hi guys,i just bought one Ad30vt amp, sounded really nice, but after 2 days the sound like gotten abit muddy leh, when using the neck pickup on distortion, the sound tend to buzz on the thick E string, issit becus of the tube failing or wat? but the tube still glows... btw i using an epi les paul, in Sg which guitar shop got sell those tubes ah? pls help me....