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  1. #1

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    Default are bridged amps common ground?

    I have 1.2TL's and am considering bridging two 125 W Parasound amps, using one for each channel. This will give me about 300W for each channel. BUT, although DARQUENIGHT gave a great explanation of a common ground amp, I am confused about using two bridged amps. Maybe to achieve a common ground, I have to tie both chassis together? Help, please!! The last thing I want is to blow up my precious Polks. TIA.

  2. #2

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    Are the amps mono or stereo?
    Polk Audio SDA SRS 1.2TL's
    With new Exotic wood, Sonicaps, Mills & RDO198's - Born on 4-24-1989 and Signed by Matthew Polk!!!!


    My Polk SDA SRS 1.2TL's http://www.LASAREATH.com/


    It All Started here: http://tinyurl.com/lasareath2

    Part Deux: http://tinyurl.com/lasareath3

    Car Stereo---->http://www.salsleaf.com/leaf_stereo/index.htm<---- NEW for 2013

  3. #3

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    Each amp is a 2-channel stereo, 125W per channel. It is bridgeable per the manual.

  4. #4

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    The Polks do not like bridgeable amps unless they can put out 8 ohms when bridged.

    I set my two Carver TFM-35X's in stereo.

    I split the output of my pre-amp with Y's. The left output goes into the left of both amps. The right output goes into the two right inputs of both amps.

    One amp power just the tweeters and the other amp power just the Mid-Bass drivers.

    It works like a charm!

    And you dont need to worry about straping or bridging or anything.

    Sal


    I just drew the diagram below in AutoCad for you! ;)
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    Last edited by Lasareath; 09-16-2007 at 05:41 PM.
    Polk Audio SDA SRS 1.2TL's
    With new Exotic wood, Sonicaps, Mills & RDO198's - Born on 4-24-1989 and Signed by Matthew Polk!!!!


    My Polk SDA SRS 1.2TL's http://www.LASAREATH.com/


    It All Started here: http://tinyurl.com/lasareath2

    Part Deux: http://tinyurl.com/lasareath3

    Car Stereo---->http://www.salsleaf.com/leaf_stereo/index.htm<---- NEW for 2013

  5. #5

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    The manual says bridging is good for 8 ohms, no problem. But, you did remind me to re-think the connections. I will not be using the bridged amps to power the lows and highs separately. Rather, each amp will power one speaker. BUT, I still gotta get 2 Y's to split the pre-amp outputs. Thanks again for your assurance and help.

  6. #6
    GV#27
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    Quote Originally Posted by analog97 View Post
    Maybe to achieve a common ground, I have to tie both chassis together? Help, please!!
    With the amps in bridged mode you CANNOT tie the neg speaker terminals together.When the amp is bridged it is no longer common ground.In other words the negative terminals are not at ground potential(when unit is bridged).

  7. #7

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    GV#27:

    OK. I hear you. You are saying it is OK, as long as I do NOT tie the bridged amps together?

  8. #8
    GV#27
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    Quote Originally Posted by analog97 View Post
    GV#27:

    OK. I hear you. You are saying it is OK, as long as I do NOT tie the bridged amps together?
    Correct, unless the 1.2tL is an SDA design?If so you cant use the bridged amps with them.You could use a non bridged bi amp setup like Lasereath is using.
    Last edited by GV#27; 09-16-2007 at 06:56 PM.

  9. #9

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    Geepers. I have Polk SDA SRS 1.2TL's. So, now you are saying that I can't power each individual speaker with a bridged amp? Rather, I must use the configuration by Lasareath to use a classic "bi-amp" configuration?

  10. #10
    GV#27
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    OK sorry for the confusion I will try to explain it better.You cannot tie the neg speaker terminals of bridged amplifiers together to make them common ground regardless of which speaker you are using.
    However SDA's require the use of an amp with a common ground.Bridged amps are not common ground therefore eliminating them for use with SDA's.

    Does that help?

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    Of course, you can build an AI-1 and then you can use any non-ground amp(s).
    '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."

  12. #12
    GV#27
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    I should add that in a non bridged set up like Lasereaths the amps will be common ground.

  13. #13

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    Another thought for you to consider, bridged amps may net you more power, but they also net you more distortion.
    'Political Correctness'.........defined

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  14. #14

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    F1, you have raised an excellent point. What I am really trying to achieve is to really "light up" my 1.2TL's without breaking the bank. Maybe this is a pipe dream. I am listening now to my 125 W Parasound stereo amp driving the 1.2TL's. I also have an Anthem (close to 200W per channel) awaiting a fuse replacement, but that's not really that much more. Ideally, it seems to me about 500W per channel would be ideal, but these are an arm and leg to buy. What are the alternatives that most 1.2TL-owners are using? I have seen a few posts, like Hearingimpaired's 300W Adcom monoblocks, etc. But I just wonder what that would be like because I have not heard anyone's large Polk speakers except mine. Thanks for the thought. PS: the big Polks even sound great with 125W!!

