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How does a linear Tracking turntable work?

Ken Boyd said:
I own a quite few turntables, and LT tables are a few of them. I own a Mitsibushi LT30, Yamaha PX2, and a Phase Linear 8000 II. My first LT table started with a Technics SL 10, I also owned a Sansui LT table which used strings on ;pulleys to advance the carriage. That Sansui was not a very good table, as you could hear the drive motor transmit thru the tonearm. .

Thinking back on the Phase Linear I don't remember how the drive motor actually connects to the carriage. I know it has a small rotary electromagnet motor which runs a belt to some plastic gears but I don't remember how it attaches to the carriage. I know the carriage runs on some polished rods.

The Yamaha PX has a large flat belt, which is like a big conveyor belt that the tonearm carriage is attached to. I have never had the my MIt LT30 apart.
Click to expand...
PLL1000-linear 580 (1).jpg
 
You could always check out this arm. For an air bearing linear tracker it's very reasonably priced. It's $600 minus air pump. No afiliation
all.jpg

http://airtech.atspace.com/mg1.htm
 
I took the top cover off of the tracking mechanism on my Technics SL-M3 and took note of the arm advance motor while playing a record. It advanced once per revolution of the record. That means that on the average record it advances about 0.003" per revolution. The arm never really gets to far out of square than. Pretty impressive technology.
As far as the Pioneer PL-L1000 it uses a linear magnetic motor. Very impressive technology just like the Sony CD players that use it.

BillWojo
 
bimasta said:
Bravo Ken. Maybe the best explanation I've seen.
Double bravo for designing an even better method. I especially like the digital time-code (time-space code) to guide the arm.

The idea reminds me — I did sound transfers on a movie, many years ago. On-set, Sound was recorded on 1/4" mag tape (Nagra recorder). It was then converted to an "optical track" on the edge of print shown at theaters; the projector "read" the optical track and sent it to the theater's amps/speakers.

Looks like pic below (next to the sprocket-holes).

I always wondered why this tech was never used for home audio...

View attachment 1561106
Click to expand...

Too expensive, and needed really precision equipment. And would have been noisy until Dolby A was adapted for cinema use. And Dolby A is not cheap either.
 
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olddude55 said:
Looks like your "Rabco" name plate came loose during the spin cycle.
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I believe the glue failed due to time. If the washing machine was to blame, it was probably due to the wash cycle. :rolleyes:

bimasta said:
Bravo Ken. Maybe the best explanation I've seen.
Double bravo for designing an even better method. I especially like the digital time-code (time-space code) to guide the arm.

The idea reminds me — I did sound transfers on a movie, many years ago. On-set, Sound was recorded on 1/4" mag tape (Nagra recorder). It was then converted to an "optical track" on the edge of print shown at theaters; the projector "read" the optical track and sent it to the theater's amps/speakers.

Looks like pic below (next to the sprocket-holes).

I always wondered why this tech was never used for home audio...

View attachment 1561106
Click to expand...
Well, I've never seen it used for home audio, but it was used for a home keyboard known as the Optigan (Optical Organ). A celluloid disc roughly the diameter of a LP record had film soundtrack-style waveforms etched into it in concentric rings. Said rings contained loops of both organ sounds for the main keyboard, and accompaniment recordings for the chord and effect buttons. A sort-of poor man's Mellotron MkII, as well as a predecessor of the various Casio home keyboards which came later. Here's a picture of my Optigan, along with a recording of it doing its thing:
optigan1.jpg
 
The same principle was used for the Philips LaserDisc, a 12" analog optical disc for SD movies that was the precursor to CD. It had a linear tracking arm too. Just like CD.

The difference between optical laser readout and a physical diamond is that you need to aim the laser very precisely. For tracing with a diamond you don't really need to do that as long as your friction is very low. Like magnetic or air cushioned. The arm will simply follow since it has nothing to hold on to for giving counterforce. It's like trying to drill a hole on top of a ladder close to the wall. However big your drill, you can't push because you need to balance. I know, I tried to hang up a sunscreen on the 15th floor.
 
Ken Boyd said:
I own a quite few turntables, and LT tables are a few of them. I own a Mitsibushi LT30, Yamaha PX2, and a Phase Linear 8000 II. My first LT table started with a Technics SL 10, I also owned a Sansui LT table which used strings on ;pulleys to advance the carriage. That Sansui was not a very good table, as you could hear the drive motor transmit thru the tonearm. .

Thinking back on the Phase Linear I don't remember how the drive motor actually connects to the carriage. I know it has a small rotary electromagnet motor which runs a belt to some plastic gears but I don't remember how it attaches to the carriage. I know the carriage runs on some polished rods.

The Yamaha PX has a large flat belt, which is like a big conveyor belt that the tonearm carriage is attached to. I have never had the my MIt LT30 apart.
Click to expand...

The motor you're talking about on the phase linear, is for lowering and raising the tonearm. The one which moves it is side to side is linear magnetic.

I serviced one of these recently, and also I own a PL-L800, which uses the same technology. It really is a great system!
 
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bimasta said:
I did sound transfers on a movie, many years ago. On-set, Sound was recorded on 1/4" mag tape (Nagra recorder). It was then converted to an "optical track" on the edge of print shown at theaters; the projector "read" the optical track and sent it to the theater's amps/speakers.

I always wondered why this tech was never used for home audio...
Click to expand...
It kind of was, with Philco's "Beam of Light" 1941 record player, which used a light bulb and photocell to detect the vibrations of the stylus and convert them into an electrical signal. It also had a strobe and pitch control -- features that would not be common until the Technics direct-drive turntables of the 1970s!

TT-philco_beam-1.jpg


A demo of one in operation, with audio directly recorded from it:

 
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