Yes for PCM. For MQA, it depends of the Roon configuration and the MQA capabilities of the attached DAC. In either case, it decodes the FLAC (or whatever file format) on the Roon Core and sends either PCM data or MQA data to the endpoint / DAC. The endpoint / DAC never sees the original container file (FLAC, WAC, etc)
I think your problem is you are confusing different things that exist on different levels of abstraction.
- FLAC is a container file format. It contains audio data along with metadata (tags, cover image).
- The audio data contained in the FLAC are linear pulse-code modulated samples, i.e., LPCM and for short PCM. The PCM is essentially the raw audio data that gets fed into the DAC (it is the PCM data that has a bit depth like 16 or 24 bits and a sampling frequency like 44.1 or 192 kHz).
- MQA can also be contained in FLAC files like PCM. MQA is largely PCM data with some bits used cleverly for MQA data.
From Wikipedia
Design
FLAC is a lossless encoding of linear pulse-code modulation data.[10]
… which refers to this source, straight from the FLAC website:
Notable features of FLAC:
- Lossless: The encoding of audio (PCM) data incurs no loss of information, and the decoded audio is bit-for-bit identical to what went into the encoder.
The relationship between FLAC and PCM is not dissimilar to the relationship of Microsoft Word files and text. The Word file …
- contains raw text (characters)
- describes various metadata about it, like font size or who wrote it
- and is losslessly compressed with the zip compression algorithm.
You can still extract the completely unchanged original raw text from the Word file.
In the same way, the FLAC file …
- contains raw LPCM samples
- describes various metadata about it, like cover art and who the artist is
- and is losslessy compressed with FLAC’s audio-specific compression algorithm.
You can still extract the completely unchanged original raw LPCM samples from the FLAC file.
If the FLAC contains only PCM (no MQA bits tacked on), this is what the Roon Core does, and sends it to the Krell. That’s why the Krell displays “PCM” in this case because this is what it sees. It has no way to know if the LPCM was previously contained in a FLAC file, in a WAV, file, an ALAC file, or whatever other container format. It’s like me sending you the raw text that I copied from a Word file in an email or text message. You also wouldn’t know that I extracted the raw text from Word.
If using mConnect, the whole FLAC container file is sent to the Krell, and so it displays “FLAC”. This is like me sending you the whole Word file as an email attachment. Then you know it is a Word file, and if you want the raw text, you have to extract it yourself - like the Krell does from the FLAC it gets sent.
MQA on the other hand is a slightly different sample format than PCM. It includes some PCM data (so that it can be played without an MQA decoder; e.g., bits 1-13 may be PCM, while the lower-level bits contain MQA data). MQA, however, can be contained in the same file container formats that were developed for PCM, e.g., WAV, FLAC, and ALAC.
Then it depends on the Roon settings and whether the attached DAC is MQA-compatible.
- Roon can do the while first unfolding of the MQA data. This results in PCM data again, and this is sent to the DAC.
- Or, if the attached DAC is MQA-capable, Roon can send the MQA samples and leave the rest to the DAC.
In the first, case, like with FLAC, the DAC only knows that it got PCM and has no idea where it came from. In the second case, the DAC can recognize the MQA data and do the special MQA magic that only hardware is allowed to do by the MQA license.
In the second case, the Krell shows “OFS” - probably, the Krell was configured as “Renderer only” in Roon. In this case, Roon will do the MQA Core decoding, send the MQA Core signal to the Krell, and the Krell performs the MQA Rendering.
I am not an MQA expert but I believe this is totally OK. You can read more here in the expert post that was the second post in one of the threads I linked, here:
For more about Roon’s MQA handling see the help:
Krell’s answer may tell you more about the MQA interaction between Roon and the Krell DAC, how to best configure it, etc.