I think you have figured out the purpose of the EQ settings on my new Marantz PH22 phono preamp - it adjusts for pre-RIAA recordings. It is called a Marantz PH22 Phono Equalizer Amplifier on the face plate.
I played several early 1950's jazz and vocal 10" lp's. None of these ever exhibited much bass when played through my normal equipment. One of them is a Jimmy Dorsey dixieland recording that shows the name of a bass player in the credits, but he is usually not heard. I just thought he was buried in the mix.
I played this Dorsey 10" using the High MC setting (still with a MM cartridge, though) at the EQ setting that sounds the best on my modern recordings, #4. It sounded as it normally does, with little or no bass. However, as I moved the EQ setting down to #3 and #2, the bass came out loud and clear and the record sounded much, much fuller. These were settings that were unlistenable when playing modern records because the bass output was too strong. Setting #1 was still too boomy, though.
Then I went back to using the High MM setting on the same records. I posted yesterday that in the High MM setting, the EQ needed to be in the #1 position, because the higher settings caused way too much sibilance in vocals and a harsh high end. I started out in this #1 setting and the record sounded pretty good. It had more bass than when in the default #4 setting for MC that I am using for modern records. As I moved up to #2 and #3, the bass got weaker, but the highs were better sounding, and there was no sibilance on vocals like there were on the RIAA records.
This is all very cool and interesting, but now I am wondering why these old records have great bass sounds when in High MC and the EQ at the lower numbers, and great treble sounds when in High MM and the EQ at the higher numbers. I would like to be able to get both ends of the spectrum better.
The lower EQ settings enhance the bass and the higher EQ settings enhance the treble, but the magnitude of the effects are totally different depending on being in MC or MM mode. Is this still, as I guessed, also compensating for the inherent differences of frequency response of these two types of cartridges?
Anyway, it now seems obvious that this phono preamp equalizes for pre-RIAA records, but I don't know what the various settings are recommended for.
I really need to find a users manual for this cool device.
There is an eBay seller in Germany that has listed copies of the *service repair* manual for this PH22, but not the users manual. I wonder if that would give me any help in determining how to use this phono preamp.
Thanks,
Dick Schneiders