it took me 6 month to get excellent sound from MA-505 II tonearm.
I think that main culprit was the headshell. Not the original Micro Seiki, not Technics and Sumiko 12gr worked fine. Until I found the Audio Technica 12 gr headshell from 80s (current closest product is Audio Technica AT-LH13/OCC). With this headshell Signet TK10ML II gives robust, complete sound with great soundstage and resolution.
I think that main culprit was the headshell. Not the original Micro Seiki, not Technics and Sumiko 12gr worked fine. Until I found the Audio Technica 12 gr headshell from 80s (current closest product is Audio Technica AT-LH13/OCC). With this headshell Signet TK10ML II gives robust, complete sound with great soundstage and resolution.