SVT 4 pro clipping when volume is at zero?

Discussion in 'Amps and Cabs [BG]' started by greendayjustin, May 13, 2005.

  1. Hey, I just got my 4 pro brand new today and i love it. There is a minor problem though. When the master is even at zero the preamp clipping light comes on when I play. I do not play an active bass, but when I press the -15 db switch, this fixes the problem, and the pre amp clipping light only goes on when I hit hard notes. I can still get a good volume out of it, since it is mono bridged at 4 ohms, but I know if I dont use the switch, it can go way louder. I just find it strange that the preamp clipping light goes crazy even when the gain and master are at VERY low settings.
  2. Tash


    Feb 13, 2005
    Bel Air Maryland
    Try rolling your volume knob back. It sounds like you are too hot on the input, passive or not.
  3. Ummm.... I can only suggest turning the gain down. The Gain controls your input level and the master volume controls your output level. If it still clips when your gain is below 1/4 and you aren't sending a really hot signal from your bass, or through pedals then I don't know what to say?
  4. popinfresh


    Dec 23, 2004
    Melbourne, Aus
    The master volume has nothing to do with the input stage clipping (Right?).

    What you do is turn the master and gain all the way down. Then work the gain up until the clip light comes on occasionally only when you dig hard, then start bringing up the master volume until you get the desired level.
  5. BassIan

    BassIan Supporting Member

    Apr 27, 2003
    Cupertino, California

    This is exactly correct.
  6. +2. Sounds like the amp input is set up to accomodate really low output basses, and your bass has a high output. If you need to use the input pad switch to keep it from distorting, use it, that's what its for.

    It will not make your amp any quieter to use the input pad switch Its there to keep the input from clipping. Use the master volume to compensate for the input pad, and you have the same volume, minus the distortion.

  7. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    +3.....good advice above.
  8. I have been doing that, and it has been working fine. The thing is, even when the master and gain were set at almost zero, the preamp clipping light came on. I will try using it with one of my other basses, and see how it goes.

    Thanks for the help guys :bassist:
  9. There may be an input gain stage before the first gain knob, but after the -15dB input pad. If the clip light comes on when the input gain is at zero, that's got to be what's going on.

  10. I forgot to mention that I'm using a sans amp bass driver.

    Thanks, Justin.
  11. Where do you have the level and gain controls set on the SansAmp?

  12. Tash


    Feb 13, 2005
    Bel Air Maryland
    That's the problem. Sansamp DIs are designed to make a signal straight from your bass hot enough to use direct into a mixer. They can be used with regular amps too, but you have to be really careful with the settings or they will be way, way too hot for your amps input section.

    That could easily overdrive the amp input. Definitely run the -15dB pad. You do NOT LOSE ANY POTENTIAL VOLUME that way. Just turn up the master to compensate for the loss from the pad. The total output of the amp doesn't care (or even know) where the knobs are.

    Pad off, Input gain=7, master=2 is just as loud as
    pad off, input gain=2 master=7. Which could be same as
    pad=on, input gain=7, master gain =7 (if mg@7 is 15db higher than mg@2). All are perfectly legitimate settings, you choose based on what keeps the clip lights mostly off.

    Adjust pad and input gain to keep the input clip lights out most of the time, and put the master gain wherever it wants to go to get the volume you need. Doesn't matter if its at 2 or 10. Or 11 if you have the Spinal Tap version.

  14. Unless he's using the new version, which has a switch for the outputs. You can switch it to "instrument" level for use in front of an amp.
  15. What if you have the input gain on 2 and the master volume on 10 (no more room to get louder). That's not as loud as the input gain on 7 and the output gain on 10.

    I'm afraid I don't understand. When I switch the pad on my SVT 4 Pro, there's a very noticable drop in volume.
  16. Your 200W amp puts out 200 W maximum. Period. Hit the -15dB pad, the volume drops 15dB, the amp is still capable of putting out 200W. That's what I'm saying. If your bass is hot enough to require the pad turned on, you just turn up the master by 15dB to get back up to 200W.

    Not quite... 7 and 10 = more gain than 2 and 10. But if your bass is already hot enough to get to 200W with the amp at 2 and 10, setting the amp to 7 and 10 gets you no louder, only increases distortion. See the difference? Same with the pad. If you are at 200W with the pad on, it doesn't get 15 db louder when you switch the pad off, it just turns to 200w of distorted signal.

    The input clip light is there for a reason, it tells you when the input is too hot for the amp. Plug in your bass with the fishman. If you have to turn the input knob way down, say between 1/2 and 1 to keep input clip from flashing, its really touchy, hard to precisely adjust, right? Slight twitch has major consequences. So turning the pad on drops the signal 15dB so you have to turn the input knob up to compensate, get back to the same level. Now maybe the input knob should be set around 7 or 9 to get the input clip light light. But there's enough room around 7 to make small adjustments easily. If the clip light lights rarely, the signal is hot enough to get your full 200W output from the power amp with the master volume at a reasonable value. Could be anywhere, but usually somewhere between 4 and 8 or so.

    Now plug in your passive bass (no fishman), pad is still on, even with your input knob all the way to 10 the input clip light never lights, NOW you need that extra 15dB of gain to get to 200W. Turn the pad OFF. You'll probably have to turn the input knob down a bit to keep the clip light off most of the time, but its still in a reasonable range.

    With either case, you get the amp to full 200W output.

    Amp=( input jack -> optional pad -> input preamp -> input knob ->preamp2 ->clip light -> EQ -> master volume -> power amp -> speakers)

    Its like the 3 bears. The internal parts of the amp need a very specific signal level at preamp2 to avoid clipping, not too hot, not to quiet to minimize noise, and still get full output out of the power amp. The designer controls signal levels from preamp2 onward in the circuit design.

    The wide range of signal levels in various basses and effects requires the pad and input knob to accomodate all of them, but its up to you to adjust them to the correct level to match your particular bass/effect setup.

    Does that make more sense? Its hard to get without knowing how amps are put together internally.

    If different signal levels are languages, different effects and basses speak different languages. The pad and input volume perform different translations. Depending on the bass or effect you start with, different, maybe multiple translations are required, but when the appropriate translations are applied, the final result is 200W of English going to your speaker. Using the clip light as your guide, it and the input knob levels tell you what language you're feeding the amp.