MC302 driving Klipsch RF7 iis.

Discussion in 'McIntosh Audio' started by Crazeehorse, Mar 9, 2017.

  1. damacman

    damacman Blown and Injected Subscriber

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    Heat is a byproduct of any audio power amplifier. Class AB amplifiers typically waste 40% of the power they consume as heat (Class D designs less than 20% on average). The more power one makes at the loudspeaker, the more heat is generated that must be dissipated. No such thing as a free lunch. Heat is generated by the power supply and the output section. The power supply creates the most heat at WOT while the output section coasts (a fully opened valve does no work). Somewhere between WOT and OFF is the point at which the power supply and output section create the most combined heat - that is pretty widely accepted as 1/3 power (1/3 of the amplifiers rated power).

    Power is the product of current & voltage. If voltage stays the same and current doubles, so does power. Then, it's up to the heat sinks to dissipate the power which is wasted as heat. The McIntosh designs with autoformers can have less heat sink mass than comparably sized direct coupled designs with similar power ratings. The direct coupled design would need that additional mass when being used to drive low impedance loads whereas the McIntosh user would simply choose an appropriate tap.
     
  2. Velocityboat

    Velocityboat Well-Known Member

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    TX
    I put one of my yamaha X power receivers into a nasty oscillation once playing Pink Floyd The Wall on a dynamic vinyl bass peak. Talk about an echoing ringing. The yamaho pro amp fares better it has set up and mass similar to MX1000.
     
  3. Chubba

    Chubba Active Member

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    When does the new MC-302 arrive?
     
  4. Crazeehorse

    Crazeehorse Active Member

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    Pevely Mo.
    Friday March 17th is when it gets in. I will probably drive to KC to get it and then head back to St. Louis the same day. I have the option of waiting a week or 2 for it to be delivered to my home but I don't think I can wait that long. :)
     
  5. twiiii

    twiiii Super Member

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    I doubt you will be using over 2 watts most of the time even as an avid listener. One of the big differences between the 7000 series and previous amps and todays Mac amps is current reserve. This allows todays amps to drive mismatched loads more easily where older amps would fear to tread. Look at tests on old 501's. They'll meet specs driving 4 ohm and lower impedances from the 8 ohm tap. This added current capability is of real value when used with some of speakers designed with out consideration is the past. The ultimate amp for these difficulties was the 7200 and its smaller cousin the 7100 with out auto formers. A 7200 driving a 2 ohm 1.66 or 1 ohm loads is a real Goliath killer. A 501 is no slouch either capable of over 700 watts when mismatched even with autoformers. But when using these amps at high levels with extreme mis matched loads, external cooling is almost mandatory. You would dare try mismatching loads with tube amps to such an extent, the current reserve just isn't there. So if you have a 3 ohm load, no problem with a 7200, or the 4 ohm tap on your 302, but with a 275 or 2301 if the bandwidth of the 3 ohm spectrum is wide the you would have to use the 2 ohm taps on the 275 or 2301. No 2 ohm tap on an old 275, run it mono and find another one. Odds are you'll need the power anyway.
     
  6. exhippy

    exhippy Living in a trailer park in Che$terfield, MO Subscriber

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    Are your ears ringing yet?
     
  7. zebra03

    zebra03 All Audio - NO BS

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    A little off topic , but what if you want to run 2 sets of speakers off the Mac amp ? Can you hook up one set of speakers to the 8 ohm and the second set to the 4 ohm ?
     
  8. nj pheonix

    nj pheonix AK Subscriber Subscriber

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    What?
     
  9. Crazeehorse

    Crazeehorse Active Member

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    133
    Location:
    Pevely Mo.
    The ears aren't ringing yet! The amp was supposed to be delivered by this Wednesday but it looks like the snow storm last week shut the factory down a couple of days. I should have it by this weekend.... I hope!
     

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