Let me describe my procedure of testing to simplify any further question about the set up.

2 Processors are set side by side.
1 - Proceed AVP2 capable of processing both AC-3 and DTS
2 - Meridian G68XXV presuming to be capable of processing AC-3 and DTS

Source is DVD player, playing Robots with AC-3(DD) audio output

Connection - SPDIF digital from DVD player to:
1. AVP2 Digital Input #2
2. G68 Digital Input #1(DVD)

Result:
  • A. When S/PDIF cable is feed into AVP2, AVP2 responds with Dolby D. A confirmation that the signal is indeed multi-channel AC-3. Trying to change any DSP preset, like PLII Movies, AVP2 will not respond. It continue to treat the signal as AC-3.
  • B. When S/SPIF cable is feed into G68XXV, G68 show Cinema. This does indicate that it recognize the AC-3 signal, as suggest by Gianni. Cycling through DSP button will change the DSP preset to other setting, like PLIIx Movi6, Discrete, etc.
So for G68, a pretty highly touted processor, why do I have to use DSP preset? Why can't the processor just decode the raw/native AC-3 signal? Is this by implementation or my some other misconfiguration?

Main: G68XXV, ...