Hi Matthias,

Thanks for your inputs. I have finally set up the RME ADI-2 Pro as DAC (got rid of the external DAC), and now my setup is

Sonos spdif coax -> RME ADI-2 Pro (with PEQ) XLR -> Topping A-90 -> headphones

Now the questions that have been bothering me, and I am sure you can clarify, are -

1. The input digital signal from Sonos (or from any other digital sources) is very close to clipping (OVR), and if I add Parametric EQ to it, the output signal at 0dB is obviously getting clipped, so I have dialed down the volume to say -12dB. The question is how does the RME ADI-2 do pre-DAC headroom management? Everywhere, I see there's a suggestion of -6dB pre-DAC headroom adjustment to make the headroom available for EQ gain, but I do not see anything like that to adjust in the RME ADI-2. Moreover, my worry is that if the signal gets clipped after DSP -> DAC (assuming this is the sequence), the digital volume gain reduction will be working on the clipped signal, which will not help much.

2. In the chain of signal flow, where does the reference level adjustment come in? Am I thinking this correctly Digital input -> Ref Level -> DSP -> Digital Volume -> DAC -> Analog output?

Please let me know so that I can sleep better at night and prevent eyebags from appearing.

Thanks!

Dehati

Thanks for the headroom info. Considering I am using the RME ADI-2 Pro with digital inputs (coax) and analog outputs (XLR) (changed from the original topic, after forum member suggestions), what I still don't understand (even after reading the manual), is

1. How do the ref levels affect digital inputs (when the manual says it is about analog inputs)?

2. What is the sequence/flow of DSP, DAC, ref level adjustment and digital volume adjustments? I thought (applying common sense), that it will be

Digital input -> headroom, ref level gain adj -> DSP -> Digital volume -> DAC -> Analog output

What am I missing?

You have no ref levels in the digital domain.

See block diagrams ch 17.3, 17.6
https://www.rme-audio.de/downloads/adi2profsr_d.pdf
https://www.rme-audio.de/downloads/adi2profsr_e.pdf

Example AD/DA Mode:
Digital IN (AES, Coax, Optical) -> Main Output 1/2 -> DSP-> Digital Out Source -> Digital Out (AES, Coax, Optical)

The internal headroom exists by a higher internal calculation bit depth, 42 bit according to manual page 64.
This maintains the sources’ full digital resolution all through the DSP/Volume processings.
Therefore, the user simply does not need to care about the internal levels.

You can look at it like this (bold = has headroom):

Digital input -> 24 dB extended digital headroom (42 bit calculations) -> DSP -> Digital volume control -> DAC -> analog ref. level adjustment steps (+4, +13, +19, +24 dBu) -> Analog output

Now that you are going analog it might be important to know:

If “Auto Reference Level” is “ON”, “Digital volume control” and “analog ref. level adjustment steps” work together to maintain full dynamic range / SNR over 20 dB of combined volume control.

Indeed the block diagram of the ADI-2 DAC shows the ref level position, but the Pro manual does not have such a diagram.

That question makes no sense. What is '0dB' in this context? You mean dBu maybe?

Sorry, I meant dBU in the ref level context. My 1st question was related to getting the same level output level compared to the input (output level = input level, i.e. no additional gain). Not sure if that is the right question given digital input and analog output.

My second question was a follow-on to the first, which is that if such situations/combinations exist where the output level is the same as the input level, then what will give the highest SNR. I guess that is optimized internally with the Auto Ref Level.

Where I am going with this is that as I feed the analog output of RME ADI-2 Pro to three external amplifiers separately (Topping A90 headphone amp, Blue Hawaii electrostatic headphone amp, Marantz speaker amplifier), I'd like to send out the most standard, cleanest analog signal out of RME and control volume separately with these amplifiers.