When I play a CD in my DVD player with Direct Mode 'ON' on my Marantz SR-8000, the sub channel does not come on. I take it this is by design, but I guess I'm just wondering what exactly "Direct Mode" is. It sounded really good, but I need some BASS!
Its most likely meant to pass the signal without any processing, including treble and bass controls. In your case, that includes not going through the crossover. So the sound comes straight from the dvd player, through the volume control, and out the amps.
If you have a high-end CD player it may have a better processor and circuity then your preamp, or the preamp section of your receiver. So by going direct, you're taking advantage of the better component. Just remember, digital is not always better, its the better D/A converter that makes the difference.
Supposedly, SOURCE DIRECT mode, as its called on my SR 6200, bypasses all bass management, tones controls etc and the sound is supposed to be better. I resent the fact that, to me, the sound is far too noticabley different. The bass seems much better. To me, that means with my subwoofer, I'm not getting the best bass signal. With SOURCE DIRECT on, I am not able to use my sub. The way around this is to use an external amp and use a crossover between the receivers main left and right pre-outs and the amp. You route the bass to your subwoofer and thats it.
I have B&W DM603S3's (towers) and a Velodyne VX-1215 sub. The Velodyne is great for movies, but isn't exactly the last word in control or accuracy. For stereo music, I use the direct mode on my receiver, and since the front L/R speakers get a full range signal, I get the nice tight bass from my B&W's. That's the greatest single advantage to using this mode of you have full range mains.