Active and passive inputs

Discussion in 'Amps [BG]' started by Robad, Sep 25, 2006.


  1. Robad

    Robad

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    Please forgive my ignorance! I have a Trace amp with active/passive selector on the input. I have always assumed that, since both my basses need a battery, I should select 'active'. But I have read that my Streamer $$ has passive pickups. Should I select 'passive'? To confuse the issue, what if I use a footpedal? Should I select 'active' or 'passive'? :confused:
    I am considering buying a practice amp (Warwick Take12) but notice that it doesn't have active/passive selection (although the cheaper Blue Cab amps do). Is this important?

    Thanks in advance.
     
  2. Fuzzbass

    Fuzzbass Gnarsty bass tones Supporting Member

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    Having an active/passive selector on the input is a convenience, but not a necessity. Some amps have two inputs, one for active the other for passive. Others have a single input with a Gain knob rather than a selector switch. Some even have a combination: input jack with active/passive switch and Gain knob.

    These are all different ways of accomplishing the same thing: preventing a high-output active bass from pushing the amp into unwanted distortion/clipping. When set to Active, the signal is reduced, aka "attenuated", or "padded". A nice feature is a clip light or VU meter that tells you when the amp is clipping. (Note: for some of us, clipping can be a good thing, especially with tube amps or preamps).

    Active basses aren't always hotter than passive ones, but they usually are. Most active basses that I'm aware of have passive pickups with an active preamp. They are usually higher output than fully passive basses.

    I hope that helps!



    P.S. I would be wary of any amp that had a single input jack with no switch or knob to control gain.
     
  3. Shindig

    Shindig

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    I usually try both inputs regardless of what type of bass (active or passive) and chose the one with the best sound. I remember using SWR amps and getting a better sound running my active bass through the passive input because it drove the limiter better (made it work). Try 'em both and choose the one with the best sound for you. Good luck :D
     
  4. Fuzzbass

    Fuzzbass Gnarsty bass tones Supporting Member

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    Excellent suggestion!
     
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  6. luknfur

    luknfur

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    FWIW:

    the battery is to run the preamp whether it's located in the controls or pickups - either way a bass with a battery is an active bass. The vast majority of pickups in a bass are passive.

    An active amp input is a lo-gain input whereas the passive input is hi-gain. Depending on the amp and bass you may get by plugging an active bass into the passive input but often it will distort. Either way you'd want the amp volume low initially to check it out.
     
  7. Robad

    Robad

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    Thanks for the clarification. The Take12 (anyone tried one?) does have an input clipping LED and input gain control.

    What about footpedals/effects? Do they turn all basses into 'active'?
     
  8. JanusZarate

    JanusZarate

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    Not exactly. "Active" is just a reference to either the electronics (EQ, volume, etc.) on a bass, or the pickups themselves. True "active" basses will have active pickups. Most of the time, though, you'll find that basses have passive pickups and active electronics.

    However, running effects can potentially boost the input level depending on your settings, which would be like running an active bass direct to the amp. This can potentially clip the preamp. If you run your effects and notice that the clip LED is flashing, then use the active/passive (or "pad") button on a single-input amp, or the high-gain/active input on a dual-input amp. Or, you could lower the volume on your bass, and it should stop clipping.

    In most cases, if your effects are at unity gain, clipping will likely not happen at all.

    The input gain control happens after the clip LED stage. It's a separate but useful tool for cranking up the gain without "bad" overdrive.
     
  9. Fuzzbass

    Fuzzbass Gnarsty bass tones Supporting Member

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    Many effects provide no signal boost, but some can and do (compression, distortion, octaver, wah).
     

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