About a week ago I found time to start listening to my new B&W 804S and HTM3S speakers and have been trying out different modes and crossover settings on the 990.
As of now, I've found that setting the speakers to "Small", with a L/R crossover at 40Hz and Center at 60Hz produce the best results. I've also found that I have to use "Bypass" mode when listening to CDs (digital rca input), as "Upsample" now sounds too harsh in the upper frequencies.

If I were to use an External DAC (such as the VDA-2), I'd have to connect my rca digital cable to it, and then use rca analog cables to the 990. In doing so, if the 990 was in "Bypass" mode, according to the Analog Bass Matrix, the L/R Speakers and Sub would get full range sound and not use the crossover.
http://www.outlawaudio.com/support/990_analog_bm.html
If I'm using Bypass mode now with digital input and fronts set to small, it will use the crossover and send bass to the sub, but if I use analog inputs, it sends full-range sound to the fronts and sub?
This makes no sense to me.
How then can you use an external DAC and still use the 990s crossover?
According the bass matrix, I'd have to use Stereo, Upsample, or Dolby.

The 990's bass management is applied in the digital domain, so the only way to use it is to allow the 990 to convert an incoming analog signal back to digital, apply bass management, and then convert back to analog. This will happen for any analog source using any mode except bypass.

In bypass mode with analog sources, there is no bass management because the signal never enters the digital domain. What the 990 does when the fronts are set to small in this scenario is simply duplicate and sum the left/right channels and send that to the sub - the assumption being that if you have the fronts set to small, you want the sub to be engaged.

Ok, thanks for clearing that up.
So if I were to use an External DAC, or higher-end CD player, and connect it to the 990 using analog RCA inputs, my options would be:
1) Stereo: The analog input is converted to Digital, applies bass management crossover, then converts back to analog and sends to the 7500 and sub.
2) Bypass: The analog input stays in analog mode, but sends all the left/right audio to the sub. I would then have to use the Active Crossover on the LFM-1Plus to limit it to only playing low bass (under 80Hz).
3) Choose Upsample (or Dolby PL II), have the analog be converted to digital, apply bass management crossover, then convert is back to analog to send to the 7500 and sub.

If I were to use a high-end external DAC or CD/SACD player (Marantz), which of these 3 options would be the "best" to choose from?
I'm not sure if I like the idea of the external DAC (or CD player) doing a D/A conversion, then have another A/D/A conversion done by the 990. Wouldn't that lessen the quality some?

With a high end external DAC or disc player, your probably already employing some upsampling , re-processing on the 990 wouldn't buy you much. for Prologic IIX or other processing modes you'd be reprocessing the analog signal again. I've had better luck just processing the digital signal directly when I want this effect or using bypass when I want stereo.

I'd prefer "Bypass" with a high-end DAC - there's no reason to pay a premium for such a DAC and then stick it upstream of another DAC, which is what will happen with either Stereo or Upsample.

As for Pro Logic II, NEO:6, Stereo 5/7, or any other such mode, in my mind that doubly negates the point of a premium two-channel DAC. If you are going to use a mode like this with a digital source (CD, DVD, PC, ...), I'd just use a digital connection.

I've resurrected this old thread because I recently added a Cambridge Audio DacMagic to my system and I've got a couple of questions I'm hoping someone can answer. FYI, I will eventually use the DacMagic in a separate stereo system but for now the optical output from an Apple Airport Extreme feeds the DacMagic and then is connected to my 990's auxilary analog input. The DacMagic upconverts so I use Bypass mode as suggested above. I get more bass with this mode.

Just checking, but is the increased bass when using Bypass due to the subwoofer receiving full range signals from both the Left and Right channels?

Is there a way to define/determine how much this bass increase is in dB?

I have "small" speakers so I have set my subwoofer's crossover at maximum as my 990 handles all the bass management. However, when using Bypass should the sub's crossover be set near the left and right speaker's -3dB point?

I want to do an A-B comparison between the DacMagic and the 990's DACs when using the Airport Express to determine if there will be any impacts on audio quaility when I move the DACMagic to my stereo setup. The DacMagic gets some positive buzz because it reclocks the digital signal (apparently the Airport Express messes this up) to remove jitter that can degrade the sound. This may all be audiophile mumbo jumbo (and the 990 may reclock too) so I'd like to do a listening test. The DacMagic has a pass-through digital output that should make this test easy to set up. I believe I'd set the 990's digital audio input to Upsample mode (matching the DacMagic) and leave the Aux analog input from the DacMagic in Bypass. Correct? Is there a way to get the bass output equal without resorting to adjusting the subwoofer gain each time I switch between inputs?

Thanks for the help!