I've been having this problem for a very long time and have searched extensively for a solution. Nothing much out there, so I’m wondering if it’s not really a problem or if I’m the only one that has the problem. I noticed it first with my MOBO and its Intel HD audio integrated sound chip, decided to try something new with a HT Omega Claro PCI soundcard, and I still have the same issue. When I play MP3’s, FLAC’s, whatever, my sub sounds great at 48KHz, but when I switch the soundcard to 96KHz there is hardly any bass at all. If I switch to 192KHz there is not sound what so ever and the 990 shows no connection. My configuration is:

My 990 was purchased a couple of years ago, no software updates
HTPC HT Omega Claro PCI sound card connected to the 990 via a digital coax cable that is 25 ft long
The front 2 channels from the 990 are connected to a Behringer CX2310 crossover (two-way stereo) with Outlaw balanced lines
The cossover is then connected to 4 Outlaw 2200 mono-blocks via Outlaw balanced lines
These mono-blocks bi-amp Magnepan speakers
The 990 front channels are set to “small”
The 990 subwoofer out is connected to a 2200 mono-block directly via a balanced line
This amp supplies a passive sub
The 990 subwoofer low-pass is set to 100Hz

Besides the bass being a problem, my volume has always seemed to be low. I have to boost the sound through computer software which doesn’t always complement the music (slight distortion, incorrect stereo separation, complete loss of bass at higher levels). This isn’t necessarily a problem because with a more conservative boost on the HTPC it still gets plenty loud with crystal clear sound. Just seems like the signal from the HTPC is weak.

Why do I lose so much bass at 96KHz? Is it because of the high quality signal causing less distortion in the lower ranger? What I mean by this, is a portion of the bass you hear is produced by distortion, where as a higher quality signal won’t reproduce this effect resulting in the appearance of a loss of bass.

Why can’t the 990 recognize 192KHz through its digital coax input?

Does any of this have anything to do with the source’s frequency bitrate/sampling frequency? For example, the 990’s DAC’s are 24bit/192KHz, the music played on the HTPC is 16bit/48KHz with the sound card set to 96KHz.