Sunn Concert Slave (later red knob version) ohm rating?

Discussion in 'Amps and Cabs [BG]' started by BlkHeli, Jan 27, 2014.

  1. BlkHeli


    Feb 2, 2013
    Boston, MA
    I've been using my Sunn PB-10 preamp into a Sunn concert slave head to push two ampeg svt 610 cabinets. Each cab is 4 ohms for a total of 2 ohms.

    The rig sounds great but since I was unsure of the ability of the head to handle a 2ohm load, I upgraded to a sunn coliseum slave which is known for its 2ohm capability.

    Problem: despite the lower wattage, the concert slave sounded better.
    I also ran a Crown 1000xls and still prefer the souns of the Concert Slave.

    If the concert cannot handle the load, I'd consider getting a second identical one for a dual concert slave setup so each is running at 4ohms. The head sounds great with a single cab as well.

    My question: can the concert slave reliable handle 2ohms?

    Second question: anyone into doing a straight trade 70's black knob coliseum slave or Crown 1000xls for 80's red knob concert slave?
  2. I do not think the Concert can reliably handle 2 ohms.
  3. BlkHeli


    Feb 2, 2013
    Boston, MA
    I don't think so either. Can't seem to find a person or a resource that can confirm that as fact.
  4. Steve Dallman

    Steve Dallman Supporting Member

    Looking at the schematic, and the four 3055 output devices as well as the lousy heatsinking, it's 150 watts RMS would be at 4 ohms, not 2 ohms. There is no protection for shorts, or overheating as with modern amps. At 2 ohms, the power amp would try to develop more power than the components are rated for.

    The power amp is the same as the power amp in the Concert Lead and Concert Bass amp. You are right, info is sparse.
  5. I concur; though I sold my Concert Bass years ago, as I recall there isn't much of a heatsink. Trying to run four 2N3055's into 2 ohms would likely put them well outside their SOA.
  6. BlkHeli


    Feb 2, 2013
    Boston, MA
    Thanks folks. I'll take those 3 opinions to the bank.

    Is there a way to circumvent the onboard preamp on a sunn concert bass head to make it a slave head?
  7. ryco


    Apr 24, 2005
    This is a good place to go for info on all things Sunn.
    Great guys on this forum! Can answer all questions as a lot of them worked for Sunn.
    Lots of specs and schematics, too!
  8. Yes, you can just use the power amp section by bypassing the preamp: there is a switching jack on the back, I think it's labeled "Power Amp In". Plug your preamp into it.
  9. BlkHeli


    Feb 2, 2013
    Boston, MA
    Thanks guys! That label is confusing. Gonna grab a nice concert amp off FeEBay now. Oddly enough they're easier to find than the slave versions.