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amp head + no speaker load = trouble ?

Discussion in 'Amps and Cabs [BG]' started by Funkateer, Jul 5, 2002.

  1. Funkateer


    Jul 5, 2002
    Los Gatos, CA
    Hartke 3500 manual advises against. I want to be able to use either the effect send, or the direct out, to go to a mixer/headphone amp for silent practice use when my wife starts to get that 'When does the naval bombardment stop?' look. Want to be able to disconnect the cab, and still be able to use the bass head EQ and compression.
  2. Perhaps the effects send or the DI will still output via the preamp gain while the master volume is zeroed.
  3. in theory it shouldn't matter.. i think..

    because it needs a minimum load of 4 ohms..
    if there are no speakers, there is a HUGE (!) load on it ( serveral bilion ohms ), which is more than 4 ohms ofcourse..

    but in practice.. dunno.. my SWR does fine without cabs, IF you put the mute switch on.
  4. pkr2


    Apr 28, 2000
    coastal N.C.
    I've always thought the rule of thumb was solid state with no load=OK, tube output with no load= very quick destruction.

    I would be surprised if there aren't exceptions to this rule.

    I wouldn't take the chance.

  5. Mark Reccord

    Mark Reccord Supporting Member

    Theoretically, you shouldn't run any amp with no load connected to it. That being said, it's pretty harmless to run solid state amps without a load connected. Like Allodox said, the main concern is with minimum impedence with SS amps. You will cook the output transformer of a tube amp pretty quickly with no load attached, though, so don't do that!
    Despite the fact that it probably doesn't matter if you run your Hartke without speakers connected, if they advise against it, I wouldn't do it.
  6. JMX

    JMX Vorsprung durch Technik

    Sep 4, 2000
    Cologne, Germany
    At least as long as the warranty is still valid... ;)
  7. Mark Reccord

    Mark Reccord Supporting Member

    Exactly. :D
  8. lneal


    Apr 12, 2002
    Lee County, Alabama
    Actually, the opposite is true. With no load connected, the impedance the amp sees is infinite, IE, infinitely small. The lower the load impedance, the higher the load on the amp. According to Ohm's law:current=voltage/resistance. If resistance goes up current goes down, therefore less load, loosely put.
  9. I thought all SWR amps state that (unlike some) the amp can run without speakers even plugged in.
    Or so says my SWR manual.

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