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Bi-Amping advice

Discussion in 'AV Pre-Amp/Processors & Power Amps' started by Ademdb, Dec 10, 2004.

  1. Ademdb

    Ademdb
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    Hi all, I currently have a Denon 3802 and Mission 77X speakers, the fronts are 775s. I would like to Bi-Amp the fronts and as I understand it, things should go as follows.

    :Aquire Power amp

    :Connect the Front L+R pre outs from the 3802 to an input pair on the power amp

    :Connect a pair of speaker terminals to each amp

    :Set the Power amps volume to 1/2 way

    Now a few questions ....

    Is that the right train of thought ?
    What Power Amp would be a good match (Im presuming a Denon) ?
    Does it matter what input pair I use on the Power Amp ?
    Does it matter what Speaker Terminals I use on the Speakers i.e. are the lower pair LFE and the top pair HFE ?

    Thanks for any help

    Adrian
     
  2. davehk

    davehk
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    Setting the power amp volume 1/2 way isn't going to do it unless you are really lucky. You have to match the gain of the additional amp to that of the power amp in the denon.

    In other words, the output level from both amps must be identical. I would do this using a 1Khz test tone and a dual trace oscilloscope. Without any speakers connected, I'd feed the output of each amp into the two 'scope inputs, invert and add.

    Then adjust the gain on the second amp for zero signal on the scope.

    Instead of a scope, a you could use a decent AC voltmeter, preferably digital. Just set the amp gain to get the same output from both amps for a given input.

    You could try to do it by ear, but that is difficult unless you have an accurate graph/information of the crossover response of the speaker - you have to use the frequency where both halves of the speaker have the same output, ie the exact crossover point. And you need a variable frequency signal generator so generate the test tone at that frequency.

    Alternatively, start with the control at 1/2 way and play with it until it sounds right.
     
  3. eviljohn2

    eviljohn2
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    As dave says, you're on the right track apart from the half gain bit. You really need to match it reasonably accurately (his OScope method is the ideal) but just by tuning it to your hearing would probably be fine. :)
     
  4. Ademdb

    Ademdb
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    Thanks for all that .... one more question. Does the Power Amp have to output the same power as the Demon ? I believe the Denons fronts are 105w - will I need that power or will a reasonable 30w amp be ok ?

    Thanks again

    Adrian
     
  5. gizlaroc

    gizlaroc
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    To be honest there really is no point, you would be better to just buy a decent power amp for your processor or even just your front channels.
    Why bother Bi-amping them?
     

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