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Jack Holmes - Linear Tracking Turntables |
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Jack Holmes is an experienced audio guy. He is also an active participant
in our 70sAudioMindset
discussion group. Here are some of his thoughts on Linear Tracking
Turntables. |
Rick,
I've thought a great deal about why most of the linear tracking
arms /tables that I have heard sound dreadful. I think it is due
to the same reasons that cheaper pivot arm tables sound bad but
to an even greater degree due to the complexity of the servo motor
controls on the vast majority of linear arms.
The reasons are undamped internal resonances of the arm combined
with excessive "play" or sloppiness in the bearings both vertically
and horizontally. Combine these problems with a resonating lightweight
platter and minimal isolation (no sub-chassis) and you get a cacophony
of resonances so large that the sound coming out of the cartridge
is a total distorted mess.
In the worst designs, the cartridge /stylus is so confused that
it is unable to track the groove at any decent modulation level
such that mistracking is often and severe. I have owned three B&O
(Bang and Olufsen) linear tracking tables and all had this problem.
One had the MMC 20 CL cartridge, one had a MMC 20 EN and the other
had the MMC 1. All pretty decent cartridges that when mounted in
a good pivot arm /table sound good and track very well, yet when
mounted in the B&O linear tracking units, frequently mistracked
and in general sounded bad.
To show you the degree that I believe these resonances affect the
sound, about a year ago I purchased an old (1965) Weathers synchronous
turntable with the Weathers wooden tone arm off eBay. When the unit
arrived, I disassembled it and thoroughly cleaned the unit, oiled
the main spindle bearing and motor. I mounted a NOS (New Old Stock)
Pickering AT-3 cartridge in it and re-wired the arm /cables.
For those that don't know it, the weathers arm was a solid piece
of mahogany wood and the bearings both vertically and horizontally
were heavily silicon damped and have essentially no "play" in them.
Additionally, the horizontal bearing of the Weathers arm sits tightly
into a 1 1/2 inch diameter larger rubber grommet. There is no direct
mount of the arm to the table plinth. The arm is held in that large
rubber cone shaped grommet. I think that isolates the arm from any
resonances being transmitted from the plinth. The platter of the
Weathers is a very thin stamped sheet metal. I placed a sorbothane
mat on the platter to stop its resonances.
Also for those that don' t know, the Pickering AT-3, it was basically
a bottom of the line design that had a spherical stylus and tracked
at 2 to 4 grams. I set the tracking force at 2.75 grams and then
hooked this table up to my main system. WOW!!!!!
You could not believe the sound that came out of that table. That
old table sounded better than most tables I have had on my system.
No mistracking, I mean none. Extremely silent groove noise (ticks,
pops, etc.), astounding bass response and smooth detailed highs,
albeit, slightly rolled off at the very extreme highs above 12 kHz
due to the Pickering cartridge, but just a tad.
Now, just as a point of reference, I am comparing this versus my
Oracle Delphi with an SME III arm and a Grado Sonata cartridge.
That old Weathers was a delight to listen to. I am convinced that
it was that arm that made that table sound so spectacular. Thoroughly
damped and controlled resonances.
By the way, at the same time that I had the Weathers, I also had
a Thorens TD-125 MkII with the factory TP-12 tonearm. I mounted
a Grado Prestige Gold in it. The Weathers trounced the Thorens.
Again, it was the arm. The TP-12 has a lot of play in the bearings
and many internal resonances. The Thorens TD-125 is a good table
though, very heavy platter, good isolated subchassis, deserves a
better arm.
Anyway, that's my thoughts on the whole linear tracking arm question.
By the way, if you look at the really good linear arms such as the
Emminent Technology and a couple others, you will see a great deal
of effort expended to control resonances and eliminate "play" in
the bearings.
Jack |
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