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Plugging an active bass into Pwr Amp

Discussion in 'Amps and Cabs [BG]' started by JOME77, Nov 7, 2003.

  1. JOME77

    JOME77 Supporting Member

    Aug 18, 2002
    Ok guys,
    I've searched and searched and I know that there was a tread on the subject concerning plugging your bass straight into a power amp (with out using an external preamp) but I can't find it. A friend asked some questions in this area and I wanted to forward the thread link to him. If anyone knows which thread(s) contains some good info on this subject please let me know. Any other input on this subject would be greatly appreciated (specifically which on-board preamps are hot enough to drive an amp and which brand power amps work better in this scenareo).
  2. jondog


    Mar 14, 2002
    NYC metro area
    It should work, but it's probably not the best way to go. I went w/out my regular preamp for the 3rd set of my last show due to a beer spill, and while it did work I didn't have as much gain control as I like (maxed out too soon) and tone control was limited. I've got an 18v EMG BTC pre in my bass and a Mackie 1400i power amp.
  3. BillyB_from_LZ

    BillyB_from_LZ Supporting Member

    Sep 7, 2000
    jondog, running EMG electronics doesn't increase the gain, it just increases headroom.

    JOME77...this comes up from time to time. I looked back at my subscribed threads and didn't find any specific threads.

    I doubt that most on-board preamps would have enough gain to drive a power amp to full power...even my Stu Hamm Urge bass which is quite hot.

    Ebtech makes a passive device called a line level shifter that converts (transforms I suppose) a -10 dbV (instrument level signal) to a +4 dBU signal needed to drive a power amp. They cost $70 at zzounds.com

    Described as "Studio-quality direct box. Converts back and forth between -10dbV and +4dBu. Eliminates ground loop hum. Converts back and forth between balanced and unbalanced signals."

    Walter Harley built himself a tone stack-less preamp that provides gain for his fully EQ equipped bass. See the schematic at http://www.cafewalter.com

    Or as an alternative...QSC PLX amps can have their input sensitivity changed quite easily. It can be a factory mod for a new amp (like mine was to accomodate my output challenged Pearce BC-1) or done as an aftermarket by a QSC service tech. Lord Valve used to offer this mod to his customers for about $50 IIRC.

    Have fun!!!

    Here's a picture of the Ebtech...
  4. jondog


    Mar 14, 2002
    NYC metro area
    Well, that explains why I wasn't happy. I guess I'm not clear on the difference between gain and headroom.

    If JOME77 is going to buy a DI box, there are manymany options.