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GK 700RB-II input/pre-amp section questions

Discussion in 'Amps and Cabs [BG]' started by Big AL-Muncher, Feb 21, 2018.


  1. I just got this amp, but not sure what's up with the input section. On my old SWR amp, the manual basically says to turn the input up until it barely clips (light blinks) on your loudest notes. It also says clipping won't hurt the preamp. Should I operate the GK amp in the same way? When I crank the input gain on the GK, the clip light never comes on, even though I can clearly hear it clipping like crazy. Is it just a bad light then? Will clipping harm it, or just sound bad?
     
  2. wave rider

    wave rider

    Jan 5, 2005
    The GK gain staging differs from most others. The clip light comes before the preamp section so only a super hot bass will light it up.

    Most seem to like the input around 11 o'clock, boost to taste, and woofer used as master volume. Boost and woofer are interactive, experiment to find the flavor you like.
     
    Kro and Big AL-Muncher like this.
  3. Thanks! I just started using the RB700 today, and I'm blown away so far.
     
    The Thinker and wave rider like this.
  4. The Thinker

    The Thinker

    Sep 17, 2003
    Chicago, IL
    What you are hearing is the famous “GK hitting the rails” sound—it’s there by design and is not the kind of clipping you need to avoid :). The more input you dial in, the more distortion you’ll hear as you turn up the boost knob. Just a touch will warm up your sound, or you can go full-on gnarly. It’s a wonderful amp—rock it hard :).
     
    Big AL-Muncher likes this.
  5. SunnBass

    SunnBass All these blankets saved my life.

    Aug 31, 2010
    Columbia, Mo
    This is correct information.
    Do your best to try to not let the light come on at all.
    Even a pedal set too aggressively can clip the preamp.
    Clipping, on a GK can damage the preamp.



     
    Big AL-Muncher likes this.
  6. groovaholic

    groovaholic The louder the better. Supporting Member

    Sep 19, 2004
    Mount Prospect, IL
    Yes and no.
    The clipping won't damage the preamp, but you're correct when you say that cranking the input gain is NOT the way to get the best performance out of this amp.

    As a 700RB user I'll recommend this:
    Start with your VOLUME and CONTOUR all the way off (counterclockwise).
    Set the PRESENCE, TREBLE, HI MID, LOW MID, BASS, BOOST, and WOOFER controls to "noon".
    Play something aggressive--if the Clip LED lights up, hit the Pad switch.
    Slowly! Turn up your VOLUME control until you get to your desired sound level, then adjust your EQ to taste.

    The interaction between VOLUME, BOOST, and WOOFER is different than other amps, and rewards some experimentation and listening...
     
    Big AL-Muncher and SunnBass like this.
  7. SunnBass

    SunnBass All these blankets saved my life.

    Aug 31, 2010
    Columbia, Mo
    Funny thing is, the clip light comes on when the pre-amp is being clipped.
    So, if too hot a signal hits the pre-amp, the light comes on.

    So, many years ago I purchased a 700rb-II floor model from Guitar Center. (Yes, I played it in the store, at "store volume")
    I got it home, and it blew two 15" Black Widows, almost immediately when played at practice.
    I thought that maybe the speakers were already getting ready to fail as they were quite old, and a decent amount of wattage finally pushed them over the edge.
    So I ordered two new speakers, installed them (yes correctly). We play a show that night and I notice halfway through the set I lost some volume. When we loaded back into our practice space that night I checked the cab and it was down to 8 Ohms (wired to be 4, showed 4 earlier). Come to find out that one of them had blown. The next day I went out to the space and played, just to see what was going on. Every time I hit a note, there was this strange, almost mechanical sounding "after-note" for lack of a better term. The next day I took it to my amp repair guy (GK licensed) and he hooked it up to the oscilloscope and yes, there was an extra, extremely spiked wave following the initial. He verified that this could have been the cause of the speakers blowing. So I left the amp with him. I get a call a few days later and he told me that he had to replace the entire pre-amp because it was fried. He then sent the pre-amp to GK so they could check it out. The tech from GK that he had been in contact with told him in no more, or less terms that the pre-amp had been hit too hard on the front end, either by a super hot active bass, or any signal boosted too hard. I have never owned an active bass, and any and all of my pedals are always at unity volume. So it wasn't me.
    So yes, the clip light comes on when too hot a signal hits the pre-amp.
    Why else would it even come on, or be there for that matter?
    If that happens too much...poof!
    It happened to me, and it can happen to anyone.
    Take care of your gear ladies and gentlemen.
     
    Big AL-Muncher likes this.
  8. Stevorebob

    Stevorebob Well... I Am Here, Aren't I? Supporting Member

    Sep 29, 2011
    Los Angeles
    On a GK, the clip light is the input clipping with a hot input signal not the pre clipping, and it comes on just before clipping. So, if it flashes a little, you’re okay, but more than a little and you need to reduce the input or hit the pad.

    GK suggests starting by setting the woofer to noon and then adjusting the pre to the desired volume. I prefer the tone of power amp working harder — hitting the rails — so I set my woofer to 2-3 o’clock and volume as needed. The boost also adds volume, start at noon and adjust from there working with your volume for the desired tone.
     
    Big AL-Muncher likes this.
  9. The input clip light has never come on with my bass which is passive. I thought the light was not working, but apparently it just takes a lot more juice than i have to light it up. So - the light coming on can indeed damage the preamp...good to know. Thanks
     
    SunnBass likes this.
  10. It seems there are some differing answers to my question. I seriously wonder if the input clip light is working. I turned my bass all the way up and turned the input gain all the way up until it was very distorted, not growling, distorting big time..but no clip light whatsoever. The manual says the boost knob in the main volume section is what adds the growl. IS there a way to carefully test this light without blowing up the pre-amp? Also, it seems to me I could just turn the boost all the way down, then "by ear" slowly bring up the preamp until its hot, but not distorting. then use the boost knob for growl, right? Sorry this thread has gotten confusing for me. Thanks for hanging in there so far :)
     
  11. groovaholic

    groovaholic The louder the better. Supporting Member

    Sep 19, 2004
    Mount Prospect, IL
    Re-read what I wrote: the clip LED is before the VOLUME control, therefore it is not affected by any setting of that gain control--only by the pad button.
     
  12. Ahaa. I get it now. Thank you!
     
  13. Primary

    Primary TB Assistant

    Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products.

     
    May 17, 2021

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