Saturday, 18 May 2013

The Turntable, Part II – the motor unit

At the beginning I have to mention that this article is a survey to nirwana lands about motor concepts for record players like the Platine Verdier. I am publishing now my personal experiences which I made in the late 1990ties. I have not found another source in the web about somebody else with the same experience, from this point of view mine seem to be very unique. To my knowledge nobody has gone the same way. It still sounds absolutely stupid, but I am quite convinced about these uncomparable results. The improvements against ordinary concepts justifiy the tremendous work.

Before I got the Platine Verdier turntable in 1996 I had in the first step the Garrard and similiar players which all could not make me happy. So I shifted to a simple Thorens TD 160 (first version) and a SME 3009/II as tonearm for my everyday use and looked forward to find my player one day. I did do experiments with a frequency generator feed into a Quad II tube amp as power module and through a step up transformer to boost the signal up to 100 volts. Synchronous motors like the one in the little Thorens players need as foremost feed by 50/60 hertz to run their dedicated speed. A perfectly shaped sinus signal curve is rarely available from the electricity providers, if you check yours, you will see a lot of degradation of this curve. A sinus curve without distortions will improve the the sound of this sort of motors dramatically. Linn had introduced such a unit for their LP12 in the 1980ties as one of the first commercial companies for turntables, the "Vallhalla". Later they improved the concept by using a second generator unit just for the necessary phase shifted second signal wave, it was called the "Lingo".
If you compare a record player run by a synchronous motor like the Thorens or the Linn with all three different supplies, you will notice a tremendously improved soundstage with every step. You will wonder how much influence a clean sinus wave will do to the final sound stage. It improves in almost every respect, in dynamics, in resolution of details and musical insight. As a main fortune the complete soundstage will be a lot finer, warmer or let me say with other words much more natural. The quality will be improved in really huge steps from the single phase control up to the double phase control. When I did these tests I got a bit amused about myself and my set up at these times. I had a complete chain just for generating the 50 hz signal for my turntable, two signal generator units, two Quads and two big step up transformers all sitting next to my turntable. I could certify myself to be a complete typical ignorant "hifi nut" just by looking at this setup. I did burn 500 watts of energy to turn a 20w motor unit with a pure sinus wave. This is a real "inviromental friendly exercise", in particular if you see the today music consumer at the other end without any hardware for the same reason. But this is a different story once, may be two.

The customized "Valhalla" frequency generator unit underneath my subchassis motor board with the Thorens 16 pole synchronous motor

Back to the topic. I remember the day when I did put the parts of the Verdier together and I placed it on a little table next to my ordinary set up. The player needed a lot of space and I had to arrange everything new, but was very anxious to get a first impression of this heavy monster. When I bought it, the original motor unit was burnt, so I did not have a "real" motor unit to make it work. It was sitting next to my Thorens and I decided, why not using the Thorens to turn it? I tested it and of course it did not have enough torque to start the 15 kg platter of the Verdier. But with a little help of my hands it turned up and could stay in speed. My first impression was completely overhelming and I do remember still today that I did play all my favourite records till the late night without eating anything. I was totally impressed and did already know, this is going to be a life time companion and said: "If it is that good, how good might it be with a "real" dedicated motor unit?"

As everybody knows who is experienced with this turntable, every little change is listenable. You can perfectly sort out if you use a thick or thin string, if it is made from silk, wool or plastic. You will notice if the string has two or five meters lenght. And if the motor unit is placed on the same support or if the player is set on a different one. You can notice any differences in the oil viscosity as a substancial change of the dynamics in the music. It might be clear if different supports for the 60 kg player will be heard, it is very important which motor will do the job. In 1999 the swiss hifi magazine "Hifi Scene" published almost a complete issue about motor concepts for the Platine Verdier turntable. This article was a very interesting contribution to questions about pulley motors, magnets, strings, supports, energy, physics and finally the influence of the earth magnetism to the pick up process. This article ended with a very individual conclusion about the only possible motor solution. To my experience it was a bit of a dead end street conclusion, but it showed in a amazing way how different motor concepts finally will lead to completely different record players. Motors will create a substancial difference to the inherent musical information, its overall dynamics, their speed, timing and their amount of listenable air.

