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Amplifier and HEAT

Discussion in 'Amps and Cabs [BG]' started by CitricGuy, Jul 11, 2003.


  1. I was just remembered another thread here on this site talking about liquid cooling computer parts, but that aside it got me thinking about amplifiers and heat.

    How does heat effect an amp, how much is too much, and will I ever notice a difference in tone/sound/quality because of it or does it simply eat away at the life of my amp?

    Granted I would probably never install a liquid cooler on any of bought amps (because they all work fine) but what about installing fans and such to cool them faster?

    At this point I’m just brainstorming and asking questions, but I hope this is the right forum to be asking it in.
     
  2. Paul A

    Paul A

    Dec 13, 1999
    Hertfordshire U.K!
    Yeah,
    the cooler you can make things the better.
    Components will last much longer (especially tubes and power transistors).
    I don't know about having any effect on tone but since installing fans in my tube amp it seems much "Punchier".
     
  3. I’ve got a friends amp that he practically destroyed that he gave to me and I was able to fix up but it always had the problem of over heating. It’s not a tube amp. Do you think replacing the old aluminum heat sinks with actual "standardized" heat sinks (copper) would help? Fans wouldn't cut it by them selves; it just wasn’t dispersing the heat fast enough. It's more of an antique kind of amp, that’s the reason I don’t just throw it out.
     
  4. Paul A

    Paul A

    Dec 13, 1999
    Hertfordshire U.K!
    Yeah,
    Bigger heatsinks would help, but fans would help a great deal.
    A couple of computer power supply fans would be great, small and pretty powerful.
    You should be able to get them for next to nothing (an old 386/486 pc).
    What are the output transistors? you might be better off changing them for something the same rating but more "Modern".
     
  5. I just planned a trip to radio shack tommorow morning! :hyper:
     
  6. Paul A

    Paul A

    Dec 13, 1999
    Hertfordshire U.K!
    Good Stuff!
     
  7. Thanks for your help Paul, you may have turned my unstable, unsafe, deathtrap of a fire amp into a vintage practice amp. There are some OLD pieces on that thing, I’m going to replace and re-solder a bunch of stuff to it to get it back up to date :)
     
  8. Paul A

    Paul A

    Dec 13, 1999
    Hertfordshire U.K!
    Glad I could help,
    I just did the same thing with an old tube amp, you wouldn't believe the difference it made!
     
  9. Here's how it works.

    The output stages of SS amps develop heat as a by-product of passing the current from it, to the speakers. It comes about because the transistors / FETs have internal resistance. And when you pass ?? watts (voltage across it x current through it) through a resistor it gets hot.

    The transistors, etc, are designed to work properly within certain temperature limits. Go over that limit and you're looking at an expensive repair job:bawl: Amp designers, therefore, arrange their product to get rid of as much heat as is necessary for the amp to work - and carry on working - when being used flat out...least, that's how good designs are done!

    To get rid of the heat the designer fits the output devices with heatsinks. These things are rated with a spec. that shows how much its temperature will rise with each watt (Degrees C / Watt): that spec is usually quoted in "free air" with the fins virtical and unobstructed. There are thermal junctions created by the very nature of bolting a transistor to its 'sink so that, too, has to be considered by the designer.

    But, heatsinks cost money. The bigger the 'sink the more the ££. But, the bigger the 'sink the cooler it runs. So the designer uses the smallest 'sink he can and may well under-rate it on the grounds that amps aren't used flat out.

    A fan significantly increases the amount of heat removed from the 'sink (therefore from the transistors) which makes it possible to squeeze a little more from the amp, assuming that in so doing other electrical specs aren't exceeded. Or, it keeps the same amp running generally cooler which should help to prolong it's life.

    Some years ago I saw a guy trying to repair his 600 Watt SS PA amp. He didn't know what he was doing. He switched on BEFORE he'd gone to the trouble to check out all the components for failures. That much current passed through one of the output transistors (a good one he'd just swapped) that it actually melted a small hole in the transistor's METAL case:eek: :eek: :eek:

    Cheers.

    John
     
  10. Lol, sounds like something I would have done back during my Techie training days :crying: