Does Bridging an AMP affect Sound Quality?

Discussion in 'Archived Threads 2001-2004' started by Kevin. W, Sep 7, 2001.

  1. Kevin. W

    Kevin. W Screenwriter

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    Any reviews, magazine articles to explain this?
    Kevin
     
  2. Kevin C Brown

    Kevin C Brown Producer

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    It can.
    "Bridging" is one of my favorite topics, just because it's so (potentially) misunderstood. "Yeah, I bridged my 200 watt per channel stereo amplifier to get a 400 watt monoblock." Sounds cool, doesn't it?
    The problem is that now, because of the bridging, that stereo amp which is now a single channel monoblock, "sees" the impedance of the speaker hooked up to it as halved. So a nominally 8 ohm speaker now "looks like" 4 ohms to the bridged amp.
    So, the problem with the impedance being halved, is that now the current required by the amp to create those 400 watts must be doubled. The amp's output stage might not be up to the task.
    Plus: a "nominal" 8 ohm speaker is not a constant 8 ohms across it's freq range. I have seen "8" ohm speakers dip to 3.6 ohms or lower. That would "look like" 1.8 ohms to a bridged amp.
    So, if the output stage of the amp can't handle that current draw, the sound quality will be affected. Negatively. And slightly worse case, a fuse blows. Worst case is that you fry the output stage, and you have a very heavy, expensive, paperweight.
    Some people say that bridged amps sound better. I don't know if there is any scientific reason for this, except that you're getting more power out of the amp. But then why not get a reasonably powered amp in the 1st place so that you don't have to bridge an underpowered one?
    Hopefully some others will chime in too.
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  3. Kevin. W

    Kevin. W Screenwriter

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    Kevin,
    Thanks for the post. I understand what your saying about the impedance being cut in half, impedance swings over its frequency range and therefore the AMP having to produce more power. But wouldn't a reputable manufacturer such as Rotel, Adcom, etc who produce bridged AMPs be taking this impedance swing into consideration(Protection circuits, Torroidal Transformer, etc)
    Kevin
     
  4. Kevin C Brown

    Kevin C Brown Producer

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    K.W.- The answer to your question is possibly.
    But I still ask, why not just get a properly powered amp in the 1st place, then you don't have to bridge it?
    My current faves, Acurus 200x3 and A200x3. Tested by Audio magazine a while back. 315W into 8 ohms, and 515W into 4 ohms. "200" x 3 indeed! No need to bridge an amp this powerful. Great sounding too.
    And incidentally, and I know others will disagree, I don't think Adcom amps are that great. If you can dig up some older Stereo Review and Audio articles, or basically any review article where they open one up and look at the insides, Adcom amps are not that well built. Circuit board quality, solder joint quality, the components used, etc. Expensive Adcom amps may be OK, but not the cheap ones.
    Rotel makes good stuff though. Their THX certified stuff is nice.
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  5. Kevin. W

    Kevin. W Screenwriter

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    K.C,
    I basically boils down too price. The Rotel RMB-1066 is in my range while other High Powered 3 channel AMPS are not. Since I am only powering Paradigm Mini Monitors I really have no need for a high powered AMP but its the Rotels capability to be bridged that I like. More power in the future if needed. I've read a review on the RB-976(few generations back of this AMP) and they never mentioned anything about sound degredation.
    Kevin
    [Edited last by Kevin. W on September 11, 2001 at 05:56 PM]
    [Edited last by Kevin. W on September 11, 2001 at 08:48 PM]
     
  6. Kevin C Brown

    Kevin C Brown Producer

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    Kevin- I don't know if you're adverse to it, but I have seen a bunch of A200x3's on ebay and ubid lately. ~$600 or so.
    Rotel makes good stuff, so that's not a bad choice either. They have a 5 channel THX amp that Stereophile liked a lot.
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  7. Kevin. W

    Kevin. W Screenwriter

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    K.C
    That $600US converts to nearly $1000CDN. Then you have to take into Duty and Taxes when it crosses the border. I've was keeping my eye on ebay.ca but nothing. I've ended up getting the Rotel and so far I'm very pleased with it.
    Kevin
    [Edited last by Kevin. W on September 11, 2001 at 08:50 PM]
     
  8. Kevin C Brown

    Kevin C Brown Producer

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    Hee, hee, our own private thread!
    What do you use for a pre-pro/receiver?
    Rotel makes some good pre/pros too!!
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  9. Kevin. W

    Kevin. W Screenwriter

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    My Pre/Pro is a Denon 1801. Though I love my Denon very much it just doesn't compare to the Rotel. It looks like I'll be watching all my movies again to hear the sounds I never heard before. Down the road I will sell this and pickup a Rotel Pre/Pro if the price is right.
    Kevin
     

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