BillFitzmaurice.info

First off, I'm a bass player not a guitarist so I don't know much about guitar amps. At a show this weekend our guitarist set up his rig and it started making noise. It was kinda squealy, and making crackling noises like a bad cable would make. It almost sounded like some sort of radio interference. It started when he first set up, then it went away for a couple of minutes, then it started back up again as we were getting ready to sound check.

I unplugged the guitar cable, so it was just the head, speaker cable and cab and it still made the noises. He ended up borrowing a head from another band and there was no noise, so that eliminates the speaker cable and the cab. They were also both plugged into the same power source.

I brought it to my house after the show and it was fine (of course).

Any ideas what could cause something like that?

It is an 1980's Laney Pro-Tube AOR30.

Sounds like radio wave interference. I have a preamp that does that when I fire it up in my garage. Never happened at a gig when I used it.

I think it's an issue with the tubes that pick up the radio signals. He could try replacing the tubes.

How cold was it? Did he leave the amp in a cold car for an extended period? Going from cold to warm will cause some condensation, and that can cause noise, especially with the high voltages of tube amps.

Bruce Weldy wrote:I think it's an issue with the tubes that pick up the radio signals. He could try replacing the tubes.

That's kinda what I was thinking. Tubes are probably four years old, but the amp doesn't get used that often.

Bill Fitzmaurice wrote:How cold was it? Did he leave the amp in a cold car for an extended period? Going from cold to warm will cause some condensation, and that can cause noise, especially with the high voltages of tube amps.

It was about 35 degrees out and it had been in the bed of my truck in the garage all day. It rode up in the bed of the truck (covered) and we played first so it is possible that it was condensation.

Repeat the conditions in an experiment, so you can be sure?

jswingchun wrote: It was about 35 degrees out and it had been in the bed of my truck in the garage all day.

I wouldn't do that, condensation is a given.