My tube amp, a late 90s Mesa/Boogie DC-3, developed a crackle. I searched the internet, but couldn’t find any information that directly corresponded to the problem I was experiencing. So, while this is not specifically home-recording related, I decided to add my experience to the internet in hopes it will help someone else.
The problem was a low-volume intermittent crackle coming through the speaker. It was not a hum, hiss, or pop – it sounded similar to a faulty cable or connection, but more subtle and less urgent. It would crackle for several seconds and then stop. As time progressed, over several months, it got worse. Interestingly, the crackle did not get louder if you turned up the volume. No matter how loud or quiet the amp volume was, the crackle was the same level.
I tried all the diagnostics I could, and nothing pointed toward the problem. I swapped pre-amp tubes one-by-one with known good ones. I tapped on the power tubes with a pencil. I checked the speaker connection. As a last resort, I replaced all four power tubes with new ones, and that finally fixed it. It was a $40 gamble, but it paid off.
So, internet, absorb my knowledge: if your tube amp gets the crackle, replace the power tubes.1 comment