I figured my little experimentation might prove helpful to someone else so I'll post it here as well. (I posted this basic comment in Gorilla83's home theater thread, but figured it was more applicable here:)
I had some buzzing with my Sherbourn 7-350 and it wasn't too bad so I wasn't too worried about it, but I'm a tinkerer and am always messing with stuff. Whenever I'd unplug or plug in my Monoprice premium RCA cables I'd fear I was going to break one of the RCA jacks because the connectors are so tight. In the course of buying new RCA cables I learned that cables really DO matter for noise inductance. I would never have believed it mattered much myself, but here's my experience.
Being unhappy with the difficult tight connections on the monoprice RCAs. I bought this set of cables from Emotiva when it was on sale for $35, but tried to cancel when I found out the cables fit really tight like the monoprice cables. Ultimately Emotiva failed to cancel my order, even though they said they would when I called and I ended up with the cables a week later. Not that big of a deal, they are nice cables and an okay price.
So when I tried to cancel the Emotiva's I intended to use this set of Hosa off Amazon, so I bought these.
Comparing the three - Monoprice Premium, Emotiva, and Hosa, they all had different noise levels. Who would have thought?
The quality of cable as relates to noise inuctance from best to worst was:
Emotiva > Monoprice > Hosa.
But even the Emotiva had a bit of noise. Probably detectable to my ears from a foot or two. The Monoprice had noise probably detectable to 2-3 feet to my ears. The Hosa cables could be heard from 6-8 feet away to my ears.
So ultimately I bought a Preamp, and am using true monoprice premium XLR cables from XLR out on the pre-amp to XLR in on the Sherbourn. Now the buzzing noise is gone unless my ear is like an inch or two from the speaker.
The best of the RCA cables all had a little buzz from no less than a foot or two away and with the worst set of cables the buzzing was horrible.
With the balanced XLR out on the Onkyo PR-SC5508 and monoprice XLR cables to the Sherbourn 7-350 XLR in I now have now have no distinguishable noise!
BUTTTTTTTTTTT, my Onkyo pre-amp can't calibrate Audyssey or AVR test tones to 75dB in my room because the amp's unmanageable gain setting of 29dB is too hot for the pre-amps voltage output and the minimum -12 channel trim is actually still like 83dB in my room at the listening position. This trim issue was not a problem with my previous Onkyo TX-NR1007 and the RCA outs, as it calibrated my speakers to about -9 or -10dB trim levels.
I give up. I can't win for losing.