after searching today for some new ES9038Q2M-boards/-infos, i´ve found also this „Upgraded version of ES9038Q2M decoder board I2S input OPA1612+AD8397ADRZ“ (it was also mentioned in these diyaudio.com-forum)->Link
it costs only about 42$ (incl.shipping), and interesting is (besides all the disadvantages like the 5V-9Vplug, the only-headphone 3,5mm jack and so on) that they use „OPA1612“ for the AVCC-section and some „AD8397ADRZ“ for the „output“-section..
i´ve googled immediately for „AD8397ADRZ“ and according to this post/article->https://www.head-fi.org/threads/audio-gd-discrete-op-amps-reviewed-opa-earth-opa-moon-opa-sun-v-2.397691/ its only in the „Category 2 – nice but incomplete sound“ 😉 (posted the link+excerpts also in the forum here->Link)
the author there also said, that for him (and thats interesting for me) the AD797BRZ (i have the AD797ANZ here) are the only ones in the „Category 5 – complete sound traveling in the clean air“
„..roughly, it’s like the AD79ANZ with all advantages of the OPA627BP added“ and as u know, i just wanted to buy lately an OPA627 (the „Bugatti Veyron“ on the OP-Amps) to „finalize“ my op-amp-experiences..
so i guess i have to check-out these AD797BRZ some time too 😉
another thing is that they are now at Volumio V2.457 (PI Kernel bump to 4.14.69 and some fixes), i´ve tested it immediately with the ES9038Q2M and the „Allo-Katana“-setting, and it was, as said in an earlier post, „massive“ (ES9038Q2M+2*AD797) again !!
this time had the chance to test it before with the ES9028Q2M-option (in Volumio) and some minutes before also with the i-sabre-k2m option in Dietpi V6.16..
last time i thought it could also be by the changed footprint/pi-kernel-bump but today i would say the „Allo Katana“-overlay is more specialized on the ES9038Q2M-core->
finally, at present, i must really say that i have the best sound (on all distros) with the newer Volumio (V2.452 and up) + „Allo Katana“-settings on an ES9038Q2M+2*AD797 !! (okay, its really tight between them but Volumio is absolutely easy to handle at present)
DietPi is now at V6.16, i just wanted to set up the new „mympd“-(fork of ympd), ran into trouble, theres a workaround now and its fixed in DietPi V6.17..(„Allo Katana“ works NOT on DietPi (with the ES9038Q2M) but with the „i-sabre-k2m“ overlay i got 32/384..)
more to come, greets for now 😉