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Speaker buzzes - but only on three notes

Discussion in 'Amps and Cabs [BG]' started by thejumpcat, Apr 8, 2010.


  1. thejumpcat

    thejumpcat thejumpcat

    Sep 30, 2007
    metro-Detroit
    I have an Ampeg BA115T, one year old.
    At practice last night, the speaker was buzzing -- but only on Db, D and D#, and didn't matter where I played those notes. All other notes were fine. What's up with that????

    Is the speaker blown or does it sound like something is loose inside?

    And how do I check the speaker on this amp? Does the grill pry off or do I have to take the chassis out?

    Thanks for any help. Got gigs Friday and Saturday and must fix.
     
  2. THPBass

    THPBass

    Dec 15, 2008
    Terre Haute, IN
    Sounds like that frequency is making something rattle. Check all your screws first. If that's a no go, could be an amp component vibrating at that frequency.
     
  3. thejumpcat

    thejumpcat thejumpcat

    Sep 30, 2007
    metro-Detroit
    So you don't think it's the speaker? I can't figure out how to get the damn chassis out anyway. I'll try just tigthtening every screw that's showing and see what happens.
     
  4. Tim C.

    Tim C.

    Feb 4, 2010
    Chicago
    I'd contact Ampeg's customer service and see what they say about it.
     
  5. My bet is the screws that hold the speaker in are loose.
     
  6. thejumpcat

    thejumpcat thejumpcat

    Sep 30, 2007
    metro-Detroit
    This is so frustrating. I've taken out every obvious screw and I still can't figure out how to get the cassis out to check the speaker screws.
     
  7. CPplaysBASS

    CPplaysBASS

    Mar 17, 2007
    Ontario
    Hey Jumpcat.
    I had the EXACT same problem and was -> <- close to buying two new 10" speakers for my 2 X10 cab assuming the speakers were shot ... my second guess was that there was an air leak in the cab (a theory that I read about here on TB although I still don't understand it).

    In my case it was only when playing a C or C# that I heard a buzz or distorted sound on either the E or A string. I thought I was going bonkers.

    The ONLY reason why I didn't spend $180+ for new speakers was I couldn't find any 16-ohm 150W replacement speakers that were available commerically.

    So into the shop the cab went, and I told the guy right from the start that I needed new speakers installed, so he knew he had me me for at least $180 plus the cost of installation.

    Now I wish I could find my receipt to give you the exact wording of the problem, but the speakers were 100% fine. The problem was that there was oxidation on the speaker contacts, creating some kind of interference only within the frequency range of the C and C# notes.

    It sounds crazy I know, and I certainly don't understand it ... all I know is that now my cab is 100% fine with all notes, spraying the contacts with some kind of anti-oxidation stuff was the only thing the repair guy did ... still cost me $75 for his time, but that was way less than replacing the speakers!
     
    BluesOnBass likes this.
  8. thejumpcat

    thejumpcat thejumpcat

    Sep 30, 2007
    metro-Detroit
    Thanx, CP.

    I think I got it. I searched some other threads to figure out how to get the grill off. (There's a SERIOUS velcro tab in each of the four corners, and you have to really pry - I used a butter knife - one of the corners until the grill pops up.)

    Once I could access the screws holding on the speaker, every damn one of them was loose. I tightened them, plugged the bass in and fired it up. No more buzzes!

    But, God forbid I have to change the preamp tube in this pig. I STILL have no idea how the chassis comes out of this thing. I'm used to blackface Fender guitar amps, which are like working on an old 350 Chevy motor.

    I'm going to pre-empt the foreseable problem and call the Ampeg tech service tomorrow to find out how to get the chassis out now, before I HAVE to remove it.

    Anyway, problem solved. Thanks TB'ers for the input.
     
    BluesOnBass likes this.
  9. CPplaysBASS

    CPplaysBASS

    Mar 17, 2007
    Ontario
    That sounded even easier to fix than my problem ... haha. I did check the screws on mine before taking it in for my $75 repair. Glad you figured it out!

    Maybe my post will help someone else down the line ...

    Enjoy the weekend gigs!!
     
    BluesOnBass likes this.
  10. thejumpcat

    thejumpcat thejumpcat

    Sep 30, 2007
    metro-Detroit
    And I kept searching other threads and found one about swapping tubes on an Ampeg BA115HP, a similar model. In the thread, the OP describes how to get the chassis out. I was 99% there -- I just didn't pull hard enough on the chassis to get it out. It was in there REAL tight. It's out; now I'm going to check some different preamp tubes to see how it sounds. Well, in the morning I'll check. It's 10:15 now; neighbors will be pissed if I start thumping this late.
     
  11. Ric5

    Ric5 Supporting Member Commercial User

    Jan 29, 2008
    Colorado
    I grow organic carrots and they are not for sale
    Back in the 70s I had an acoustic head that would only buzz when I played an A.
     
