Hello,
for better understanding how the RIAA coupling triode acts in the circuit I made some drawings for you.
In the coupling triode AC modes you can see first the "triode transformer mode" explained here:
https://www.vintage-radio.net/forum/...ad.php?t=16509
In this mode the input voltage (and resistance) is divieded micro times.
In the "diode mode" (see post#1) input and output is the same.
The "vari u" mode makes it possible to get a reduced micro to get less damping in triode coupled stages for example.
The RIAA-triode operates in the "filter mode". In my case the RIAA characteristec is made in two steps.
In the next drawing you can see the block diagram.
The flat part of the RIAA curve and the enhanced RIAA (eRIAA) is
set by micro of the coupling triode. Note that triodes micro has no aging.
Kind regards,
Darius