To be Completed.
The Garrard 301 is such a great old turntable that many are still in use and there is active interest in “improving” it. There are several areas where it comes in for criticism – poor speed regulation, excessive rumble, electrical noise and sensitivity to mounting. I think with care and attention it can be brought to a standard that challenges virtually anything built before or since. Some years ago I obtained a 1957 Garrard 301 turntable in a swap for a case of wine and an old SS amplifier. When I got the 301 it was noisy, with a sloppy bearing which leaked oil and no plinth. I spent a fair bit of time and effort bringing it up to standard and I thought it would be worth telling you about it, since much of what I learned is applicable to other great old tables like Thorens, Goldring / Lenco and the Orpheus Silex
As part of this process I designed and built a V/T power oscillator to act as a variable speed motor drive.
On the road I learnt a fair bit about motors and drives for turntables.
Some aspects of the Garrard worth mentioning:
One cause of the dreaded speed wobble is a worn or damaged idler wheel rubber. Replacement idler wheels are very hard to find and horribly expensive. There are a couple of services that can refurbish your old idler wheel such as Svalander audio in Sweden : http://www.svalander.se/vinyl/wheelseng.php .
The other main problem is the eddy current brake system on the 301. This comes in for a fair amount of criticism, in fact one of the standard recommendations of the "improvers" is to completely detach the eddy current brake. If you do this you then need to compensate the speed increase , one standard recommendation is to reduce the voltage to the motor using a light bulb in series or a transformer (Ref 1). I am not convinced that removing the eddy current brake improves the 301. There is a lot of evidence that increasing the effective drag on the motor will damp speed variations and vibration – just look at La Platine Verdier, which was designed on this principle. Eddy current brakes are used on many of the most highly regarded old turntables, such as the Thorens TD124, the Orpheus Silex and the extraordinary EMTs. The grease bearing version of the 301 is considered more desireable than the oil bearing and one of the principal effects of a grease bearing is an increase in viscous drag.
I believe that the problems with the speed control are due to the control linkage rather than the eddy current brake itself. The control linkage is attached to the motor at one end and the chassis at the other. Any relative motion between the two, such as motor vibration, will result in speed control variation, which will result in relative motion – a positive feedback loop. The speed control linkage is provided with a spring isolation mechanism to reduce this, but it seems inadequate for the job – in fact this seems to be an afterthought as it's not up to the standard of the rest of the engineering of the table. My solution is to leave the eddy current brake in place but take out the linkage. The tolerances in Garrard's engineering are so good that the brake will hold any position you give it, but you can put a drop of Loctite™ on the bushing to make sure, once you have set the best position.
Of course, this means that you now must provide another method of varying table speed. The motor in the 301 is an AC shaded pole induction motor, meaning that it runs slower than the synchronous speed which in turn is set by the frequency of the supply. The speed difference is called slip and is required to induce current in the rotor windingsand the current required by the windings is influenced by the torque requirement. Running the motor at a higher voltage reduces the current required for a given torque.
Altogether, this means that there are three methods of controlling motor speed – changing each of frequency, voltage or load. The eddy current brake works by changing load and the commonly used method of wiring a lamp or other resistance in series with the motor works by changing voltage. For any induction motor there will be an optimal combination of voltage and load which gives the least vibration, so for a vibration sensitive application like a turntable motor it would seem best to leave these at their optima and change the frequency. This was the origin of the variable speed motor drive linked at the top of this section.
To understand the causes of rumble we must first understand what rumble is. A basic definition is that rumble is mechanically derived noise which is picked up by the phono cartridge. The noise is caused by small deviations from perfectly circular motion of the turntable platter relative to the cartridge. Assuming the cartridge is effectively stationary with respect to the rotational centre of the platter (for audio frequencies) this is the same as saying any deviation from an ideal perfectly circular motion about the rotational centre. Note that this includes anything which causes the actual pivot to deviate from the rotational centre. The main causes of rumble in the 301 have to do with the condition of the idler wheel bearing, the main (platter) bearing and the motor. Poor mounting may also contribute but I'll deal with mounting later.
The idler wheel bearing consists of a 2.45mm steel shaft running in a pair of sintered bronze bushings supported by a thrust pad. Because the bushings are stationary the reaction force from the idler wheel pressing against the motor spindle and the platter rim always occurs at the same place and this causes the bushing holes to gradually elongate. You can check this easily by rocking the idler wheel gently from side to side. If it rocks and rattles it need attention. The bushings are pressed in and are easy to replace if you can find a manufacturer of that size of sintered bronze bushing. I tried replacing mine with a modern thermoplastic sleeve bearing (Iglidur by Igus, UK) and was very happy with the results for about a year. They got steadily worse and were eventually worse than the bronze bearings they had replaced. These need to be considered as throwaway items.
I next experimented with re-sizing the old bronze bearing by placing it in a small diameter four jaw chuck (the ones used to hold small diameter thread taps) and compressing it until the fit on the spindle came back to within tolerance. This seems to have worked, we'll see how long it lasts. I suspect the solution is to redesign the idler with a stationary shaft and rotating bushing, I understand that the Lenco tables use this system.
To perform at their best the bearings need to be cleaned and relubricated. I favour the use of a modern synthetic oil such as Amsoil or Mobil 1. Of course this will only be of benefit if the new oil completely replaces the old oil. To clean the sintered bronze bearings of the old oil I developed a system using kerosene and butane as cleaners. Having removed the bearing from its mount I heat the bearing until oil starts to bubble to the surface (usually black dirty oxidised oil), then I drop the bearing into a small bath of kerosene, pick it out of the bath and wipe it over with a clean cloth. I repeat this until no dirty oilcomes out any longer.
