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Two power amps into one cabinet?

Discussion in 'Amps and Cabs [BG]' started by MtnGoat, Feb 28, 2005.


  1. MtnGoat

    MtnGoat

    May 7, 2000
    MA/NH
    I have been playing a regular gig where I take my electric bass and my elec. upright bass and switch between them several times during the set. I have several amps, but not one of them by itself can provide me two inputs, separate input gain, and the ability to have equal volume between the two instruments on stage. I don't want to use any device that requires stepping on an A/B box or similar thing becaue I barely have time as it is to get the next instrument in my hands and be ready to go by the end of the count off--songs are played back to back with with next count off starting immediately after one song ends.

    I am considering using a power amps for each bass and running the two signals into one cabinet, plugging them both into the parrallel inputs. Both amps will be on continuously, but only one bass will be played at a time. Is there any reason I should not do this?
    thanks.
     
  2. CrackBass

    CrackBass

    Aug 10, 2004
    huntsville,AL
    oh my god. that sounds like a VERY BAD IDEA! i'm not an electrical engineer but you will be sending a powered signal into the imput of one of your amps at any given time. i think even connecting the amps in that way and turning them on once will probably take out both of them. i you were really lucky the cab might survive. please don't ever try this. you might look at the users manual for one of your amps and see if it doesn't mention something like that. look under the warning section. an a/b switch or a two channel preamp may be your only choice unless you get two different rigs.
     
  3. Lowtonejoe

    Lowtonejoe Supporting Member

    Jul 3, 2004
    Richland, WA
    Do not under any circumstances do this!

    I can't give you the specific Electrical Engineering reasons for not doing this but trust me, that would be very bad!

    Get a mixer.

    Look at this one
    .

    :)

    Joe.
     
  4. IvanMike

    IvanMike Player Characters fear me... Staff Member Supporting Member

    Nov 10, 2002
    Middletown CT, USA
    NO!!!!! don't do it.
     
  5. ESP-LTD

    ESP-LTD

    Sep 9, 2001
    Idaho
    As others have said, this is a very bad idea and would almost certainly destroy one or both amps in seconds.

    The easy solution, is change your setlist so you minimize instrument changes, and have someone do a little talking to buy you an extra 10 seconds.
     
  6. pjhandlin

    pjhandlin Gold Supporting Member

    Sep 17, 2002
    Grand Rapids, MI
    I agree with all posts... if you connect two power amps into one cab, something will fry.

    I do see another solution though:

    Checking your sig, you have a couple of integrated amp heads, SWR and GK as well as the pre/power Aggie setup.....

    You could use the GK (or SWR) as the main amp connecting one input (bass) the to your cabs. Then use your Aggie preamp for the URB and send the output back into the effects loop return of the GK essentially setting up another preamp channel running into the poweramp of the GK. Two different preamp inputs into the poweramp section of the GK should run fine.

    I don't have the same gear that you do, but I have had to improvise while doubling before without being able to use my regular setup and have run a preamp into multiple different amp heads via the effects return loop to add an additional preamp channel.

    This is simply offered as a quick solution... I agree that in the long run if you frequently double with an URB... you will want to look into a two channel preamp blender. For me, my Walter Woods Ultra has solved any/all similar issues with its dual preamp channels.

    Hope this helps.
     
  7. Lowtonejoe

    Lowtonejoe Supporting Member

    Jul 3, 2004
    Richland, WA
    Well now...that's a thought!

    :D

    Joe.
     
  8. pjhandlin

    pjhandlin Gold Supporting Member

    Sep 17, 2002
    Grand Rapids, MI
    yeah, I used to double a ton... and once upon a time I didnt have much gear so I figured out ways to get er' done.

    With a really hot onboard preamp this will also work, although not as well: I have played gigs running my URB into the preamp and then plugging my Sadowsky or previous Lakland into the effects return. Usually have to crank the bass pre and dime the master/poweramp output gain... but it will work when you dont have time to unplug/plug in then reset gain levels, eq .... as long as you can get enough volume/drive the power section hard enough with your bass. This has only worked in quieter situations where I didnt need to be too loud.
     
  9. slinkp

    slinkp

    Aug 29, 2003
    brooklyn, NY, USA
  10. I agree. The Raven Labs MDB1 is designed exactly for this purpose. You'll find it HERE.
     
  11. MtnGoat

    MtnGoat

    May 7, 2000
    MA/NH
    Thanks for the replies. It did send off a red flag in my mind, but our sound engineer (who works for Shure) didn't think it would be a problem.
    I'll check into the MDB-1.
     
  12. bugbass

    bugbass

    Apr 8, 2004
    Norway
    You might also have a look at the Radial Tonebone and the EBS Microbass, it dosen`t take SO long to step on a switch
     
  13. Joe P

    Joe P

    Jul 15, 2004
    Milwaukee, WI
    I'd use a switch, but if you wanted to custom-engineer something, there's a device that ham radio operators use when they are employing sensitive recieve preamps that would be similarly destroyed if the transmitter power were sent through them. It's a fairly simple mechanical relay based automatic bypass affair, I believe.

    Someone could probably make one for what you're doing, but... hmm.

    Joe
     
  14. Yep, this is mucho bad mojo. You'll surely let all the magic smoke out of one or both of the amps.
     
  15. The amp with the better power supply and output devices will win.....:D

    I've seen it happen. A newbie at a pro audio shop I worked at indavertantly connected the outputs of a Crown K2 to the outputs of a Macrotech 2400. After a brief tug of war the K2's output stage exploded. The Macrotech was unharmed.
     
  16. RevGroove

    RevGroove Commercial User

    Jul 21, 2002
    Burlington ON Canada
    Manager, Account Services: Long & McQuade Ltd. (Burlington); MTD Kingston Basses International Emerging Artist; Bartolini Electronics Emerging Artist
    Bug Bass mentioned the Tonebone from Radial, I think he meant the "Cab Bone" from the Tonebone line: Cab Bone link
     
  17. Kael

    Kael Supporting Member

    Dec 26, 2004
    Oklahoma City
    Just run out the effects send of one amp into the return of the other as mentioned above. That is unless you just feel like frying some electronics.
     
  18. I'm no sound engineer, but even I know that that's bad.