I'm running an Onkyo tx-nr1000, a Toshiba HD-A1, and a Sony BDP-S1. I have them both connceted to the two multichannel audio inputs, using a high grade Y-splitter for the rear channels, as to get psudeo-7.1 surround. For some odd reason I am getting a very harsh buzzing noise from the HD-A1, and a very minor to near inaudible at lower levels, buzzing on the sony blu ray player, when i have it connected to the 5.1 analog outputs. This is my only option for TrueHD and LPCM support. Any help or suggestions to fix my buzzing problem would be greatly appriciated.

Remove the splitter from the equation and try running one of the two players direct. If the buzzing goes away you know where the issue lies.

Is the buzzing coming from all channels?

I would double check all cable connects, and make sure there is not any metal connections touching.

Also, you might try removing the Y splitter just to test if that corrects the issue!

yep, the buzzing is from all channels