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  1. #1

    Member Sales Rating: (9)

    Join Date
    Dec 2005
    Quebec, Canada

    Default Bridging Amplifiers

    I always thought that you can't bridge amplifiers unless they were designed to do so. Until I found this.....

    Any thoughts?

    Amplifiers: 1-SAE Mark IV, 4-SAE 2400, 1-SAE 2500, 2-SAE 2600, 1-Buttkicker BKA 1000N w/2-tactile transducers. Sources: Sony BDP CX7000es, Sony CX300/CX400/CX450/CX455, SAE 8000 tuner, Akai 4000D R2R, Technics 1100A TT, Epson 8500UB with Carada 100". Speakers:Polk SDA SRS, 3.1TL, FXi5, FXi3, 2-SVS 20-29, Yamaha, SVS center sub. Power:2-Monster HTS3500, Furman M-8D & RR16 Plus. 2-SAE 4000 X-overs, SAE 5000a noise reduction, MSB Link DAC III, MSB Powerbase, Behringer 2496, Monarchy DIP 24/96.

  2. #2

    Member Sales Rating: (43)

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    Nov 2006


    For that price I would sell the amps I was going to bridge, and buy what I was looking for power wise. I would have to question the SQ, and the reliability of the amps after using such a device. No matter how you bridge the amps would still see an 8ohm load as a 4, and a 4ohm as a 2.
    Please. Please contact me a ben62670 @ Make sure to include who you are, and you are from Polk so I don't delete your email. Also I am now physically unable to work on any projects. If you need help let these guys know. There are many people who will help if you let them know where you are.

  3. #3

    Member Sales Rating: (13)

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    Mar 2002
    The Mars Hotel


    ^ What he said ^
    'Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end."

  4. #4

    Member Sales Rating: (6)

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    Feb 2002
    Rockledge, Florida


    Well I was a bit shocked on the price myself, as I could do it with a handful of parts under $15 bucks. An op amp and a small power supply, I understand that maybe higher quality but $650. I'd be pissed when I opened that up. So I'm in 100% agreement with Ben.

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  5. #5

    Member Sales Rating: (1)

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    Feb 2006
    Over the mountain watching the watcher


    Okay, so here's the diagram for bridged mono operation with two amps:

    Name:  bridge_hookup_two_amps.jpg
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    So (and I'm in Learning Mode here), on the pre-outs, you're taking the "normal" hot left to the left speaker, and the "normal" hot right to the right.

    This gizmo than takes the those "normal" hot signals, inverts them, than sends inverted left to the left speaker, and inverted right to the right.

    Got that (I think).

    So .... they say, "There is no better way to get such extraordinarily high power"

    Well ..... wouldn't the weak link still be the power/quality of the power amps ?

    "This sums the voltage swing of the two channels, that. Simple electronics.

    " at least triples the power, "

    ....that depends on your power amps' guts, right ?
    You have an Onkyo 100 watt/channel amp, you're not going to find some miraculous 300 watts out of ether, correct ?

    " and eliminates common mode distortion.

    .... that may be true. In fact, it probably is.
    But the inversion process will introduce time lag; it has to.
    What effect this has on the end result (you sitting in your sweet spot) is unknown, I guess. But there has to be an effect.

    Wouldn't a better route be to simply juice up your power amps with common ground amps ?

    Inverters are good for driving variable speed motors, but ..... I don't know about their use for audio.
    Inverters are "noisy", so I guess you better spend a couple of hundred extra bucks for shielding.

    Usually right, but sometimes not entirely factually correct.
    Shifting to Plan B

  6. #6

    Member Sales Rating: (4)

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    Feb 2007


    IMO it's not worth it, you could buy a better amp for $650.
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  7. #7

    Member Sales Rating: (6)

    Join Date
    Sep 2003


    Soundcraftsmen used this same approach with the AB-1 bridger for bridging of their stereo amps. The AB-1 was like $49 though....

    Transport: Oppo BDP-103/USB HDD (flac)
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  8. #8

    Member Sales Rating: (4)

    Join Date
    Feb 2005


    If you have XLR inputs or a phase switch (for each channel) on your amp you can do it for a few bucks. AMPS MUST BE COMMON GROUND!

    Phase switch:
    Flip the phase on one channel, y adapter so L&R channels get the same signal (but one will be flipped phase); tie ground posts (black); speaker wires go to hot posts (red)

    If you've got xlr output on your pre, just get an XLR y-adapter, flip the +/- pins on one side of the adapter; tie ground posts (black); speaker wires go to hot posts (red)

    RCA (With XLR input on amp):
    Again, take an RCA Y-adapter; On one channel you'll put the RCA tip to the +XLR and tie the RCA ground to the -XLR and XLR ground; On the other channel put the RCA tip to the -XLR and tie the RCA ground to the +XLR and XLR ground. As above, tie ground posts (black); speaker wires go to hot posts (red).

    With the last method, you'll lose 3 db of gain on the input stage, but you've got the extra headroom.

    If you only have RCA inputs, then yep, it's a $15 circuit to flip the phase for the one channel.
    Last edited by unc2701; 05-23-2008 at 02:59 PM.

  9. #9

    Member Sales Rating: (1)

    Join Date
    Jan 2008


    Can't you just couple many outputs with transformers to make them float?

    Bam! 10 amplifiers on 1 speaker.

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