Equipment:
Behringer UCA202 USB audio interface
Alto S-8 mixer
Audacity (free DAW software)

Sound was taken from AUX1 send of mixer - so it was not going through any EQ or something else yet, just preamplified

Recordings:
FPGA PSG from Carnivore 2 (from the 3.5 mm audio out, not going via internal audio circuitry)
FPGA PSG from MFRSCC512+SD (taken from Modulon expander which has been disconnected from pin 49 so not going via internal audio circuitry, Philips audio fix present)
PSG from Panasonic A1WX
PSG from Yamaha YIS503IIIR

UPDATE:
FPGA PSG from Carnivore 2 - betatesting of new firmware, also: two capacitors removed
FPGA PSG from MFRSCC512+SD - firmware updated to latest by M.Pazos, also: soldered external output and cut off pin 49, Philips audio fix present
FPGA PSG from Zemmix Neo by 8bits4ever - firmware updated to KdL 3.6.1

UPDATE 2:
So, the reason of the flat envelope of MFR sound was investigated, it was because of the Philips audio volume sound fix, and after the removal of that "fix" it became good:
FPGA PSG from MFRSCC512+SD - firmware updated to latest, Philips audio fix removed
... and out of curiousity, as an illustration about how the Carnivore would sound if it has high frequencies fixed, i recorded the output after mixer (not from AUX send, but from MAIN output) with slightly up higher frequency band on EQ:
FPGA PSG from Carnivore 2 - new firmware, Equalized high frequencies

UPDATE 3:
Zemmix Neo
Zemmix Neo: with ground loop isolator
Zemmix Neo: with ground loop isolator, connected other way around

UPDATE 4:
GR8NET PSG - latest firmware has one ;)

And, a "Dark Horse" of MSX sound cards - Darky by Supersoniqs
Darky, default (after boot, has some 3D effect and chorus-reverb turned on)
Darky, some effects turned off, but i don't know yet how to turn off DSP completely, so it is not a dry sound