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Buzzing Vox AC15


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  • Buzzing Vox AC15

    It seems every tube amp I've ever owned that I really liked had a similar problem. I always assumed it was bad tubes, or tubes rattling. There is this buzzing or sort of ringing sound that resonates with a certain note or a few when played, and turned up loud. I returned a crate palomino, which sounded really sweet, because it had this problem, years ago. My blues jr had this issue but I found that I could dampen the noise by stuffing a block of wood between the reverb tank and the power tube retainer. One thing all three of these amps have in common, are el84 power tubes.


    But it seems worse on this vox.

    I tried replacing all of the stock tubes with new JJs. It definitely improved the tone and I think made the amp louder as well. But the buzzing is still there, maybe even worse, but resonating with a different note, a higher one. To be honest, it's really bumming me out, because I love this amp, but it sounds like crap when it makes all this noise.

    I didn't want to have to pay somebody to go through it but I may have to. Could it be a capacitor? Or something else? Anyone encounter a similar problem and find a solution?

    I'm beginning to feel I should just sell it to somebody else and let them deal with it, and get one that doesn't have this issue.


    I've tried tapping on the tubes with a pencil, before I swapped them for the new JJs, and I found nothing too unusual.


    It seems though that one of the preamp tubes, where its socket is attached to the circuit board, the board bends a bit, and that tube seems more susceptible to noise when being tapped, but especially if I tap the circuit board above that tube. That makes me wonder if there is some issue with the circuit or the socket there.  


    Any tips would be appreciated!

  • #2

    Since you've had the same exact and wierd problem with 3 different amps, has it occurred to you it might not be your amps? Sounds to me like something in your practice room is rattling or resonating. Try moving your amp into another room and see if it does the same thing there. I know at my house when I'm playing bass there's 3 or 4 notes that make something in the house vibrate and rattle. I don't hear when the whole band is playing. 

    Make sure the speaker screws are tight, and the amp chassis screws too. 

    This space left intentionally blank.


    • #3

      Hey man, did you ever figure out the issue with the amp. I have the same exact problem with my AC15 CC1. I've taken the chassis out and taped on all caps, etc, tapped on tubes. Can't really see any oozing caps either. I get the same kinda overtones when playing certain notes along with a kind of rattle or distortion. The rattle doesn't seem to be in the chassis or cab and it dies out before the note dies. Seriously annoying!


      Let me know if you figured anything out. I can do the work myself as I wanna save $$, but would like a good place to start. 




      • #4

        I get this annoying hiss on all of the amps be it tube or solid state that I bring home. This happens when our dimming lights are on. I usually turn them off when I am playing. Not sure what causes this effect.


        • #5

          I have a similar problem. It’s not a hizz or high frequency note; it’s more like a synthesis at the combining notes that delivers a low frequency buzz. At any kind of interval, at any kind frequency. It´s low, so I assume it’s not a small vibrating component, like a tube or so. Should be the chassis or the hole box. I write to Vox/Korg, and I’m still waiting