Since purchasing my twin Velo DLS-3750Rs in July, I've been plagued with varying degrees of hum. The only way to minimize it was to connect the receiver to the subs using only the subs' L & R Line Input Jacks. Using a Y-Connector to L & R Inputs easily doubled the humming so I just ran with L Inputs till this weekend.
After finding in these forums that the problem is probably the CATV connection - something that I'd never heard of. I disconnected the cable from the system. Voila - all humming gone!
Luckily, this weekend I was able to talk to a cable technician who was doing a trouble call on our street & described my problem. He was well aware of this condition but couldn't help me then as he had another call - but he took my info. I asked him about 'Ground Loop Isolators' & he said that in rare cases they use them but they like to solve the problem at the source - their cable system. I'm still awaiting their call, ha!!
Being inquisitive, I then rigged a probe on a wire that I plugged into the third hole (house ground) of the wall socket. I touched numerous metallic points around my system including the barrel (shielding) of the TV Cable, all to no avail. Finally I touched the outside barrel of the sub Audio Jacks. Voila - the hum was gone!
I had some unused quality Audio Plugs so I soldered 4 of them so that the barrels only were connected to 4 wires (zip cord)with the center pins floating (not connected). I fashioned them into a harness so that all 4 wires were connected together with a probe at the other end. I plugged them into the 4 sub Line Out Jacks (that I don't use) with the probe connected into the house ground. Voila - the hum is gone! I'll temporarily use this until the cable company fixes it.
What is interesting is that twin subs' output is much greater now with both the L & R Line Inputs being used. My Audyssey Calibration has required me to drop the sub channel from 40 to 30 & it still needs to come down as it is now sitting at -11 db. Probably 25 will be close. The Velo default factory preset is 35.
Interestingly, I was at my old fart's garage band last night where my buddy has been plagued with a huge hum/buzz in his computer audio system (that we use for backgound tracks) for years. I had him disconnect the CATV. Voila - the hum is gone! He's calling the cable company today, ha!!
Tom
Comox, BC
