Well bad news for me. The replacement pre is actually worse than the original. The right channel has a huge amount of static type noise coming out of it. All the others are about the same. I put the original back in and the right channel is fine is back to the way it was. I'm glad I was able try the new one before I returned the original one I had.
Now the question is what to do next. The dealer I purchased this from does not have any other preamps in my price range that have the features I want. I may get a loaner of another company to try out. He has Denon (which I really don't want), NAD (way over priced), pioneer, Arcam (see NAD) and Krell
Uggh. This stinks.
Sorry, I have not been following this thread. I thought you were out of the woods.
Unless there has been a serious downgrade, I doubt those Marantz units are both faulty. The second might be, but I doubt the first is, unless there has been a serious lapse in standards, since my AV 8003. That unit has a superb massive power supply, and robust well thought out ground plane.
An internal ground loop is unlikely to result from a manufacture problem and would almost certainly have to be a design problem. So they would all be doing it, and I find it hard to believe Marantz would not know about it. You never know though in these days of the race to the bottom
You can tell if the Marantz has an internal ground loop. Listen via the headphone jack, with nothing else connected. If you here hum they are lousy units.
To make sure, make a lead up going xlr to in line phone socket. Unbalanced at the phone end. Connect to a pair of balanced outputs. That will drive any phones. See if you hear hum then. Him=lousy product. No hum, no internal ground loop.
Now you have a complex system and when you have that things can happen.
You should know it took a lot of work to quieten this system down.
I had a sub panel put in with a big ground to the main panel. I constructed a robust star cluster ground plane, grounding in all of the racks. I made sure all rack mounted units had good bonding to the racks, scraping paint where necessary. Check for good grounding with a meter.
Even after that, I had to redo Direct TVs work, and tie in the satellite system and the FM antenna.
Still there were big problems. There was definite RF interference from the Lutron Maestro light dimmers, of which there are a large number in this house.
This necessitated my redesigning the Luton Maestro dimmers. I have to say there engineers were highly cooperative. All production since then has this redesign. They still emit some RF. It is impossible to make an SCR dimmer that does not emit some RF and have a decent dimmer.
Still not there yet. I had to redo the whole house ground, and replace it with three seven foot copper rods tied together.
Still a problem. The phone ground was at the front of the house, a long way from the house ground. This was still causing a an earth loop. It was more than the 20 ft max, allowing me to tie it to the main house ground. So I gave the phone system its own 7 ft copper rod ground. This has still left me with a very slight ground loop, but you can only hear it with your ear right into a speaker driver. You can not hear it from any seated position. This will be eliminated in the next month or so, as Paul Bunyan telephone are constructing the first fiver optic PON pushed deep into a remote areas. The fiber cable, placed right by the main house ground will be hooked up as soon as the snow is gone. That will tie the phone ground to the main house ground. I expect that to rid my of the last vestige of hum.
One other issue is that my downstairs system, uses the FM and Direct TV connections. It is too far to tie the ground to the studio ground. You can not use ground isolators with Direct TV, because of phantom powering and signaling. So that whole system has to be totally disconnected from the house ground, and only grounds via the two Direct TV cables and the FM cable ground. Not the best situation, but there is no other way. If you ground it both system hum loud as you get a ground loop from the house ground and antenna cables.
So these situations are highly complex.
Here are pictures of some of the grounding.
TV and Antenna grounding.
The main house ground.
So I think you have a lot more work to do, before blaming it on Marantz, or changing units again.
