Dr. Analogue's Corner

Taking the Tone Out of the Tonearm – Part One

By August 30, 2017 No Comments

To play a vinyl record one needs the following components: a phono cartridge; a tonearm; a turntable; a phono equaliser/preamplifier; and a suitable shelf or platform. Optimising each of these pieces of the audio puzzle matters a great deal if the goal is to be transported back to the time and place of the original recording. One can, of course, ascribe an order of relative importance in which case the tonearm would share a position at the top of the list along with the phono equaliser/preamplifier. The latter will be the subject of a future article so today we will focus our attention on the critical role of the tonearm.

To the casual observer, the tonearm’s job is simple; it holds the phono cartridge during its journey from the outermost to the innermost groove of the vinyl record. But there is so much more than meets the eye.

The ideal tonearm is particularly effective at funnelling mechanical energy away from the phono cartridge and into the turntable. At the same time, the ideal tonearm also exhibits a high degree of damping, transforming some of the mechanical energy from the cartridge into heat to minimise any parasitic resonances.

One of the fastest conductors of mechanical energy, is titanium. On the other hand, one of the best damped materials is carbon fibre, which explains its popularity in high end camera tripods. The AQUILAR and AXIOM tonearms from Acoustical Systems utilise both materials to stunning effect. An outer thin-walled tube of hardened titanium and an inner tube of carbon fibre is sealed at both ends. The void space between the inner and outer tubes is entirely occupied by a special liquid damping compound. The resultant arm wand is somewhat analogous to the theoretically perfect loudspeaker cabinet; it does not store and release energy which would otherwise corrupt the delicate musical signal from the transduction process.

The ideal tonearm must also strike a balance between two seemingly mutually exclusive objectives; zero bearing friction during both horizontal and vertical motion, and zero bearing resonance. When both ideals are approached, we are one step closer to a tonearm without tone. In other words, a neutral platform for the cartridge to show just how much musically-relevant information it can recover from the record. But how is this vanishing act achieved in the real world?

The Acoustical Systems AQUILAR and AXIOM tonearms are double gimbal designs which use aerospace-grade nano ball bearings with vanishingly low levels of friction AND play (commonly referred to as bearing chatter). Assembly mandates pre-heating of the bearing housing and takes place under certified clean room conditions. No other tonearm on the market is built using such high-grade materials or to such tolerances.

Tune in next time as we delve into the geometry behind tonearms.

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