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  1. #1

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    Default Bridging amps and creating a common ground?

    This may have been discussed but I can not seem to find and answer or at least and answer I understand. If I take either (2) Adcom GFA-555s or (2) Carver TFM-25s and bridged them so I would have one amp per channel. Is there a way to tie these amps together using the negative terminals to create a common ground? I would like to give this a try on my new SDA SRS 2, however I do not think mine even though modded will accept the dreadnaught.
    Speakers: Polk Audio SDA 1C, SDA SRS-2 (fully modded), Monitor 4A, Infinity RS-6b and Infinity Kappa 8.
    Amplifiers: Carver TFM-25 (x2), Adcom GFA 555 and a Dynaco ST-70
    Pre: Carver C-1, Adcom GFP 710, Adcom GFP 555

  2. #2
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    It is not suggested. The better option would be to bi-amp using one amp on the highs and one on the lows; if you wanted to use two amps. That is one of the limitations of SDA speakers that you have to live with...

  3. #3

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    Also, having recently played with my LSi15s and bridged 555s, I can tell you that the trade offs aren't worth it. The SQ suffered. I got a horrible thump/pop on power on that I hadn't had before and overall, I only gained a little bit in volume at a given level.
    The benefits are outweighed by the negatives IMHO.
    "Unwad those panties and have a good time man. We're all here to help each other, no matter how it might appear." DSkip
    I may have an addiction... RTA-15TL, SDA 2, LSi25, LSi15, LSi9, LSi7, LSiCx2, LSiFX, LS/FX, RT/FX, DSW MP2000...and that's just the Polks...

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    I'll say it again-- bridging 555's is painful. Save your monies and get a high current/power/quality amp.No disrespect here,, been there done that with the 555's.
    JC approves....he told me so. (F-1 nut)

  5. #5

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    Is there a way to tie these amps together using the negative terminals to create a common ground?
    No sir.
    '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."

  6. #6

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    Thanks for all the input, I wont bother trying then if its not worth it. I thought it might be a fun adventure.
    Speakers: Polk Audio SDA 1C, SDA SRS-2 (fully modded), Monitor 4A, Infinity RS-6b and Infinity Kappa 8.
    Amplifiers: Carver TFM-25 (x2), Adcom GFA 555 and a Dynaco ST-70
    Pre: Carver C-1, Adcom GFP 710, Adcom GFP 555

  7. #7

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    It's not that it is not worth it, it's that you can't do it.
    '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."

  8. #8

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    Quote Originally Posted by F1nut View Post
    It's not that it is not worth it, it's that you can't do it.
    Thanks!

    Just for my own educational purposes what are the benefits, if there are any, of biamping and or bridging amps. I know the difference between the two and from my understanding its much better to biamp when possible. Currently my 1Cs can use the dreadnaught but I do not have a pair that are biamp capable.
    Speakers: Polk Audio SDA 1C, SDA SRS-2 (fully modded), Monitor 4A, Infinity RS-6b and Infinity Kappa 8.
    Amplifiers: Carver TFM-25 (x2), Adcom GFA 555 and a Dynaco ST-70
    Pre: Carver C-1, Adcom GFP 710, Adcom GFP 555

  9. #9

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    When a single amp is driving a multi-way speaker system, back EMF from the woofer can result in increased low frequency intermodulation (IM) distortion of the audio signal, which affects the mids and highs to some small degree. When the woofer voice coil is being driven by the amp, movement of the voice coil in the magnetic pole is also generating a current (back EMF). Driving the woofer and mid/tweeter with separate amps solves the issue of interaction between the two, but you also need an active crossover to replace the passive crossovers. How well you match crossover frequency and slope to the speakers will determine the final results. Biamping can also be useful in taking advantage of two amps that have particular sonic strengths in the highs/midrange, and bass.

    Bridging an amp is useful where you want more power, often at modest increase in cost. One may already have an amp that is bridgeable and find that you need more power. It may be more cost effective to buy a second identical amp, and operate both in bridged mode versus purchasing a new higher powered stereo amp. At other times, bridged amps may just be a good bargain period. In my party system, I use three 50-watt-per channel amps in bridged mode, delivering 150 watts each. Total cost for all three amps is $225.00, which works out to $0.50 per watt. The downside of bridged amps can be increased distortion, heating, and inability to drive 4 ohm and lower loads. Amps that can drive 4 ohm loads when in bridged mode tend to be the exception rather than the norm.
    Last edited by Glen B; 06-28-2013 at 01:21 PM.
    Main system: Denon DP-59L | Audio-Technica AT33EV | Marantz Reference Series SA-11S2 | Classé CP-50, modified | Classé CA-300, modified | Classé DR-10, modified | Classé RC-1 | PSB Stratus Gold i's | DIY Balanced AC Power Conditioner with surge/spike suppression | Acoustic Zen and NeoTech cables | Oyaide and Furutech AC power connectors and receptacles | Hi-Fi Tuning Supreme fuses | Dedicated 20A IG AC line

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