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Alright to use an amplifier head without a cab?

Discussion in 'Amps and Cabs [BG]' started by Simski, Sep 21, 2008.

  1. I am doing some homerecording for my band and wish to use my Ashdown ABM500 head as the recording preamp but I cannot really hook the whole rig up at the dormitory so I was wondering if it is okay to just use the head with DI and not hook up a cabinet to it?
  2. No.
  3. bassermaniac


    Jun 30, 2007
    i think you should always connect the amp with speaker.check the amp instructions
  4. Also, try the search function...
  5. bongomania

    bongomania Gold Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs

    An amp that has a tube power section may not be run without a load (speaker). An amp that has a solid-state power section may be run without a load all day every day with no risk. It does not matter whether the preamp has a tube.
  6. Why wouldn't it be OK? Doesn't the ashdown only have tubes in the preamp section? SS amps can be run without a load.
  7. Bongo beat me.

    But in a good way. :)
  8. I have heard that tube amps react badly to not having a cabinet plugged in but that solid state amps are indifferent but I was still unsure. I may end up buying a small cabinet anyway so there may not be a problem but if I have to play in a small room and not annoy neighbours, I'd prefer not to have to connect the head to a cab.
  9. bongomania

    bongomania Gold Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    Seriously, don't listen to the kids who said you needed a speaker for that amp.
  10. Check your manual... with most amps it's a no-no, but some amps are designed to work this way, i.e. the SWR Bass 350.
  11. Munjibunga

    Munjibunga Retired Member

    May 6, 2000
    San Diego (when not at Groom Lake)
    Independent Contractor to Bass San Diego
    In your case yes. Amps with a tube power section, no. With solid state amps, you're safe running at any impedance greater than the amp's rated minimum. The minimum impedance for your amp is 4 ohms. You want to run it at an impedance of infinity, which is greater than 4. You'll be fine.
  12. Munjibunga

    Munjibunga Retired Member

    May 6, 2000
    San Diego (when not at Groom Lake)
    Independent Contractor to Bass San Diego
    Assuming most bass amps to have solid state power sections, with most amps it's a yes-yes.
  13. fireincairo


    Jul 8, 2008
    Yeah, tube amps will blow the output transformer if turned on without a load. That doesn't mean you can't do it by accident for a moment without harming the transformer. Do it for longer, however, and you will likely have to replace it.
  14. Nick Kay

    Nick Kay

    Jul 26, 2007
    Toronto, Ontario
    Actually, yes. As it's a solidstate power amp, the output transistors can handle any impedance above a certain point. If you don't connect anything to the speaker outputs, that's theoretically infinite impedance.

    Just don't try that with a tube power amp. Something WILL die. I'm not sure how SS amps with output transformers fit into that equation, but those things are so rare either way.

    EDIT: Well, damn, that's what I get for having a slow connection. Whole topic gets in before my post finishes posting. hah
  15. Thanks for the quick response, everyone. I appreciate it. The Ashdown ABM manual is actually not too keen to reveal anything about this topic so that did not help but I trust that you know your stuff and if it is wrong, I have the whole rig insured, just in case.
  16. Rick Auricchio

    Rick Auricchio Registered Bass Offender

    Would your insurance cover misuse by you? Usually they don't.

    But you are indeed OK to use it without a speaker if it's got a solid-state power amp section.
  17. An amp with a transformer-coupled output stage, be it solid state or tube, NEEDS to have a load present on its outputs. Damaging the transformer is rarely the issue. Matter of fact, that's usually the last thing to go in a case of no load.
  18. puff father

    puff father Supporting Member

    Jan 20, 2006
    Endicott, NY
    Just leave the Master volume all the way down. Your gain knob should control the output to the DI, no? I have recorded before with my GK800RB just using the DI and had no issues at all.

    Of course if your head blows up I have no recollection of ever having said this! :eek:

  19. Stumbo

    Stumbo Wherever you go, there you are. Supporting Member Commercial User

    Feb 11, 2008
    Song Surgeon slow downer. https://tinyurl.com/y5dcuqjg
  20. fireincairo


    Jul 8, 2008
    I don't know about solid state amps, which is why I didn't mention them. Please, though, explain more specifically what you're talking about. What would "go" before an output transformer?

    I guess I would like to say that it's pretty widely accepted that turning a tube amp on without a load will blow the output transformer. I'm not an electrical engineer, but it doesn't really appear you're disgreeing with that, anyhow.

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