I started paying attention to the preemphasis icon (PEI) in the top left corner of the display (under the “gear” icon) of my DAC and I am concerned with what I hear.
I get PEI when I play/stream 44.1/16 files through USB input (via Optical Rendu); and when I play CDs on my Jay’s CDT and use AES/EBU link to DAC w/o upsampling.
I don’t get PEI when I play/stream hi-rez files or have Roon upsample 44.1/16 files to 88.2 or 176.4; when I use I2S connection from CDT to DAC; or when I program CDT to upsample to 176.4 and use AES/EBU.
I spent quite a bit of time A/Bing preemphasis and have to conclude that in my system it degrades the sound: there is less high-frequency extension and less “air”. It may not be night and day, but it is quite noticeable. Fortunately, now that I have diagnosed the problem, I know how to avoid it.
Only 44.1k signals have a preemphasis option or flag. If it’s accidentally set on a higher res file the DS ignores it.
Non PS Audio I2S sources probably don’t correctly signal whether the material is preemphasized (it’s done over other control wires on the HDMI connector.
There is a signal that the source is preemphasized when using AES3, S/PDIF and TOSLink. They should be reliable from most physical transports.
Whether a ripping program would detect preemphasis during ripping, set a metadata flag in the resultant file and then your playing program/hardware would notice that flag and send the right signal over AES3, S/PDIF or TOSLink is a lower probability.
I don’t think there’s a path thru USB for the preemphasis flag, but I could be mistaken.
If a file is preemphasized then there’s a standard shelving filter applied to it, basically a 10.458dB raise in level between 3.183kHz and 10.610kHz and then a flat 10.458dB from there to 22.05k.
If the DAC gets the proper deemphasis signal the output will be flat. If the file wasn’t preemphasized file but the DAC is told that it did you’ll end up with a drop off starting at 3.183kHz. If the file was preemphasized but the DAC isn’t told about it, you’ll get a rise starting there.
AES3 is the newer name for AES/EBU and indeed (as I stated) that’s an input that will work with a “standard” source, e.g. a physical player or a source that is setting the flag correctly from some metadata somewhere. There are many combinations of hardware and software that punt entirely on the preemphasis flag and (fewer) that set it on when it shouldn’t be.
The out of band signaling in USB isn’t something I have any experience with, hence my equivocation.
just happen to come across this, but there is a thread that deals with i2s out of the OPPO, that showed that i2s can come across on pin 15 of the connector, BUT, I believe that was in context of an HDMI breakout box that they were fiddling with. The breakout board took standard hdmi and one of the outputs was i2s in LVDS.