Bridged/ Paralleled Amplification.

Discussion in 'Hi-Fi and General Audio' started by Snoo, Jan 16, 2007.

  1. Snoo

    Snoo

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    Can somebody explain if it is possible to run 2 amplifiers as one?

    I've heard of bridging and parralelled but don't really understand the mechanics.

    For example if you have 2 power amps that are the same can you somehow link the outputs so that they drive a set of speakers singularly (ie. not bi-amped > Bi-wired). The aim being to increase the power to the speakers.

    Thankyou.
     
    Snoo, Jan 16, 2007
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  2. Snoo

    felix part-time Horta

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    Yes, you can, and the usual way is 'bridging'. Basically, you drive two amps out-of-phase (drive one with an input signal which is an inverted copy of the input to the other) The speaker is then connected between the two 'hot' speaker outputs (no connections to the grounds)

    The voltage swing across the speaker is then effectively doubled, becasue one amp 'pulls' while teh other 'pushes'; so you get four times the power output of the one amp (in theory, anyway). That said it's probably not a good idea with many speakers, especiallly with low (4ohm) impedance. The reason being that, in a bridged arrangement, each power amp 'sees' only half the load impedance: for a given input, it is supplying twice the output current. So driving a speaker of, say, 4ohms nominal, each amp 'sees' a 2ohm load. If the amps struggle with the load already, bridging will likely not address the problem but invite amp failure!

    It is possible to connect amps in parallel to increase current output, but for practical reasons the results will be rather less satisfactory than one amp alone. Note, for paralleled amps, the total power will not increase - because the total voltage drive into the speaker is unchanged.
     
    felix, Jan 16, 2007
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  3. Snoo

    stevehi-fi stevehi-fi

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    Very good technical explanation by "felix ". I have two Creek bridged power amps (A52SE's) driving my Tannoy R2's(bi-wired), and very good it sounds too! If you go onto Creekaudio website, and look up archived product - A52, page 3 of the manual gives a diagram on how it's done. It looks complicated, but a methodical approach and faith in Mr Creek's products has it's own rewards.
     
    stevehi-fi, Jan 16, 2007
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  4. Snoo

    I-S Good Evening.... Infidel

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    It is important to note that it does depend on the amplifier. Some amplifiers are designed as bridged amplifiers from the outset and can not be bridged again. For example, the Rotel RB1080 and RB1090 are already bridged, hence they do not offer the bridging mode that the lower models do. The terminology "single ended" is usually understood by consumers only in the realms of valve amplifiers, but it also applies to linear transistor amplifiers as well as switching amplifiers. In short, a single-ended amplifier (where one of the amplifier's speaker terminals is ground) can be bridged, while a differential, push-pull or bridged amplifier (where speaker terminals are both actively driven) can not be.

    In theory, bridging should quadruple the amplifier's power (since power is proportional to voltage squared and voltage is doubled by bridging). In practice this is rarely the case because it also demands greater current and typically the power supply will not be designed for the maximum possible bridged power level as that would significantly increase cost for a configuration that very few people will use.
     
    I-S, Jan 16, 2007
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  5. Snoo

    Snoo

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    Thanks for all the information, folks. Much appreciated.
     
    Snoo, Jan 18, 2007
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