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Still getting feedback at times...

Discussion in 'Live Sound [BG]' started by mello_bedwetter, Jul 30, 2012.


  1. I'm not sure what section to put this thread so I'll try here. I had a gig this past Saturday night at a small "dive" of a place. Since we were limited in space I used the following:
    Standard Jazz Bass(MIM)
    GK MB210 Combo
    GK 210MBE ext cab
    speakon cable to connect cabs
    instrument cable
    About a month ago I used this same "combo" of gear for practices. Everything sounded good until my practice last week. I started getting crazy loud feedback. The only changes I had made from previous practices was changing from "flats" to "tapes" for my strings. When using the tapes I got the feedback. I have read that tapes could cause feedback at times so I went back to the flats. Saturday during the 1st set I experienced the loud feedback again. I turned off the amp quickly just to get rid of the noise. I didn't get the noise anymore that night. I'm not sure what's causing the problem now...I was hoping it was the strings but that must not be it. On break I looked the amp over, visually, and the only thing I saw was I had the horn engaged on the amp but the ext cab's horn was off. I wouldn't think that would cause it but not sure.
    Now what....check the cables being used, have the bass checked, have the whole set up checked out by a shop....? I can't simulate the problem at home. Not really sure what to do.
    Thanks
    Note: we were playing with no PA support. Only vocals were going through the PA.
     
  2. wcriley

    wcriley

    Apr 5, 2010
    Western PA
    If the feedback goes away when you completely turn down the volume on the instrument, it's most likely a microphonic or improperly mounted pickup.

    If turning down the instrument's volume doesn't kill the feedback, it's likely that something is loose or oscillating in the amp.
     
  3. Does your feedback go away if you turn down the volume
    control on your bass?

    If so, it sounds like a microphonic pickup. They can get
    microphonic with age.

    Another test for a microphonic pickup, is to mute all of the
    strings, turn up the volume, hold your bass up to your cab
    and hit your strings once to induce a noise. If it feeds back,
    you have a microphonic pickup.
     
  4. Turn up the volume on the amp and bass? Hit the strings while muted or not muted? Sorry, just not clear to me. Thanks for your response though....I appreciate any help I can get.
    The pickups aren't the stock Jazz(MIM)...they are Dimarzio that I had put in. It's just crazy that I haven't had this happen until my last practice and the one time at the gig.
     
  5. I do know the sound didn't go away until I turned the amp off. I turned off the gain and master and the sound didn't stop til I actually turned off the amp. Maybe the amp needs checked out?
     
  6. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    alpha-music.com
    What exactly was the sound? "feedback" might not be the right word at all.

    hum? squeal? crackling? Was it just the bass strings ringing out and sustaining?
     
  7. A real loud hum...wasn't sustain. I was about 18 feet away from the amp playing at one time when it occurred, actually standing, not playing.
     
  8. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    alpha-music.com
    Yeah, that's not "feedback"; a loud hum that just blasts out of the amp regardless of what the bass is doing is an internal amp problem.

    Time to get it looked at I'm afraid.
     
  9. Turn up the volume on both amp and bass.
    Keep strings muted (keep fingers pressed over strings).
    Just hit the strings once to make a noise; then resume muting.

    The idea is that, if your pickup is microphonic, it will create
    sounds (and feedback) even without string motion. It picks up
    the sounds directly; not only through string motion.

    You could remove your strings and perform the same test
    (except you would have to tap on the pickup to induce a noise).
    It's a real eye-opener to see a bass with no strings causing
    feedback. But it happens.
     
  10. happycat

    happycat

    Jan 20, 2009
    Australia
    I agree with walterw - I was using an amp a few years ago that would produce a sound that you could describe as a bit like feedback. This amp would do this when change settings (mostly eq). It was definitely a problem with the amp - had it looked at and it came back working perfectly.
    There was no problem with pickups etc.
     
  11. I usually run the master at 1:00 and the gain around 11:00, I may have the boost on, very little though. The last 2 times we played the drums and guitars were so loud I did have to adjust. I increased the master to 3:00 and the gain to 12:00 or 1:00, also increasing the boost to around 9:00. Maybe that change in the EQ did it but I'm not sure. I can't get it to do it here at home. But if I really dig in here while I play I would blow out the windows with these settings.
     
  12. Floyd Eye

    Floyd Eye Banned

    Feb 21, 2010
    St. Louis
    Just noticed we must be neighbors. I also live in Mo. south of St. Louis. :)
     
  13. it seems that you have a ground problem. i would take a loot inside the cab as you may have rattled loose the ground cable which is normally attached to the amps chassis(internally). the other thing is that because the MB210 is a class D amplifier (lightweight) they are way more prone to ground noise and ground loops than what the old style amps are.

    there are very few ways to get rid of this issue. there isn't a problem with the amp, its a venue power issue. if it was me i would buy a good quality power conditioner that isolates the ground signal path and plug your amp into that.

    the reason i say that its a grounding issue is that you aren't having problems with it at home. just at this venue?

    also are the dimazio pickups you put in single coil?
     
  14. The pickups are: Unlike traditional pickups, these DiMarzio DP123 pickups are individually humbucking. They're not a stack: each coil picks up one pair of strings. By doing it this way they keep the resistance down and the tone clean and clear.
    I'll have to see what I have to do to get to the ground in the amp.
     
  15. are the pickups single coil? sorry too lazy to google the info...lol but they sound really nice....

    i wouldn't go all out to gut out the amp. i would just simply crack it open to see if the ground cable has come loose from the chassis. if not, find a way to clean up the power where possible(its not always possible either). i would suggest also to go into the local music shop (not chain music shop, usually they don't know too much) and have a chat with someone in person too. they might be able to shed some more light on the situation. however i have heard that GK's warranty is amazing, so if it is under warranty, call them up and they will replace it for you and you don't have to pay anything. at least that's what i have read online about them.

    i was researching the MB combo series and apparently there have been a bunch of random issues with the amp modules, so peeps had phoned GK and they replaced them. sometimes a few times, but once they got that "good one" it was pretty solid. so if it is under warranty, don't open it up, juts send it back. if its not, then go for gold. last thing you want to do is void a perfectly good warranty.
     
  16. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    alpha-music.com
    uh, unless you actually know how to work on solid state amplifiers, don't bother even opening it up; the phrase "no user-serviceable parts inside" means what it says.

    since lay people seem to want to call any electronic noise "feedback", i'd suggest just taking it in.
     
  17. It's out of warranty by 6 weeks, ain't that the luck? I'll take it by a local shop here and let them take a look at it.Thanks.
     
  18. Don't worry I'm not going to open it up. I'll find a shop that works on them. I don't think it's feedback per say. It must be something in the EQ.
     
  19. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    alpha-music.com
    you might find that a good shop with lots of business sometimes has the "pull" to squeeze in a unit that's just out of warranty and get it covered.
     
  20. I actually thought GK would take care of it since this model had some problems when it came out. I got this combo May of 2010 and I don't use it that often. This isn't the 1st problem I had with it either.
     

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