MC302 driving Klipsch RF7 iis.

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

  1. damacman

    damacman Blown and Injected Subscriber

    Messages:
    5,780
    Location:
    Gilbert, AZ
    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

    Messages:
    673
    Location:
    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

    Messages:
    330
    Location:
    StCatharines Ont Canada
    When does the new MC-302 arrive?
     
  4. Crazeehorse

    Crazeehorse Active Member

    Messages:
    138
    Location:
    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

    Messages:
    3,864
    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 wouldn't 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 then 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.
     
    Last edited: Apr 1, 2017
  6. exhippy

    exhippy I use to have long hair. Now I'm lucky to have any Subscriber

    Messages:
    1,115
    Location:
    St. Louis County, MO. U.S.A.
    Are your ears ringing yet?
     
  7. zebra03

    zebra03 All Audio - NO BS

    Messages:
    9,949
    Location:
    West of Weedville
    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

    Messages:
    7,070
    Location:
    New Jersey
    What?
     
  9. Crazeehorse

    Crazeehorse Active Member

    Messages:
    138
    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!
     
  10. Crazeehorse

    Crazeehorse Active Member

    Messages:
    138
    Location:
    Pevely Mo.
    It finally arrived. Spent about 3 hours with it last night. Apparently I like it loud because my meters were floating around 30 watts most of the time. It does run hotter than the MX1000, but the sound stage is so much deeper and wider. I am on the 8ohm taps and it gets pretty warm. Much warmer than my MX-1000 did. I'm still wondering if these should be on the 8ohm taps. Klipsch says 8ohm compatible but I wounder if they are more like 6ohm. stereo 1.jpg
     
    exhippy likes this.
  11. Velocityboat

    Velocityboat Well-Known Member

    Messages:
    673
    Location:
    TX
    Thirty watts is healthy volume if subs are active. Maybe being quad balanced more amps mean more heat.

    I have been running my PC2602 with just XRT20s until my MC1000 is fixed and a MC2500 is free. It runs cooler than it did running four ohm speaker load. My MC2500s run at around 10 to 100 watts friving XR290s and fans run alot.
     
    Last edited: Apr 1, 2017
  12. Crazeehorse

    Crazeehorse Active Member

    Messages:
    138
    Location:
    Pevely Mo.
    The sub is active. SVS SB-13 Ultra. Just want to make sure Ive got it setup correct. These speakers can dip into the 3 ohm range when aggressivly driven.
     
  13. exhippy

    exhippy I use to have long hair. Now I'm lucky to have any Subscriber

    Messages:
    1,115
    Location:
    St. Louis County, MO. U.S.A.

    I'll tell you what would tie it all together...

    A C48....;)

    :D
    .
     
  14. Velocityboat

    Velocityboat Well-Known Member

    Messages:
    673
    Location:
    TX
    I would do the 4 ohm taps then. If it does not run cooler same volume. Go back to 8.
     
    Last edited: Apr 1, 2017
  15. Crazeehorse

    Crazeehorse Active Member

    Messages:
    138
    Location:
    Pevely Mo.
    Yes it would!
     
  16. Chubba

    Chubba Active Member

    Messages:
    330
    Location:
    StCatharines Ont Canada
    Congrats Crazeehorse on your new amp.I agree with what you said about the speakers impedence.Cheers
     
  17. 04blackmaxx

    04blackmaxx Active Member

    Messages:
    481
    Location:
    New York
    Nice choice
     
  18. Velocityboat

    Velocityboat Well-Known Member

    Messages:
    673
    Location:
    TX
    crazeehorse,

    What type of pre amp are you running? I am impressed with a McIntosh convert who jumps all in with a factory purchase. What was the driving factor to jump all in?
     
  19. Crazeehorse

    Crazeehorse Active Member

    Messages:
    138
    Location:
    Pevely Mo.
    For now it's my trusty Yamaha CX-1000 pre amp. I recapped and refurbished it a couple years back, put Elna Silmic IIs everywhere in the signal path. Im now saving for a C47, C48, C50, C52, C2500, or C2600. I know I need to narrow it down. I have to have a MC phono stage. I chose to dive in now because I can now afford it! All 4 kids are raised and gone so Ive got my toy money back. I went new on the amp since that does all the heavy lifting. Ive got about 4 hours on the amp now and could not be more impressed. Did some AB with my MX-1000 and no sub. The wall of sound is full and complete now. What impresses me the most is how effortless the low end sounds now no matter what the volume. Correct me if Im wrong but this amp sounds like it has warmth. Cant wait for it to be broke in.
     
  20. S6A

    S6A New Member

    Messages:
    2
    Timely discussion for me as I'm in the market and considering very strongly the MC302. I would pair it with a MC8207 to drive the remainder of the 7-channels and have a couple left over for Zone 2.
    What do you guys think about mixing the models - '3' series Mac vs. the '2' series? Would I notice a significant difference between the Front L/R and Center (which would be driven from a channel on the MC8207?

    Considering the two above against the 'AT4000' series of ATI - the AT4002 Sig paired with AT4007 Sig. Opinions on that?

    Thanks.
     

Share This Page