Let the Lenco secret begin
So here we go into the second installment of Lenco Idler Wheel Drive MK2 by Jean Nantais. This is very elaborate, so please take your time and go through it. Matej Isak
"The Mono and Stereo project starts, while the Yellow Cedar Burl becomes ready for further work - after milling from a green stump last summer it is still air-drying, almost ready - with a Lenco L75. The good models, with the single, heavy, cast, machined and balanced low-slung platter which is characteristic of the sleek “Lenco Look”, came in various models: L75, L78, L70 and various iterations as these were very popular and widespread machines at the time the idler still reigned and up until well beyond the time the belt-drive took over, sold also under the Goldring name, as well as Bogen, and others. So, for this installment in my work with Lencos we’ll focus on the Lenco proper, in this case a classic Lenco L75, see how it works, and so focus on the mechanical work I do as well as the metalwork, being the new pieces I have made as well as treatment of the existing parts and pieces.
So, to start, why the Lenco? I'll partly quote from my posting, under my system, on Audiogon, 11-05-04, taking in context that this was still within the first year I started the Audiogon thread and the Lenco was still new to the world, and developmental work on the Lenco was just beginning:
“Idler wheel drives in general were originally designed to overcome stylus drag [the braking action of the stylus in the groove, caused by pressure/friction], as in their day cartridges tracked at 10 grams. As tracking forces diminished, idler-wheel drives became more refined, but retained their resistance to stylus drag.
As time went on and VTF dropped to below 2 grams, it was thought stylus drag could be combated by the simple use of mass, and not the brute force of rumbly idler-wheel drives, which were discredited, even though their rumble figures were in fact better than those of the then-rising Linn LP12. If you remember your history, you will remember that CD as well was touted by the majority of the press and the industry as superior to the previous technology, vinyl. The Lencos do not rumble, and they prove that in fact it does take a certain amount of (refined) brute force to counteract the all-too-audible problem of stylus drag, which belt-drives are ill-equipped to combat, their Achilles Heel being their belts and weak motors. This is clearly audible in the attack of a Lenco (or large Garrard), the tremendous bass reach (bottomless) and bass detail of a Lenco (which affects both air and imaging), and of course its perfect timing and speed stability under real-world conditions (actually playing a record).
The Lenco, as I've written, uses the same drive system as the Garrard. The motor, a high-torque four-pole motor which spins at something like 1600 RPMs, is suspended from the metal chassis by springs, thus cancelling much of the noise problems caused by heavy high-torque motors suspended by rubber grommets. The issue, once again, is mass.
Due to the high rotational speed of these motors, great relative mass and so high torque, no expensive solutions need be made to address the weak motors now used in high-end decks. The platters on the Lencos weigh about 8-10 pounds, with much of the mass concentrated on the periphery: the old boys understood flywheel effect to ensure stable speed. The Lenco platter is a single cast piece, of a zinc alloy of some sort, very inert for a metal, and then machined and hand-balanced in a lab. No ringing two-piece platter problems to overcome. Even the motor is hand-balanced in a lab, and weighs something like 3-4 pounds, and runs silently on its lubricated bearings. Think of it: a high-torque motor spinning at well over 1500 RPMs (compared to a belt-drive motor's average 150-300) which pretty well wipes out speed variations by itself. The idler wheel contacts the motor spindle directly, while contacting the platter directly on its other side, thus transmitting most/all of that torque without any belt stretching. Many high-end decks offer thread belts which don't stretch, thus giving an improvement in sound. The Lenco does the same with its wheel. But the platter is also a flywheel, and so evens out whatever speed variations there may be in the motor. It's a closed system (motor-platter, platter-motor) and speed variations brought on by groove modulations don't stand a chance in this rig, and it is clearly audible.”
As-is, without any embellishments (except a better tonearm), the Lenco sounds fluid, rich, dynamic, and with levels of PRaT - pace, rhythm and timing, which I can clearly hear and so which I treat as physically real - unmatched by perhaps anything else in the analogue universe: it is sheerest exciting poetry, and even at this simplest level, shockingly detailed and natural. As always in audio, there are those who chase detail to the exclusion of all else, or follow faulty theories or fads to the exclusion of all else, and so lose the musical message via “improvements” which damage the bigger musical picture. I treat the fundamental Lenco sonic characteristics, especially the poetry and excitement, with the greatest respect: this fundamental Lenco sound must not be diminished in any way by my modifications, only enhanced.
