A little update on C9 alternatives.
This cap is critical and changing it has an important effect on sound quality.
I've tried so far:
Nichicon KW (audio grade cap)
Elna Silmic II (audio grade cap)
VR was honest, nothing special, closed but fair.
KW was very good, nice balance, detail, dinamics but bass were a little 'resonant'
Silmic II was good, romantic sounding but closed.
Panasonic FM was very good, nice balance, detail, snappy dinamic but a little harsh and bass a little bloating.
Rubycon ZL was the strangest sounding very clear but also harsh with a totally wrong sound.
So, apart VR that was just a test, the worst sounding were the ZLs and Silmic IIs
Those listening test were done without bypass cap.
With MKP1837 10nF bypass cap FMs gain was low and harshness still there
, otherwise KWs gained a lot: the bass resonance is gone and highs are even better.
Also Silmics had benefits from bypass but FMs and KWs were in another league.
Normally the Silmics after burn-in opens up so they could deserve a second opportunity in the future but now the best sounding are FMs and KWs with Nichicons (bypassed) as clear winners, IMHO.
I'll try some more bypass caps (I've Wima MKS2, AVX BQ, Evox-Rifa MMK all 100nF)