Servo Controlled Arm

Hiho...An important detail about the Sony linear tracking servo is that it does not move in and out, as you suggested. It only moves in. (Unless you pick up the arm). This is because the servo only modifies the RATE of movement, which is always in. Because of this feature, bearing friction (which is very low) does not result in jerky motion. (In technical circles this is called stiction). Finally, with a servo, friction, as long as it is constant and especially doesn't change direction, is not very important. The purpose of the servo is to create a virtual frictionless bearing.

Eldartford, I was mainly referring and complaining about the Pioneer PL-L1000 servo arm that it uses a linear motor and it moves laterally BOTH directions, ie, left AND right. Almost like a air-bearing arm, hence the tendency to jerky motion on eccentric records. Pioneer is the only manufacturer I can think of that did something like this. It works great in theory but it puts a lot of demand on quality of the roller bearing. It certainly is fun to operate though. Yes, I still prefer the Sony, Yamaha, Technics, Rabco, or Goldmund approach. Thanks for the comment.

I just received a JVC QL-Y5F today and the servo controlled tonearm does work! It sound very good and very stable and no problem tracking warp record. Now, I really wonder why people don't use more of such design...

Hiho...Most people, audiophiles included, don't understand servo design, or appreciate the performance potential. Perhaps they have experienced crude servos, like early cruise control in cars, and not been impressed. Most audio manufacturers don't have people with control system expertese, and would prefer to stay with tried and true pivoting arms. Design and development of a good servo arm requires a large investment, and the small market does not justify it.

Besides, pivoting arms work well (if you can ever get them set up right).

Eldartford, thanks for the comment and explanation. I understand the financial difficulty in such project but I just wish audiophiles are more open-minded about such devices and not write it off so handily by preconceived notions. Look what happened to decades of engineering in direct-drive turntables being almost completely dismissed by audiophiles. Many esoteric turntables are made not even based on real engineering and, in fact, by someone with a band saw in their garage, while the flagship product by whole team of R&D in a electronics giant never even got noticed in The Absolute Stereophool land. It's our loss. Sometimes, I wonder what would happen to analog if CD were introduced a decade later than its original date. Think of the possibilities in vinyl playback...