Speaker buzzes - but only on three notes

thejumpcat · #1 04-08-2010, 06:35 PM

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.

THPBass · #2 04-08-2010, 06:37 PM

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.

thejumpcat · #3 04-08-2010, 06:50 PM

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.

Tim C. · #4 04-08-2010, 06:59 PM

I'd contact Ampeg's customer service and see what they say about it.

topper · #5 04-08-2010, 07:02 PM

My bet is the screws that hold the speaker in are loose.

thejumpcat · #6 04-08-2010, 07:09 PM

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.

CPplaysBASS · #7 04-08-2010, 07:29 PM

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!

thejumpcat · #8 04-08-2010, 07:38 PM

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.

CPplaysBASS · #9 04-08-2010, 07:47 PM

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!!

thejumpcat · #10 04-08-2010, 08:17 PM

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.

Ric5 · #11 04-08-2010, 08:21 PM

Back in the 70s I had an acoustic head that would only buzz when I played an A.

M0ses · #12 04-08-2010, 08:24 PM

Quote:

Originally Posted by thejumpcat

I was 99% there -- I just didn't pull hard enough on the chassis to get it out. It was in there REAL tight.

I hate it when that sort of thing happens.

Randall · #13 04-09-2010, 10:37 AM

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

bcst9 · #14 Yesterday, 09:45 AM

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

http://www.youtube.com/watch?v=M4TiVVgl4lE

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.