  12. M0ses

    M0ses

    Sep 11, 2009
    Los Angeles
    I hate it when that sort of thing happens.
     
  13. Randall

    Randall

    Aug 6, 2009
    Canada.
    You might want to throw some blue locktight on those screws if they are going into a metal insert. May save you some grief in the future. If they go into wood ignore;)
     
  14. bcst9

    bcst9

    May 27, 2012
    There is an excellent youtube video that has a neat trick to remove the grill with no prying.



    or search Ampeg speaker grill removal.

    I had the exact same problem with buzzing on certain notes. The screws were loose and giving each a 1/4 to 1/2 turn eliminated the buzz. :)
     
  15. LowNloud1

    LowNloud1 Commercial User

    Jun 11, 2012
    Wilmington NC
    I am a hobbyist making stone picks that I occasionally sell but mostly give away. They made me do this anyways.
    Great tip! I just tried it and the cover came off easily. Sure enough, some of the speaker mount screws were loose and I am hoping this will kill the buzz like everyone else experienced.
     
  16. LeDuck

    LeDuck

    May 26, 2012
    I once had a similar problem on an old Peavey bass head. The culprit was a loose rivet that mounted the transformer. Drilling out the rivets and using real screws, nuts and lock washers solved the problem.

    You SHOULD be using blue Loc-Tite on the speaker mounting screws on any bass cab you own. If this was not done at the factory, then it should be the first thing you do to a new bass cab or combo.

    On my recently upgraded Marshall AVT50, when I replaced the crummy stock Celestion with a Celestion G12H-80, the original lock washers were INSIDE the speaker basket mounting holes and were serving no purpose. Typical English electronic product where a basic flaw is repeated over and over and any nitwit could have seen the lockwasher and hole diameter were the same size. Threw away the lockwashers and used blue Loc-Tite.

    I noticed that the AVT transformers are also rivet mounted, but since I am selling the AVT50 I left it as-is.

    Tubes are also notorious for becoming microphonic at a particular frequency and may sound just fine until you play the "wolf note". May NOT buzz when you tap it, as you are ONLY exciting the tube self resonance, and not the wolf note resonance frequency. No tube tester checks for microphonics, it can only be tested in the circuit under actual use.

    A signal generator set to the frequency that causes buzzing will help you quickly locate the cause of the buzz. If you don't have a sig-gen, then plug in a microphone and sing at the particular note frequency, or have somebody fret the note on the instrument and use high gain to sustain the note. Easy to rig a guitar with some tape and foam rubber under the strings to mute unplayed notes as the amp sustains the problem note. You can probe away in the amp and cab to your heart's content until the buzz is found.

    My biggest problem is objects in the room that buzz, like cabinet doors. If you live in a home with sheetrock or paneled walls, then you already have a very low frequency resonance problem that will cause a peak and dip in your bass response that may not be perceived as a "buzz", and large cardboard boxes cause a similar problem at their box wall resonant frequency. Washing machines, clothes dryers, refrigerators, freezer chests, toaster ovens and unoccupied metal chairs can all have Hi-Q resonant panels that ring and buzz. A door knob with loose internal parts is one of many things that can drive you crazy when playing bass in a house.
     
    BluesOnBass likes this.
  17. basscooker

    basscooker Commercial User

    Apr 11, 2010
    cincy ky
    Owner, ChopShopAmps
    +1. always my first guess, before i go tearing into my gear or overtightening grill mounts.
     
    BluesOnBass likes this.
  18. Old Fart

    Old Fart

    Mar 11, 2011
    I had the same problem with my BA-115HPT. I pulled the grille off (that's how you get access to the speaker mounting screws). I tightened them up, and Voila! No more buzz.

    Then, later, a new buzz developed. That buzz turned out to be the magnet buzzing against the metal speaker frame to which it is attached. I took two fairly long (about a foot or ten inches) zipties, zipped them together so they could fit around the mating surface between the speaker frame and the magnet, and tightened them up. Problem fixed. My amp does not buzz at all now.
     
    BluesOnBass likes this.
  19. Qlanq

    Qlanq

    Jul 9, 2007
    Swansea
    As LeDuck said, in my office/studio door there is a glass section at the top-I can play most notes ok but playing around C and D on the A string has it rattling like it's going to explode, all other notes are fine though.
     
  20. Old Fart

    Old Fart

    Mar 11, 2011
    In the first instance, the buzzing was only on certain notes. One in particular. "D", I believe.

    In the second instance, the buzzing happened any time the amp was turned up LOUD.

    I would strongly recommend you look into these two simple fixes. I suspect one or the other will solve the problem. For free.

    Then, you can do your tube rolling any time you want. And yes, that amp chassis fits tightly. Also, small things such as paper clips, which roll off the the top of the cabinet, can easily get into that amp chassis. Paper clips are not ideal things to be rolling around in bass amp chassis'.
     

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