sound card/speaker question

[jharris]

I have a SB Live with a single digital out jack (yellow) on it. I have a Altec Lansing 4.1 speaker setup (ATP5) with both analog and digital (front and rear for each) inputs on the subwoofer. I can get the system working in 4-speaker surround sound using the analog signals to the speakers, but I'd like to try out the digital sound for comparison. So, here's what I think I've got (digitally): a sound card with a single SPDIF out (1/8" jack) and speaker system with two RCA digital inputs (front and rear).

Altec Lansing provided a dongle -- 1/8" jack to RCA -- for games (they say). I tried using this on the SPDIF signal, but only hear sound from the front speakers. I made sure to go through the SB utilities and turn on the 4-speaker setup and enable digital output. No success.

I called Altec Lansing and they said I needed a 1/8" minijack to SPDIF (RCA) converter (no part #), and they said I only needed the signal into the front speaker port -- that the system was smart enough to figure it out as long as I didn't plug anything into the rear speaker port. Meanwhile, the SB manual shows a multi-plug, digital I/O module plugged into the digital out port. No part numbers are provided in their manual.

Does anyone have firsthand experience with making this type of setup work? Since I have the technology (I think), I'd like to hear the difference between digital and analog audio.

Thanks

P.S. -- Evidently, SB makes its systems so they'll easily configure with their own line of digital speakers (Cambridge?).