What you
want may not be what you
need. You'll be making it very hard on yourself (to say the least) if you try to evaluate the performance of electronics by ear, actually it's a good way of driving yourself crazy.
You'd be doing yourself a massive favor if you were to record not only music samples but also e.g. a complete RMAA 6.4.5 test signal matching the recording sample rate. RMAA is Windows-only but can do offline analysis as well (saving and loading WAV files), so you just need access to a Windows (virtual) machine. If you want, I could save a range of test tones (up to 32 bit, 384 kHz) and resample them for use at various lower playback sample rates - it's not really difficult to do, more tedious. Do you have a player that'll accept 32-bit int samples and FLAC? I'd have to install an encoder for ALAC first but this would also be feasible.
As far as the hardware side goes, do you have any specific budget in mind? You may want to keep an eye on the neighboring "best ADC" thread and fellow member
@IVX's Cosmos ADC release.
Yes, unfortunately, that's exactly what I need. However, I've been doing this for 30 years and I'm far from going insane because of it (there are much worse things; o)
So far, I have left the measurement to others who understand more about it.
I use pieces of music that I've already heard live and that were recorded with the same musicians and instruments in the studio. Or unplugged recordings that I was there myself.
I've done this before, but I only really realized it when I came into contact with musicians with some very well-known instruments 20 years ago. These musicians complained that they did not recognize their own (acoustic) instrument even on expensive hi-fi systems. That was very interesting and insightful back then, especially when a musician played his recording on CD and then played the same piece again live on his instrument.
This is also what concerns me when I listen to devices to see whether the instruments and voices are reproduced as I know them.
Thanks for the offer to create test files for me, if I start with measurements, I'll be happy to come back to them. Player for 32-bit int samples and FLAC is no problem.
I don't have a Windows PC, but I can borrow a high-performance notebook from our company, if necessary a large HP workstation.
Budget, preferably as little as possible and as many as necessary.
But I've already seen that if I want to achieve more than with a normal audio interface, then I'm in the four-digit range.
I will first test how far I can get and whether the whole thing can be implemented in a promising manner.