Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!decvax!wivax!linus!allegra!eagle!harpo!floyd!vax135!cornell!uw-beaver!tektronix!tekmdp!michaelk From: michaelk@tekmdp.UUCP Newsgroups: net.audio Subject: Re: linear tracking turntable inquiry Message-ID: <1998@tekmdp.UUCP> Date: Thu, 2-Jun-83 14:30:15 EDT Article-I.D.: tekmdp.1998 Posted: Thu Jun 2 14:30:15 1983 Date-Received: Wed, 8-Jun-83 22:46:43 EDT References: tesla.85 Lines: 37 Yes the Sony PSX-800 "learning" is not turned off after the first few tracks, it is continuously learning, and correcting , it is just the first few track revolutions that some error is guaranteed. The point I was trying to make is that unlike "dumb" tonearms that are ONLY drug across the face of the record, or linear trackers that do a sawtooth correction (a simple correction loop that has a tracking angle sensor, and just "corrects" the position whenever the sensor trips, thereby giving a sawtooth error), the SONY does try to establish a horizontal movement, that given a record with evenly spaced grooves, would sit dead center in the groove, with zero tracking angle error for the entire record. Now then, this learning mechanism in addition to the linear tracking construction results in the first order errors corrected. The error correction closed loop (with the tracking angle sensor, etc) becomes a second order effect corrector, rather than first order corrector. I might point out that all words "error" above refer to very small numbers on an absolute scale, and refer generally to relative error in a linear tracking environment. While I am at it, I might explain the SONY biotracer construction. The linear tonearm has (obviously) freedom of movement on a grand scale horizontally when the whole arm moves. The arm also has a large vertical movement freedom (up and down) that is obvious. But, it also has a limited horizontal movement a little either side of perpendicular to the carriage. In the arm (near the pivot point) are vertical and horizontal oriented velocity sensors, and linear motors. It uses these to actively null out arm resonances, and gives the arm a measurable, effective mass of zero. Some of the interesting side benefits are that it automatically balances the arm everytime it picks it up. So if you change the cartridge (that universal mount) to a different weight one, instant re-balance. Additionally, it uses a bias on its vertical linear motor to generate the vertical tracking force. This makes the tracking force knob a potentiometer off to the side, and you can turn it while playing the turntable to see how the cartridge tracking is doing "real-time". Likewise, it provides a more consistant vertical force on warps. The innards of the thing is PC board galore. Scratches on the records still go pop though. Mike Kersenbrock Tektronix Microcomputer Development Products Aloha, Oregon