1) At 20Hz, the old high inductance (400H approx.) and standard cored OPT TI-57613 (ch1) is seen to make the amplifier
unstable, while it's clearly stable while using my new (100H approx) TI-57613-C OPT. The inductance itself is however
probably not responsible while the low "Class AB"-tolerance of the old OPT more likely is. Power output is 4.6W@20Hz/8R.

2) At 1kHz, the old OPT is seen to be somewhat better regarding overloading conditions (+50% beyond maximum input).
Moreover it's clear that maximum output power is somewhat less. This is however probably due to a significantly wider
B/H-loop and therefore core loss (and/or a estimated +/-10% load tolerance). It's also and therefore suspected that the
overshot is a due to this fact. Maximum power using the new OPT is obviously 18W@/1kHz/8R.

3) At 20kHz the new OPT is seen to behave somewhat better than the old one, but while the output level has been chosen
in such a way that the slightly higher ch1 level just about breaks up (which is true for note 1 also), this is not true. The rise
time has however obviously increased some which indicates a slightly lower HF power response. However, a rise time of
6.52us still indicates a upper limit of approximately 0.35/6.52MHz or 54kHz@6.6W/8R.