Let’s consider one aspect, visible in the photos, to help explain one reason the Lenco is sonically great, the platter: one can see the great amount of mass concentrated in the oversized ring on the periphery, as well as the platter itself being somewhat oversized (12 ½”), which adds to the rotational inertia. Consider a weight on a string traveling at 33 revolutions per minute: the greater the distance from the center of rotation, the greater the speed it travels at and the harder to stop the weight will be, as it covers a greater distance in the same time, 33 revolutions per minute. Conversely, the opposite is true: the closer to the center of rotation a mass is, the slower it goes, thus losing speed and so inertia. Any mass directly above the center of rotation has no inertia, remaining weak to an unspecified distance from the point of rotation. A common sight in modern belt-drive design are massive solid platters, several inches thick, crushing the bearing underneath (which consequently will have shorter lives). This is a waste of material resources, as the mass directly above the point of rotation has no inertia/effect, and anywhere near the point of rotation has little effect. The Lenco platter is a masterpiece of engineering elegance: the great majority of the mass is concentrated on the rim, and furthermore the rim is extended further out from the edge of the record than most other platters thus ensuring greater speed/inertia: the Lenco makes its mass count, far out from the center of rotation. And if this elegant attribution of mass/inertia isn’t enough, it enhances this by a massive motor with tremendous torque, coupled to the platter by a wheel which remains in contact all the time, and which does not stretch, contract, or slip, remaining perfectly stable. The two torques – inertial and active/mechanical (motor) combine to make an unstoppable combination, ignoring stylus force drag, and so ensuring lightning-fast transients, extremely deep and detailed bass, a full dynamic palette (micro and macro) and ensuring excellent PRaT, or more simply, perfect timing.
The motor and the platter are, when considered closely, an engineering tour de force. Consider as well, the vertical wheel of the Lenco, as opposed to the usual horizontal wheels of rim-drives. In a rim-drive, the platter is forever being pushed to one side, thus causing wear on the bearing, as the platter then tries to execute some sort of deformed elliptical, instead of circular, rotation. The Lenco, on the other hand, exerts pressure upwards, thus leaving the balanced platter to revolve, like a ballerina, on its toe, as perfectly centred as an imperfect physical manifestation can be (ALL physical manifestations are imperfect, perfection belongs to Plato’s realm of ideals).
Next on the list is the drive system, so let’s consider a case of design in which a modification of mine enhances the Lenco by understanding and working with it. Idler-wheel drives are driven by idler wheels, and idler wheels are moved into position and held between the motor and the platter by means of springs. But, in introducing a spring, we are RE-introducing the same problem which affects belt-drives: a rubber belt is an elastic which contracts and expands, and of course a spring also contracts and expands. Not only did the spring get tired over the years (thus leading to loss of engagement of the wheel with the platter and so reducing torque), it also ceasessly expanded and contracted, introducing torque instability (i.e. the torque increased and decreased), and torque is the reason idler-wheel drives sound as they do. So I set out to solve the problem: I suspended an effectively weightless cradle (string and Saran Wrap) from a Lenco idler-wheel spring, and added weight to it until I had stretched the spring to its “comfortable” zone (i.e. not so far it became permanently deformed/stretched, and not so little it didn’t stretch). I then removed the weights and measured them, thus arriving at the force the spring is meant to exert to hold the wheel in place between motor and platter (verified as the motor was driving the platter as well, adding and subtracting weights). This experiment I reported publicly to the Audiogon “Building high-end ‘tables cheap at Home Despot” thread, with photos, Jan.31st, 2011, both because this important modification was too good and simple and effective not to share, and to generate the usual verifications worldwide to prove my point about both torque and idler-wheel drives, as I did with the Lenco itself when I started the Audiogon thread.
TORQUE was the reason idler-wheel drives, including the Lenco, sounded so good, in fact superior to belt-drives. I then, with the help of my machinist, designed the TJN Kit, which I make available to DIYers as well as making them a part of my own work, which is a hollow screw, a brass weight, and a system of claps and rings which replace the spring by a weight on a string, thus ensuring a perfectly stable and constant force. A weight on a string will never contract or expand, will always hang with precisely the same force (unless someone takes their Lenco into outer space), and so will always, at all speeds, hold the wheel between the platter and the motor with precisely the same unvarying force. Note as well, that when the spring is left in place, it exerts less force depending at what speed it is set at: given how the wheel travels along the graduated motor shaft, the higher the speed the closer to the motor shaft the wheel is, and the closer to the shaft it is the looser the spring is (i.e. more contracted), meaning there is greater torque, and so better sound quality, at 33 rpm than at 45 rpm. With the success of the TJN mod, which increased and stabilized torque, in improving sound quality - reported worldwide - the issue was proven. The improvement, again, is fundamental, and clearly improves clarity, transient speed, detail, imaging, bass detail and impact, and so on, the usual improvement across the board. The TJN Mod has now been adopted and verified by pretty well everyone rebuilding Lencos, opposed only by the usual suspects and for the usual reasons (i.e. personal reasons having nothing to do with results, or the usual refusal to accept the death of a favoured theory).
Now, let’s consider the chassis: it’s time, for this monoandstereo project, to prepare the Lenco chassis for various modifications and improvements. First of all the Lenco is removed from the plinth, and the chassis stripped of all parts as well of the metal trim, if any. At this point the chassis and platter are taken to professional recoaters out in the countryside to be bead-blasted. As an aside, four other local high-end manufacturers of note use this same paint shop for their products: Tetra loudspeakers, Wyetech Labs (electronics), North Audio (electronics) and Audio Note Kits (electronics and speakers). As another aside, I own equipment from each of these manufacturers and enjoy them greatly.
