Delta 2496 AC3 S/PDIF passthrough

[LemuelG]

While researching before buying my Delta 2496 I came accross the FAQ
(http://www.m-audio.com/index.php?do=support.faq&ID=f630bdaf508d194c424020851017692f)
which says that I should be able to pass an AC3 input through S/PDIF to the S/PDIF output.

Q: Is it possible, to pass an AC3/DTS encoded signal through (S/PDIF Input to S/PDIF Output) to an AC3/DTS decoder?

A: Yes, set the MasterClock setting in the Delta Control Panel (Hardware Settings tab) to S/PDIF in. Then switch to the Patchbay/Router window and activate "S/PDIF in" for the "H/W Out S/PDIF".


I've tried this with different versions of the driver on different version of Windows from 98SE, XP Pro (with each SP release) and Vista 32 bit (before and after SP1). No combination of OS and drivers has allowed this to work for me. As I have hard drives is removable trays, I can swap between O/Ss with all other hardware configuration unchanged, so if there is any driver and O/S combination where this has been demonstrated to work I would be happy to try it.

As I have an older Home Cinema receiver which has only one co-ax input, and use it to listen to cable tv, DVD player and PC, the ability to pass-through as described in the FAQ would be really helpful.

[JA]

We're going to test this here, I'll let you know what we find out.

[JA]

We just tested and successfully passed AC3 from input to output on Vista 32 SP1 w/ the 5069 driver. Did you select S/PDIF in or S/PDIF INV in as the output source? INV = inverted (reverses L & R). Does it detect a sample rate or does it show unlocked on the hardware tab? Do you see the levels max'd for the S/PDIF input on the mixer?

[LemuelG]

We just tested and successfully passed AC3 from input to output on Vista 32 SP1 w/ the 5069 driver.

Thanks for confirming that it should work.

Did you select S/PDIF in or S/PDIF INV in as the output source? INV = inverted (reverses L & R).
Yes, I had S/PDIF IN selected as the output source. I also should have mentioned that it would work fine when the sources were set to MPEG PCM output.

Does it detect a sample rate or does it show unlocked on the hardware tab? Do you see the levels max'd for the S/PDIF input on the mixer?

When sources were set to AC3 it would show a lock for the external clock, but no input level was indicated.

Since you confirmed that it should work, I tried a clean installation of Vista Ultimate (32 bit, no SP) and the Delta 5069 driver. I wasn't sure if I was hoping it would work (which would have indicated that some other driver/software was causing a problem) or that it wouldn't (indicating a hardware problem.)

Instead what I found was that I can pass-through AC3 input. But of the 3 sources I tested, I can only pass-through the AC3 from one.
The S/PDIF out from the motherboard of another PC, encoded with AC3Filter software, will pass-through as 5.1 Dolby Digital AC3 as desired. (From this source the input level is indicated as 0 as expected)
The outputs from my cable tv and DVD player will only pass-through when set to PCM. (When set to AC3 there is a lock, but no input level is indicated.)

All 3 are decoded correctly by my receiver as 5.1 AC3. I tested using the same cable to the receiver and the sound card, and with 2 different cables, with consistent results.

So I know the card can work as I wanted, but it looks like there is something incompatible with the sources I am trying to use.