MI 0808 - hear a polling hiss / hum through speakers?

traymond

Hello all. Have a site with 8 zones of audio and whatever source you choose, you can hear a slight polling from the amplifier. At first thought it might be interference but went to some other locations to hear it and I did? It is faint however if vol is ramped up and a break in track or pause in a program, it is considerably loud. Anyone else experience this sound? When i called tech support they were quick to issue an RMA and not do any troubleshooting and I was told hat they had this issue in 2008, which has been rectified. However several sites, different speakers and source gear, short runs, long runs, similar sound?
Thanks.