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    Figure out which of your amps has more current, that's the one you want.
    '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."

  16. #16

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    Quote Originally Posted by GV#27 View Post
    I should add that in a non bridged set up like Lasereaths the amps will be common ground.
    This is why I went this route. It was simple and easy. a couple of Y's, (4) pieces of speaker cable and I was all done.

    I'm getting around 600 Watts per channel. I cant put it up past 3 on my receiver or it gets really painful
    Polk Audio SDA SRS 1.2TL's
    With new Exotic wood, Sonicaps, Mills & RDO198's - Born on 4-24-1989 and Signed by Matthew Polk!!!!


    My Polk SDA SRS 1.2TL's http://www.LASAREATH.com/


    It All Started here: http://tinyurl.com/lasareath2

    Part Deux: http://tinyurl.com/lasareath3

    Car Stereo---->http://www.salsleaf.com/leaf_stereo/index.htm<---- NEW for 2013

  17. #17

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    Quote Originally Posted by analog97 View Post
    like Hearingimpaired's 300W Adcom monoblocks, etc. But I just wonder what that would be like because I have not heard anyone's large Polk speakers except mine. Thanks for the thought. PS: the big Polks even sound great with 125W!!
    Joe's System sounds amazing. TT or SACD, but it may be because the rest of his system is very good.

    My setup is way powerful, I paid $774 for two Carver TFM-35X's shipped on eBay. I could have bought Two Adcoms like Joe's but they were like $900. I'm not saying $900 is too much, I just didn't want to strap anything.

    Sal
    Polk Audio SDA SRS 1.2TL's
    With new Exotic wood, Sonicaps, Mills & RDO198's - Born on 4-24-1989 and Signed by Matthew Polk!!!!


    My Polk SDA SRS 1.2TL's http://www.LASAREATH.com/


    It All Started here: http://tinyurl.com/lasareath2

    Part Deux: http://tinyurl.com/lasareath3

    Car Stereo---->http://www.salsleaf.com/leaf_stereo/index.htm<---- NEW for 2013

  18. #18

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    OK. Thanks again. Seems the answer for me is to use the 2 Parasound amps in the bi-amp configuration as outlined by Lasareath. All I need is more speaker wire, bananas and a couple Y's. Apparently, bridging each amp to mono and powering one SDA with each amp will violate the "common ground" principle. Thanks!:) :)

  19. #19

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    I'm getting around 600 Watts per channel. I cant put it up past 3 on my receiver or it gets really painful
    The gain in the pre amp section is too high if that's the case.
    'Political Correctness'.........defined

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    My Crown XLS 602 amplifier in bridged mono has an output of 1200 watts at 8ohms. Does this mean that I can use 1 amp for each speaker without needing an AI-1 cable? thanks Here is a link to Crown's website http://www.crownaudio.com/amp_htm/xls.htm I have 1.2 TL's btw.
    Last edited by michaeljhsda2; 10-09-2007 at 12:25 AM. Reason: Additional info

  21. #21
    GV#27
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    Quote Originally Posted by michaeljhsda2 View Post
    My Crown XLS 602 amplifier in bridged mono has an output of 1200 watts at 8ohms. Does this mean that I can use 1 amp for each speaker without needing an AI-1 cable? thanks Here is a link to Crown's website http://www.crownaudio.com/amp_htm/xls.htm
    If you run them bridged then you will need the cable.

  22. #22

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    Thanks GV#27, my quest for the cable now begins......

  23. #23

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    Another idea would be to buy an amp worthy of the 1.2TL's.
    'Political Correctness'.........defined

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  24. #24

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    Maybe a Carver TFM-75. :D
    Richard? Who's your favorite Little Rascal? Alfalfa? Or is it........................Spanky?................. ................Sinner.

  25. #25

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    And which amp would that be?

  26. #26

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    There's a whole host of amps made for quality sound reproduction in the home, take your pick. Massive wpc ratings mean very little in relation to sound quality and fans are a no-no.
    'Political Correctness'.........defined

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  27. #27

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    and why are fans a no no?

  28. #28

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    Shhhh...because you can hear them during quite passages...and they draw power from where you want it to go.

    Why would you want to bridge anyway? Yeah, you have higher voltage....but where's the beef?
    In search of accurate reproduction of music. Real sound is my reference and while perfection may not be attainable? If I chase it, I might just catch excellence.

    The best way to enjoy digital music reproduction is to never listen to good analogue reproduction.

  29. #29

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    Default monster

    anyone else have monster power? i have the monster backbone, i have owned many amps(carver, adcom, pioneer elite, etc.) and the power of these amps are truly amazing! i've seen over 1200 watts registered-600 a side into my 2.3's, and they just keep going. if you can find a deal, these babies really sing! all reviews are excellent. LC

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    All I wanted to know is if I need the AI-1 cable when using bridged mono amplifiers with the SDA SRS 1.2 TL's and I got my answer from GV#27. Thanks again GV#27

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