The Song Fight Bulletin Board

Hey all, long time.

Been experiencing some sound issues the past couple of weeks, and I think I've isolated it to the amplifier. But as I know very little about amp quirks, I thought I'd put the question to y'all...

The amp in question is a Vox AD50VT (flame on, gear snobs, if you must ). Yes, I know it's a solid-state hybrid amp with a tube for the sweetener.

At the past couple of band practices, I'll be playing and the sound coming out of the amp just dies to a whisper, ssst!, then comes back, stutteringly at first, then full force, after ±15 seconds. Not just once, but repeatedly, and usually when things are just getting good with the rest of the band.

The details: volume knob's @ ten o'clock, wattage knob's at ±35 watts. Miked through a PA. Doesn't seem to happen when it's run direct to the board (which cancels the speaker output), but that's for "quiet" practice, so I'm not... pushing things... quite so hard. Smoking studio (yes, flame on again, heh). Amp's maybe 3 years old (4?).

What I've done: Swapped guitar cables. Swapped guitars. Plugged guitar directly into the amp (removing the pedal board from the signal path). All for naught. Percussive maintenance (aka a good firm smack) did work last night, but I haven't had the opportunity to repeat that experiment for better quantified data.

The WTF: Is this a tube characteristic/quirk/peccadillo? Have I given the amp cancer? Will you help me get my cat out of the tree, officer?

How long are you playing before the amp cuts out?

I'm tempted to say it is a speaker issue if you can connect it to other things and have it work fine. Try connecting the amplifer part to a different speaker cabinet and see if you have the same issues.

Ken

About an hour before the fizzle comes, ken. Yah, this weekend I'll experimenting with that to further narrow it down.

I'm not an amp guy in the least, but the symptoms make me immediately think power. Swap the tube, 3+ years is plenty of time for degradation, especially if you're moving the amp around a lot from gig to gig. If that doesn't help, check the other power components. Make sure the amp is ventilated, as overheating could cause the delayed powersink issues you're getting.

That sssst! and stutter... This definitely sounds like a tube problem to me, especially since it only seems to happen when you push hard.

I'm going with tube also. I've a similar problem before. If it were a thermal cutoff, it would just die when it got hot and come back on when it cooled off.

Thanks for your help, y'all. Much appreciated.

I think Ken wins the long-distance diagnostic with speaker. Amp completely fizzed out in last night's practice, right after tuning up. Not even percussive maintenance worked this time.

But plugging the line-out into the pa's board saved the day, so the neighbors got to be serenaded to the soothing sounds of Troll Feet aka how long can I play a G major chord, heh.

I'll crack the case this weekend and see if there's anything obviously wrong in the guts.

Just in time for Nur Ein, too.

Rabid Garfunkel wrote:percussive maintenance

Band alert!