Help With 60Hz Hum PLEASE

Good call! Yes, it appears that it could be a thermistor. Ironically, though, I believe that the symbol for R55 shown nearby on the schematic (connecting digital ground to chassis) is one of the symbols that are used to represent thermistors, yet R55 appears in the photo to be just a jumper. Also, I don’t see any listing at all for R55 in the parts list.

So if the photo is considered to be gospel, as opposed to the schematic and the parts list, it appears that XLR pin 1 is connected directly to chassis (via the R49 jumper); digital ground is also connected to chassis; and analog ground is connected to those points through a thermistor.

Given the flexibility that is provided by the board design for how these circuit points are utilized I doubt that there would have been a reason for them to modify the related circuit traces under or within the board. But given the inconsistencies between the various documents it’s all hard to figure.

Best regards,
-- Al

I would try the cable fix . They ran the power and cable through the same hole in my house . I had a 20k new system and there was a slight hum . I took some speaker wire , strip the ends and twisted it around the cable splitter and connected the other end to a water pipe with vise grips . Problem solved . 

GOOD EVENING,

I have been busy all day, but I stayed up late last night putting everything together. Here is what I found works....not 100% sure I understand why yet, but I think I understand what has happened.

jea48, The link you provided to www.rane.com coupled with discussions about grounding and ground loops really helped solve this. Also, some dumb luck played a part.

After spending an hour reading through www.rane.com/note110.html and subsequent pages I began to understand the difficulties manufactures face with using balanced and unbalanced connections on the same unit.

I ended up modifying all of my XLR interconnects to match "cable 1" at www.rane.com/note110.html. I did this to one cable first, and after doing so the noise that was being produced changed greatly. Not is was much louder. It also sounded more like a 120hz hmm instead of the 60 cycle buzz.

It was good to have something different and right away I thought to now chases ground the two units together. Since the amp and pre-amp were so far apart, and I was in a hurry to test my theory. I just plugged an RCA cable into the unbalanced connection point above the XLR IC on the amp and then touched the outer ring against the chases of the Marantz. The following silence was only broken from my cheering. No more buzz or hum. Just a very soft hiss that I find to be common in systems.

Right after this I posted the success and then went to work reinstalling my system.

After installing all my components and plugging the amp and pre-amp into the power source, I checked to verify the noise was still gone. I made a custom lead to go from the frame of my amp to the frame of the pre-amp. Hooked up just one speaker fired it up and.....BZZZZZZ. "What the heck?" I think to myself.

Taking a step back and reviewing the changes the main thing that has changed, other than the proximity of the components, is where I am grounding the two components together.

Grabbing an old RCA IC I cut it apart and plug into the amp unbalanced input, and connect the shield wire to the frame of the Marantz. For some reason there is still a 60 cycle buzz.

"Wait", I think to myself. I have plugged into a different channel than what channel is hooked up to the speaker. So I switch the RCA plug to the same channel that the speaker is hooked up to and voila. The noise is completely gone again.

What I ended up doing is jumping all of the RCA outer rings together and then linking that to chassis of the Marantz.

Keep in mind I am using the XLR ICs for my sound path. The RCA outer ring is just for grounding to the Marantz.

I think by doing this I have bonded all of the signal and chassis grounds in the amp and joined the Marantz eliminating any kind of ground loop effect.

The one thing that is still present is a pop or clicking sound when I turn on the system or mute the pre-amp. Don’t know why.

My system has been running all day, and it has never sounded better.

Thank you all again for your help! Especially jea48 and almarg! Your awesome!

P.S. My back is just fine.