Bridging VS Strapping - the differences explained

Discussion in 'McIntosh Audio' started by damacman, Nov 12, 2015.

  1. leftside

    leftside AK Member Subscriber

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    I just gave mine a listen at max volume. 100 on the C2300 and full gain on both amps - with no music playing. Couldn't really detect any "noise" until I hit 78 on the C2300. Gradually got a little more hiss as I went higher than 78. Though, I've never actually had the C2300 any higher than 60. At this volume it was causing the drainpipes outside to rattle.
     

     

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  2. damacman

    damacman Blown and Injected Subscriber

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    Well that's to be expected. This is a reflection of the Signal to Noise ratio of each component.

    When you start lighting the PG lamps while playing music ... then you're having fun.
     
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  3. 4-2-7

    4-2-7 Smart Ass Sponsor Subscriber

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    BTW this is a great thread Tony with lots of info and time taken to post.

    We need it to be a sticky since a lot of mac owners double up.
     
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  4. W9TR

    W9TR Well-Known Member

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    damacman,
    Thanks for the great explanation. Much appreciated. I had two MC2102's which can be run bridged or parallel mono with a flip of a switch on the back and rewiring the speaker terminals.

    The big thing I noticed was that when I ran the amps bridged they sounded much clearer and cleaner. This is because a lot of the distortion is cancelled out when the amps are run this way. In parallel mono I got a sound that had a little better bass, but was very much "more of the same". It was a lot of fun to play with both options. For this specific amp the results were very different. I was running Vienna Acoustics Beethoven Grand speakers.
     
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  5. 62caddy

    62caddy Trust but verify Subscriber

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    I just learned the MC2155 is also designed for both - mono parallel AND bridged operation allowing for 300W into 0.5, 1, 2, 4, 8 and 16 ohm.
     
    Last edited: Dec 13, 2015
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  6. kevzep

    kevzep Its all about the Music Subscriber

    This is what I would expect from bridging as opposed to parallel mono, the cancelling effect of the bridge will improve noise and distortion....
     
  7. damacman

    damacman Blown and Injected Subscriber

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    kev, many car audio amplifiers that can be bridged use the LEFT + / RIGHT - scheme where the right channel is inverted and its negative is the hot.

    Interestingly enough, McIntosh amps are the only that I'm aware of that do not quadruple power when bridged - comparing say the 8 Ohm single channel rating to the 8 Ohm mono rating. whoareu99's math in post 2 is spot on and addresses that.

    Finally, MC2105s cannot be operated in mono without being modified to do so ... which looks to be simple.
     
  8. 62caddy

    62caddy Trust but verify Subscriber

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    I agree. It should be "stickified". :)
     
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  9. kevzep

    kevzep Its all about the Music Subscriber

    Thats very interesting about the car amplifiers. They must be fully floating (each channel in normal stereo configuration) if they can do that, and it then simplifies the inversion requirement which can then be done at the output....

    Crown Macro-techs are 1300 watts per channel @ 8Ω, in bridged mono they are 4000watts @ 8Ω, so they don't quite quadruple either. Perhaps the McIntosh don't because of the autoformers? The Crown, not sure why they don't....
     

     

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  10. teisco

    teisco Active Member

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    Is there anyway to tell if an amp can be bridged? I have a couple of Proficient M2's that I would like to bridge or strap but there is no info on how that I can find. Only thing that gives me a clue is a brochure that states they can be bridged but leaves it at that.
     
  11. damacman

    damacman Blown and Injected Subscriber

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    I'd call them in regards.
     
  12. teisco

    teisco Active Member

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    Old amps so not sure they are even in business anymore.
     
  13. chef free

    chef free AK Subscriber Subscriber

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    Great info in this thread, thanks to all! I run a pair of strapped MC2200s and I'm wondering about damping factor. Would it be cut in half?
     
  14. whoaru99

    whoaru99 Epic Member

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    Go back to your original thread about bridging the amp. I'll give you some ideas on way(s) you might be able to tell if it can somehow bridge itself.
     
  15. Mike Gibson

    Mike Gibson Modulator Staff Member Super Mod Subscriber

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    OK, it's now a sticky. Just lets not let it degenerate into a mess.. Thanks.
     
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  16. mech986

    mech986 Text ↓ optional Posts:>18,000 Subscriber

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    They're still around, they even have a webpage about the M2, you should be able to get some guidance from them if they will talk technical with you over the phone or supply

    http://www.proficientaudio.com/products/archived-products/m2-power-amplifier

    Manual if you don't already have it.
    http://www.proficientaudio.com/images/stories/pdf/manuals/M2Manual.pdf
     
  17. welcomdmat

    welcomdmat AK Subscriber Subscriber

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    I believe this should be available to all folks. There is solid information in the post.
     

     

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  18. whoaru99

    whoaru99 Epic Member

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    Older sticky, but since it's a sticky the loop probably should be closed on this question/point.

    Quadrupling power by bridging is generally theoretical, on the basis that an amplifier is operating as a true voltage source. That is to say, the amp will hold output voltage without sagging regardless of load impedance. Some amps claim to do that but the vast majority do not (even some of those that claim to don't, actually, but that is a different matter).

    So the theory (re. true voltage source) would be if, for example, the 2-ch amp can swing 20V @ 8 ohms, 20V @ 4 ohms, and 20V @ 2 ohms, the power would double with each numerical halving of load impedance; 50W, 100W, 200W, respectively.

    Continuing with that, since bridging is the sum of the voltage swing of the two channels, from the above example you'd get 40V @ 8 ohms, or 200W, which is 4x (quadruple) the 50W per channel @ 8 ohms in this example.

    The fly in quadrupling where rubber meets the road is that very few amps actually operate as true voltage source, so they can't "double down" which of course then precludes quadrupling.

    For the specific example of the Crown MA-5000, yes, the 8 ohm rating is 1300WPC but when you look at the 4 ohm rating it is "only" 2000WPC, not 2600WPC that would be indicative of true voltage source operation. So, where does 4000W @ 8 ohms bridged come from? Since each channel sees half the load you have to look at the 4 ohm rating. 2000W @ 4 ohms is 89.44 volts. Double that, 178.88V, figure that back against 8 ohms, and you get the 4000W @ 8 ohms bridged rating. Or, just refer back to the progression examples in post #2.
     

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