Finally got my GK working.. problems arise

Discussion in 'Amps and Cabs [BG]' started by Dgl44, Dec 9, 2014.

  1. Dgl44


    Oct 30, 2014
    Hi everyone.

    As some of you may have noticed I was in the process of buying a US market made GK 200RCB, and using it on european current. Well I bought a 500W step down transformer and got it working.

    For rehearsing at home it was loud enough, but as soon as I got to band practice problems appeared.

    First thing was that it wasn't loud enough through an ampeg b200r's 220W 4ohm 115 speaker cab (the head has a 4ohm output). The place is rather poopy acousticly but I've played as a drummer with bassists that used less powered amps in worse acoustic rooms.

    When I finally got it loud enough it buzzed a lot. That being I suppose from the transformer. It settled if I lowered the high frequencies. Could it be bad grounding in the power outlet or is that the step down itself? It really really buzzed like crazy when cranked if the 4.0kHz knob was on 12 o'clock or over. So we got through practice with me barely hearing what I was playing. Mind that the volume and master knobs were turned to max, as was lowest and low mid frequencies, high mids at about 3 and highs at about 12 o'clock. Towards the end I was left jamming with the drummer when my amp started acting weird all of a sudden. It sounded like it would have really high compression (compressor was turned off and even if it were on the distortion was way beyond the capabilites of it) and the sound was in "loudness changing" waves of bass sound and crackling and buzzing. If I try to describe the problem: It sounded like a bad cable or input (checked, none of that), it was in waves and if I didn't mute the strings, even unplayed, it buzzed and crackled immensely. When played the first moment the sound was clear and loud then it immediately got more silent, more compressed and with weird side noises. The limit light at the master knob turned on and off in waves even if unplayed, that stopped (either when I switched the outlets or when I lowered the master, didn't pay enough attention to which was it) then when I tried to play a tone it flickered on and off in weird wave form again corresponding the sound coming out of the cab. I turned down the master. At about 2 o'clock on master with volume (gain) still on max and with the 60Hz knob turned down (but still over 12 o'clock) it was acting normally. If the lows were cranked higher it started again, so as if they were turned even more down and master was cranked. I switched from a power strip to a clean - empty outlet 2 meters to the left of the one that had the power strip plugged in. I believe it was a little better, as in could crank it higher before distorting, but it's hard to say for sure. The low and low mid knobs certainly did a world of difference depending on whether they were cranked high or not.

    My questions are (if you can tell from the info that I wrote):

    1. The cause of the sound distorting - fried amp, bad or too weak step down transformer or someone in the house just plugged in a washing machine or something else and we didn't get enough current in the attic?

    2. If it's a simple problem and I manage to sort it out, would an 8ohm 410 cab be louder or "clearer" enough to cut through the guitars where a 4ohm 115 can't, or do I inevitably need a stronger head?
    Mind that I had to disable the contour filter and compressor and leave the high boost on because the highs and mids would be the only thing that cut through enough so that I could hear what I was playing.

    Thanks for taking the time to read and possibly answer my questions.

    NOTE: The cab is 100% fine. I plugged in the default combo head and it didn't distort at all no matter how loud I cranked it.

    NOTE-2: I DIDN'T play the head through the combo amp section. The b200r's cab has inputs to change from horn to no horn and so you can unplug the head alltogether. The ampeg also was not connected to power during playing the GK.

    Thanks in advance for all your help!
  2. Dgl44


    Oct 30, 2014
    Or could have the amp just overheated and it'll be fine next time, I just shouldn't push it so much?
    My friend, a bass player too, said he encountered a similar problem on his Fender Rumble 75 combo when he maxed it out, and when it cooled down it worked fine again.
  3. Dgl44


    Oct 30, 2014
    This is becoming quite a monologue here lol.

    Ok, I figured it out.
    I probably cooked the amp a bit because the gain (volume) knob offers a bit more distorted (but not unhealthy) sound at high levels, but unless you really crack it up, it sounds clean as a whistle. It's also the only knob to affect that, the master and 60Hz knob are all passive to it.
    Which leaves me to my master plan. :p I'll slave the b200r, because of it's immense power for it's small size and a tube preamp, and even with the line-out on the GK already used the speaker output still works which leaves me freedom to buy another cab of choice and make a very interesting stack!
  4. BassmanPaul

    BassmanPaul Inactive

    Put an AC voltmeter across the transformers secondary. Ensure that it IS actually giving you 120V. Watch it as you play and see how much the voltage fluctuates as you play ever louder. That should give you an idea of how stable your supply is.
    Dgl44 and SunnBass like this.
  5. Dgl44


    Oct 30, 2014
    Didn't think about that..
    Thanks, definetly will do!
  6. mbelue


    Dec 11, 2010
    Sounds like you were asking too much of a 100w amp.
    Having the lowest EQ knob cranked really kills your headroom and maximum volume.
    I'm certain your amp was running beyond its clean capability and in such circumstances performed in a nonlinear fashion.(You can read that as noisy)
    You need more volume then you need more speakers.
    I really hope the amp isn't damaged permanently and you can get back to playing music.
    Good luck dude!
    Dgl44 likes this.
  7. Jim Carr

    Jim Carr Dr. Jim

    Jan 21, 2006
    Denton, TX or Kailua, HI
    fEARful Kool-Aid dispensing liberal academic card-carrying union member Musicians Local 72-147
    Running the gain at max is, as you have probably figured out, supposed to give you more distorted/over-driven sound. Run the gain at 50-60% and increase the mid-range. Keep the bass at ~50% and the treble low enough to kill the hum. Mids are where your volume lies.
    Dgl44 likes this.
  8. Dgl44


    Oct 30, 2014
    The amp seems to be working fine, played it in the evening when I came home with a line out to the b200r and had no problems if I ran settings similar to what you wrote, even if I cranked it there was no problem except of the mentioned distortion because of high gain. So I guess It'll be fine. The tips about the eq eill definetly be noted, thanks!