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800RB distorting

Discussion in 'Amps and Cabs [BG]' started by srbguitar, Jul 19, 2003.

  1. srbguitar

    srbguitar Guest

    Jul 19, 2002
    Fremont CA
    previously this amp was cuting out after about half an hour of playing. after going through a lot of trouble finding somewhere to get it fixed the repair man told me it has a comon problem with the effects loop (the contacts for the effects loop jack connect when there is nothing in the jack therefor ending the signal). so to fix the problem i just have to send a chord through the effects loop.
    recently i had a problem with distortion. i have the master volume for the lows (300w to a sunn 2x15 cab)all the way and at about 12:00 for the highs (100w to an avatar 4x10). the problem is when i turn up the pre volume to the volume that i need to get over the drums and guitar the sound of my bass is destorted.

    1. could the distortion be coming from the amp being under powered to drive the speakers,
    2. is it from having to much power for the speakers
    3. is it possible to get the same volume with out the distortion
  2. tripwamsley


    Jan 31, 2002
    Sulphur La,
    My vote would be number one. I think you might be asking too much of it.
  3. Cantstandsya

    Cantstandsya Supporting Member

    Jul 27, 2001
    Fontana, CA
    Where do you have the Boost set at?Try lowering it a bit and see if that works.
  4. srbguitar

    srbguitar Guest

    Jul 19, 2002
    Fremont CA
    Even with the boost off and the -10 db switch pushed in with the volume at 12:00 and the rest like i said it still distorts
  5. I kind of doubt that you're OVERpowering your speaker cabs. Remember that the low amp is only putting out about 225W into an 8 ohm cab, which a 2x15 cab should be able to handle ...

    My guess is that you're clipping the 100W amp. Even if it's putting out 100W, that's WAY too little to effectively drive that 4x10 cab. (I speak from experience, having tried the same thing with a 1x15 + 4x10 with my 800RB)

    Have you tried turning off biamp, and running both cabs off the "low" amp? At least this way, you're pushing 150W into both cabs ...

    (BUT - make sure your total impedance with the two cabs in parallel isn't less than 4 ohms - PM me if you're not sure!)
  6. srbguitar

    srbguitar Guest

    Jul 19, 2002
    Fremont CA
    the sunn 2x15 is a 4 ohm cab (and so are most 2x15"s that i have seen) and on the back it says that the power handling is 160 watts (it's an old 215b), but i'm pretty sure that isn't all that it can handle. also the sunn cab being a 4 ohm cab i can't run both the cabs off of the 300w amp because it would be less than 4 ohms.
  7. Cantstandsya

    Cantstandsya Supporting Member

    Jul 27, 2001
    Fontana, CA
    Have you tried both cabs separately with the 300 Watt amp and/or the 4*10 with the 100 watt amp without the 2x15 hooked up to the 300 watt amp?You should try every possible combination to isolate where the distortion is coming from.
  8. Are you getting amp distortion or speaker distortion? If it's amp distortion, you want the first volume stage to be 12 oclock or lower. Turn your boost up to 12 oclock or higher then set your master volume to whatever you need for each channel.

    If it's speaker distortion, keep in mind you are putting 300 watts into a 160 cabinet. How much power does your guitar player have? If they have 100 watt amps totally cranked and your drummer is a pounder, you just don't have enough power to keep up. You would need to get into a 1001RB-II which puts out 700 watts into 4 ohms. Of course your Sunn cabinet would be totally useless for this.
  9. Is it your horn farting out? I have a GK 800RB and an Avatar 2x10, 1x15 setup. I have tried running it every way possible(biamp, straight, etc...)

    I was having the same problem, but it ended up being the horn in my 2x10 cab.( I don't think it is blown, the GK is just harsh) I haven't had a gig or rehearsal in a couple of weeks, so I haven't experimented with it enough.

    I also had the problem with the effects loop. Seems to be common.

    My newest problem is a grounding problem. BUZZZZZZ!!!!! I rewired my P-bass about 5 times trying to find the ground problem, took it to a pro twice, only to find out that is was my amp. It may be simple, so any suggestions are appreciated. When I plug in through my Digitech BP-8 the problems go away.

    Guitar Center has 0% interest for 1 year, and I am tired of fighting it. I will be playing through a new SWR rig tomorrow. GK sounds great, but it can get a little harsh if it isn't played through properly matched cabs. I always loved the sound of an 800rb and a Hartke 4.5xl(for electric-not upright)

    I will probably keep the head because I haven't spent enough time with it and the problems may have simple remedies. The other day I plugged into a SWR Black beauty with all the EQ set flat and VOILA. I am wanting to get back to a combo, plus I am tired of having to haul a full stack to get a good tone.

    I may not be much help, but I sympathize.
  10. Is the buzz in the DI or in the speaker cabinets? The 800RB head is about the most popular bass head for live rock shows there is. I've never heard anyone ever call it harsh before.
  11. tripwamsley


    Jan 31, 2002
    Sulphur La,
    "I've never heard anyone ever call it harsh before."

    Ditto on that one Dan!
  12. The buzz isn't in the DI. It pretty much goes away when I play through a pedal board that I have. It is mainly when I play my P-Bass. I have an acitve Jazz, and I can still hear a little hissing, but not near as bad. Any suggestions are appreciated.
  13. BTW

    I passed on the SWR rig. I plugged the SWR in side by side with a GK 800rb. I liked the tone a little better but not $1200 better.
  14. Larzito


    Aug 1, 2000
    Dallas, Texas
    I bought a used 400RB a while back, and sometimes it would distort when I turned it on. I could turn it off, then back on and the problem seemed to go away. But then the problem became progressively worse, and then it would begin to distort after playing it a while. I took it to the shop, where the repairman cleaned and resoldered some of the connections. General tidying up I suppose. Works better than ever now. He said this was common for an amp that's seen lots of use...time and travel have that affect on elcetronic devices. Cost me just under $100. Much cheaper than replacement.

    BTW, GK's ARE a bit harsh compared to many of the tube preamp units on the market today. One person's harsh is another's clarity...depends on your personal taste. I personally wish GK wasn't SO aggressive on the treble (I have mine turned down to about 8 o'clock). I suspect my 400RB was designed to enhance treble because back in the late 70's, early 80's, cabinets didn't have tweaters yet, but players wanted more aggressive sounds. Any one else out there wish GK made a power amp only? I mated my Eden preamp from a WT800 to the 400RB once and it was quite tasty!
  15. Thanks,

    I always thought it could get harsh (very trebly) I just didn't want to get hammered for saying so. I play some Upright, and it can get very pingy & have too much fingerboard noise if not EQ'd properly. (not the desired fingerboard noise)

    It is a good head, I just need to have a tech look at it and get the bugs worked out.

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