I'm in what I think is an unusual situation. I have a ca 1999 Sunfire True Subwoofer Signature (that's what is on the back plate, with Bob Carver's signature). Not EQ, STS, etc. From the owner's manual which I still have it has 2700w amplifier output, response is claimed 16-100Hz +0/-3dB, dimension is a 13" cube and weight is 53 lbs. I may have one of the earliest units (I recall it was something getting a good amount of attention at the time) as it appears the owner's manual is actually for a Sunfire True Subwoofer with an addendum page added for the Signature specs.
Anyway: since new I've had a problem with this beast. The bass is phenomenal - and still is. But whenever there is a passage with loud bass components, a loud hum develops. The only way to "fix" this is to turn the sub's volume all the way up - which will induce a pretty loud, low "thud", then back it down to normal setting (generally 6 or 7 o'clock position). Once "reset" there is no hum, even if the sub's volume is turned up considerably. I struggled with this for a while, even calling up the manufacturer (who answered the phone back then). I tried removing cable/satellite TV input from the receiver; tried removing the equipment ground from the sub; tried plugging in to the same power strip as the receiver. No luck. I decided (with little to go on) that it was just an artifact of the various components I have and over time, found that getting up to "reset" the sub was too much of a bother, so kept the volume set to almost off. I was running a Marantz SR880 MkII receiver. Then finally I unplugged it completely and there it sat in the corner.
I have just received a Marantz SR6010 AVR as a gift. I've now replace the SR880, and love all the new format processing, connectivity, switching, convenience, etc. I was optimistic and enthusiastic in thinking I would now, finally, be able to enjoy the Sunfire sub after all these years. Turns out that's not so.
I've removed the electronics and visually inspected for anything obvious. I re-seated the leads to the driver. I don't see any bulging electrolytic capacitors. At this point and from reading this thread in entirety (I've not been keeping up with subwoofer developments otherwise) it sounds like this unit is now one of those "they don't make them like that anymore" (meaning superior to current models) and can't be replaced. I really like the amount, depth, and visceral impact of this sub (when not humming to much I can't hear) especially for it's size. And it doesn't feel "sloppy" but tight and controlled.
Not sure if this should be a separate thread (if so, moderators please fix and accept my apologies). Are there experts with this unit that can help walk me through debugging this problem? Surely someone must be running a Marantz AVR with a similar Sunfire sub that doesn't have this problem (which I'm hoping for as an indicator that there is not some incredibly bizarre interaction between the Marantz HDAM/current feedback circuitry and the Sunfire amp).
Any help will be greatly appreciated. Thanks in advance.