Preouts?

Discussion in 'AV Receivers & Amplifiers' started by jmlane, Jan 17, 2001.

  1. jmlane

    jmlane
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    I have a Sony STRDB940 reciever, I know that you can power speakers from another amp by connecting it to the corresponding preout socket. Am I correct in thinking this is only suitable for connecting to a power amp, and what sort of benefits am I likely to gain from doing so (musically as well as with movies)?

    Cheers.
     
  2. darrellk

    darrellk
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    Although the preouts are designed to feed a power amp, I get good results feeding an integrated amp (Marantz PM66KIS) from the preouts on my Yamaha A5. The Yamaha is connected to the AUX input on the Marantz which drives the main front speakers. I leave the Marantz volume control at 12 o'clock and control the level from the Yamaha.

    The benefits for me are quite large, - much better sound, particularly at high volume - I've got quite demanding and transparent loudspeakers and the Yamaha isn't quite up to the job of driving them.
     
  3. tomson

    tomson
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    I have just added a Rotel power amp to drive the front speaker of my Yamaha DSPA595a and even though the Rotel is only 50 wpc ( its an old model bought second hand) the sound has noticeably improved. Its definitely worth doing.

    Or as darrellk suggests, you could add an integrated amp - the only reason I didn't was that the Rotel appeared to be a bargain and sounded excellent.
     
  4. fenton

    fenton
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    Be carefull the new amp is not too powerfull (talking power amp here).
    I had a Musical Fidelity power amp (100Watt per channel) linked up to my old Yamy492 processor and I could never get the fronts and rears matched in volume.
    I only really realised what I was missing when I installed my new integrated AV amp (Marantz SR5000OSE, great bit of kit)
     
  5. darrellk

    darrellk
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    It's the gain of the power anp which is important, not its maximum power output. To explain:

    The gain of a power amp is the ratio between the input signal and the output to the loudspeakers. If the gain of an external power amp is higher than that of the centre/rear amplifiers in the surround amp/receiver, given equally sensitive speakers all round, the front channels will be too loud, relatively. Of course, the various speakers in a 5 channel set up will very rarely all have the same sensitivity, even when they come from the same manufacturer, which is why level controls are usually provided on the surround amp to trim the relative loudspeaker levels using a test signal or SPL meter. My Yamaha also has the facility to cut the main output by 20db, if the usual range of adjustment is inadequate.

    Gain is not the same as the maximum power output of an amplifier. the max power is determined by the capacity of the amp's power supply and the quality of other components (and the impedance of the speakers, but this is another story). If you have a 100W per channel external front channel amp, and only 20W each for the centre and rear channels, as long as the gain of the amplifiers is roughly the same, you should be able to balance the levels. Arcam and Musical Fidelity (there must be others) advertise the fact that all their amps have the same gain, and can therefore be mixed and matched for surround or bi-amped installations.

    The difference in available power output between the channels will only show itself when you crank the volume up and find the centre and rear channels running out of steam first. Even this might not be as important as some people think, given that you need 10 times the amplifier power to get twice the loudness.

    Lastly, manufacturer's power figures are quite misleading (even if all quoted at 8 ohms, which is not always the case), when driving real loudspeakers, whose impedance will usually vary widely depending on frequency. My 50 watts per channel stereo amp is MUCH more powerful in my system than my Surround amp which is rated at 70 or 80 WPC.

    Darrell.
     

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