Rosty
Auditioning
- Joined
- Nov 2, 2004
- Messages
- 11
I have recently aquired a barely used (12 months old ) Rotel RB 1090. Awesom amp - I like the sound very much. Better then built in amps of my Denon AVR 5803 and then Adcom GFA 565 300W monoblocks. A few observations about hum, buzz, hiss, etc. When I had only Denon AVR 5803 it was dead silent. When I added Adcom GFA 565 to power my front L/F channels I immediately noticed an audiable hum. The hum would disappear if I disconnected the input cables (a sign of the ground loop problem) or if I used the cheater AC plugs. Denon has 2 wire power cord, Adcom uses 3 wire power cord. Again, obviously - this was a ground loop problem. Not willing to go the cheater plug route I investigated the problem further and found out that humming was caused by my digital TV cable hookup. The moment I disconnected the coax cable from my cable box the hum was gone. I looked around the Internet for advice and installed a ground loop isolator similar to Jensen VRD-1FF (It is sold by partsexpress.com as "DAYTON VIDEO ISOLATION TRANSFORMER"). I was able to remove the cheater plugs from the Adcom power cords. Problem was solved.
When Rotel RB 1090 was added to the system to replace Adcom monoblocks it exhibited a slight hissing sound which could only be heard from no more then 1 ft from the speakers (Paradigm Studio 100 v.3). What is interesting - the sound did not change when I disconnected the input wires so initially I attributed it to some design flaw of this particular unit. Being a curious person by nature I decided, though, to try a cheater plug here too and guess what, - the amp became dead silent!!! Hissing was gone for good!!!I don't have a reasonable explanation other then a thought that the grounding wire of Rotel's power cord receives some sort of interference from outside and being so wide frequency amp (-6 dB at 6 HZ - to -3 db at 275KHz) Rotel then produces this hissing noise. I built a two wire power cord for Rotel (could cut of the ground prong on the OEM cord, but wanted to use the thicker shielded wires and better connectors) and the hissing became a history.
Now, how about the safety issues, you would ask. All safety concerns were addressed by installing a GCFI outlet insted of the regular AC outlet ($13) . In the unlike case an unsafe voltage ever appears on the Rotel's case, the GCFI cirquit will cut the AC power off microseconds after someone touches the Rotel's case.
Just my $0.02
Rosty
When Rotel RB 1090 was added to the system to replace Adcom monoblocks it exhibited a slight hissing sound which could only be heard from no more then 1 ft from the speakers (Paradigm Studio 100 v.3). What is interesting - the sound did not change when I disconnected the input wires so initially I attributed it to some design flaw of this particular unit. Being a curious person by nature I decided, though, to try a cheater plug here too and guess what, - the amp became dead silent!!! Hissing was gone for good!!!I don't have a reasonable explanation other then a thought that the grounding wire of Rotel's power cord receives some sort of interference from outside and being so wide frequency amp (-6 dB at 6 HZ - to -3 db at 275KHz) Rotel then produces this hissing noise. I built a two wire power cord for Rotel (could cut of the ground prong on the OEM cord, but wanted to use the thicker shielded wires and better connectors) and the hissing became a history.
Now, how about the safety issues, you would ask. All safety concerns were addressed by installing a GCFI outlet insted of the regular AC outlet ($13) . In the unlike case an unsafe voltage ever appears on the Rotel's case, the GCFI cirquit will cut the AC power off microseconds after someone touches the Rotel's case.
Just my $0.02
Rosty
