New here. I have a Fender Stage160 that was gently used when I bought it 8 years ago. I am a drummer and use it to play my IPad through for practice. Lately the amp crackles and loses volume after about 20 minutes and adjusting the controls does bring it back somewhat for brief periods. The only time it was used for anything else was with a Fender-Rhodes piano layout 7 months ago, and volume was high. Love the amp but don't want to spend a fortune to fix it. Any thoughts ??