[Phil Allison[_3_]]

"Alex Pogossov"

Note that op-amp IC1 is firtually out of the GNFB loop. It is only as a
preamp with gain of 15 and for DC stabilisation.


** IC1 has four jobs:

1. An inverting stage with gain of 15 times making the total gain 56 times.

2. A DC offset servo with C2, R4 & R5.

3. A sub sonic filter, -3dB at 13Hz and -20dB at 5 Hz.

4. With R11 fitted, it clamps the input signal so the max power becomes
half.

These last three together make to 405 safe to use with an ESL57.


.... Phil