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  1. #1
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    Query: can passive bi-amping cause damage if done incorrectly?

    I understand the view that passive bi-amping is a waste of time. However, over the last 3 years I've replaced all the components of my stereo system except my power amp (Quad 909). Indeed, I tried a Classe CA2200 in my system at home a while ago and actually prefer the sound of the Quad!

    I now have a range of perfectly good components sitting unused in a spare room and have just bought a second hand 909 from Audio Emotion at a fantastic price. The plan is to use it in a second system. However, it will also be fun, if ultimately a waste of time, to try bi-amping with the 909.

    My query is this: is there any risk that the two 909s might be inadvertently damaged by sharing outputs from the preamp? Here are the details: my preamp (Music First Classic) has two sets of outputs, call them A and B. The signal out from right channel A is simply wired with a one inch length of wire to signal out right channel B, and the same is true of left channel A and B. Using these two sets of outputs to bi-amp is effectively like using a Y-splitter. So, if I bi-amp by using one 909 to feed the woofers on both speakers and the other 909 to feed the midrange/tweeters, aren't the right channel inputs on both 909s connected at the preamp? Likewise, if I bi-amped by using one 909 per speaker and took preamp right channel from output A to one input on the 909 and took preamp right channel output B to the other input on the same 909 (and then used one set of poweramp speaker connectors to connect to the midrange/tweeters and the other to the woofers of the same speaker), aren't I effectively connecting the right and left channel inputs on the poweramp at the preamp end?

    It might be that these problems are non-existent, but I'd thought I'd check before potentially causing any damage. I've checked with Music First who state there is no issue with impedance when using their preamp for biamping, and Quad stated the obvious, i.e., remove the connectors between the two sets of terminals on each speaker!

    Many thanks for any help.

    The Wiz
    Last edited by wizons; 11-04-2011 at 12:12 PM.

  2. #2
    Deaf Wammer Tel's Avatar
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    Of course they are sharing outputs. They couldn't be doing anything else.
    "We could have saved the Earth but we were too damned cheap" Kurt Vonnegut

  3. #3
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    Quote Originally Posted by Tel View Post
    Of course they are sharing outputs. They couldn't be doing anything else.
    Tel - I've edited the message since your speedy reply. Of course the preamp outputs are shared, but I have no idea if this a problem?

    Thanks

  4. #4
    Moderator meninblack's Avatar
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    You have to split the signal somewhere unless you are going for two preamps and two CD players, which could get messy!

    The preamp is where it is usually done in a bi-amped setup - and yes, it is exactly like using a Y-cable between the pre and the two powers. They all work like this; you won't damage anything.

  5. #5
    Super Wammer stewartwen's Avatar
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    "is there any risk that the two 909s might be inadvertently damaged by sharing outputs from the preamp?"
    Simple answer..................................NO!
    I am just a soul boy at heart.

  6. #6
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    Quote Originally Posted by stewartwen View Post
    "is there any risk that the two 909s might be inadvertently damaged by sharing outputs from the preamp?"
    Simple answer..................................NO!
    Excellent!!

  7. #7
    Wammer Lokes's Avatar
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    I know passive biamping is generally regarded as a waste of time, But when I used it, it worked a treat, This is why.

    I wanted to drive the Apogee speakers I used back then (Stages ) with a valve amplifier but I didn't have one powerful enough to do the job properly, so I used a Perreaux solid state amp on the current hungry bass panels and a modest 35 watt valve amp on the mid / tweeter ribbon ,
    it was bit of a faff but I enjoyed this set up for a couple of years and was better than
    using the Perreaux on it's own.
    "If it measures good and sounds bad, it is bad. If it measures bad and sounds good, you've measured the wrong thing."

  8. #8
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    Quote Originally Posted by Lokes View Post
    I know passive biamping is generally regarded as a waste of time, But when I used it, it worked a treat, This is why.

    I wanted to drive the Apogee speakers I used back then (Stages ) with a valve amplifier but I didn't have one powerful enough to do the job properly, so I used a Perreaux solid state amp on the current hungry bass panels and a modest 35 watt valve amp on the mid / tweeter ribbon ,
    it was bit of a faff but I enjoyed this set up for a couple of years and was better than
    using the Perreaux on it's own.
    Yes I've read about this approach. How did you balance the respective volume levels of each power amp? Doesn't an even balance between woofers and tweeters require power amps of exactly the same gain?

    The Wiz

  9. #9
    Wammer Lokes's Avatar
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    The valve amp was an integrated and was slightly more sensitive than the Perreaux, so all I had to do was back off the volume a little on the valve amp and all was well, like I say it was far from ideal, hence the big monster amps I have now, but however unlikely, it made a very nice noise.
    "If it measures good and sounds bad, it is bad. If it measures bad and sounds good, you've measured the wrong thing."

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