QRONO Technical White Paper:
Link
Oh.
Where to start? Maybe with Kunchur in the references. Is this what a company with Bob Stuart still consulting, has come to?
Let's pull out a few quotes.
Yet, despite these advancements, there was something about digital audio that was less engaging, less lifelike than pure analogue audio.
Uh huh.
Imagine if your car started bouncing up and down before you hit a bump in the road!
... let's complete the analogy..."but you couldn't feel it". Anyway, it seems that they use a filter without pre-ringing in all of their later diagrams.
To design better filters, MQA Labs started by concentrating on the actual spectrum of natural sounds and music which are the signals we want to listen to.
This reads like old MQA. The triangle. They decide what music is. Of course, the vast majority of music did sit inside the MQA triangle. Still...
Most DAC chips also use the same filters for inputs at different sample rates. This often means they are unnecessarily aggressive with high resolution inputs of 88.2kHz and higher. By contrast, QRONO d2a filters are optimised for the musical spectrum of each input sample rate. In all cases, they preserve musicality but ensure there are no ultrasonic outputs that could damage downstream equipment like amplifiers and loudspeakers.
I'll admit to being confused by this passage. What do they mean by "musical spectrum". What is "too aggressive"? Are they claiming to process the ultrasonic element of a high bitrate signal while conventional DACs don't? Are they claiming not to process ultrasonic outputs to protect downstream equipment? Are they processing ultrasonic signal then throwing it away? Is this a dig at DSD? - but why then talk about 88.2kHZ which is obviously PCM? And what do they mean by "musicality" anyway? What If I send movie sound through this DAC - is it not designed for that, or does it make all the normal sounds or special effects more musical?
Still, this part is new. I don't remember any evidence that they used different filters for different bitrates in old MQA as they do here.
Finally, we use a technique called noise shaping to mask any low-level imaging in the ultrasonic region with benign noise. This noise also helps improve the performance of the DAC chip. The shaped noise maintains the signal’s dynamic range in the audible band but reduces the number of bits required to represent the signal. This means we can use the most linear region of the DAC chip’s dynamic range. [5]
So reference 5 is to a paper about dither. Given the fuss about this with old MQA, one might expect a White Paper on a replacement to be a bit more honest and tell us how much dither they are using, at least.
Each QRONO d2a implementation is specifically tuned for the DAC chip in that product.
They claimed that for old MQA as well. I'm not sure that was really the case then. Still, let's see.
Going backwards for the last quote...
One of the most surprising recent discoveries in neuroscience has been the precision of our hearing when discriminating sounds with fine time detail. We can perceive distinct auditory signals as close together as 7 microseconds [1-3]. This precision was critical for early humanity’s survival. As it applies to music perception, it provides the fine texture, clear delineation and spatial impression of musical instruments. Audio processing that fails to preserve these time details will blur sounds together.
Much of what you will read later in this white paper is not new information. But the fact we can perceive sounds as close together as 7 microseconds is new information. ...
Note that references 1-3 are used for this "new information" claim. The references date from 2003-2010. So, no matter whether there is any truth in the quoted papers, all three are pretty much 15 years old, and predate old MQA by 6 years. Calling it "new information" is a stretch. If I remember correctly, older information tells us something quite different. I must go and watch Monty again!
You'll forgive me for thinking, though, that there is nothing new or special in any of this until proven. It reads like they've taken a chunk of what they wrote about MQA and thrown it in this document. There are no real details of what they are doing, and the claim of audibility is not backed up by solid testing.
Before you'll get a yes or no from me on QRONO, I want to see independent testing. There's not enough in this document to call it either way, but there's enough to make me suspicious, after what we got from original MQA.