I wanna add my experience with passive mod on the caiman

removed the analog section and connected wm8716 exit to the rca via two big MKP film foil cap, Audyn Mcap Plus 3.3uF

Dramatic improvement in clarity, definition, smothness, 3D... every aspect improved noticeably

but

the bass became too light for my taste

With this combination the bass is stronger, better defined, rock solid, tigth, but lack that depth in the very low frequency, that was present with the opamp stage

so just for fun I bypassed those two big caps with two small rubycon 47u

the bass is back !!!

but

midrange and high are messed up

in Italy we say "you can't have the bottle full and the wife drunk" ....

ok

so I replaced everything with two MKP film foil, always Audyn Mcap plus, but 6.8u (I had them on another DAC)

ok, this seem a reasonable compromise

mid and high seem loosing nothing, and bass quite a bit deeper, probably 10u
would be better, but when you speak about resolution on coupling cap, less is more, I mean, the bigger the cap, the greater the attenuation and phase shift due to dielectric absorption

But what I really can't understand is why I need such a big cap value when the math tell me that 3.3u should be more than enough (my amp has a MEASURED input impedance of 44k)

a fellow here in another thread told me it could be just a matter of dac output impedance

hmm, good explanation, but a lot of people in this thread affirmed they had good result with lower capacity, 2.2 or even 1.6u

this puzzle my mind