Sometimes we think that forums are the center of the universe, but they are not. We are shipping the DAC with ESS for more than 2 weeks already, and not a single customer has released that information. Because most of them don't even write in forums!
The printed manual (version 2.6, online now is 2.7) does not hide this fact. Here is what page 4 has to say:
Note about the current ADI-2 DAC
At the end of 2020 a fire destroyed AKM's production facilities for AD and DA converter chips. A resumption of production and thus availability of these components is not expected before 2022. Therefore, many manufacturers - like RME - are forced to either discontinue products based on AKM chips, or to use other chips for the foreseeable future.
The ADI-2 DAC was initially based on an AK4490, later on the AK4493. The current unit uses an ES9028Q2M for its high-quality DA conversion. This chip is very similar to the AK4493 in features and technical specifications, which allows RME to continue offering the ADI-2 DAC in its well-known supreme quality, and with a nearly identical feature set.
Even though this chip is a central (sometimes sole) quality determining element, the ADI-2 DAC is just not a normal DAC. Tech specs and features are based on RME technologies, and they are available unchanged also with the ESS chip:
- Complete DSP functionality (PEQ, Bass/Treble, Loudness etc.).
- All sample rates, PCM as well as DSD
- All digital formats (SPDIF/AES/ADAT)
- Analog input and output circuitry, including Auto Ref and 2.5 dB digital headroom
- Extreme Power headphone output stage
- SteadyClock FS, including the latest 1 Hz filter technology
- Lightning fast sample rate change on playback
- Remote, display, general behavior, operation and handling....
ADI-2 DACs with AK4493 and ES9028Q2M are neither sonically nor visually easily distinguishable. However, the ESS version is recognized by a small C at the end of the serial number sticker (B stood for AKM 4493). Furthermore, the units differ in the available filters. The unit with AKM has a filter called Short Delay Low Dispersion, while the one with ESS has a filter called Brickwall (the other filters, SD Sharp, SD Slow, Sharp, Slow, NOS, are identical). Further Chip dependent differences are mentioned in this manual.
Regarding Tech Specs: forget the data sheet tech specs. AKM and ESS both have their pros and cons, a simple THD+N comparison won't do it. Additionally we needed to reserve 2.5 dB headroom as that feature of the 4493 DAC should be there as well, and - even more important - the ESS chips do not handle intersample overs as gracefully as AKM chips do. So that headroom is a must - and naturally already steals 2.5 dB of SNR and THD+N.
Reading the manual you might notice the new Loopback feature (mainly for Mac DIGICheck to show playback data) - it will come to all DAC and Pro, don't worry.
And yes, we added all missing filters ourselves by loading them into the ESS chip in real-time.