Why Are Vintage Lenco Turntables Interesting?
Turntables are electromechanical systems used to extract musical signals cut as modulations into vinyl or shellac records. As a system, a turntable typically consists of a platter and drive system (mounted on a plinth), a tonearm, and a phono cartridge. The platter provides the rotational energy to the record placed upon it via the platter drive system, energy which the phono cartridge transducer (held above the record by the tonearm) needs to trace and convert the modulations into electrical signals. These electrical signals are then amplified and re-equalized, and finally converted into musical sound-waves by loudspeakers. A key functional requirement of a turntable system is the consistency of the platters rotational velocity, especially when high level modulations (loud sounds, typically with low frequency content) provide greater friction to the phono transducer, creating a dynamic load on the platter drive system. Various techniques are used to rotate the platter and to generate the required rotational energy; an "idler" rotation system was made by the now defunct Swiss turntable manufacturer Lenco.
Vintage Swiss made Lenco and Lenco OEM/re-badged Barthe, Benjamin, Bogen, Goldring, Grundig, Komet, and Voxon turntables used a vertical "idler-drive" to rotate the platter, as opposed to a belt drive or more recent direct drive turntables. This idler-driver directly couples the rotating motor force to the platter via a solid rubber disc or rubberized wheel. When coupled to a heavy platter (early model Lenco's have cast non-ferrous metal platters of almost 4 kg), and modified ,the idler-drive can provide steady rotational consistency, even when heavily modulated passages are tracked by a phono cartridge. Many audiophiles believe that this "rotational consistency" translates into bass "slam" (audiophile jargon for impactful bass) and rhythmic fidelity. As a system to impart the needed rotational energy to a vinyl record, the idler-drive is something of a brute-force technique, and the engineering that Lenco used, especially in older models, was both simple and cost effective.
Idler-drive turntable systems are not, however, without drawbacks – coupling the platter directly to the motor means that vibrations from the motor can be passed to the platter, where they can be picked up and amplified by the sensitive phono cartridge transducer. As an example, small variations in the concentricity of the rubberized idler wheel can cause small speed variations and rumble. This will color and degrade the musical signals being amplified. Moreover, the fabrication techniques used to build Lenco turntables exacerbated problems with vibration control, as the idler-drive motor was housed in a "cavity" that allowed resonance reinforcement, and the motor was not sufficiently damped or decoupled from the plinth to prevent certain colorations.
Modern day hobbyists have addressed these short-comings in vintage Lenco turntables by modifying them, eliminating the cavities and providing a high mass chassis/plinth for the turntable, and by refurbishing the idler wheels, using precision machined idler wheels with engineering grade o'rings. The results can be satisfying to these hobbyists, especially as the cost to refurbish and modify a used vintage Lenco turntable can be small in comparison with the cost of buying a new turntable (provided that one has invested in the tools needed to tackle such a project – chief among these a table-saw and router). Subjectively, these turntables are often compared to "Audiophile-grade" turntable systems.
In addition to the above, it should be noted that despite being a mass-market product, the Lenco idler system enjoyed a unique system of engagement when compared to most of its contemporaries. Unlike the proliferation of internal rim-drives, the 4.3KG platter (in the case of the L75) was/is driven by the idler against the flat, horizontal underside. This had, and continues to have two inherent advantages:
1) – inconsistencies in platter formation, be it in casting or machining which inevitably affect rim drives are no longer effectual in terms of mechanical engagement. 2) - as a result of the non-linear protraction of a circularly finite contact medium (not confined to the engagement with a specific radius) a totally variable/infinite speed is selectable.
Being of origination a brilliant design, the cheaply available Lencos, simple in their format, lend themselves easily to modification. Such modifications, when taken to extreme using state of the art modifications such as top-plate, plinth and bearing modifications/replacements have on unbiased listening easily out-performed contemporary state of the art commercial offerings.
The idea that idlers are noisy is a mere artefact from 1960's advertising – simply look at the underside of an idler; any idler: compare it to a belt drive. It will become immediately apparent as to why the leading manufacturers switched to belt drive as soon as 78's (which by definition could not use any means other than idler-drive owing to the obvious speed variation incumbent with massive groove modulation) became the fading fashion. Idlers are far more expensive to build than belt drives.
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