MQA unfolding question

[joel]

Hi Hector,

@Itotron

But what actual DAC actually does the second unfold and authentication over TOSLINK?

@Itotron

TOSLINK (SPDIF) has a real world limitation of passing audio at 24/96

High resolution non-MQA digital audio at 176k and higher sample rates needs a digital input at least as capable as the audio sample rate. As you quite rightly point out, typically only USB provides greater than 96k (non-network) input capability.

However, this does not apply to MQA which is transported to the DAC at either 44.1/48k (fully folded) or 88.2/96k (first unfold to “MQA Core”). A 96k digital input (TOSLINK, coax SPDIF, etc.) is therefore not a limitation when passing an MQA stream to a DAC.

The MQA stream that enters the DAC at max 96k is unfolded/processed inside the DAC. Depending on the hardware implementation in the DAC, the signal may be up-sampled to a sample rate higher than the 96k MQA transport sample rate. This secondary unfolding/processing is known as rendering.

@Itotron

I would love to see a full MQA decoder that doesn’t have a USB input

Most do… TOSLINK and coax SPDIF.

@Itotron

Does MQA require two way communication?

No.

---

MQA sample rates are confusing. Perhaps this post of mine may help?

MQA 44.1kHz and signal path?

There are four different rates here, which causes no end of confusion: The MQA container rate (i.e. 44.1k or 48k) which is how the MQA gets to you. It has nothing to do with anything else and has no bearing on rendering rates. The transport rate of decoded MQA (“MQA Core”) from the MQA decoder to the rendering part of a DAC. This can be from Roon (or any other MQA decoder) to the DAC, or within the DAC itself. MQA Core is always 2x rate (88.2k or 96k) and has no bearing on rendering rates. T…

This Roon Knowledge Base article might also be useful: https://kb.roonlabs.com/Roon_x_MQA