I then make a small bath of liquid propane in a plastic container - propane is a gas at room temperature but the heat loss on exit from the cylinder refrigerates it enough that a small pool will take a minute or so to boil away. I roll the bearing in the liquid propane and then transfer it to a bath of warm oil. The warm oil evaporates the remaining propane which bubbles out of the bearingand is replaced by oil.
The major cause of rumble in turntables is the platter main bearing spindle moving relative to the rotational centre, often as a response to gyroscopic precession induced by the reaction force of the drive (idler or belt) on the spinning platter. Anything which allows, or worse forces, uneven motion will contribute to rumble, such as excessive wear, differences in wear between parts or the presence of foreign bodies. In my opinion it is worth disassembling, cleaning and re-greasing (or oiling) the main bearing if any problems are suspected. If after this procedure your bearing shows play and cannot be tightened it needs professional attention. (By the way the tighter the coupling between spindle and bearing housing the smaller the motion it will allow but the energy is the same so the speed of the motion and thus the frequency of the resulting noise increases. This means that tight coupling is not necessarily the answer).
One thing to watch out for – when I got my table it was quite sloppy and leaked oil. Turned out that the table is a schedule 1 grease bearing unit, but some idiot had replaced the grease with oil. Reversing this and adjusting the bearing fixed it totally. I am looking at the issue of the ideal grease at the moment - check back soon.
The motor is another matter entirely. This thing is a bit of a beast and if it isn't looked after can cause all sorts of problems. The worst of these is if it comes out of dynamic balance (eg a bent spindle) if it has been abused but again that's a specialist job to fix. Other problems that occur more frequently are the bearings becoming sticky or loose and the spring mounting becoming unbalanced. Fortunately the quality of Garrard's engineering is such that the motor is easy to overhaul as long as you are careful. I have put a new section on disassembly and maintenance as Part Two of this article
It is generally held that these big old things need a fairly massive plinth into which to sink energy to sound their best and there are several on offer made from materials ranging from granite to MDF. I can't cut granite and I'm not a big fan of MDF so I built a plinth from six layers of hardwood flooring planks with each layer oriented at 90 degrees to the one before – sort of like plywood on steroids. This also made it easy to follow the cutout diagram provided with the 301. I built the plinth with the top two layers forming an “L” shape to accommodate a 300mm tone arm and an inbuilt phono preamp.
I used Jarrah ( Eucalyptus marginata ) – a hardwood from a tree found only in the magnificent forests of the southwest corner of Western Australia, where it grows to great heights in the presence of some of the windiest conditions around. These forests are unfortunately being destroyed by short sighted mismanagement, so get it while you can. The resulting timber is very dense, very hard wearing and very beautiful. It's also virtually rotproof so lots of the timber pulled from these great forests ends up as garden stakes! I glued my planks together building up one layer at a time starting with the top layer and its cutout. This enabled me to simply cut planks to length to get the rest of the cutout for the motor and bearing etc. When the first two layers were together I drilled the holes for the mounting screws and banged four ¼” T-nuts into the bottom end of the holes. I also cut the hole for the tonearm base. I put a false front strip over the end grain of the second layer and now wish I'd done that for all six layers.
Once I had all the layers together I sanded it smooth and top coated it. One thing to be aware of – sanding hardwood produces tiny respirable particles so you must use a dust mask. I applied several coats of clear gloss polyurethane finish, sanding all but the last coat as per instructions. The last coat was left to harden for a week and then polished with a pumice-containing metal polish. This is a technique I learned from an old radio restorer – it produces a finish which looks almost as good as French polish but is very resistant to abuse. The chassis attaches to the plinth with four 50mm C/S machine screws, I used brass ones because my table didn't come with its original screws.
I said above that I built the plinth to accommodate a 300mm arm but unfortunately I didn't own one of those so I decided to build it myself. I pulled the bearings, fixings and arm stub out of a Linn Basik arm and changed the bearing block to a brass one which I machined to the new angle (a 300mm arm needs an offset of 18 degrees instead of 24 degrees for a 225mm arm). I provided this with a new arm tube which I cut from the end of a broken cross country ski racing pole. This was an Exel Carbon fibre pole with kevlar wrapping which is designed to provide abrasion resistance and increased fracture strength, which last obviously didn't work. I figured it should act as a nice lightweight but well damped arm tube. I machined a right angle step in the narrow end of the pole and fabricated a small carbon fibre cartridge mount platform and cross piece to fit. I cut the pole off with an 18 degree mitre at 300mm length. I filled the bearing end with epoxy based filler to a depth of about 50mm then drilled this out to accept a 50mm long piece of the original arm which I glued in. I used the original counterweight from the Linn arm but discarded the isolation / adjustment mechanism, replacing it with a sleeve made from isodamp sheet. I drilled and tapped a 6mm hole through the counterweight and used a 6mm Stainless Allen head screw as a clamp on the sheet. The arm appears to have an effective mass of 9 grams which suits my old Grace F9 cartridge.
Next I needed to wire the arm, so I made my own by braiding 3 strands of 0.125mm enamelled copper winding wire in a litz configuration (one braid for each pin) and running it through Teflon tube at the high abrasion points at the ends of the arm. I decided to place the phono pre in the crook of the L to allow me to minimize cable run so as to reduce the loading capacitance on the cartridge as per Ref 2. I soldered the headshell ends of the tonearm litz wires to the cartridge clips and headshell wires I'd pulled from the Linn arm and the distal ends to four 2mm gold plate test sockets. I made a separate braided earth wire which I attached to the cartridge end of a tinned copper wire spiral running the length of the arm carbon arm tube at one end and the ground bus of the phono amp at the other. The capacitance between phases of this setup measures at 35pF.
1. Turning the Tables Sound Practices No5 Spring 1994 H Boardman.
2. The LP Terminator. R.A. Futrell, AudioeXpress 1/03