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Ampeg SVT CL plugging in an active bass in the 0 decibel input

Discussion in 'Amps and Cabs [BG]' started by mydog213, Jul 17, 2012.

  1. mydog213


    Jul 15, 2012
    Howdy there again, me again with noob questions.

    What are the consequences of plugging an active bass into the 0 decibel input, vs the -15db input

    I understand active basses are supposed to go into the -15db
    but the 0db is so much louder, and I only own active basses and i really want to use the 0db, but i dont want to mess anything up

    Sorry again for the noob questions, but you guys are the best!
  2. There is no rule that you MUST plug actives into the "active input".

    The only time you need to utilize that input is if your bass is so hot that it overdrives the input.
  3. hodgy


    May 5, 2004
    Bothell, WA
    Customer Support- Ampeg/ Line 6
    If it sounds good, do it.
  4. This. I''ve only ever used the "active", padded input when my bass is so hot that it overdrives the pre amp so much that I couldn't get a clean signal any other way.
  5. christw

    christw Get low!

    May 11, 2008
    Dayton OH
    I want to be Tesla (tinkerer at Dayton Amp Co)
    ^ This guy gets to build Ampegs as his job.

    Using the active input is equivalent to rolling off your volume knob on your bass a bit or turning down the gain knob.
  6. JimmyM


    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    Been using active basses off and on since 1991. Number of times I've used the active input or switch on an amp: 0. That includes SVT's.
  7. rickdog

    rickdog Gold Supporting Member

    Mar 27, 2010
    Almost. The SVT-CL has a tube stage before the gain control. If you have a really hot active bass, you might be able to get some noticeable distortion out of it with the volume on the bass turned up all the way. So the -15 dB input is for people who want a really clean tube preamp sound with a hot bass.

    But if you like a little bit of tube dirt (like I do), plug into the 0 dB input and crank 'er up! You won't hurt anything (except maybe your hearing).
  8. mydog213


    Jul 15, 2012
    So putting in a hot ass ****ing bass in a 0db input wont **** **** up?
  9. JimmyM


    Apr 11, 2005
    Apopka, FL
    Endorsing: Ampeg Amps, EMG Pickups
    No, it ******* won't.
  10. Bassoballs


    Nov 14, 2009
    Mid Michigan
    I think the pad is a tone suck. I use active basses, so what I did was replace V-1 with a 12AT7 to lower the gain.
  11. beans-on-toast

    beans-on-toast Supporting Member

    Aug 7, 2008
    The important thing to keep in mind is that an active bass puts out a stronger signal than a passive bass. On some amps, the stronger signal from the active will overpower the input of the first stage, resulting in distortion. They add a -15 db pad on one of the inputs of the SVT-CL to allow you to lower the signal that the amp sees from the instrument. The pad isn't anything magical, it's a couple of resistors.

    As has been said, if you plug the active bass into the normal (0 db) input and it sounds good, it is best to use this input. If the signal is too strong, plug into the -15 db input.


    What follows is optional and is a simplified explanation of what is going on. :p

    Below is the input stage of the SVT CL.

    Plug into the -15 db input and your instruments signal flows through a voltage divider which consists of the 100K ohm resistor on top connected to the 22K and 3.3M ohm resistors in parallel and connected to ground. This voltage divider attenuates the signal by about 15 db before it is fed into the input of the 12AX7 tube.

    Plug into the 0 db input and you instrument signal flows through a different voltage divider that doesn't attenuate the signal. The signal path is through a voltage divider consisting of the 22K ohm resistor parallel to the 100K ohm resistor, and the 3.3M ohm resistor to ground, and then the signal flows into the input of the 12AX7 tube.

    With both inputs, the signal path is through a voltage divider. One pads or attenuates, the other doesn't. A pad can affect tone. In general, the less complicated the signal path, the purer the tone.



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