Firstly, which version of Pyramix are you running these tests with? My comments below will refer to version 11.0.5.
Lars Nilsson wrote:When I put a single stereo file on timeline, set the fader to -0.1 or 0.1 dB and export it using Mix Down, the result sounds different than the source file.
What happens if you apply 0.0 db? Perceive any difference? Invert the polarity of this mixdown file and then mix it with your original file. Does it null properly?
The difference is subtle, but audible - I'm able to pick the Pyramix file in proper ABX double blind test with 100% confidence. The difference is most definitely more than 0.1 dB of gain.
Going back to your 0.1 dB gain change experiments, what wordlength did you select for the output file? 16 bit? 24 bit? 32 bit? Try 32 bit and see if you still hear a difference in sound quality. I'll assume that you chose to output to a WAV or an MTFF file format (you certainly don't want to use one of the data compressed formats for this experiment).
Also, what happens if you change the panning scheme used to send the source file's mixer strip output to the Mix Bus, from a Panner to a Routing to the Mix Bus? You do this by clicking on the Red "Pan" at the very top of the Strip - click on it and change from Pan to the Routing Options, where you'll set the L side of the source signal to send 100% to the Mix Bus's L input, and the R, 100% to the MB's R. (See the manual page 227.) I'm curious whether the use of the panpot vs. direct routing makes any difference to what you're hearing.
What happens if you do a Mix with the Strip gain set at -0.1 dB gain, and then do a second mix, with the gain at -0.2 dB - and then compare those
two through your ABX test?
There are no plugins on my inserts, no dithering, no other proccessing, panner is set to None and source and output formats match. I have left most of the settings on default. Both of the files have plenty of headroom and no clipping.
Anyone expirienced this? Am I doing something wrong? I'm complete newbie to the Pyramix.
I believe you'd be hard pressed to find any
DAW which does not impart some change to a file when you run it through its mixer, especially when you've applied some gain change. Even a minuscule gain change will result in a completely re-written file, since the change of gain requires the whole file to be re-calculated. Pyramix uses 32 bit floating point math for its mixdown, as do a lot of DAWs these days. However, some DAWs are going to be kinder to the mixdown results than others.
To be fair, mixing a two track file down through a two track Mix Bus isn't something that a lot of people are going to be doing all that often, unless they want to change it in some way (gain, effects, etc.). I'm reminded of a quotation from famed mastering engineer Bob Ohlsson which I thought was so incisive that it's printed out and hanging on my wall:
"Signal Processing is always a trade-off between sonic degradation and a perceived
improvement in sound."