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amp & pre volume ratio question.....

Discussion in 'Amps and Cabs [BG]' started by BullCityBass, Jul 25, 2005.

  1. BullCityBass


    Jun 14, 2005
    Durham, NC
    I am running seperates (alembic f-1x & plx 2402) and I am wondering what is the best way to run my volumes on each. Right now I am running the pre at 12 o'clock and the amp at 1 o'clock (in my house) and I am not sure if this is the best way to control volume. It sounds fine but I am wondering if I should be running my pre higher and my amp lower or vice versa. Is there a standard practice or does it not matter?!?

    I am looking for the best signal coming out to my cab with the least amount of noise.

  2. theshadow2001


    Jun 17, 2004
    I'm probably not the best qualified to answer but if there's a clip LED on the amp input or the pre output, you set the gain on the pre so that the cliping indicator is lighting occasionally at high peaks when playing hard.

    A few good salps on the open E should get it flash on and back off for a very short time just make sure that its not on constantly.

    Maybe we could get a second opinion on this though.
  3. seanm

    seanm I'd kill for a Nobel Peace Prize! Supporting Member

    Feb 19, 2004
    Ottawa, Canada
    Ok, do I count as a second opinion? I agree. When I first bought my iAMP I was nervous about running the gain more then 12:00. John at EA said it was best to run the gain until the overload led came on once in a while.

    Well, long story short, I had speaker farting problems and finally ran with the gain cranked. Speaker farting problems are gone and I run at much lower volumes.

    So crank that gain and then use the volume control to adjust levels.
  4. BullCityBass


    Jun 14, 2005
    Durham, NC
    cool, i will give that a try. Makes complete sense though now that I think about it. duh I was just use to my older integrated amp which had the gain light to adjust by, there are no lights on my preamp now but that is what the lights on the amp are for...

  5. yup, I agree.

    Gain structure is one of those tricky things that gets a lot of folks into trouble. That's one of the reasons why there are so many bad "sound engineers" out there!

    Usually we want as much input gain at every stage as we can get without causing clipping. This means the signal to noise ratio is at it's lowest and the circuitry is being fully utilised.

    Too low and you risk introducing noise, too high and you risk clipping distortion. Ocassional clipping is considered to be ok.

    Use the very last gain or volume knob in the chain to affect overall volume changes.
  6. 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
    Fixed it for ya. :)

    Don't worry about getting it set all too precisely. Even if you're a few dB off from what would give you the absolute best possible signal-to-noise, unless your gear is really crap it should be fine. Avoid anything more than occasional brief, insignificant clipping. There is no "ratio" of where you should set one in relation to another.
  7. r379


    Jul 28, 2004
    Dallas, Texas
    Excuse me if I seem dense, but is the idea to use the knob on the amp and not the preamp to control volume? I've been leaving the amp on full and using the master volume on my SVP Pro to control volume.
  8. Lonnybass

    Lonnybass Supporting Member

    Jul 19, 2000
    San Diego
    Endorsing Artist: Pedulla Basses
    Bob Lee is a wise man. :cool:

    I too use an Alembic F-1x and find that it delivers the goods at about 12 to 1 o'clock, without pushing the tube too hard and getting any distortion.

    I use my power amp (Stewart 2.1) to control overall volume, but I rarely have much of a need to go much higher than 1 o'clock.

    Of course, these settings will differ from amp to amp and from stage to stage, depending on your overall volume needs. But personally, I don't like the idea of maxing out volume on the power amp because all it takes is one accidental twist or bump of a knob and -poof- there go your speakers!

  9. If you can, and it's not inconvenient, I would consider it preferable. However, using the master on the pre-amp is probably not a bad way of going about it. Unfortunately, not all preamps have a master gain knob.

    Consider the case of large concert PA rigs. The mixer isn't standing there adjusting the volume of every power amplifier as the gig goes along, he's riding the master outputs of the mixing desk!