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diagrame/info how to bi-amp rotel 985mk1 please

Discussion in 'AV Pre-Amp/Processors & Power Amps' started by mick23, Mar 13, 2003.

  1. mick23

    mick23
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    i have just purchased rotel 985mk1 which i am using with mordaunt-short ms540 as main f/l front ,m/short surrounds and 3802 powering rear speakers and doing processing duties.

    not really had a great amount of time to evaluate 985vs 3802 amplification, but 985 is certainlly not worse than 3802 amps and seems to give more bass as regards 2 chan sterio,

    i did notice the 985 mk1 manual quotes damping facter of (180)
    985mk2 d/f (260) 1075 d/p (180)

    985mk1 manual states 985 ideal for bi-amping sterio only system,have e.mailed rotel on how to do this, reply go to rotel dealer,

    so can any forum member give me "the idiots guide" link /diagrame etc on how i bi-amp my front l/r speakers using just the (985) and front preouts from 3802 so i can try for "2-channel sterio only"

    ps have no idea "what the revallence of damping facter is regarding amps"

    thank you
     
  2. Steve.EX

    Steve.EX
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    Mick.
    Firstly damping factor is (to put it crudely) an amps grip on a speaker i.e the ability to electrically "stop the motor" i.e forward/backward motion of the cone.
    This can be relavent to the large cone area's of big drivers but for "sit up and beg" 6 " drivers and the like it does not have perhaps the same significance.
    A quoted damping factor is one of those "how long is a piece of string" quotes that tells you very little in real world terms about an amp.
    It is always quoted at an 8 ohm load and can be derived from dividing the speaker impedance (8) by the output impedance of an amp (0.05) to obtain a DF of 160.
    As you can see it is relative only to the speaker placed upon it and is "a consequence" of the output impedance which is an important part of design.
    To bi-amp using your Denon/Rotel:
    Firstly and most importantly REMOVE any straps between the two sets of speaker terminals on your Mordaunt Shorts (linking the two blacks together and the two reds together) This will avoid spontaneous combustion of amplifiers!
    Next (via a Y splitter and a pair of phono-phono interconnects) connect the Front Left pre-out of the Denon (a single phono socket) the the Front Left AND Rear Left phono sockets of the Rotel.
    With another Y splitter and pair of phono interconnects connect the Front Right pre-out of the Denon (another single phono socket located directly next to the Front Left pre-out) to the Front Right AND Rear Right phono sockets of the Rotel.
    Take TWO lengths of speaker cable and connect 1 end of one to the Front Left terminals of the Rotel and the other end to the bottom pair of terminals of your Front left Mordaunt Short (keeping red to red and black to black) just as you would normally connect a speaker up.
    Take the second length and connect one end to the Rear Left terminals of the Rotel and the other end to the top terminals of your Front left Mordaunt Short (keeping red to red and black to black) just as you would normally connect a speaker up
    Copy this for the other speaker using Front/Rear Right terminals of the Rotel.
    I am aware that Rotel use other colours than Red for their speaker terminals so just ensure that black of the Rotel goes to black of the speaker and ???? of the Rotel goes to Red of the Speaker.
    This is as dummy proof as i can make it.

    Steve
     
  3. mick23

    mick23
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    thanks steve i think iv got the (gist) of it now , got to get some y splitters etc
     
  4. sounddog

    sounddog
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    mick ... Maplins do some reasonable looking phone Y-splitter (single socket - 2 plugs) £5 each ... will try to remember to let you know how they are tomorrow when we do the bi-amping thing with out RMB985 MkII

    Vikki
     

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