I own a 20 year old Sony SA-W30 powered subwoofer. Ths thing has an automatic on/off switch that activates when it receives a signal. I have two problems with it. One, in the half dozen moves from country to country and state to state I have made with it, I have lost the manual. Second, unless the video receiver is playing at a loud level, this sub turns itself on and off with a loud thump a half dozen times a song. I have played with the reveivers crossover settings and have played with every adjustment on the sub. Is there a way to simply turn the thing on and leave it on. All the thumps are driving me crazy. When operating with a movie it works, despite its age and battered appearance, pretty well.