When you switch to 192 kHz or 176 kHz, there are only 16 channels of I/O so if you have more than 2 AES interfaces, the last two in the chain are disabled, not addressable from Totalmix or the DAW.

This I knew, but it still took me a while to set up my MADI system for the first time to record 192 kHz from an external source (ADC via AES). Everything is synced to word clock, the interfaces are set to automatically configure the AES based on the wordclock.

When I switch to 192 kHz, the front panels of the last two AES interfaces out of four change from saying "Auto03" and "Auto04" to   ------   and ------. This means they are in nevernever land and I figured this display was normal, but I discovered this dispaly also also means that they are not passing the MADI stream back to the PCI card. You have to manually go to each interface and force them to say "AUTO" and then they will pass the MADI stream even though they are technically disabled. Perhaps a firmware revision would allow this to happen automatically?  The interfaces might be smart enough to know that since the sample rate changed and they are the last two interfaces in line they should still pass MADI but otherwise not do anything.

But perhaps this current behavior is logical, because perhaps the "disabled" interfaces could still be used manually as additional AES routers as long as they talk to the first 16 channels of the MADI stream and do not need to be addressed by the DAW. Perhaps they could even be used to feed 192 kHz signals from the first 16 channels via AES EBU to another (redundant) DAW?

Comments?