Noisy AC-15

[miltric]

Hello folks. I posted this on another forum several days ago, but haven't gotten a response. I'm hoping for better luck here.

I bought a Vox AC-15 (with Wharfedale speaker) a couple of months ago. Love the tone (as many, many posters have said, it certainly knows how to treat my Ricks), especially with the top boost volume between at about 2:00, but when I turn it up, the amp is extremely noisy. I'm used to some of that (my other amp is a Fender Vibrolux), but the Vox is starting to worry me. Even with a noise gate on, there's a persistent buzzing; I can even hear it in quieter guitar passages.

Is this normal for this amp? Could it be bad tubes? (I've read, on this forum and elsewhere, that the tubes in the AC-15 often have to be replaced pretty quickly.) Also: when the gain is cranked, I hear a kind of glassy, high-pitched noise, especially if I really lay into a chord. Again, could it be tubes? Or am I barking up the wrong tree?

Any help would be appreciated. Thanks.

[jps]

How old is this amp? Is the buzzing power supply related (60 or 120 Hz).

[miltric]

The amp is brand new. I'm not sure if it's power-supply related. If it were, would the buzzing be present whatever the volume? The buzzing gets worse as the master volume is increased.

[jps]

Power supply hum and buzz would be constant, and as this is a new amp that shouldn't apply here. Does it buzz with nothing plugged in to the input?

[paologregorio]

Try replacing the preamp tubes; many of the folks who've bought Chinese made Vox tube amps (with those horrible Chinese preamp tubes) who have had similar issues, myself included, have solved the problem by changing the preamp tubes. Borrow three of the 12AX7s from your vibrolux and see if there's a difference. If so then buy some nice, new 12AX7s.