I'm new to the whole pre/ power thing..anything I should know?

Discussion in 'Amps and Cabs [BG]' started by jiant., Mar 1, 2006.

  1. jiant.


    Jul 3, 2004
    Fort Mill, SC
    So I did what I've been wanting to do for awhile now, I got rid of my amp and moved on to a pre/power setup. I have a BBE Bmax-T and a Mackie 1400i on the way to me from fellow TB'er pgurns, and while I know how to set everything up, how far should I turn up the gains on the power amp? (I'll be mono-bridging it into an Ampeg SVT 410 HLF) Is it possible to get a growly tone out of the Bmax-T? Is it ok not to have a space between the power amp and preamp in my rack case, or should I upgrade to a bigger one? Please help!
  2. jondog


    Mar 14, 2002
    NYC metro area
    Start working out, that amp is heavy. Bridge mono into 8 ohms is a good idea, but if your cab is 4 ohms that's 1400 watts so be careful.

    I'm not familiar w/ the Bmax but I usually set the input gain so the light just blinks red (signal is hot but not too hot), set the output volume to where it just makes the red light blink on the power amp, and then use the power amp knobs (attenuators) to control how loud it is. Enjoy!
  3. IvanMike

    IvanMike Player Characters fear me... Staff Member Supporting Member

    Nov 10, 2002
    Middletown CT, USA
    most modern poweramps do ok with no spaces above or below, i ws in a band that used two 1400 amps for the pa stacked on atop the other in a 4 space case. IF you are runnign the amps flat out they might get a bit hot, but i wouldn't sweat it. Of course, if you can its always nice to give the amsp some ventilation room.

    For the most part i tend to set the preamp volume gain to a level under clipping for a good signal to noise ratio (just like you would on a head with seperate pre and master volumes). Then i use the attenuators on the poweramp for "volume controls". when running bridge mono typically you only use the attenuator on channel A/1.
  4. Bob Lee (QSC)

    Bob Lee (QSC) In case you missed it, I work for QSC Audio! Gold Supporting Member Commercial User

    Jul 3, 2001
    Costa Mesa, Calif.
    Technical Communications Developer, QSC Audio
    If the amp is cooled by a fan blowing air through it--that is, active convection--then its cooling needs are probably met by that air flow and not by dissipation from the top, bottom and sides. In that case, you don't need extra space above and below it unless the neighboring gear give off a lot of heat.

    If the amp is cooled by passive convection--no fan, just external heat sinks with exposed fins--then you might need to have some space if the adjacent gear would inhibit the flow of air through the fins. If you have several pieces of gear with external, vertically oriented heat sink fins that are in about the same place on the chassis, you can often get a nice chimney air flow effect, which will help the cooling, when the pieces are stacked one on top of the other.