Vinyl Old timers: HK's and Rabco's

Sean,

You should follow this recent thread at AA for info on Rabcos, esp. Dave Shreve: http://www.audioasylum.com/audio/vinyl/messages/129076.html

Shreve is well-known for his modified Rabco SL-8E and his pioneering work on optimizing VTA/SRA.

Rabco marketed the expensive (active servo) SL-8E and cheaper turntable/arm ST-4 combo under their own name, and contributed the rotating tube/tire-rider arm design to the H/K turntables. In the H/K ST7 and ST8, the tubular arm is terminated at the rear with a tire that rides on the rear rotating tube. The arm moves laterally, "passively", to maintain even tire contact with the rotating tube. When the tire wears down or when the tube rotation drive becomes uneven, tangential tracking is compromised as angular errors become larger before the rear of the arm moves in reaction to stylus drag motion at the front.

Sean,

There is a better description of the mechanism in Jason Gold's review of the ST-7 at Audio Review (of all places!):

http://www.audioreview.com/TurnTables/Harman,Kardon,RABCO,ST-7/PRD_121324_1597crx.aspx

Because the rotating tracking arm is coupled to the rotation at the platter spindle, I don't think the HK versions of the Rabco arm can be fitted readily to other turntables.

I thought the HK was a pretty good-sounding turntable, but I don't know how it would compare to today's "meat and potatoes", like Regas.