tonearm

Beatrice, she got a phonograph
And it won’t say a lonesome word
Beatrice, she got a phonograph
And it won’t say a lonesome word
What evil have I done
What evil has the poor girl heard
Beatrice I love my phonograph
But you have broke my windin chain

– Robert Johnson

If you read my piece on expensive record players you will have seen that you can spend over $300,000 on a turntable and they don’t even give you a fucking tonearm! What’s that all about?

And to add insult to injury many of those ultra-fi turntables will actually allow you to mount two or even three tonearms. It turns out of course, that the world of tonearms is just as exotic as that of turntables.

The tonearm is the device that holds the cartridge over the groove in the record. The stylus in the cartridge must track the groove with the required force to give the best compromise between proper tracking along with minimizing wear of both the stylus and of the record grooves. Basically a tonearm is a pivoted lever, which is free to move in both the horizontal and vertical axes. It also has some form of counterbalance in order to maintain tracking pressure.

The tonearm’s name is a holdover from early grammaphonic devices where they served as a mechanical means to actually physically transmit sound waves from the pickup to the amplifying horn. Over the years they evolved to match the many improvements in cartridges, players, electronics, and vinyl records themselves.

The specific requirements of high-fidelity sound reproduction from vinyl records place contradictory and pretty much impossible to achieve demands on tonearm design. The tonearm must allow the stylus to track the groove, but without distorting the actual stylus. So in an ideal universe the arm itself would have zero mass, along with frictionless bearings, thus requiring no force to move it. The tonearm should not oscillate at all so it should be both light and stiff, and/or be damped or decoupled somehow. Additionally the tonearm must not resonate with vibrations induced by the stylus, the turntable motor, or plinth. Therefore it should be heavy enough to be immune to vibrations, and/or it must be damped to absorb them. And finally the tonearm should hold the stylus in a tangential aspect to the groove as it moves across the record, with minimal angular variation.

Solutions to these problems vary, but in the end compromises must be made. Modern tonearms are typically relatively lightweight and rigid designs, with high precision, extremely low friction pivot bearings in both axes. Many tone arms are made from aluminum but some manufacturers actually use wood. At the higher end carbon fiber or graphite are employed in the construction.

Tonearms use an adjustable counterweight to offset the mass of the arm and cartridge. After balancing the arm, the stylus force can then be fine tuned to the desired value.

Two types of tonearm / cartridge tracking errors can affect the sound quality. The first error is called skating. As the tonearm tracks the groove, the stylus exerts a frictional force that is tangential to the arc of the groove; this force does not intersect the tone arm pivot, therefore a clockwise rotational force happens and a reaction force is exerted on the stylus by the record groove wall in a direction away from center of the disc. This is counteracted by an anti-skating mechanism, often times using springs, hanging weights, or magnets to produce an offsetting anti-clockwise force at the pivot, resulting in the net lateral force on the groove walls to be near to zero. Or at least that’s the goal.

The second error occurs because of the pivot. The tonearm necessarily sweeps in an arc across the disc, causing the angle between the stylus and groove to change. A change in angle, even if very small, will have a negative effect by creating different forces on the two groove walls. There will also be a timing shift between left/right channels on stereo recordings. (If you listen to mono it’s not a big deal) Making the arm longer to reduce the angle is a partial solution, but for practical reasons a tone arm can only be physically so long.*

Additionally the pivoted tonearm produces yet another problem. The record master was originally cut in a linear direction from the edge towards the center, but of course the stylus on the pivoted arm always traces an arc. The contact point of the stylus will wander farther from the linear path between the starting point and center of the record. As this happens the tempo and pitch will tend to decrease towards the middle of the record, to the point where the arc reaches its apex. Once past that, the tempo and pitch will increase towards the end because the contact point becomes closer to the linear path again. Since however, the surface speed of the record is lower at the end, and this relative speed error from the same absolute distance error is higher at the end, and therefore the increase in tempo is more notable towards the end than the decrease towards the middle. One way that this can be mitigated a bit is by using a curved tonearm pivoted so that the end point of the arc remains farther from the linear path than the starting point. However the tempo drop at the middle can be completely avoided by employing a linear tracking tonearm.

So without any more background stuff lets dive into the money…

The Graham Engineering Phantom Elite falls in at the low-end of serious coin. Made in the U.S.A. With the exception of the pivot assembly which is made in Switzerland.

Features: ‘Magneglide‘ magnetic stabilization which ensures pivoting in a true vertical plane with no azimuth deviation | Since the arm is also in true neutral balance – again the result of  magnetic stabilization controlling azimuth in a uni-pivot arm | The tonearm features a pivot assembly utilizing constrained-layer damping of two different metals, both having a high weight to size ratio | A high-density, non-magnetic tungsten insert insures zero-tolerance  bearing contact and high energy absorption | The arm itself is made of titanium, and comes in 9, 10, and 12” lengths | The internal wiring of the entire tonearm is Litz-based construction and approaches the ideal dielectric absorption factor of “1” This results in signal transfer that is whip-fast, and not impeded by the typical insulation materials that absorb and re-introduce energy into the wire at unpredictable intervals | The cable to the phono preamp, has the same high speed transfer properties of the internal wire.  The result is signal transfer virtually unchanged from the output of the cartridge all the way to the phono preamplifier..

German designed and built.

Features: VTF (vertical tracking force) non-touch-adjustment | on-the-fly – during play | SRA adjustment is independent from tonearm height | Dynamic antiskating  | Carbide hardend titanium / carbon-composite arm pipe with Internal liquid dampening on whole inner surface | Exchangeable inserts in counterweight tuned to cartridge’s compliance | The axiom and it’s bearing axis can be precisely levelled on it’s own

German.

Features: 2 point linear tracking | High precision ball bearings running in a calibrated polished glass tube | Bridge is constructed of wood | Wand is conical carbon fiber

England.

Features: Fused Titanium head-shell and arm | Tungsten Carbide Counterweight | Micron Thick Kevlar bearings | Battery Powered LED Cueing Light | Hand-built and continuous wiring | Triple Thickness Gold Plated Connectors

*Here’s an example of a tonearm bordering on impracticality…

I hope you enjoyed reading a little bit about tonearms, especially the high dollar ones. Stay tuned for an article about cartridges.

Got me the strangest woman
Believe it, this chick’s no sinch
But I really get her goin’
Then I take out my Big Ten Inch

Record of the band that plays the blues
The band that plays the blues
She just loved that Big Ten Inch
Record of her favorite blues

Last night I tried to tease her
I gave her a little pinch
But she said now stop that jivin
And get out that big ten-inch

– Fred Weismantel / Bull Moose Jackson