Mesa Boogie Amp Ringing/Whistling Problem

Hi All,

Hoping for some advice in relation to an amp issue. I bought a new Mesa Boogie 50:5 Combo about 18 months back.

Ever since I bought it, I get a high pitched ringing or whistling sound along with whatever I'm playing on guitar (the prominence/level varies). I have audio files which demonstrate the problem, however it seems I am unable to attach them to this forum. It can be reduced to some extent by the amps eq (to the point that it's passable for a live gig) but on a studio recording, it still sounds horrible.

I have been back to the Mesa dealer who has unfortunately been of little help. After denying that there was any problem, they sold me some new pre-amp valves, which I installed, however the problem persisted. They also recommended that I some someone hold the power valves with a tea towel while playing (to see whether they might be ringing), however that also made no difference.

I've asked around some friends and a couple of other forums, with no luck.

Does anyone have any ideas as to what the issue could be?

Thanks in advance!

Are you playing with a semi-hollow or hollow body guitar? How loud is the ringing?

Also, there is a screw in the middle of the chassis that butts up against the Headshell/Cabinet. This prevent vibration in the chassis which could cause the noise you are hearing. Make sure that screw is good and tight against the cabinet.

Thanks for getting back to me.

Nope, solid body guitars. I've now changed the power tubes, and tested the pre-amp tubes individually.

Re the screw, there is a screw, which is pushed up against the top of the cabinet (I've tightened it to make sure). Strangely enough, the position of the screw is rather strange. It's far too long, and can't actually be screwed in all the way (ie there is excess screw!). Not sure if this is normal. However, it does seem to be pretty securely fastened.

Waiting to hear back from Mesa now, hopefully they can solve the issue!

Hello,

The "screw" is really a narrow diameter bolt with a slot head.

As others have noted, the bolt is intended to add tension the large, flat, horizontal panel of the chassis and reduce its vibrations. The extra length seems to be intentional as well. If you over-tighten the bolt, it will push through the inner surface and create a hole :-( If you ever remove the chassis from the cabinet, be sure back off on the bolt before trying to pull out the chassis. Otherwise, you will probably have a difficult time and may gouge the inner surface or bend the bolt.

As for the whistling/ringing sound ... Hmmm. You have tried replacing pre-amp tubes. Have you tried the power tubes? (In my case, they made the sound of a tambourine when you hit certain notes. Changing the power tubes solved it.) Also try calling Mesa.

Well first guess would have been a tube gone monophonic and out of control but you've changed the tubes. Sounds like a trip to the shop is due.

I just experienced an issue similar to this with a 2x12 recto cab hooked up and using the combo speaker at the same time. There seems to be some kind of out of phase issue going on when playing at volume. The issue goes away if I just use the cab alone, or the combo speaker alone.