I send this to SVS support, but thought that I would run it past the "pros" here.

Here is what I sent them (with some modifications)...
I bought my 20-39 PCi sub back in November of last year (when I bought my awesome Axioms), and I just love it!

I have a question though. Last night (actually early this morning around 6AM) for no apparent reason, I was woken up by a loud, low "hum" (not low grounding loop hum) but like something was sending a VERY loud, low test tone to the subwoofer. My sub is in my basement, and we have a 2 story house. It was enough to wake me up, and when I started going down to the first floor, I could actually FEEL the bass. Not that feeling the bass is unusual, but when the system is off, it sure was odd.

I made it to the basement and turned off the sub right away (it was on Auto) I checked everything, and the crossover on the sub was set at 80, the volume as at about 50%. The receiver (a Pioneer Elite VSX-54TX) was off, and there seemed to be no reason for the bass to kick in.

Even though I bought the sub (and actually all equipment) in November/December 2004, I didn't use them regularly until about 2 months ago when I finished my home theater. I am using good quality wiring and have never had anything strange like this happen before.

Any ideas? Anything I should check? I really don't want to have to turn the sub on and off every time I watch a movie, but right now that looks like the only sure fire way to make sure I don't damage the sub.

Nick, I've heard that emergency hot-lines have gotten calls like "Help! I can't hear my sub!!", but your situation is a new one on me. I doubt that even Tom at SVS can help in this case and I suggest that a priest be called in. Seriously, even when the sub is set on auto, a voltage of a certain amount has to be input to "wake up" the sub amp. If someone there wasn't playing games with you it's hard to figure where the power came from. If Tom or anybody at SVS has a reasonable idea, tell us about it.

You know, your story is kinda creepy. I'm with JohnK--call a priest.

not just one priest 2 an old one and a young one.

I had a pair of Definitive Technology speakers with a built in amp that used to do the same thing.I had to send them back to get the amps replaced.

My 20-39PC+ started doing the same thing about a month after I received it. The amplifier assembly had to be replaced -- SVS suspected the power supply. I switched on and off manually while the new amp was being shipped out.

Replacement was a no-brainer and no problems since. Here's the patient in the middle of the operation :

I was thinking very seriously about using an SVS 25-31CS with my plate amp, but the Wife made some comment about placing the new sub out in the utility room next to the other hot water tank....

You would still get pretty good bass...

No response yet from SVS, but it is the weekend, so I am not expecting anything until Monday sometime.

Hopefully they will have a solution for me and it will be under warranty.

Yeah! That's true!

I hear the bass quite well now while in the shower, it would be even better with the sub near the actual water heater!!