The 990/7700 combo will have the same hum if you have a ground loop caused by the cable connection. I used the Jensen isolator to solve that very same problem.
_________________________
AvFan
Outlaw 976 | ATI 2005 | M&K 850s Left, Center & Right, Surround-55s, MX-70B Sub | Harmony 950 remote | Panamax 5100 | OPPO UDP-203 | LG OLED55B7