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Ah! need help! GK 800RB

Discussion in 'Amps and Cabs [BG]' started by JBass1, Mar 12, 2009.

  1. JBass1


    Dec 6, 2005
    So I just got a GK 800RB and have it running through an SBX Plus 4x10

    I am experiencing some distortion when I play, especially in the upper register of the bass. I have messed with the EQ to no end and I can't seem to get rid of the distortion...even with the amp turned to extremely low volume (so I'm pretty sure it's not the cab). Does anyone have any ideas? Could it be from the amp being old?


    oh, and the cab can handle 800w, impedence 8ohm ..the head puts out 100w at 8ohm
  2. John Webb

    John Webb

    Apr 20, 2006
    Myrtle Beach,SC
    Is that a GK Cab? If so are you running in Bi -amp mode.
    This amp has 200W on the low side into 8 ohms, 300w INTO 4 ohms and 100 Watts on the high side into 8 ohms only.
  3. Dan55


    Apr 26, 2006
    That head has two amps - the main(low) one is 200w @ 8ohms/300w @ 4ohms. The high amp (unused unless you're bi-amping) is 100w @ 8ohms.
    I'd start with the eq levels at 12 o'clock, volume at 11 o'clock and main amp output as needed. If that doesn't give you a clean signal, you may indeed have a problem.
    Also, if you're playing an active bass, you might need to engage the db pad at the input.

  4. SanDiegoHarry

    SanDiegoHarry Banned Supporting Member

    Aug 11, 2008
    San Diego, CA
    1) check your cables
    2) Check your bass - if active, change batteries
    3) check the cab - you may have a blown tweeter/driver

    Lastly, you may be overloading your amp (as John Webb said above) - Normally, that GK head is very clean, but if you overdrive any amp it will start breaking up (or blowing up!)
  5. John Webb

    John Webb

    Apr 20, 2006
    Myrtle Beach,SC
    You really need to understand how that amp functions.
    Download the 800RB manual on the GK website!!

  6. allexcosta


    Apr 7, 2004
  7. 20db pad

    20db pad

    Feb 11, 2003
    I been everywhere, man...
    None. At all.
    I sort of collect old GK 400RB and 800RB models as tributes to my lost youth - they were the big thing in bass heads back then. The 800RB requires a thorough study of the owner's manual, as some simple mistakes can be very bad for the future performance of the amp.

    There's been a couple times when I would fire up an old GK and experience the same thing - distortion at any volume. In all these cases, a thorough cleaning of the input jack with Q-Tips and alcohol eliminated the problem. The proper way to do this is to use contact cleaner, but the method I used works. Either way, make sure the amp is not connected to a wall outlet when you do it.

    In other instances, I've replaced the input jack, as they do wear out due to the fact that they are subject to stress and strain because of their unsupported location on the circuit board.

    I'll also echo the advice to try a new battery in the bass or testing the amp rig with another bass.
  8. SanDiegoHarry

    SanDiegoHarry Banned Supporting Member

    Aug 11, 2008
    San Diego, CA
    Hey, I have a question for you: I'm still convinced the 400rb is one of the best sounding bass amps ever; When these were new items (in the late '80s) I was a sales man at a guitar store here in town, and I did *extensive* side by side comparisons with the 800RB and found that I liked the sound of the 400 better... Now, I know the 800 was designed specifically for bi-amping, so the cabs I was using likely had much to do with my decision - I used a GK 4x10 cab for the 400; a 4x10 & a 1x15 for the 800.... no matter what I tried, I thought the 400 sounded better. Was it just me - they seem to use the same preamp arrangement...
  9. What kind of distortion is it? It's hard to give advice without more info.

    The 800RB head is a very growly head, and it can get quite dirty with the boost turned up. Are you used to very very clean amps? It could just be that you're confusing this with bad distortion.

    You didn't really say whether this was good distortion or not... if it sounds good, and your speakers aren't farting out, you shouldn't have a problem.
  10. Ah, I missed this tiny detail.

    As mentioned, the 800RB has two amps. Be sure you are connecting to the bottom set of speaker jacks, the woofer amp.
  11. 20db pad

    20db pad

    Feb 11, 2003
    I been everywhere, man...
    None. At all.
    I've had this conversation many times over the years - the preference between the 400 and the 800 seems to sway towards the 400RB. I can't offer any reason why, outside of the fact that the 400RB is more user-friendly than the 800RB.
  12. JBass1


    Dec 6, 2005
    As for my bass - it has an active/passive switch and the distortion comes through on each

    the distortion isn't necessarily bad...it sounds kind of cool, if I wanted distortion...but I can't get rid of it. The cab is plugged into the High 8ohm jack...would it work if I plugged it into the 4ohm low jack?

    BTW I have the GK SBX Plus which is different than the regular SBX...it has 800w instead of 400w

    I have tried switching the bi-amp on and off and and I still get it

    I have tried the boost all the way down and that didn't do it.

    I have had the EQ set flat and still I get distortion.

    I was under the impression that I couldn't plug the cab into the 4 ohm jack since the cab is 8 ohms...should I try the low 4 ohm jack?

    How can i tell if the tweeter/driver has been broken on the cab?

    I'll try cleaning the jack when I get home with a Q-tip

    And John Webb, i have looked at the manual it wasn't much of a help
  13. allexcosta


    Apr 7, 2004
    Wrong, someone has already said that you need to use the bottom outputs...
  14. Yup, that may be your issue. You should also be hearing almost no low end (?)

    But yes, use the bottom jacks.

    The 4 ohms is the MINIMUM load. With a solid state amp, you can safely use a higher load.
  15. David Cardoza

    David Cardoza

    Apr 16, 2004
    An old tip for 800rb owners, give this a try...

    The rear insert jacks for "effects in" and "effects out" tend to
    get corroded or lose thier internal contact over time. Take
    a short cable and connect the two, and leave it there.

    I FREAKED the firat time those same symptoms showed up,
    (as I was auditioning with a new band), but haven't had the
    problem return after leaving this cable in place.

    hope this helps...

  16. JBass1


    Dec 6, 2005
    problem is gone after plugging into bottom jacks...thanks you guys so much!!!!:hyper::hyper::hyper::hyper::hyper:
  17. Nice. Now enjoy one of the greatest heads ever made :bassist:
  18. YES another satisfied customer, and welcome to the GK family as well.
    File that effects loop trick listed above away in the back of your mind. It may come in handy for you one day.

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