible.

    I have another question. I've seen jacks that are labeled 3 conductor, then I've seen some labeled Stereo that are also 3 conductor as well. Are they the same or is there a difference?

    Thanks very much for your time and patience in answering my questions.

    JB
     
  17. Nope, no difference, a "stereo" 1/4 inch jack is the same as a "3 conductor" 1/4 inch jack. The home stereo folks use them for headphones.
     
  18. JazzBassvb

    JazzBassvb

    Aug 5, 2003
    Alright!

    Great deal! Thanks for the answer!

    Again, I appreciate the time!

    JB
     
  19. JazzBassvb

    JazzBassvb

    Aug 5, 2003
    Hey all,

    Well, I got all the parts I need except a pushbutton switch, which I have an email into a local electronics supply place to see if they have any. While at RadioShack, I found a rocker switch with a low profile that seems would work in a pinch.

    Anyway, I got to thinking and I've come to the conclusion that it would be sweet to have my tuner hooked into my little box here and not have to plug and unplug directly into my bass to tune it.

    I understand I need to direct the output signal to the tuner, but was wondering what would be the best way to do so.

    Connect another wire at the appropriate connection at the output jack to another output jack for the tuner?

    Connect another wire at the switch output lug?

    Just asking for the best possible way to do it.

    Thanks,
    JB
     
  20. DaftCat

    DaftCat

    Jul 26, 2004
    Medicine Hat
    Why not an A/B/C switch?

    That way in the C position(tuner) your audio won't go to the amp and hassle the crowd(or the rest of the band).

    In C position, the A and B signal just goes to C and not output.

    Hope this helps,