The suspended subplatter with belt drive built into my own platform to fit the smallest circular enclosure in the size of the platter and the string guard in the foreground
For almost one year I did follow up different ideas and built a lot of motor concepts. Under these I built the Maxon concept (from "HiFi-Scene") and a lot of other dc-motors, ending with a three-motor-unit each with own string. As well I did slaughter a Revox A77 in order to get the famous pulley motor with its own tachymeter controlled electronics and PSU, a 15 kg set up which is used with a tape as a string (I have it still in my cellar if somebody is interested to buy). I used servo controlled step motors, as I tried steam operated piston motors to the electric alternatives. I introduced the eddy current brake to the verdier and experimented at different viscous oils with different motors…, – but I always came back to the chunky Thorens TD 160 record player as a motor unit. This set up was always a whole lot better than any other motor. I could not really believe it, but it was like that. I did not know why, but every aspect was better resolved when I switched to this system. First there was the synchronous motor itsself, completely different than any other dc unit, second with a 30 cm platter there is a big difference to a small pulley in terms of slipping for the thin string. I thought may be with the 1:1 transmission of the string has no more slip and this makes the difference to all small pulleys where slips are common. Again I said to myself: "if it is that good, how good might is be when you incorporate a lot better turntable like the Linn LP12 with motor control instead of the chunky Thorens". A friend of mine did use a Linn LP12 in advanced configuration with latest bearing, springs, etc. and the Lingo (two phase frequency generator). He brought the 6000 EUR player over to my place to test it as motor unit for my Platine Verdier! – As motor unit –. You might believe me or not, but the simple Thorens did the job better, – a lot better, I could not understand what I did hear. The Linn is basically the same construction like a Thorens, with several hundred percent better components, tolerances and materials. It uses a Phillips synchronous motor and a perfect built two phase frequency generator, – and it can not even come close to the Thorens in sound qualities when used as a motor unit. What is the secret of the Thorens?

Both record players use the same slipless pulley (platter) and the subchassis spring damping as identical mechanical base. The Phillips motor is a 32 pole synchronous type, the Thorens motor is the same with 16 poles. Both use a rubber belt to drive the sub platter, both players use casted metal platters. So far the only difference is the motor. In theory the 32 pole Philips motor has a 100% advantage above the 16 pole Thorens unit. With every turn the energy will initiate a double amount of smaller steps to the pulley, to my understanding it will be a double smooth contribution comparing the  16 poles.
I made the final test to conclude. I changed the motors against each other. I played both with perfectly  customized Valhalla boards, because the Lingo is phase optimized for the 32 pole motor (the 16 pole motor needs a different shifting capacitor in the output of the Valhalla for the other half sinus wave). Now the Linn with Thorens motor was a lot better than the Thorens with Philips motor. I did not understand why, but the 16 pole Thorens motor plays so much smoother than the Philips type, that I still cannot believe, nor do I understand why. But sometimes things have to be accepted.

For a long time I had a armless Thorens TD 160 torso with Valhalla board underneath close to my Platine Verdier as motor unit. It was ugly, but I did know it is so much better than any dc motor, so I accepted its appearance. When people visited me they asked: "For what reason do you need two turntables?" When I answered the small one is the motor for the big one, I noticed incredulous eyes and just could a little bit foresee what they might have thought about me...?

The underside shows the opening for the Valahlla board and the gas filled dampers for the spring suspension of the whole unit.

In 2004 I wanted to end this unpleasent situation and started to build a housing for my motor unit. I wanted to keep the three spring suported subchassis, the subplatter and the platter. I needed space for the motor, as well for the Valhalla board and I wanted to isolate the whole unit with suspended feet. First I thought about a 30 cm diameter plywood ring, where all will be built into. I did not like the idea of building a new wooden resonant instrument as housing for the motor unit. That brought me to the idea to make it from concrete. For this idea I needed to find a 30 cm round mold, where to cast the concrete in. It took me a while to find something adequat. I visited several household shops in order to find a perfectly shaped cover for cakes. They all are in the range of the searched size, but differ for 3 cm smaller or larger. And at least it needed to be slightly conical, so that the finished concrete cake will perfectly slide out. For the different flats inside I did cut excact negative forms from styrofoam, which have got glued together as sandwich. This block got fixed with two bars overall the top border of the mold (the later underside). I did use very special high tech industrial concrete, which is normally used for highly strained floors. This has a lot of unhealthy epoxy components in its mixture but gets harder as any other. I did the cast and waited for 24 hours for the first step. After that time I added a final layer of 2 cm of pure epoxy component on top of the cast (the later underside). The sandwich of concrete and epoxy got everted after a resting for another 24 hours and than it was looking good to get it out the mold. I pulled out all styrofoam parts and was able to see that it had air inclusions inside or outside. Now it could harden for the next 30 days on air, after that period it got a industrial floor paint in concrete gray as a final finish. Two days later I could assemble the whole unit. Everything adapted perfectly and it did look quite good.

Here you can see the inside mold still with styrofoam texture

Now I had a quite compact (it is only compact comparing the Verdier), reasonable looking motor housing, which did not need to be hided anymore. So I took the chance to visit a friend of mine and he could compare the unit to his original Verdier dc motor. Late at night when I came home I had to carry my unit up to my apartment. To protect it during this transport I had packed it in a card board box with styrofoam stuffing. When I took the box out of the trunk of my car the bottom of the box suddenly opened and the whole unit smashed on the street. The concrete housing did burst into 100 pieces and lots of dust – a complete desaster. I had no other chance than to do all the work again for a second time.

The finished complete motor unit

Today I know that I don't move the unit anymore, and if, than only perfectly packed bomb proof in a strong container.

Read on soon, Volker