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On-board pre amps

Discussion in 'Amps and Cabs [BG]' started by The Chancellor, Jan 26, 2003.

  1. Just a small question, can I run a bass with an on-board preamp (Say an Aguilar) straight into a power amp onto a cab? I'm thinking it sounds reasonable but please tell me if there would be an impedance mismatch or something.
  2. Benjamin Strange

    Benjamin Strange Commercial User

    Dec 25, 2002
    New Orleans, LA
    Owner / Tech: Strange Guitarworks
    I've got an Aguilar preamp in my bass, and I've tried running it straight into a power amp. It sounded pretty good, but it's a bit umm, too natural sounding(?), as the Aguilar is designed to be run into a bass amp or preamp of some sort. It essentially made it sound like I just amplified the natural acoustic sound of my bass. This could be great if that's what you are going for.
  3. Thats the exact thing I was going for. Thanks.
  4. Captain Awesome

    Captain Awesome

    Apr 2, 2001
    If you do that, you probably won't have enough gain to drive the power amp to its potential.

    My Washburn has a pretty high gain Bart preamp in it, but if I go directly into the power amp on my Carvin head, bypassing the Carvin preamp, it's definitely not nearly as loud as when I plug into the front end.
  5. Primusdude is exactly right, chancellor. Check the input sensitivity of the power amp and the output voltage level of the preamp. It is highly unlikely you will be able to push the 1.7+ volts most power amps require for max output with any on-board preamp. There may also be an impedance mismatch that would affect the subsequent output as well.

    All power amps have different input requirements, most of that spec info is available on the Mfr's websites. Your on-board preamp specs should also be available from the manufacturer.
  6. xyllion

    xyllion Commercial User

    Jan 14, 2003
    San Jose, CA, USA
    Owner, Looperlative Audio Products
    It really depends on the power amp and the preamp. I can put my two basses directly into my power and I get plenty of output. My Godin A4 has an LR Baggs preamp and my Lakland has a J Retro. I'm using a SoundTech power amp.

    This said, I still use a Kern preamp because I like the sound better than if I go directly into the power amp.
  7. chucko58


    Jan 17, 2002
    Silicon Valley, CA, USA
    I paid for all my gear myself. Well, me and MasterCard.
    Here are a few things I've learned over the years.

    - Many guitar and bass pickups can easily generate enough voltage to drive a typical power amp directly, but they don't put out enough current to do so.

    - IMHO, the primary reason for an on-board preamp is to buffer the pickup(s), and provide a low impedance output to drive long cables with minimal loss of high frequencies. Coincidentally, the low impedance output signal is adequate to drive most power amps.

    - A preamp powered by a 9 V battery doesn't offer much headroom. I would not try to get much gain out of such a circuit. However, it can still produce enough voltage to overdrive most bass amps' - and power amps' - inputs. (Not to mention effects pedals and the like!) Input clipping is not a pretty thing to hear, and you can't get rid of it by dialing back the amp's volume in most cases.

    - An 18 V (or higher) preamp can easily overdrive most bass amps. You either need to plug it into an "active" input, or use an attenuator with a normal "passive" input. Or just go direct to the power amp or board...

    - Most on-board preamps don't offer enough tone control (or the right kind of control) to make a bass sound good by themselves. There are exceptions, and there are bassists who prefer the "sterile" sound.

    Just MHO, your experience may differ.

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