We also have an I-Tech doing the same thing for quite some time now possibly a year and a half. Hiss that slowly builds to a pop, and crackling. This happens when first turned on and is sitting idle and only on channel 1. Once the amp is hit with a good amount of input signal (warmed up?) it stops. Also in quiet situations, or like the situation mpjonathan had, I'll disconnect the speaker output and send a strong level of music to it for 10-15 minutes then it don't happen again. Hope some of my troubleshooting helps.