Marantz AV7703 vs AV7704?

[aceinc]

I got lucky on the deal. You win some, you lose some, trust me I have lost many.

Two things;

1) I haven't tested it as I should, so I can't say with certainty that it is great. I can say it isn't terrible. I think I will need to tweak it some. The Audyssey freq graphs are very different than similar graphs from Dirac, and what I measure using REW. Both of those seem to use better quality calibrated microphones.

2) Regarding hum, I had a problem with hum which started when I introduced cable (Comcast/Xfinity) into my system (to test, disconnect the coax and the problem goes away). I fixed the problem by going to the box where the cable came into my house and changed the ground. The cable company had grounded it to the electrical conduit that my meter is mounted on. While I am sure that is probably an OK ground, they may not have screwed the ground screw through all the paint (50 year old house). So I stretched the ground about 3 feet to the actual copper grounding rod that goes into the ground. Voila, problem solved.

BTW I use RCAs. Although I have ordered, and am waiting on delivery of 11 XLRs (I was ordering monitor cables for a customer and added the XLRs for S&G).

 

[davidahn]

Hey AceInc, thanks for the prompt reply.

That's good troubleshooting on your ground problem!

In my case, I noticed wicked buzz when I connected the A8X's to my Sony STR-DA5800ES via cheap unshielded RCA cables, but even disconnected from the receiver, still the exact same buzz, disappeared when I unplugged the cables from the speakers. Then I got dual shielded RCA cables, and voila, barely noticeable low pitched hum. I'm hoping balanced XLR cables should eliminate the hum.

But first, I have to get separates: 1) for XLR connections and 2) for Atmos. I bought the Sony STR-DA5800ES JUST before Atmos became a bona fide hit; terrible timing.

 

[aceinc]

Based on what I understand, your amplified speakers without cables plugged in do not hum. If the cables are plugged into the speakers only they hum, a little with "good" RCA cables, and a lot with "cheap" RCA cables.

Does the hum get better or worse when plugged into the receiver (as well)?

It sounds as though the RCA cable is inducing noise from somewhere. You don't bundle it with power cables do you?

I have seen and experienced mismatched grounds from different circuits in a house. Actually seen neutral and hot swapped on a circuit. When (in my case computer equipment) two pieces of equipment were plugged into different circuits and then connected to each other things fried in a hurry.

I have also seen two separate earth grounds on different ends of a house used that provided a low voltage differential (potential?) when attempting to connect them together.

 

[davidahn]

Yes, amplified speakers, no hum with no cables, loud buzz with unshielded thin RCA cables whether connected to receiver or not, receiver powered on or not. Very low volume hum with dual shielded thick RCA cables, I have not yet tried connecting the shielded cables to the receiver.

Agreed, the cables are clearly picking up noise from somewhere. They are simply coiled next to power cables. It's kind of a mess right now with a temporary setup, cables everywhere. My theater is not yet set up, my remodel was a 5-year nightmare, finally getting close, carpet in the theater, screen in place, but I just wanted to do a test movie, so I set up the receiver on the ground (HDMI cable doesn't reach the projector). I will definitely have to hunt down the source of the noise when I get the permanent setup.

 

[anthonyrizzo84]

Is the earc work on this receiver?

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