Gain Control options?

Discussion in 'Amps and Cabs [BG]' started by StoutXXX, Apr 15, 2004.

  1. OK I have an SVT3 with a DBX compressor. I usually run my master wide open for headroom with my pregain turned just before clipping and I use my gain knob on the compressor for overall volume. My idea is that Trimming the gain down in the loop/compressor (cause I dont want to turn down preamp gain) allows the amp to run at full(master) headroom without being pushed as hard overall. Is this a correct way of thinking and any other suggestions?
  2. BassIan

    BassIan Supporting Member

    Apr 27, 2003
    Cupertino, California
    I would consider rethinking the situation. First you need to understand that your amplifier will be quite capable of its maximum output at well below full on master volume. The master volume doesn't dictate your "headroom" really at all. The power is available even if the volume knob isn't at maximum (provided your preamp allows for it, different amps respond differently). You are correct to set the pregain just before clipping, though on the SVT3, I believe you can drive the preamp into clipping to overdrive your sound a bit, if you so desire anyway.

    I'm not familiar with your compressor, but on many compressors the gain affects the compression characteristics. Assuming this is the case with your DBX (if it's not, ignore me for a few sentences), your adjustment of the gain will affect more than just volume. Use that to set up the compression characteristics, use the pregain on your Ampeg to set up the tone, and use master volume to control *only* the volume.

    Just my thoughts... hope this is helpful!
  3. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    Do you mean an SVT-III or an SVT-3PRO? I assume the 3PRO, since it has a master that is after the loop.

    You can do that, if I understand you right. I THINK you are saying that you are using the compressor to set a constant max level, and then are using the output of it to adjust your volume so you won't go over the level the compressor sets. You are putting the master up to "get it out of the way".

    That can work, as long as the compressor can deal with the signal. Might be that you need to mess with the attack time and compression ratio to get what you want without squashing the signal too much.

    The 3PRO has no power amp limiter.

    Well, you do want to get the bass signal in as hot as won't distort too much.

    The master headroom idea is OK, "pushing" will depend on the level you set.But it would be OK if you didn't use the limiter too. Then master would do pretty much what your compressor volume is doing.

    It isn't a "calibrated dial", its relative. Halfway up isn't half power.

    What you get with the compressor is a somewhat "guaranteed" max output level even if input goes up. Overall average loudness is also raised as you compress the signal.

    I am not too sure that is what you think you are getting. I don't see any big advantage other than the max level deal, if for some reason you didn't want to get too loud no matter what.

    The 3PRO can be "booked" without trouble or damage, just turn up the master and tube gain and go, no limiter needed. The tube gain also gives *some* compression if turned down.

    One issue with *real" compression is that it tends to exaggerate EQ etc if done to excess.
    If you turn up lows prior to the compressor, it will track them, and tend to squash highs, or vice-versa. It pretty much tracks volume along with the largest signals. The more compression, the worse this is. Kinda like the crowd noise on the baseball broadcasts used to be. The announcer would speak, and the crowd noise would go away, then come back up when he stopped. Sometimes called "pumping".

    So I wouldn't get too far out with it unless you want that sort of effect.
  4. Well it is a pro. I do run pre amp gain sometimes for warmth/ clipping and I always run full drive on the tubes. Anway I have the three knob DBX160 and run 5:1 compression with threshold at -10decibles and trim gain at compressor anywhere from -10 to +10 for practice/ gig situations while leaving the mapeg head master at 10. I love the compressor for thick lows and harmonic sustain as I tend to pump the amp with 80hz and cut everything below40hz on a 6X10hlf.