GK800RB totally supprised me (long rambling post)

Discussion in 'Amps and Cabs [BG]' started by OneWayPunk, Oct 22, 2004.

  1. So, I have been working on the project rebuilding a totally fried GK 800RB. This think was so fried it you couldn't even see the green on the circuit board, only charcoal black. After replacing all of the power transistors, 50% of the other components and a shorted bridge rectifier (the cause of the above frying) I held my breath and plugged it in...seemed to be good. No smoke or things blowing up.
    So I take it to band rehearsal last night and hook it up to my Ampeg cabs (1x15 & 2x10) crank it up and all I can say is WOW...I was blown away at how good this head sounded.
    Very transparent, but got nice and growly if you pushed the boost up some, and did I mention LOUD...holy crap...this thing was blowing everyone away. I only had it set on like 1/3 of the master volume and it was overpowering two 100W marshal JCM800 stacks.
    If I turned it up any more than that it just got stupid loud...like gut rumbling.
    My only previous experience with GK heads was jamming through a 400RB that I had repaired for a buddy...and I hated that head.
    After playing for 3-4 hours on this 800RB I think I might be a convert.
    The thing that blows me away is that this head is rated at
    100W @ 8 Ohms for the high amp (I had my 210 plugged in here) and 300W @ 4Ohms or 200W at 8Ohms for the low amp (I had my 8ohm 15 plugged in here). So I was only running 300W max and blowing away the rest of my band.
    I think this amp may be way underrated.
    Blows away my SVT350H hands down, but without the "Ampeg" tone. I can get it close though, close enough for me not to miss the Ampeg.
    I wouldn't recommend this head if you have a cheap bass though, it's so transparent that it'll pass whatever crappy tone a cheap bass puts out right on through.

    Great Job on this old 800RB GK, color me impressed.
  2. thumbs up to this baby!! I love mine. i ran an Ampeg B4-R bridged 1000 watts mono the 2 4x10 cabs (before they were stolen) and then had to settle on the 800RB with a single old SVT410E. like you said it's something like only 200 watts to a single 8ohm cab through the lows, and last night i was on top of 2 mesa's!!! 2 Double Rec's and i was still way louder than them. I thought my Ampeg rig was monstrous, but this GK head really does the trick. I'm afraid to really crank the thing because my cab is easily 20 years old with the original speakers.

    Can't beat the weight either!!!
  3. lsimy

    lsimy Supporting Member

    Apr 18, 2003
    Virginia, USA

    Did you end up upgrading any of the components ?? Did you find any sections that could benefit from improvement or did you just use OEM ??

    I know at one time, 800's were notorious for killing transformers but that might have been due to user error running loads below 8 ohms on the high side.

    I too have always dug these amps. The have outrageous power.
  4. The only way I modified the amp was when I replaced the two large power transistors on the 100W amp I upgraded them to the ones that are used in the current version 800RB. The reason I did this is because the ones used in the older amp are kinda hard to get. The newer version power transistors are the same ones used on the 300W side , and have a higher power rating.
    This is a 1988 800RB so it's slightly different than the current model.
    My main goal was just to get the amp functioning, and quite honestly after playing through it I don't think it needs any modification.
  5. Thumbs Up!!!

    Looks like you did a really good job on this head.
    I had the chance to play on a 800RB that's a good amp.
  6. gfab333


    Mar 22, 2000
    Honolulu, Hawaii
    I played through one for about 10 years. It even took a five-foot fall onto a concrete loading dock and kept on playing without needing servicing. It's a very durable amp.
  7. Gallien Krueger heads always somehow sounds louder than they should be and never get lost in the mix.. does anyone have a technical explanation as for why this is so?