After a certain period of time (usually a week or so), I get the call from my colleagues from the paint shop (who also help me with other ideas, pending) to come pick up the record player parts to do the Glass Mod and the bodywork to prepare it for spraying. The Glass Mod follows my philosophy in record player design: avoid all absorptive materials (such as lead shot, sand, sorbothane, etc.) in the building/modification of a record player, as these materials do not discriminate, damping not only noise, but also the musical signal itself, which I consider sacrilege (NO damping of dynamics or speed!!). So, rather than the usual Dynamat and other such means of damping the stamped chassis, I pour marine-grade epoxy-resin into all the voids in the underside of the Lenco chassis to inhibit flexing and so vibration of the stamped metal chassis, and leave it to harden for 24 hours. Once this done, the increased detail, clarity, focus, transient speed and so on can clearly be heard, as compared with other means of damping, or none at all. The now-glass-hard epoxy-resin also serves to fill in the various holes for the tonearm and mechanisms, so allowing me to flip it over and finish the body work from above. Once all this done, it’s back to the paint shop with the prepared pieces, to wait for the second call to come get them (usually two weeks or so).
To complement the improvements to the motor, I have designed a new main bearing, which is also a critical part, as the entire “Turn-Table” (i.e. the platter on which the LP rides) rides on the main bearing: changes here affect the entire sonic picture. Keeping things on a somewhat personal footing as much as I can, as always to find the best way to where I want to go sonically and mechanically, I rely on the help of my machinist (the younger one in the photos) in designing my various substitute Lenco pieces, who I consult and to whom I give some free rein in my designs, as he knows metals, methods of fastening, and other metal machining esoterica, and we discuss the best ways to get where I want, and so keep things practical and effective. These days everyone is fixated on CNC machinery and manufacturers use them as a form of advertising, but let’s not forget the astonishing levels of accuracy (and performance) reached by record player manufacturer/legends Garrard, Thorens, EMT, of course Lenco and others using the traditional lathe. As well as lathes, my machinist’s shop also includes a couple of CNC machines, to be used where they are best suited. He is from Liechtenstein, trained in Switzerland, coincidentally the country of origin of the Lencos, and has fallen in love with the space in Canada and lives out in the smaller villages out in the wilderness along the upper reaches of the Ottawa River, home as well to moose, wolves, bears, deer and the mighty woodpecker. He works in a well-equipped if small shop (like mine) with his business partner (the older one in the photos): many times I have driven out in the dead of night far along unlit country roads in -20C, to pick up newly-machined prototypes and finished pieces (summer drives are less exciting but more pleasurable :-)). He has been excellent to work with, and I will stand by him, which means I must have my parts made in small limited runs, but I prefer this business model, which suits the limited number of Reference and Classic Lencos I can build a year anyway.
The new Reference Lenco main bearing (for the Classic it is a modified original main bearing), is manufactured to increase speed stability and so let the motor-wheel-platter system do its work unimpeded, but is also built to increase sound quality on its own. The bearing was designed with an ear to the sound of metals, and not only metals, but also the proper thickness of metals, as not only do some metals sound much better than others in this application, but also the thicknesses involved have an optimum sonic range. I started with a theory as to which metals to use (and which to avoid), but in order to be certain I had several prototypes made of a variety of metals, in a variety of thicknesses, in order to test the theory. Once the prototypes all lined up, I spent months inserting first one, then the other, into my Reference Lenco, and listening to each extensively, especially with an ear to PRaT (to which I am extremely sensitive and so treat, physically and intellectually, as a real physical artifact) and coherence (i.e. the sense of the musicians playing together to reach a greater whole), and naturalness (i.e. no unnatural brightnesses or emphasis of detail). In the end my preferred choice was the winner, with much greater naturalness, retrieval of air over other metal combinations, and with the usual increase in all aspects of sound quality across the frequency range. Interestingly enough, when I hear a material or process which clearly enhances PRaT and coherence, it also always turns out to be superior in terms of the usual audiophile obsessions of detail, imaging, frequency extension at both ends, and so on. Greater PRaT and coherence allow greater differentiation between instruments and vocals, as the better timing and transient speed more clearly makes audible various sonic details and their individual realities.
I have designed other new metal parts which address the fundamentals of idler-wheel design, but I’ll save these for later as they belong to the suite of mods which leads to the Reference Lenco MKII (a cumulative set of mods which includes the TJN Mod and new motor treatment as well) which will be featured in the next installment, so goodbye for now. I'll end with photos of Salvatore's Reference Lenco (the first finished one, a musician bought the prototype) and system, for the curious. I have designed other new metal pieces which address the fundamentals of idler-wheel design, but I'll save these for now, so goodbye for now, until the next installment, building the plinth and Final Assembly.