thank you so much for your detailed help and explanations. I really appreciate that very much! You are the professional audio engineer here and I´m only an unknowing layman compared with your great knowledge concerning recording-technique. So, I want to try my best here (as you do at the piano with great success, btw)!
No Andreas you did not get my point. If the question of interest is whether 192 kHz sampling performed by an ideal converter is better, in general, than 44 kHz sampling performed also by an ideal converter, then you cannot compare a recording done by means of your ADC at 44 with a recording done by means of your ADC at 192 since your test proved to your ears that your 44 ADC is not as good as the 44 ADC that you get by combining your 192 ADC with 192-->44 SRC.
O.k., I think, I have got that know, really. To find out in general, if 44 or 192 Khz is the best I should test the two best converters of the world in each samplerate-category, isn´t it?
So your reference 44 ADC should be this latter one. How to compare it with a 192 ADC ? Of course you must use the same DAC performing at the same rate. If you would use your 44 DAC, you would have to convert the 192 kHz digital output of your 192 ADC in a 44 kHz digital signal and would get exactly the digital signal from your reference 44 kHz ADC... That's why I suggested that you should use rather your 192 DAC. But 88 or 96 DAC would be fine also.
I have a question here. If you talk about a 44 ADC, 192 ADC and so on, do you mean two different devices or do you mean one device? I have only one device: a sound-card by M-Audio (Audiophile 192), which I can set to different samplerates for recording like 44, 96 and 192 Khz.
In that sense I don´t hear a difference between 192 ADC-->44 SRC and a 44 ADC recording taken with my sound-card. But I hear a difference between a 44 ADC, 96 and 192 ADC recording. The 192 ADC has the best quality, so I suppose that to be the best setting for my device. The 96 is also very good, but has a bit less of the "ambience" and "soul" respective "atmosphere" of the sound.
Back to the piano ?
Nope, I would like to learn as much as possible about these things.