[BlueSky]

Ever since getting my F212, I've been plagued with audible 60 Hz. hum coming from the F212's internal toroidal power transformer. The hum was elusive and would come and go without warning. Sometimes the hum was persistent for many minutes at a time. At other times, it was cyclical and would come and go with a periodicity of a three or four seconds between peaks and valleys. I reached out to several people who said it could be dimmers installed on the lighting or that it could be D.C. riding on the A.C. line. Disconnecting the dimmers didn't help and selectively powering down various circuits at the breaker panel didn't help. I also ran separate 10 AWG feeds from the breaker panel to the sub. I even tried both sides of the A.C. line to no avail. Heck, I even invested in a toroidal isolation transformer only to find the isolation transformer itself hummed quiet loudly.

At my wits end, I decided to invest in a little $100 device known as the Emotiva CMX-2 AC Line Restoration and Common Mode Filter. I also investigated a PS audio device that I found info on only to find that it was no longer being manufactured. The CMX-2 arrived several days ago and appeared to be a well-built and solid unit. To my utter surprise the problem has been resolved! The F212 is dead quiet even with my ear pressed against the cabinet of the sub! I can highly recommend this little gadget if you suspect you may be fighting D.C. riding on your A.C. line.