Weird noise. Sounds like a pocket full of change.

[stoneattic]

Crate Blue Vodoo BV6212 with a new set of WGS Veteran 60 and ET65 speakers.

I'm getting a weird noise that we figured is best described as a "pocket full of change". I can not for the life of me figure out where it's coming from. I sound like it's coming from the amp itself, not through the speakers. I can't find anything obviously loose. It only seems to do it when I hit the G (3rd fret, low E). I little bit at Gb and G#, but no where else. I tried tapping the tubes thinking one might be microphonic but no luck. Any thoughts?

[jmaf]

Does it happen at any volume?

[Enzo]

Cabinets can buzz, meaning vibrate in a fashion that some loose-ness somewhere in it makes noise. So can the speakers themselves. And for that matter, a loose speaker mount can cause this. The simple test is to unplug the internal speakers, and connect a speaker cable to some other cab. Does the noise end? Does it remain the same? Does it remain but change?

Common cabinet buzzez are loose hardware on handles, chassis, speaker, corner protectors, cracked or loose joints between body panels, etc. Speaker buzzes are usually defective/failed speakers, if it is nor loose mounting. But sometimes debris falls inside the4 speaker frame behind the cone. Like you threw a guitar pick back there and it went into the openings in teh speaker frame. Now it is down in hte bottom leaning against the cone, and vibrating agasint it. Sometimes the speaker wires lay against the cone.

The amp chassis itself can buzz. Loose bolts. Then sometimes the bottom front edge of the chasis buzzes against the upper edge of the front speaker grille. A stripe of weatherstripping in ther usually cures that. Within the chassis, lookse transformer bolts, loose board mount hardware, loose screws and nuts on any part, the copper strip around the power transformer can space itself away from the tranny enough to buzz, loose nuts on controls.

ANd if you were operating without the speaker (And PLEASE don;t do that, it can destroy the output transformer in a heartbeat) you can often hear the output transformer "ssinging," making sound with the music. That is actually mostly normal, but you never hear it because of the sound from the speaker.

Have someone play the notes that make it buzz, or appply a test signal from a signal generator and sweep through the frequencies to find ones that resonat the buzz, then listen around the amp to locate the sound. Roll up a magazine and hold the resulting tube to your ear, then use that like a stethoscope to better localize the noise.

Also try just pressing various points on the amp. Press down on the handle, press up on the chassis. Push the chassis toward the front, or toward the back. Not trying to move it, just applying pressure. Push against the tops and sides of the wooden cab. Puch against the back of the speaker.

Got wheels? Pull them off, or set the amp on a folded towel or two to damp them.

[jmaf]

One time I was fooling around with an amp at 1 AM, I had disconnected the load accidentally(a resistor rig, 1 AM you know....) and it took me a while to realize I was hearing my playing.... I thought wait a minute, I shouldn't be hearing this.....

Turns out the transformer was sssssinging. Scared the heck out of me.

[Jazz P Bass]

I had a repair in a while back, for a buzzing, rattling noise.
As Enzo instructs, I played the amp into a separate cabinet.
No buzzing, rattling.
Check out the speaker and lo & behold there is a metal bottle cap inside the speaker frame.
60 bucks please.

[Chuck H]

FWIW did you tap the power tubes as well as the preamp tubes? Power tubes can become microphonic as well and it sound pretty much like change jangling. Have you tried moving the amp to a different room in case there's something in the room jangling?.. Like loose change? I am being sarcastic, but it's happened to me and probably many others.

Other than that I can't add. Cabinet isolation is a good idea. Loose hardware, etc.

[d. spree]

Crate Blue Vodoo BV6212 with a new set of WGS Veteran 60 and ET65 speakers.

I'm getting a weird noise that we figured is best described as a "pocket full of change". I can not for the life of me figure out where it's coming from. I sound like it's coming from the amp itself, not through the speakers. I can't find anything obviously loose. It only seems to do it when I hit the G (3rd fret, low E). I little bit at Gb and G#, but no where else. I tried tapping the tubes thinking one might be microphonic but no luck. Any thoughts?

I had the same issue with a tweed deluxe I built in June - I went over it in every detail and tightened up the speaker nuts and chassis nuts etc. Problem only went away when I swapped out the output tubes.

Oh, and I should add it only sounded like that on the G string 3rd fret

[stoneattic]

Thanks for the suggestions. I had a couple of minutes to mess with it last night and found that when I plugged into a different cab the sound was gone. So I believe that means it's not a microphonic tube or anything "electronic". I also tried just plugging one of the 2x12 speakers in at a time (it has plenty of taps for different speaker configs), but the sound was the same regardless of which speaker I played through. I also tried pushing on various areas including the reverb tank (which I recently had out and remounted since someone else had had it out before and was really poorly mounted) with no change.

The speakers are new so I'm going to remove each one to see if maybe it's a speaker, even though it seems that if it were a bad speaker it wouldn't be a problem if it wasn't plugged in. If that doesn't lead anywhere I'm going to pull it apart and look for anything that seems loose.

[Jazz P Bass]

You may be hearing the resonant frequency of the cabinet.
You can try to tighten the cab by running Elmer's Wood Glue (or other) down every joint in the cabinet.

[d. spree]

Thanks for the suggestions. I had a couple of minutes to mess with it last night and found that when I plugged into a different cab the sound was gone. So I believe that means it's not a microphonic tube or anything "electronic". I also tried just plugging one of the 2x12 speakers in at a time (it has plenty of taps for different speaker configs), but the sound was the same regardless of which speaker I played through. I also tried pushing on various areas including the reverb tank (which I recently had out and remounted since someone else had had it out before and was really poorly mounted) with no change.

The speakers are new so I'm going to remove each one to see if maybe it's a speaker, even though it seems that if it were a bad speaker it wouldn't be a problem if it wasn't plugged in. If that doesn't lead anywhere I'm going to pull it apart and look for anything that seems loose.

If you have a loose component on a speaker it could still rattle and roll when not in use. I had this problem on a tweed deluxe I built even though the speaker mounting screws had rubber gaskets built in. Good luck.

[Jazz P Bass]

Can you (did you) try another amp into the cabinet speakers?

[stoneattic]

It's the EL34s.

I pulled everything apart chasing the noise and finally figured it out. Weird, it's not a microphonic tube, but a mechanical rattle that resonates with the low G. I'm going to ignore it. It doesn't get amplified so no one in the audience is likely to hear it anyway.

Thanks guys.

[Jazz P Bass]

May I ask what brand?

[johnk_10]

just saw this thread, but i was going to say that a sound like that usually is an output tube with loose innards. it's very common.

[stoneattic]

May I ask what brand?

MESA EL34 STR 442

They were in it when i got it, supposedly new:

EL34 STR-442 Russia - Svetlana
An incredibly warm and rich sounding EL-34 that is reminiscent of the US 6CA7 - Thick rich low end that is still defined and light, with a Euro-voiced mid range edge and sparkling highs that are incredibly smooth and musical - Its tonal character falls between and EL-34 and a 6L6, striking a perfect balance of the best attributes from both - Excellent build quality provides exceptional consistency and reliability - Capable of handling higher voltage requirements