Well, part quality is not meaningful when we are determining is something clone of something else..
(that is other topic, and yes: parts matter..), schematic and values is. Whats is different is feedback network.
-Is it really enough?
I know there is very little new under the sun when it comes to amplifier circuit design, but i would not feel comfortable claiming that this circuit design is my own..
I can only refrain someone more expert opinion on this:
"STUDER A68 power amplifier (REVOX A740 shared circuit)
It was introduced in 40 years ago about 1977. It according to the Recording Industry standard, the distortion is less than 0.1% .
I start simulate A68 in TINA-TI, and feel the schematic looked a bit familiar . Then I find the Voltage-Amplification-Stage (VAS) is almost same with the darTZeel NHB-108 internet uncovered schematic, there are 12 resistors value all fully equal and the all 4 pairs of transistor structure are exactly the same, only the feedback networks are different."
and:
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