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GK400RB EQ question

Discussion in 'Amps and Cabs [BG]' started by LarryR, Oct 19, 2005.

  1. LarryR


    Feb 2, 2003
    Los Angeles
    I've spent some time searching the archives to no avail.

    Can someone explain the relationship (and ideal settings) of the Volume, Boost* and Master on the older 400RB heads?
    I'm not entirely sure where to set these controls and have a hard time discovering any no-no's with certain settings - bad example being: input VOL at full, Master for loudness - just the opposite of what I'd do). Conversely, should Master be near full and input VOL for loudness? Is the Boost additional Volume or does it mess with the EQ as well?

    * FWIW, I won't be using a pedal on the boost channel.

    Thanks for any advice.
  2. put input volume at 9 oclock, boost at maximum, and master volume to volume needed.
  3. tadawson


    Aug 24, 2005
    Lewisville, TX
    Volume determines preamp gain, and is mostly used to get a decent level without clipping the front end. Boost gives overdrive into the front end of the power amp, for "growl", etc, and master is the final output level control to the power amp.

    Myself, I would be inclined to set volume and boost for sound, and the master for volume.

    - Tim
  4. LarryR


    Feb 2, 2003
    Los Angeles
    Just what I was looking for. Thanks guys.
  5. Lowtonejoe

    Lowtonejoe Supporting Member

    Jul 3, 2004
    Richland, WA

    I guess to each their own but on my 700RBII running the boost at maximum sounds terrible to me!

    The boost introduces even order harmonic distortion into your signal. I think it sounds great at medium settings but after 3 o'clock it gets too harsh.

    You can download a manual for your unit by clicking here.

    I run the boost around 12o'clock with really excellent results.

    But hey, to each their own.


  6. 4Mal

    4Mal Supporting Member

    Jun 2, 2002
    Columbia River Gorge
    +1 - Hi Joe!
  7. Lowtonejoe

    Lowtonejoe Supporting Member

    Jul 3, 2004
    Richland, WA
    Hi Mal!


  8. tornadobass

    tornadobass Supporting Member

    Nov 20, 2000
    Iowa City, Iowa
    Endorsing Artist: Black Diamond & SuperSensitive strings
    Volume between 9 and noon, boost between 10 and noon, master to set actual sound level.

    The manual cautions not to set the volume (first knob) past noon. With the boost all the way down, the output is much lower. The amp gets pretty wild once the boost goes past noon.

    BTW, at least on the 700RB (I've had both 700RB and 400RB), the clip light measures signal before the first knob, unlike most amps. Changing the volume setting will not stop the clip light...that has to be done at the bass or with the pad button...somewhat unexpected.

    BTW, check the centers of the knobs on the 400RB. I thought I'd been using my 400RB at 1/2 to 3/4 volume, but the center had actually turned and I'd been running it close to full volume much of the time...and it didn't distort...amazing!
  9. for some really interesting results, try turning the volume and the boost all the way up and turn the master down. Maybe an alternative to moog bass?
  10. LarryR


    Feb 2, 2003
    Los Angeles
    Thank you all for your input. It is appreciated.
    Thank you Joe for the link.

    Funny thing, Modern Growl's suggestion to pin the Boost is extreme, but, still good info. It let me hear what the extreme setting will achieve. It's not my taste, but, finding a sweet spot where the amp gets a bit "driven" is good to know IF you're stuck at a gig and someone wants that tube sound.

    Sure, it aint an SVT, but, it satisfy's on a certain level.

    Thanks again guys.