Nice to have a rumble filter but would have liked a more flat response above 20 Hz.
This will almost certainly be the IEC amendment to the RIAA curve - Self has written about this in his books, and expressed concern about early bass roll off which begins just above 40 Hz. I have mentioned this in previous phono amp reviews here but my comments appear to have been ignored....
I quote from his excellent
book (Small Signal Audio Design):
"Figure 7.1(c) shows in dotted lines an extra response corner at 20.02 Hz, corresponding to
a time-constant of 7950 m s. This extra roll-off is called the ‘IEC Amendment’ and it was added
to what was then IEC 98 in 1976"
<snip>
"On the other hand, there were loud complaints that the extra unwanted
replay time-constant caused significant frequency response errors at the low end of the audio
band, namely -3.0 dB at 20 Hz and -1.0 dB at 40 Hz."