adamdea
You are not a sound quality evaluation device
To check that I understand you-all of the files apart from the 2L are upsampled 96kHz with a filter with not much image rejection.Reviving this old thread.
I spent some time analysing the analogue output of an Explorer2 while playing 'three-LED' MQA files. Three LEDs lit means that the signal is of 4x rate or higher (i.e. 192k, 176.4k, or DXD rates).
I recorded with my Tascam DVRA1000 running at 192kHz. Theoretically this gives me a view of the MQA DAC's output up to 96kHz. However, the PCM1804 ADC in the Tascam has a large bump of sigma-delta modulator noise above 60kHz, so for payload ultrasonics to be discerned in the 60-96kHz band they, the ultrasonics, would have to be very very loud.
Normal music does not have high-level ultrasonics. In fact most music does not contain much above 30kHz. This makes analysis hard, because in order to spot the effect of upsampling in the signal chain you want to find pairs of matching frequencies symmetrically around Fs/2. Luckily many studios are a bit dirty, EMC-wise, and have spurious signal related to CRTs and switch mode supplies running through their cables. These signals make it onto recordings and then act as tell-take signs...
A-ha:
Spuriae mirror clearly around 48kHz. This is a 96k signal upsampled to 192k.
Eagles:
Spuriae mirror clearly around 48kHz. This is a 96k signal upsampled to 192k.
Some jazz track, don't remember what (Bill Evans?)
Same story. In addition, the master was heavily filtered while converting to 96k.
Roberta Flack:
Spuriae mirror clearly around 48kHz. This is a 96k signal upsampled to 192k.
Television:
Idem.
2L, possibly the Mozart
Clean recording, no spuriae. All the 2L recordings I tried had very little treble content, too littly to allow searching for images. This was the best. Even so I had to eyeball this in real time (all other graphs were averaged), and freeze the spectral plot when the suspected image finally peaked above the noise bump. You can see that here at 26kHz and 70kHz.
In case you wonder ... all examples, except 2L, contain a strong pair at 29kHz/67kHz. This is not an artefact of my setup. I verified that the 29kHz component is present in the digital signal as it comes from Tidal.
Does this mean that they were originally 96khz i.e. that they have not had the lazy downsampling from 192 to preserve the >48kHz material as aliases which then re-expand to the 48-96khz zone on upsampling (I think this is what Jim calls the origami)