Ideally, I’d like Damien to answer the following question of mine since he is the creator of Audirvana, but others feel free to chime in too.
Damien… I understand, fundamentally at least, that Direct Mode is a custom audiophile driver you wrote to bypass Mac OS’ Core Audio driver. What I’d like really to know and understand is:
Technically/scientifically/mathematically speaking, what data or sound quality ‘loss’ occurs - if at all - when I don’t use Direct Mode? What corruption of the audio signal happens at the Core Audio level - if at all?
Non-technically speaking, what sound quality loss could be perceived - i.e. possibly heard - when I don’t use Direct Mode?
For context, I have a fairly nice 2-channel system, where the MSB Reference DAC itself cost me $34k! I only listen to SACD ISO or DSD files (have multiple terabytes of files). I always listen bit-perfect, with no upsampling whatsoever.
That’s impossible to answer, MacOS is capable of outputting bit-perfect without direct mode.
There is probably some difference in terms of jitter. The only way to tell if you really need it is to try with and without direct mode and see if you can tell the difference and which you prefer.
Based on the responses from @bitracer and @Lolodesiles, I feel like I need to clarify my original question and provide some more context:
I have been using Audirvana since Jan 2015. The performance is great - no questions or issues there. I have a dedicated MacBook Air running El Capitan, which allows me to use Direct mode with no hacks. I have a very capable 2-channel setup which is quite capable of extracting the max out of any file at its native level. I have already experimented with Direct Mode on/off, and yes, I do hear some differences. The problem is, ‘different’ doesn’t necessarily equate to good or bad! Being a reasonably technical person, what I’m trying to understand is, based on the Direct Mode on/off algorithm, what are the differences I might be hearing? As @bitracer said, one thing could be Jitter. Is that really so? What else? That’s why I’d like to hear from @Antoine since he wrote the Direct Mode driver. From a purely technical standpoint, what does direct mode OFF do to the digital signal that causes it to sound different as it goes through the Mac Core Audio driver?
Harsh, if you really want to know the answer, visit www.audiosciencereview.com and hang around for a while. Members of the forum include people from across the audio industry, including engineers, manufacturers, and even some “stars” from Stereophile. I guarantee you will learn a lot, although you might not like to know the truth about a few items. I hope you do visit.
