A few years ago I purchased a Technics SA-DX940 AV Receiver. I use it solely for watching films and have 5 Technics SS AFC 140 surround speakers and had an Eltax SW20 active sub attached via a single RCA type plug. I have enjoyed the good sound that it makes with no problems until recently. A few weeks ago the Eltax started buzzing. I was obvious that something was wrong so I went out and bought a Yamaha YST SW015. Within a hour the Yamaha had packed in. The back of it was red hot. I promptly took it back to the shop and got another. The same thing happened again. I spoke directly to Yamaha who state that they would sort it out with the dealer. The said they did not know of any probs with that sub but would check it out. They said there was nothing that I could have done that would cause that sort of problem. The man in the shop appeared highly suspicious of me but gave me a loan of another sub meantime, JPW 315. I have obviously been watching this one closely but it appears to be getting very hot as well. I have unplugged it fearing that it may go the same way. I have plugged it into another amp and yes it does get hot but not as hot as it gets plugged into the Technics. What can be causing this.......Anyone?