At last my HEX-code staring has led to some practical results. Turns out SS40 does support directly ripping CDs into ATRAC3 @ 105 and 66 kpbs. It does not provide any controls to select these modes, so you have to select them via the registry. Do not worry - these registry modifications are reversible, and will be reset as soon as you select any other bitrate in SS40. So, here goes:
1. Close SonicStage.
2a. For 105kbps modify the registry in the following way (or use the 105.reg file from the attached archive):
REGEDIT4
[HKEY_CURRENT_USER\Software\Sony Corporation\SonicStage\CDRipper]
"Bitrate_00090010"=dword:00019a28
"FileType"=dword:00090010
2b. For 66 kbps modify the registry in the following way (or use the 66.reg file from the attached archive):
REGEDIT4
[HKEY_CURRENT_USER\Software\Sony Corporation\SonicStage\CDRipper]
"Bitrate_00090010"=dword:000101d0
"FileType"=dword:00090010
3. Start SonicStage. Do not change any settings, but proceed directly to ripping CDs (you will see the selected bitrate in the CD-ripping window). These settings will be kept until you change them in SonicStage by pressing the "Briefcase".
Both these bitrates may then be transferred to a Hi-MD without any problems. The unit shows them as "ATRAC3 105k" and "ATRAC3 66k" respectively, and plays them just fine. BTW, ATRAC3 files don't have any "padding" bits when recorded in Hi-MD mode.
For NetMD these bitrates are, unfortunately, almost useless. If you attempt to tranfer them, the program adds copy copy protection, and the unit pads 105kbps up to 146kbps (same as 132kbps LP2 - that's why the unit then shows such tracks as "LP2 Stereo") and pads 66kbps up to 73 kbps. There is no actual re-encoding during the process. When recording to a NetMD unit from an external source, all tracks are also "padded" with additional bits, as usual.
Now for some analysis. Both these bitrates have a cut-off frequency of about 13.8 kHz. This means that ATRAC3@66kbps may sound better for some material than ATRAC3plus@64k with its 15.5 kHz cut-off frequency, since there is less information to encode, which leads to less artifacts.
Most probably these modifications will also work in SS34, although I haven't tested them with that version.
Enjoy!
UPDATE 17.05.2008: padding and re-encoding information corrected.