Help!! Low level hum from FM cable sgnl

Sounds very much like a ground loop problem. Your cable connection is grounded where it enters the house; if this is not the same physical point as the ground for your power panel feeding the preamp, you typically have a voltage differntial betweenteh two ground points, which is manifested as a hum in the system. Easiest solution typically is to reroute the cable ground to the same physical connection as the power system ground.

Had this problem as well... Monster 1200 (nor any other filter device) will remove this completely. One thing to do is to make the grounds common (keep in mind NEC & local ordinances)(I disagree with the previous post that this is the easiest solution in all cases). The other thing to do is to take $50 to your local high end AV dealer and get an isolation transformer for your cable. This device will pysically disconnect the ground from the cable respective to your tuner. I took the latter approach with wonderful results. Write me if you need help finding this device.

Per J-k a hum-bucker is probably the best answer. But I did find a cheaper solution for my rig. I happened to have on-hand a car-audio isolation transformer. Actually this is two transformers (left & right channels) in 1 package, available from a car-audio shop. Run the audio coax's thru them to your preamps' inputs. These coupling transformers are probably not the nicest thing for your FM audio signal, especially a Dynalab (I have one too) so the hum-bucker is the best solution.