Topic: ADI-2 Pro Firmware Update 144 DSP 81
The last major firmware update 141/76, see
made a lot of people happy. Let's try this again, making a lot of people more happy - the users not hanging around in studios and not used to clock configurations and such - the HiFi guys.
They expected to be able to just switch the input from USB to SPDIF and back. As we all know this is usually not possible. The interface (AD/DA, digital I/Os, FPGA, DSP) runs with a common clock, and getting SPDIF from a CD-player needs the interface to change to the clock of said player. Now if you just played back files via USB at 192 kHz, changing the hardware to 44.1 would wreak havoc on whatever operating system you use, as fully unexpectedly either the hardware is removed, or put into a state that the OS' audio engine can not handle.
One often found solution is to use a sample rate converter for the incoming SPDIF signal, so the interface can stay at the current USB sample rate, and one can still listen to the SPDIF signal. Unfortunately the first thing a 'HiFi guy' does is to disable said SRC. Oops! But even if not, the SRC will fail when USB is used with higher than 192 kHz, as the SRC in the ADI-2 Pro is limited to these 192 kHz.
Turning the ADI-2 Pro into a typical, simple to use stereo DAC therefore needs a different approach, one that is quite unusual in the studio world, because one expects to be able to use all I/Os at the same time. The user will take care that all sample rates and clocks match for full multichannel operation. And USB is the main connection active all the time. But here it is either SPDIF OR USB - not both, even if their clocks would allow to do so. RME's solution is to isolate the USB engine in the interface from the main clocking when an external clock source is used that does not match the current USB clock. Example:
- USB is used to play back a 384 kHz file. The ADI's main clock (SteadyClock) is using internal clock mode at 384 kHz.
- During this playback the clock source is changed to SPDIF (or AES), and SPDIF is selected as audio source. The ADI's main clock (SteadyClock) is now using the SPDIF signal at (example) 44.1 kHz, and SPDIF can be heard at the ADI's outputs. USB sound is no longer available.
- The magic part: USB stays at 384 kHz, and playback continuous. Neither the OS nor the driver (under Windows) notice that the data they send are thrown away within the ADI-2 Pro. Playback continues seamlessly and uninterruptedly in whatever DAW or iDevice. One can even stop playback, change to a different sample rate, play a different song. It all works, but no audio will be audible.
- Then change input source back to USB, and clock source to INT. The ADI's main clock (SteadyClock) is using internal clock mode at 384 kHz (or whatever is now current) and USB playback is immediately heard at the ADI's output.
Now let's couple the clock source to the monitoring source so that the above two steps of switching are reduced to one, and here it is: the new Basic Mode called DAC.
The updated manual (with revision number in footer, currently 1.8a) explains this mode with text and block diagram, although it is so easy that neither manual nor further explanation seem necessary. Note that the analog input (ADC) is still working as USB record source and is also available as monitoring source. And while outputs 1/2 and 3/4 will always play out the same source signal, they are still fully independent in setting volume, EQ etc., thanks to the double DAC design of the ADI-2 Pro.
The new clock isolation of the USB engine is also used in all other Basic modes, whenever SPDIF or AES is used as clock source and input source, and sample rates of SPDIF/AES and USB do not match. USB audio is automatically muted then. This feature brings improved stability and usablility even in studio use, as clocking to an external signal can no longer have negative impact on simultaneous USB operation.
- USB descriptor changed to show 32 bit audio
- Clock Source SPDIF and AES use INT if no respective input signal is available ('preferred mode' removed)
- A key that has been re-assigned via Key Remap Function to load a stored Setup will issue a confirmation dialog before loading said Setup. This prevents losing all current settings by unintended activation of the Setup loading.
- Bug fix: Relay noise when navigating within the menu.
All updated files (firmware, manuals) are available on the ADI-2 Pro's web page:
Please report back here if you think you found a bug or error.