I'm building a new system and just added the last component, a Soundblaster Audigy 2 Platinum ex. I mated it to an older Cambridge Soundworks DTT2500 5.1 speaker system which has been working fine on my old computer. I connected the SPDIF output from the external Audigy 2 processor to the AC-3 input on the DTT2500 processor. I get a very loud hissing noise from the speakers when I turn the units on. I can faintly hear music playing when I attempt to play something but it sounds pretty bad. I have a Gigabyte GA-8INXP motherboard with on-board sound. I disabled the on-board sound in the BIOS and even removed the connections from the motherboard - still the same results. I ran the Soundblaster diagnostics and they passed fine. I set the sampling rate to 48KHz (I read somewhere the DTT2500 couldn't handle the 98KHz rate the Soundblaster was outputting) and also tried disabling the Dolby processing on the external Audigy 2 unit to allow the DTT2500 processor to process the Dolby signal - still the same hissing sound. I'm running out of ideas. Does anyone have any suggestions on anything else to consider?