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Sunn 1200s problems

Discussion in 'Amps and Cabs [BG]' started by haxattax, Oct 2, 2013.

  1. haxattax


    Oct 1, 2013
    I bought this thing used by a guy that gigged it a lot, its a fender re-issue Sunn 1200s. When I first got it home and practiced with it, it was super loud very decent tone. I've had it for about 4-5 months now and its starting to act crazy. I have it running into an Ampeg 8x10 cab. Its seems like its clipping (red LED in front) at way lower levels than it used sound awesome at. Anywhere past 3 on master and speakers sound distorted like they've blown. I've tried changing speaker cables, tested new speaker cables by running them into another head and cab sounded fine. Changed the battery for pick-ups still the same thing.


    Edit: Forgot to mention it only says, "2 Ohm Minimum" for impedence(?)
  2. When you are saying it is clipping, which light is flashing red? If it is the comp light, I'm
    pretty sure that shows input clip, not output

    Have you replaced the valves?
  3. haxattax


    Oct 1, 2013
    I believe its the compressor light. Its right between my High and Low comp knobs. Is it bad if its constantly red/orange? It used to stay green.

    And no, replacing the tubes is the only thing I haven't done yet.
  4. Here is the link to the manual: http://www.google.com/url?sa=t&rct=...=GtrNQtQoFuHVsV8eG5Ttng&bvm=bv.53371865,d.dGI

    Item 14 talks about distortion. I would set up both channels for a clean tone with the same gain and switch between te channels. If only 1 channel is distorted, it may well be a tube.

    These amps have so much power and head room there is no need to drive the input super hard. You can get your volume with the output.

    Have you changed basses from when you first purchased the amp? If so, has the new bass got a hotter gain possibly and you haven't adjusted the input gain to suit? Just a thought.
  5. Jeff Scott

    Jeff Scott Rickenbacker guru.......... Supporting Member

    Apr 11, 2006
    This is no reisuue, SUNN never made a 1200S that was anything like the Fender amp you speak of. JFYI. :cool:
  6. haxattax


    Oct 1, 2013
    It's strange because it's only distorting one or two speakers out of the 8 in the cab. I looked at the speakers uncovered and 6 are vibrating fine and 2 random speakers are pushing out unevenly. But like I said the cab works beautifully with any other head. I'll try switching channels to check if it's the tube.
  7. Amps cannot "decide" what speakers in a cab to drive. They all get the same signal from the amp. You may have a problem with the amp that is damaging speakers and those two are now showing the damage more than the others. Or your cab is just showing some stress and age.

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