jmcari wrote:

To add to my previous post (no hum-990/7500)-I am using Outlaw balanced cables...

Right-on. I just spoke with Scott and earlier Steve. They agree that this may eliminate whatever differences in potential to ground exists.

My system needs to go unbalanced, so I'm going to see if the balanced cable will carry whatever benefits accrue while unbalanced will make my life easier. For example I like an EQ between 990 & amp. Also I am going to be using KEF 107s and these use bass management (i.e. the KEF "CUBE") about which I'm just finding out. Will post results of balanced plus unbalanced later.

Followup info:
Seems like so long as at least one channel carries the balanced signal and the switch is set to balance that the amp is dead quiet....absolutely no hum.

Conclusion ground loops SEEM to be eliminated by at least one balanced run.

Opinions??

Experience ???

FWIW, my 7700 with XLR's is dead quiet. Even putting my ear up to the speakers I can hear no hum or hiss. I do get an occasional mechanical transformer hum from the amp itself but that is a separate issue with an interaction between my display and single circuit feeding all of the HT devises.

Wharg: My experience with balanced is same. Absolute dead-dead-dead quiet.

I wrote above that my system needs to be balanced because of the KEF 107 CUBE. OTOH, my DEQ830 which is a balanced EQ may sufficiently do the job instead of CUBEs.

The 7500 is on my short list of amplifiers. I look forward to the solution of this hum problem because I will not be using balanced inputs.

Rat wrote:

I look forward to the solution of this hum problem because I will not be using balanced inputs.

I would also prefer to not use balanced inputs, as it would simplify my life...interfacing with an outboard EQ, for example.

After solving your hum (probably ground loop)situation, please post the details of what it was and how you fixed it.

Run it by Steve and Scott
They were very helpful.

If it is any consolation, I had a similar inconsistent hum situation in my own comparisons last year of the Outlaw 755, Rotel RMB-1095 and Anthem MCA-50 amps. With exact cable swaps (using all unbalanced RCA connections), the Outlaw and Anthem were completely quiet, but the Rotel had a noticeable hum. The Rotel dealer suggested trying a cheater adapter to disconnect the ground -- not as a permanent solution. This made most but not quite all of the hum go away.

I am new to this forum.I hope someone can give me some valuable information. I am looking into purchasing a new amplifier. I was looking at the Rotel 1095 But have deceided to go with the Outlaw 7700. My question is if I am considering using my Yamaha 3300 Receiver as a processor (I am also thinking about selling it and getting the Outlaw 990) this HUM issue bothers me.I have no hum having everything grounded and using two surge protectors from Monster. If I keep my Yamaha I will not be using balanced cables rather monster interconnects. Of course if I go with 990 I will probably buy Outlaws cables as well. Does anybody have any thought as to what way to go with this new set up? Yamaha, keep it or sell it, balanced cables or interconnects?
Thanks,
Frank

So far the hum issues are related to ground loops, which are a risk no matter what hardware you use. Many receivers and source components aren't as susceptible to it because they don't use three-prong power cords, while big power amps typically do and are therefore often the trigger for ground loop chases. Unfortunately for them, they are usually not the culprit - cable TV is the primary source of ground loops, due mostly to problems with the cable installation and the way it ties to the house's electrical ground. There are inexpensive methods of fixing such ground loop problems, so I would not let the risk of a ground loop prevent you from moving to a good amp like the 7700.

Balanced interconnects are not necessary to get a good, quiet system - plenty of us have had great success getting dead-quiet setups with standard unbalanced cables. I wouldn't get rid of the Yamaha just for the sake of having the option to use balanced interconnects. On the other hand, the 990 is a great piece of gear that offers some nice features the 3300 lacks (DVI switching, Pro Logic IIx, more robust bass management, video transcoding from s-video and composite to component, a third component input).

I had the hum as well it was not a ground loop.
We have a new house and had installed some lights under the counter in the kitchen with bult in dimmers. When those dimmers were on there was a
loud hum from the 7700. When off no hum. Strange but true.