separate pre & power amps...which to crank?

Discussion in 'Amps and Cabs [BG]' started by peteroberts, Apr 6, 2003.

  1. I'm going to start using a separate pre/power amp configuration...should I turn the power amps all the way up and run the pre master lower or run the pre high and the power amps lower, or does it matter?
  2. Petebass


    Dec 22, 2002
    QLD Australia
    There's 2 schools of thought on this. Whichever way you go, keep an eye on the clip lights.

    Personally I believe it's better to crank the power amp, especially if you don't have a clip light on the pre-amp. Typically this method results in a much lower input gain position and makes it virtually impossible to send a clipped signal to the amp. PA guys always use this method.

    If you want to go the other way, set the pre-amp gain so that you don't clip the input. Do this by hitting your bass as hard as you can and adjusting the gain so the clip light on the pre-amp only flickers every now and then. Then adjust the volume of the poweramp to get the SPL you need.
  3. I run my preamp master all the way up, adjust the preamp gain depending on what bass I'm using, and use the poweramp levels for volume control. It was explained to me this give the best signal to noise ratio, and has worked great for me.

    Eden Navigator and QSC Poweramp.
  4. PollyBass

    PollyBass ******

    Jun 25, 2001
    Shreveport, LA
    To get the most power out of you're amp, crank the master volume, then turn on the gain, and play till you only get red flashes if you smack you're bass pretty hard.
  5. Tecx

    Tecx Radio Rock Leads To Sterility

    Jun 9, 2002
    Halifax, NS, Canada
    I keep my RBI at half master volume, and my poweramp between half and 3/4's...

  6. Planet Boulder

    Planet Boulder Hey, this is a private Supporting Member

    Nov 10, 2001
    6,482 feet above sea level
    I once had impure thoughts. Oh, and I pluck my ear hair.
    I've fiddled around with this and I have found that, for me, the best option is to turn the power amp all the way up and then adjust the preamp gain accordingly. A someone else stated, this takes care of the clipping problems more effectively.

    In fact, the manual for my Carvin power amp states that you should do it this way. Seems to work best for me.
  7. So what do you set your preamp master volume at?

    I've had no problems with clipping with my setup. I mean, the preamp gain stage can clip no matter what is happening after it, especially if you have a hot bass and really crank the EQ on the bass.
  8. BruceWane


    Oct 31, 2002
    Houston, TX
    Depends on the layout of the preamp, i.e. if it has separate gain and master volume controls. Preamps sound different depending on how hard you push them (especially tube preamps). So, if you only have one control, your best bet for a consistent sound is to dial in the sound you want at the preamp and then adjust your overall volume with the poweramp. If you have a separate master volume, then you could crank the power amp and use the master to adjust volume level.
  9. Bob Lee (QSC)

    Bob Lee (QSC) In case you missed it, I work for QSC Audio! Gold Supporting Member Commercial User

    Jul 3, 2001
    Costa Mesa, Calif.
    Technical Communications Developer, QSC Audio
    I usually recommend that you turn the power amp down to use only as much gain as you need to, and put a reasonably hot signal into it from the preamp. This will help maximize your signal-to-noise ratio.

    However, the precise mix of preamp and power amp gain is not all that critical unless you're going for an overdrive sound that comes only at certain levels.
  10. redneck2wild


    Nov 27, 2002
    Memphis, TN
    I have found that I get less noise if I set my Preamp output always at 75% and use the poweramp to control the overall volume.
    If I set the poweramp at maximum and adjust the preamp output instead, high end hiss is more evident at lower volumes. I think it has something to do with the signal to noise ratio.
  11. Schwinn


    Dec 4, 2002
    Sarasota, FL
    My approach, so far, has been to turn the pre-amp master all the way up, the pre-amp gain about 3/4 of the way up, and the power amp gain also about 3/4 of the way up...

    ...and I use the volume knob on my bass to adjust actual volume.
  12. arfur


    Nov 26, 2001
    London, UK
    I guess there are lots of ways to do this.

    I leave the poweramp gain on full. I set the preamp gain to the correct level for the bass in question and use the master volume on the preamp to adjust my volume. This has the advantage that the sound man who has taken a di signal from my preamp gets a similar level no matter which bass I use and no matter how I have set my on-stage volume.
    When I used to do a bit of sound engineering the poweramps where those things by the speaker stacks at the other end of the room. You set the gain to max and left them. I guess my thinking comes from this.
  13. A lot depends on your pre-amp. I've found that with tube pre-amps, they sound better when you run them pretty hot. I've got an Alembic F1-X and its tone seems to chang a bit depending on where I set the gain. I run it at about 1:00 and adjust the gain on the power-amp. But with a SS pre-amp, I think I'd probably turn the gain up full on the power-amp adjust the volume with the pre-amp to preven clipping at the pre-amp stage. SS pre-amps really suck when the clip. jmho
  14. bassmonkeee

    bassmonkeee Supporting Member

    Sep 13, 2000
    Decatur, GA
    I'm new to the whole separate pre/power amp thing.

    I have just started using my VBass as a preamp, and a Nady SPA 850 as the power amp. I have been putting the gain on the power amp at about half way, and using the master volume on the VBass to adjust the sound level. It's worked pretty well so far, but I've only played one gig with the combination.

    Coincidentally, I'm sending a balanced XLR from the VBass to the Nady, and that seems to have a better sound than when I first tried it with the 1/4" unbalanced.

    I might try to crank the poweramp, and turn the master volume down further on the VBass. The volume goes from 0-200, and I've been setting it between 130-160 for most patches, so far.

    I picked up the Nady for $199 from Musician's Friend as a backup to my Mesa Walkabout, and so far, it's been well worth the small expense.
  15. Uh, if you turn the preamp gain all the way up, its gonna clip anyhow - certainly using any active bass with decent pickup output.

    As for the DI issue, my preamp has a DI level control, so thats not an problem with my set up.
  16. thetaurus


    May 28, 2002
    Muncy, PA
    how much damage can be done to your preamp if it the red clip light comes on. i have an ampeg svp pro, and i've been keeping the gain around 12 o'clock to avoid that light coming on, but what damage, if any, would be done if i turned the gain up alittle more and had the light come on much more frequently?
  17. Aram


    Feb 2, 2003
    New York, NY
    I might be wrong, but I think that clipping will damage your speakers (rather than your preamp) by virtue of the fact that you're amplifying a clipped signal. I think most preamps can handle the tubes being driven, so the pre should be fine if this happens, but keep an eye on the speakers.

    Even worse is power amp clipping (which I have done)...that will definitely mess up your speakers if it is in excess...
  18. Bob Lee (QSC)

    Bob Lee (QSC) In case you missed it, I work for QSC Audio! Gold Supporting Member Commercial User

    Jul 3, 2001
    Costa Mesa, Calif.
    Technical Communications Developer, QSC Audio
    You probably won't damage anything unless you're overpowering your speaker(s) when that happens.
  19. yea but amplifying a clipped signal cant yield the best sound :)