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gain levels and power amps and preamps?

Discussion in 'Amps and Cabs [BG]' started by RS, Apr 1, 2002.

  1. RS


    Aug 27, 2000
    Cleveland, OH
    How loud do you adjust the gain on your preamp vs the gain on your power amp?
    Is it better/worse to have one much higher than the other?

  2. mikemulcahy


    Jun 13, 2000
    The Abyss
    I run the amps and the post gain on the pre dimed. Adjust the volume with the pre gain.

  3. VicDamone


    Jun 25, 2000
    I'm not sure of a hard and fast rule for this setting other than to achieve your desired tone by means of a gain adjustment.
    A good place to start is to get as much input gain as possible without clipping the input signal from your instrument. This is assuming your preamp has an input gain control and an LED or a meter to determin the amount of gain entering the preamp.
    Next, turn the master gain or output gain of the preamp halfway on. With the power amplifier gain controls all off turn your system on and adjust the amplifiers gain to your desired volume.

    If your power amp doesn't have a gain adjustment or you want to run the amp at full power at all times then you'll be adjusting your volume with the master output gain on the preamp.

    There are many ways to do this so experiment and find out what works for you.
  4. For the technically correct way to do it, go here:


    Of course for bass, you can turn up the pre-gain to get the desired level of distortion, then move on to the other gain settings.

  5. PolkaHero


    Jan 5, 2002
    Interesting article, but I think this refers more to P.A. applications where you usually set the volume on the power amps higher and the pregain's on the mixer at the desired level. On a bass amp, however, I was always told to set the pregain until right before the point of clipping, then set the master volume at the desired level.
  6. Yeah, it's aimed at PA stuff, but the idea is the same. The only difference would be if you want some distortion on your bass signal, then you would turn the pregain up past the point of clipping.

    From the way I read the article, it tells you to do just what you say for bass. Set the Pre as high as possible without clipping, then set the Post for the desired sound level. That gives you the highest Signal to Noise ratio. If you want a little more clean headrooom, decrease the pregain, and increase the post gain.

    You should do the same for PA. The input clip LED's should barely be flashing on all the inputs, then use the faders for individual volume control, use the mixer output level at the 0dB point, and use the power amp volume to set the overall level limit. If you turn the power amp up all the way, and then run the gains on the mixer down real low, your gonna get extra hiss, hum, and noise, because your power amp's gain is higher than it needs to be. The hiss, hum and noise coupling onto the interconnect to the power amp is pretty much constant (except for the stuff getting amplified by the mixer), so you want the signal running down that line as large as possible, then you can turn the power amp gain down, decreasing the amplification to the hum, etc.


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