tube i/u converter tda1545

[alchemy]

hello,

i'm inetresting by the shematics of Kuei Yang Wang for the tda1545 dac.

i'm newbee with tube and i want some explain about the shematic and information by the result of this tube output.

the first tube in just fo i/u convert but between the two tube, it's a low pass filter, if i have good understand in other thread, the value are different for NOS dac and with teh good value, the cut frequencies are lower for NOS dac, it's real?

if i don't want the low pass filter for make a NOS dac and filterless, how modify shematics?

the value of the plate resistor of second tube, (near outpout) is 100ohm for NOS dac?

if anybody can quickly explain me the shematic, i'm gratfull for my entire ilfe .