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Amp running pretty hot...

Discussion in 'Amps and Cabs [BG]' started by Metal Matt, Sep 11, 2008.

  1. I have a 1976 Sunn Concert bass amp. Running it into two 8ohm cabs... 4x10 and a 1x18. Yesterday was the first time I've played it at full volume (6) for any extended period. At 6, I can just barely hear clipping, after 6 the volume doesn't even increase, it just clips more, so 6 is my max. I noticed that the transistors towards the outputs were very hot. Not so hot that they can't be touched but close. There will also be a slight "burning" smell. No smoke whatsoever though. I also noticed that the speaker cables were a bit warm at the back of the amp. I'm using 16 gauge speaker cable. I put a fan facing the heatsink and transistors of the amp and it brought the temp down to about what it would normally be with the volume at two.

    What I'm wondering is if this is something I should be really concerned about or if having a fan blowing on the amp will be enough to avoid any damage. Also, should I maybe try thicker speaker cable?
  2. JimmyM

    JimmyM Supporting Member

    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    Not familiar with the Sunn so I can't tell you anything else, but yes, a fan definitely helps keep a hot amp cooler.
  3. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Most SS amps of that vintage aren't very efficient, and do run hot. A fan is a good idea. Heavier gauge cable won't hurt, but the primary cause of heat there is the 1/4" connectors. I'd replace them with Speakon if the chassis has room for them. As for the clipping, that just as likely indicates that the speakers have run out of excursion as it does that the amp is out of headroom.
  4. Loudthud


    Dec 25, 2007
    Dallas Texas
    A fan is good insurance especially if you are playing outside or in a hot club. I wouldn't be concerned if the phone plugs at the amp seem warm because they can pickup heat from the back panel. Run a cable from each cabinet to the amp, don't daisy chain amp to cab to cab.
  5. Yeah, I figured it wasn't the most efficient amp in the world. ha The speakers really don't jump out all that much when I have the amp cranked. I've seen speakers move a whole lot more than these do. My 1x18 is supposedly 600 watts. The guy who sold it to me didn't really know. the 4x10 is something like 525. I'd hate to start hacking away at my 32 year old amp to put speakon in. But if having a fan blowing on the back of the amp is enough to keep things from getting damaged and all that, then I'm happy.

    And to loudthud, I don't daisy chain my cabs. The outputs are close to the heatsink and the speaker cables didn't feel warm anywhere but right by the amp. I guess I'm just freakin' out a little since this is my first non-combo setup, and plus it's a damn old amp. ha

    Thanks for the replies. :)
  6. mrkreuzschlitz


    Jun 30, 2008
    Dacula, GA
    I think you'll be fine, honestly. Its just an old amp and you're doing what you can with the fan.

    As for the speakers, if you don't know what they are, they might not be what you want. But if it ain't broke, don't fix it. ;) :p

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