Low buzzing through speaks

BTW, I had this issue with my Mac402 amp. The attenuator did the trick. 

I had this interference both static and hum. The static turned out to be my cell phone and the hum was fixed by better shielded interconnect cables.

You know what is weird? About 1 1/2  years ago I reached out to Simaudio (I bought my Titan amp used 2 years ago and realizing this piece although in amazing condition and was sounding just amazing, it was approaching 20 years) to see what if anything I should do to care for this unit. They recommended sending it to them for "cleaning and calibrating". So I did. Knowing I was going to be without the unit for a few months I bought a Monolith 5 channel amp as a backup (the price was right at $1599 at the time) to get me through. Once I introduced this unit with my Marantz AV8802A, there was a faint hum/buzz - come to have been thinking about it it was very similar to what I have now - but chalked it up to this being a lower end and knowing it wasn't there with the Sim, I wasn't too concerned. Once I got the Sim back and connected it, buzz/hiss gone. I just remembered this today! And from what I recall it was very faint and didn't change volume wise like this current possession of my rig! 

Just maybe the lifters or the attenuators will be the proper exorcism to get rid of this particular evil entity😂🤞

IMO, both @dpop and @russ69 give you great recommendations, if the XLR ground lift adaptoer works, it will eliminate the hum/buzz noise. Otherwise, an 10dB in-line XLR attenuator will reduce the noise 10dB (since the noise is not affected by the volume control).

https://en.wikipedia.org/wiki/Ground_lift

https://www.parts-express.com/Inline-XLR-Attenuator-Pad-10dB-240-412

Once I got the Sim back and connected it, buzz/hiss gone.

Looking at the rear panel of the Marantz AV8802A, I can’t help but notice that the iec power outlet is only 2 prongs; meaning the unit is technically not seeing an earth ground, until maybe a piece of equipment is plugged into it, *giving it* an earth ground. Really, trying to hook up equipment in the home audio world can be confusing sometimes, because you really have to take into consideration what is grounded, and what isn’t, and these manufacturers don’t make it easy. Not to be condescending, but it sometimes takes some knowledge trying to figure out grounds, and ground loops.

I mix both balanced and unbalanced analog equipment in my home system(s), and you have to know when the time is right to ground, lift shields, or transformer isolate. I admit, it took me years to learn all about this stuff.

I used to live on a very busy street in the days of kids cruising the highway with CB radio’s (man am I dating myself). Believe it or not, they were still heavily using CB’s in the early to mid 90’s (so maybe we’re not going back that far 😉). I was even then routing audio through my townhouse (at the time) using balanced audio, but even still, when they would drive past, their CB signal would many times blare through my system. Well, even at that point in time, I still hadn’t learned all I needed to know about balanced analog audio. So it too took me time to learn about shielding, and grounds, etc. etc. My former neighbor across the alley from me lived across the street from a ham operator, and she used to get so frustrated because his broadcasts many times blared through her TV speaker(s). Now that type of interference is tough to get rid of. Working at the radio stations, I used to get a lot of complaints from neighbors when our signals also permeated their home electronics. Not always easy trying to solve those problems.

It’s very possible attenuators might be needed in kingbr’s case. I’ve used them in broadcast studios, but I think it’s unfair to make homeowners research the need for them in a home audio system environment. One thing that bothers me about the Sim amp is that it doesn’t have any gain controls, so to put it one way, it’s wide open. IMO, that means that any little bit of noise on the interconnects will be magnified more than it needs to be (screwing up your S/N ratio). That’s one of the main reasons why I will never purchase a power amp without gain controls on it. It’s very possible that is what’s taking place here, but again, I think it’s unfair to put a home audio system owner through this frustration when purchasing expensive audio gear.