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on-stage "interference"

Discussion in 'Amps and Cabs [BG]' started by nil, Apr 9, 2001.


  1. Now, several times while playing live i've had problems with the amp (either my own, or rented/borrowed backline) hissing, buzzing, generally picking up some interference somewhere.

    This is mainly with my Ric. The cables are all sweet, FX are sweet, etc, etc. Could it be the Ric's pickups picking up electrical interference or something? I've in the past looked @ the grounding in the Ric and it looks OK (thin-ass wire to the bridge).

    Is there anything I could do/use to stop the noise? Ferrite choke over the instrument cable? I've got a noise gate but rather not use it.

    ???
     
  2. Is it constant the whole time? Does it come and go? Stay away from the ferrites. No need to drag them into this. :D I'd guess a bad electrical connection somewhere. How old is the bass? Are you using the stereo jack? Have you swapped to a fresh new cable that you know is good and it still does it? Tons of variables, as you can see.

    I broke out my '73 Ric 4001 the other day, and it sounded really weak. Flipped the switch to try the pickups out as singles, and the neck pickup wasn't working. So I messed with my Vol and Tone knobs, and it fixed it. So obviously my bass needs some care in the pot area because it has a bad connection, either a solder connection to the pot, or a dirty contact internal to it or even a broken connection internal to it. Visually inspect the pots and solder joints. Check the jacks and switch too. Worst case, replace the pots and the jacks to see if it fixes it.

    All this is assuming it is an intermittent problem that comes and goes without changing amp, cable, or location.

    That's my guess.

    Chris
     
  3. phil_chew

    phil_chew

    Mar 22, 2000
    Asia
    Could be a problem with stage lights, especially neon lights. I had a similar problem with crackling noise coming from my amps some time ago. We tried everything and finally concluded it must be the lights. So we switched them off one by one and managed to narrow it down to one particular set of lights. Switched that off and hey presto, the crackling noise disappeared.
     
  4. Chris : it's constant, all the time. This is with my '98 Ric 4003 (using the mono jack) and any combination of amps i've used (old tube numbers, GK400RB, Ampeg B2R, direct in the studio). Yep, i've tried different amps, instrument cables, speaker cables, you name it! I've always wondered about the pickups and their earthing...

    Phil : i'm thinking it's either stage lights (i've encountered the neon problem before, but for some reason it only affected one guitar amp, not my bass!), or un/badly-shielded power feeds to the stage. In these cases I can't do anything apart from listen to the whining by the soundperson! :)

    I was thinking a ferrite choke would/might help in this case. I don't play *that* often in these evil environments so it's hard to replicate...
     
  5. Josh Ryan

    Josh Ryan - that dog won't hunt, Monsignor. Staff Member Supporting Member

    Mar 24, 2001
    Hi, I'm a poor ignorant bastard. What's a ferrite choke? I'm guessing it's made of ferrite and acts as some type of noise suppressor, but how does it work? You guys seem to be saying it should only be used as a last resort, so maybe I don't want one. The thing is I've run into the weird light problem before too, and if this tool of the devil can help, I may want to use it! Thanks.
     
  6. DaveB

    DaveB

    Mar 29, 2000
    Toronto Ontario
    On stage interference...oops you meant something technical! Well I'm here so I'll tell you about some other on stage interference.
    It was at last weekend's two nighter at a local mid-size bar. We're in the middle of the third set and two chicks - one gorgeous and one, well....less than gorgeous have been sitting at the bar all night just watching the band.

    All of a sudden in at the beginning of SRV's "House is a Rockin'" the two of them head up to the stage and position themselves on each side of me. I should stop here in case you're wondering why they made a B-line for the bass player - I'm also the lead singer and like it or not guys it DOES raise your stock value with women.

    Anyway, they are all over me - starts off one on each side, then one in front band one in back and they are really close and really suggestive with LOTS of hands-on action.The dance floor was fulll and being the professional I am I let the song go on for at least two verses and one guitar solo longer than usual - for the benefit of the dancers, of course.

    At the end of the song they leave the stage, hang around at the bar for a couple more tunes and "poof" gone.

    Now,THAT'S on stage interference!!!!!
     
  7. Here's what I remember from class: It's used to snub out Common-mode noise. This is like noise that is running up and down your cable on BOTH conductors in the same direction. Well, kinda like that. Differential-mode would be like the signal that runs down your cable from your bass. It uses one conductor as its send, and the shield conductor as the return, and that is a complete loop. In common mode, the noise is running up the shield and center conductor together, and then returning through the air or through capacitance to ground, whatever. It's like your cable is a long antenna. The ferrite doesn't affect the bass signal, but it looks like a resistance to the antenna-like common mode signal. The currents running up Common-mode style induce a magnetic field in the ferrite circle. This magnetic field opposes the flow of the current. That's how the ferrite puts about 50 ohms or so in between the 2 ends of the cable for common mode current. The differential mode signal is not affected.

    Clear as mud? They are used to reduce radio interference that could be transmitted from computer cables, etc. Think of a Slinky spring toy, and if you were to let it hang from your hand and then bounce your hand up and down. The free end of the Slinky would spring up and down really easy. If you were to hang a weight on the end, it wouldn't move as much when you moved your hand. Ferrites do this to the electric current. Kinda. :D

    I guess that's right. No refunds if it's not. The only reason I say not to use them, is because I've never seen them used on instrument cables, and I don't think they'd be necessary. I could be wrong though. They make split ones that clamp onto a cable really easy. So you may want to try it.

    Back to the original post, sounds like it is not an intermittent problem. Those single coild pickups may just be picking up noise if it's around. I got no clue what to try next. Sorry.

    Chris
     
  8. Josh Ryan

    Josh Ryan - that dog won't hunt, Monsignor. Staff Member Supporting Member

    Mar 24, 2001
    Thanks for the well done explanation! -B
     
  9. Yup, that was a good explanation! I guess i'll have to be a hard-arse and tell the soundies to suck it :D
     
  10. SuperDuck

    SuperDuck

    Sep 26, 2000
    Wisconsin
    As a "soundie" let me tell you it's not always easy to deal with big-headed musicians who feel they are the center of the universe. Then again, there are ******* sound techs who deserve to be told off.

    A word to the wise, don't piss off the soundguy, or you may find your vocals cutting out for some mysterious reason.... :D