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How do you bridge a biamp if the amp has no bridge option?

Discussion in 'Amps and Cabs [BG]' started by rbfagin, Apr 18, 2009.


  1. rbfagin

    rbfagin

    Apr 17, 2009
    Portland
    Yo y'all,
    I have a Hartke HA5000, 250W+250W (4 ohm each) and I wanna drive a single Acme B-2 full-range cabinet which I understand requires more than 250W. Even if the Amp were bridge-able, I know that the cab would have to be 8 ohms, I got that part.
    I wonder if there some kind of kit on the market that bridges 2 amps onto one cabinet, or plans I could build to. So I'm here to ask the sharpest minds in the industry.
    This site is great! Thanks for listening.
    RB
     
  2. Hi, RB.

    You invert one input and connect the speaker between the + terminals.

    How to invert the input depends of the circuitry. Most techs can do that with the schematics, but a mod like that is hardly feasible and can result a PS failure. IMHO of course.

    Regards
    Sam
     
  3. BassmanPaul

    BassmanPaul Gold Supporting Member

    Aug 25, 2007
    Toronto Ontario Canada
  4. The simple answer is - you can't
     
  5. Nighttrain1127

    Nighttrain1127 Supporting Member

    Nov 27, 2004
    Near Worcester MA
    you could ask them to build the cab with 2- 4ohm speakers and a seperate input for each speaker then you would have 2- 4 ohm loads for your amp to drive.
     
  6. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    -1, it's a three-way cab with crossover, so you can't do that.
     
  7. rbfagin

    rbfagin

    Apr 17, 2009
    Portland
    BassmanPaul's help is tremendous, but it is a bit complicated and tricky.
    Alright then, I guess I could just get 2 of the Acme B-1 cabinets, for which 250W is enough, I think.
    But 2 B-1s doesn't sound as good as a single B-2 possibly...
    Thanks everyone, great feedback.
     
  8. kayak

    kayak

    Sep 17, 2006
    I just looked at the block diagram for the HA5000 (see http://s3.amazonaws.com/samsontech/related_docs/5000_7000_manual.pdf, page 15). Just before the speaker outputs are two amps. A technician with a full blown schematic, not just a block diagram, would have to look at it to see IF it is possible to invert the input to only one of these amplifiers in order to make this bridgeable. This would be a permanent bridge, not something that you could easily change back and forth.
     
  9. Rick Auricchio

    Rick Auricchio Registered Bass Offender

    I wouldn't attempt Paul's idea without: 1) duplicate power amps; 2) schematics; 3) plenty of knowledge about power amps; 4) money to replace if there's an accident.

    The worst thing would be worrying about reliability, night after night.
     
  10. rbfagin

    rbfagin

    Apr 17, 2009
    Portland
    Well I'm a pretty good tech, and I happen to have 2 HA5000s.
    The trickiest part is how to isolate one side from chassis ground.
    Any clue on where to find schematics for a HA5000?
     
  11. BassmanPaul

    BassmanPaul Gold Supporting Member

    Aug 25, 2007
    Toronto Ontario Canada
    I have no experience with either the B1 or the B4. I have read that Acmes are very scalable ie 2 B1s sound much like a B2 and a pair of B2s are similar to a B4.

    I question gigging with one B2. I would not think to do so, I always use a pair stacked vertically. A pair will handle just about any gig you throw at them. Mine have 350W each available to them via a DCM1000 from Carvin.

    Paul
     
  12. BassmanPaul

    BassmanPaul Gold Supporting Member

    Aug 25, 2007
    Toronto Ontario Canada
    On the subject of bridging once more, You can modify the amp to include the circuit that I posted but you will have to have knowledge of electronics to be able to do so without damaging the amplifier. If you have that knowledge then is not a hard project to do. Resale value will probably be diminished.

    I have no idea what your comment about "isolating chassis grounds" refers to. The bridge adaptor will take its power from the + and (-) supplies for the existing op amps. ground will connect to ground.

    Paul
     
  13. Hi.

    Paul sure knows his stuff, that's a great link he posted.

    Complicated and tricky? I'm a hobbyist, and I think that it's quite simple and straight forward. All You have to do is to locate the power amp inputs, on a loom/connector no less, I'd guess. Couldn't be too much simpler, IMHO.

    I have no experience about that particular Hartke, but sometimes a commercial "Bi-Amp unit" design relies on the fact that the "high" amp about idles, so the PS current draw isn't that great. That allows the PS to be really scrawny, sometimes 1/1 with the advertised output. If trying to operate a 500W amp with a 500W PS, something will give.

    Regards
    Sam
     
  14. BassmanPaul

    BassmanPaul Gold Supporting Member

    Aug 25, 2007
    Toronto Ontario Canada
    I thought about that issue too Sam but both amps are able to be run full range taking the signal from the front of the active crossover. That means that the power supply has to be sized as in a normal stereo amp. Therefore bridge should have no issues.

    Thanks for the kind words! :)

    Paul
     
  15. rbfagin

    rbfagin

    Apr 17, 2009
    Portland
    What I meant by isolating one side from chassis ground:
    I really don't want to add the circuit Paul provided, instead I thought I could just invert one of the biamps, like T-Bird suggested.
    I can invert it real easy if I could "float" it (remove the current draw from ground common). But I sorta hesitate to modify an amp in a way that isn't easy to put back in case I wish to sell it.
    I really have many many options, the easiest is to just buy a amp with decent single channel power, because the whole point is I wanna use the Acme series of cabinets.
    Right now I think I'll just buy 4 Acme B-1, power them with the 2 stock HA5000s I have. That will work perfectly with my Ripley stereo-output bass I recently acquired, with a minumum of effort.
     
  16. BassmanPaul

    BassmanPaul Gold Supporting Member

    Aug 25, 2007
    Toronto Ontario Canada
    Or you could buy 2 x B2! :)

    Paul
     

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