"Dummy Load" Question???

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by jokerjkny, Aug 11, 2004.


  1. jokerjkny

    jokerjkny Member

    Messages:
    9,590
    Joined:
    Jan 4, 2002
    hey guys,

    need some confirmation...

    so i'm using my Alessandro Basset Hound bass amp for a louder rock gig. its only 60 watts, and am trying to feed it into a more powerful 1200 watt power amp for onstage use.

    so, for our last few rehearsals, i've been plugging my Basset Hound's one speaker out into my friend's Avalon U5 (sometimes my Countryman DI, when its not available), and then into my Stewart power amp, where the power amp feeds my Acme 4x10 bass cab.

    simultaneously, with my Basset set @ 8 ohms, i take a cable from the other speaker out, and plug it into my 8 ohm THD Hotplate, which is set to "load". FYI, the U5 doesnt take a load.

    so, is this safe? as per Avalon's FAQ, i'm supposed to plug the Basset Hound into a speaker cab, but thought i could just use my hotplate instead.

    am i good to go? or am i slowly damaging my prized BH? and, does anyone know if my Countryman DI doesnt take a load, too, like the U5?
     
  2. John Phillips

    John Phillips Member

    Messages:
    13,080
    Joined:
    Mar 17, 2002
    Location:
    Scotland
    That will be safe - as long as a speaker or an attenuator is connected to the amp, the amp has a load. This is all that really matters for the safety of the amp - it doesn't matter if the load makes a sound or not.

    What you're doing is the classic 're-amping' setup. Many people do this with guitar amps to allow running effects such as delay post power-stage distortion.


    I don't know about the Countryman specifically, but no normal DI box presents any significant load to an amp's output.
     
  3. jokerjkny

    jokerjkny Member

    Messages:
    9,590
    Joined:
    Jan 4, 2002
  4. Wakarusa

    Wakarusa Member

    Messages:
    1,477
    Joined:
    May 7, 2004
    Location:
    Indianapolis, IN
    Maybe I'm missing something but isn't that exactly backwards? Don't most DI boxes have a high input Z?

    The rest is right tho'. The hotplate will bring the overall impedence down to spec for your amp (8 ohms in parallel with a hi impedence yields just a hair under 8 ohms total impedence)
     
  5. John Phillips

    John Phillips Member

    Messages:
    13,080
    Joined:
    Mar 17, 2002
    Location:
    Scotland
    Exactly, and therefore present no significant load to the amp.

    Most DI boxes will have input impedances of at the very least several tens of kilo-ohms, and many are much higher than this.

    To an amp wanting a 2, 4, 8, or 16-ohm load, that's as close to an open circuit as makes no practical difference.
     
  6. Wakarusa

    Wakarusa Member

    Messages:
    1,477
    Joined:
    May 7, 2004
    Location:
    Indianapolis, IN
    We're saying the same thing. It was the "significance of the load" comment that threw me off. Teach me to post at 3am :rolleyes:
     

Share This Page