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Passive input, active input, or both?

Discussion in 'Amps and Cabs [BG]' started by JWW88, Jan 20, 2012.

  1. JWW88


    Jan 20, 2012
    I apologize in advance as I am a newbie (to bass) and expect this is a dumb question.

    I bought a bass for recording, a Peavey T40, a couple weeks ago. My 13 year old son asked if he could use it to try out for jazz band at school. I said absolutely, but you'll need an amp...;)

    So I picked up an Acoustic 260 Mini-stack (really cool!).

    After his first practice he mentioned that he let a buddy plug in as he did not have an amp yet. His buddy has a Squire P-Bass. So they had one bass plugged into the active and one plugged into the passive input.

    My questions are, could this damage the amp/cab?
    Does it hurt to plug an active bass into the passive or vice versa?

    Thanks in advance!
  2. No. The active is just a -15db gain cut for active basses that have a very high output. Though I'm not sure if both jacks being used at once could damage the amp.
  3. JWW88


    Jan 20, 2012
    thanks duke,
    anybody know about plugging into both at the same time? I hate to tell my son not to let his friend plug in if it dosn't hurt anything.
  4. You can plug into both at the same time - I've even seen one instance where someone used the Passive as an OUT for another amp while running an Active bass into the padded (Active) input.

    No harm - no foul although if that was a Passive Bass in the Active hole, it lost some volume with the padded input cutting it down to keep the preamp from being overloaded.

    But then again, some people like the clipped sound (distortion) of putting an Active bass into a Passive input.
  5. RFord04


    Apr 8, 2009
    Flint, Michigan
    Huh? Those are inputs... how exactly are they outputting sound? Are you sure the other cab was actually producing sound?... because that sounds pretty much impossible.
  6. Yeah - they are parallel Inputs and if ONE is getting a signal, they both are, just that one goes to a pad to cut the hotter signal a little.

    Believe me, I've seen it done.
  7. I remember Leo Fender talking about being able to do that with the Twin and seeing some old photos of stage set ups with a short instrument cable going from one channel to the other using several amps. Tedward
  8. JWW88


    Jan 20, 2012
    Thanks Joe!
  9. Febs

    Febs Supporting Member

    May 7, 2007
    Philadelphia, PA
    They're parallel inputs. You can plug an instrument into one, and then patch from that input to the input of a second amp. It works in pretty much the same way as when you daisy chain multiple cabinets together.
  10. JimmyM


    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    I've seen it done too, and I've done it myself in the old days, but it never works out well. One will end up dominating the amp's attention over the other. But in a pinch like this, it'll be OK as long as nobody goes wild with the volume.
  11. BassmanPaul

    BassmanPaul Gold Supporting Member

    Aug 25, 2007
    Toronto Ontario Canada
    On a Fender amp, if you use Input 2 you have an input impedance of 136KΩ comprised of two 68KΩ resistors. The input signal is applied to the top of the first resistor, the input grid tapped off at the junction of the two and the bottom resistor grounded. Input signal level is reduced by a half. Plugging into Input 1 the two 68KΩ resistors are in parallel for 34KΩ to the grid with a 1MΩ resistor to ground allowing an input impedance of above 1MΩ. Using both creates a passive mixer from the 68KΩ resistors with the same 1MΩ to ground. Switching is done by the shorting contacts on the input jacks.
  12. BassmanPaul

    BassmanPaul Gold Supporting Member

    Aug 25, 2007
    Toronto Ontario Canada
    Daisy chaining inputs: Input into amp 1 Input 1 output from input 2 to amp2 Input 1 allows again a passive mixer between the amps. This can be continued as long as you want. The only problem will be ground loops which will have to be solved.
  13. ehque


    Jan 8, 2006
    Sometimes it doesn't work if both basses are passive. The other bass can load down the circuit into mud, depending on how each particular amp is wired. I personally use a small Barge Concepts mixer for applications like this.
  14. JWW88


    Jan 20, 2012
    Unless both boys max the power on their basses and the amp, no harm to the amp or cab is likely...and...
    It will most likely have a negative impact on the quality of the sound. Right?

    Thanks again for the help!

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