Need help with speaker hiss from new Amp

Discussion in 'AV Receivers' started by Greg Morse, Jul 7, 2002.

  1. Greg Morse

    Greg Morse Stunt Coordinator

    Jul 13, 1998
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    Ok, I picked a B&K AV5125 and am using my Outlaw 1050 as the preamp for the time being. The 1050 on its own had a little bit of hiss, but nothing distracting. The two paired together have a distracting amount of hiss during quiet passages or even when using the test tone on the receiver (you can hear it in the other speakers if you try). Here's the rub. I have an old Onkyo ED-301 DD decoder, so I decided to hook that directly up to the amp. Rock solid, not a bit of extraneous noise in the speakers. I've ruled out a problem with the amp because of this. I'm using basic monster interconnects, but before I go out and drop a ton of cash on patch cables (which may or may not be the problem), I'd like to hear other ideas on what the problem could be. Has anyone had a similar problem with the 1050 in this role?
  2. Rosty

    Rosty Auditioning

    Nov 2, 2004
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    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 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

  3. John Garcia

    John Garcia Executive Producer

    Jun 24, 1999
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    Interconnects aren't likely to solve your problem, but I'd still toss the Monster ones. I am not anti-Monster, but their ICs just aren't that good.

    I also had hum with my digital cable, and the Dayton isolation transformer solved my problem as well. I am using monoblocks and I have no noise at all, but I also have everthing plugged into either my Panamax 5100 or Sub2.

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