Anyone who has investigated the mechanics of record playback can appreciate the significant challenges that have to be overcome to achieve high sound quality. If it to succeed in connecting you emotionally to the musical experience, a turntable and tonearm must address all of the issues that affect ultimate performance. This involves mitigating microscopic vibrations – a task that requires the ultimate in intelligent design, engineering precision and a comprehensive application of available technology.
In an analogue system, vibrations emanate from the motor, bearing, stylus and drive system. These structure-born vibrations have the most negative affect on analogue playback equipment. They create various colorations and distortions that blur or veil the music, confuse the image and generally wreak sonic havoc.
Sound within the room causes vibrations which hit the turntable, arm and cartridge and cause resonances in the complete analogue system. The resonances move through the system, sometimes reflecting back from some components and creating areas of peak resonance. These vibrations induce various distortions in the signal and their effects are very audible, causing a masking or veiling of the music to occur.
An analogue system is usually connected to the ground so is susceptible to vibrations that travel through the building, through the floor and mix with the mechanical structure of the turntable. Whether its people walking past the turntable or heavy traffic outside, ground-borne vibrations are damaging to the sound quality.
Wow and Flutter
The stability of the rotational speed of the platter is specified as Wow and Flutter. ‘Wow’ refers to slow variations and ‘Flutter’ refers to fast variations in speed. These are measured as a percentage of an average or weighted value. Good performance for a belt drive design is less than 0.1% and 0.05% for a direct drive design. The design and specification of the motor is paramount to dealing with these artefacts. Poorly designed direct drive systems are more prone to have higher flutter. This can be audible as a shimmering to the sound, most noticeable in piano recordings. A good additional measurement for direct drive systems is a peak wow and flutter measurement. This can reveal the sonically audible variations that don’t show in the average measurement. High Peak Flutter levels cause a smearing of high frequency detail.
Speed accuracy is often specified as a percentage and Broadcast standard accuracy is 0.3% or better. Only a 3.3% change in speed will alter pitch one half step. A 6% change is a full sharp or flat.
Speed Drift (Due to Drive System)
Some turntables (especially DC belt drive types) will drift several percent over the 20 minutes of an LP side.
Speed Drift (Due to Static Stylus Drag)
In a freely rotating system like a turntable, any friction near the outside edge will try to slow the rotational speed. In drive systems without servo control, the turntable truly slows down the moment the stylus enters the groove, some as much as several percent. As the stylus moves towards the center or towards end of the record, the torque increases and the turntable regains most of its free rotating speed. To avoid the effects of static stylus drag, the drive system must have servo control.
Speed Drift (Due to Dynamic Stylus Drag)
When the stylus encounters a highly modulated groove, it must do extra work in the groove. During this time, friction and drag increases on the drive system and an effect is experienced similar to discharging an electrical capacitor. Based on the duration of the loud passage of music, and the weight of the spinning platter, there is a time constant that determines how quickly the platter slows down. If the platter is insufficiently heavy, the speed can slow sufficiently such that, a moment after the loud passage is over, you become subtly aware of the turntable speeding back up.
There are a host of electrical phenomena that can seriously degrade the performance of an analogue system, including unwanted AC/DC conversion ripple currents & other power supply related currents, various eddy currents, earth circuit currents, magnetic fields, air-borne RFI, etc. The electrical signal created by the cartridge is very small and highly susceptible to electrical interferences.
How have analogue designers dealt with these challenges in the past?
Through the years, each generation of turntable and tonearm designers have tackled the challenges inherent in the mechanism with greater or lesser degrees of success. Typically, there are no ‘perfect’ solutions and lots of compromise because often a remedy for one problem often introduces a host of new problems.
However, in time designs evolve as our collective understanding improves. Coupled with advanced engineering techniques and access to better materials and manufacturing methods, the sound quality of vinyl reply has been steadily improving with each generation.
Of note are the legendary EMT tables of the 1950’s and 60’s, the Thorens of the 60’s and 70’s, the Sota and Oracle tables of the 80’s and Rockport Sirius III tables of the 2000’s, just to name a few.
The analogue replay mechanism has undergone waves of development where schools of thought have created epoch-making designs. These designs have constantly shifted the sphere of influence from Europe and the UK to USA and Japan. Schools include Idler drive, belt drive, suspended vs non-suspended, solid mounted, direct drives, vacuum, ring clamp, pivoted, linear and hybrid combinations and numerous other cyclic trends, which remain instantly recognisable.
From budget entry-level to cost no object designs, the huge variety in turntables and tonearm design shows no sign of abatement. However, we believe that only a handful of designers are actually breaking new ground and making progress. This is the space that serious audiophiles observe closely as the ‘bling’ is soon differentiated from real innovation.
In our opinion, technological insights need to be balanced with an understanding of psychoacoustics (how our brain perceives music and sound) which is borne from a combination of engineering design experience and thousands of hours of making a design change, then listening to the result.