Hi, I Also am using the DD 5.1 setup with the Promedia 5.1 speaker system. This is the setup I use with the sound settings:
Control Pod Vol: 75
Control Pod Sub: 05 (I just like the added kick in the bass, but the THX standard is to leave it
at 0, but I think it sounds better like this)
Control Pod Center + Rear: 00
DD 5.1: -20 Db (This is just for standard listening, Use the DD 5.1 to control the master volume, not the Control Pod, leave that at a constant 70 or 75. When watching a DVD movie, Music, or Games, turn it up as loud as you want up to -00 Db(max), at that -00Db will be at the true 75 of your Control Pod. When the DD 5.1 is at -20 and your Pod at 75, its outputing 20 Db less than the 75 of your Control Pod, so its about the equivalent of the Pod at 55 with the DD 5.1 at -00(max))
ProLogic: Enable (This will turn all STEREO sources into a Virtual Surround, its better than STEREO but not near the quality of true 5.1 Surroud. Its safe to leave this on, if you play a DVD with a 5.1 Surround Track, it will automatically override the ProLogic and give you the 5.1)
Bass Management: OFF (All leds are Red; Large Mode; 5.1 Promedia have their own Bass Management)
Eq Settings: Band 1: +09
Band 2: +02
Band 3: +02
Band 4: 00
Band 5: +10 (I have the Eq settings adjusted like this to add extra clarity to the sound and a slightly more defined subwoofer. (http://www.soundwise.org/dd51.htm))
Well, this is the setup i'm currently using, I hope this was of some help. As for the hissing noise, I guess thats just normal at high volumes when its quite, so there really isn't anything to do about it. Don't worry, when the action kicks in in the DVD, it'll sound nice and clear
