A Technics SP10 mkII project page: The Mule
Above photo: The SP10mkII securely buttoned-up within its new "Mule" plinth. Tonearm: Graham 2.2. Cartridge: Shelter 501 type II moving coil. Old style Stillpoints cone feet and standing over a Neuance isolation platform
For detailed documentation of the process, see the linked pages below. To read an overview, continue reading this page.
This story begins with a purchase. I saw this motor unit for sale online at AudioGon. It turned out that I recognized the seller. A friend. I made contact via email. We came to terms on a price and the transaction was made.
The price, while not inexpensive, proved to be quite fair in view of the almost excellent cosmetic condition and in view of the very excellent operational condition. Just to be safe I dribbled some 20 wt turbine oil down into the tiny lube hole next to the motor spindle. I was generous just to be sure it wasn't going to run dry. But I did not take the motor apart to actually see what the bearing looked like. That would come later. Next I assembled the platter over the motor by its three unique and almost impossible-to-replace machine screws. Allowed the motor unit to stand alone on my project table. Sitting next to its standalone power supply. With the power supply plugged into the turntable, I switched it on. Then I pushed the Start - Stop button and watched as the platter took a fraction of a second to reach 33-1/3rd rpm.
Then later I noticed that I could simply push the 45 or 78 button and the speed instantly switched to it without any drama. Instantly and smoothly. With the platter powered and running I could place an index finger onto it, even firmly and watch as the strobe window would indicate the initial drag with just a hint of slowing and then almost as instantly correct and hold the speed it was assigned to maintain in spite of the added drag. Hmmm. It became quite clear, this was going to be very different from my previous belt drive and idler drive turntable experiences.
For a month I just allowed the SP10 to stand on the table wired up as it was and occasionally pushed its buttons to see if anything was going to fail or somehow falter. No errors. The strobe window, well lit and and indicating a rock steady strobe reading, gave confidence. This piece of engineering came from 1975, and is amazing still today.
Enough already, lets get this into a plinth so I can spin some Lps! Link here for the details of the initial plinth. I took plenty of photos to document my earliest experiences. See the link for that. For this current project page I just want to summarize each phase of the project. The first plinth I'll call the "early listening" phase. This is my first experience with the SP10 and my initial thoughts, which I wrote probably indicate any preconceived expectations and attitude I may have had regarding direct drive turntables whose speed was controlled by integrated circuits. (chips).
I did not spend too much time sweating over the details of that first plinth. Same concept but with different levels of mass. To keep in step with 'the then' current popular trending, I chose to build the higher mass version I had drawn. The one at the bottom.
I didn't sweat too many details. Unfinished and not all the way sanded down, I had the SP10 up in the heavy plinth spinning Lps after a couple of days work in the shop. Zeta tonearm. Denon DL-103R in a Panzerholz body by Uwe and with the ruby cantilevered fine-line diamond installed by SoundSmith I was ready to hear what this motor unit could do. Not my very best arm and cart setup, but not far from my best.
What I heard then was encouraging. Very good tones and textures. Very crisp detail articulation. Excellent overall detail delivery. Better in that way than I'd heard from my previous reference, the Teres 145. I think my earliest impression was that the Technics motor unit did not actually better my TD124 in terms of energy delivery. You know, those big notes jumping out of the speakers and into the space before you with sudden energy. But after a few weeks of listening I was reconsidering this observation and noting that it was indeed producing a very enjoyable listening session while playing different records from my Rock library. It wasn't just classical music where this player excelled. It was all of it. I knew then that I had a seriously good motor unit in house.
I listened to it like this for a few months, then took it down off the dedicated TT stand I have, and moved the motor unit to the next step. The TD124 took its place back and once again served as my primary record spinner while I could take some quality time doing mechanical stuff with the SP10mkII. My next part of the process was to disassemble the motor unit completely, and to document this so that re-assembly would not become a challenge. I think what I noticed the most during this process was how many small fasteners the thing goes together with. Those Matsushita engineers were very thorough in making certain that this baby was very well buttoned up. And it is very well buttoned up indeed. So I documented this part of the project with photos more than text.
Afterward, I boxed all of its parts in an organized and careful manner using anti-static bags for the printed circuit boards, and put the thing, disassembled and in its own box up on the shelf for several months. By now I had still other projects to get going on.
The Mule Plinth:
Fast forward nine months or thereabouts. With all other projects caught up I decided it was time to get back into this project. I had determined from my previous experiences that there weren't any obvious faults with this player. Its function was right on the dime. The platter brake didn't rub. The strobe window was rock steady. Push a button and it did the correct thing. Sound quality was sweet.
In fact the player had destroyed whatever preconceived notions I may have had about direct drive turntables. Remember those comments from M. Fremer in this or that review * about how direct drive tables from this era, and even current times, were prone to delivering that same defect that CD players do, Jitter. Honestly, I suspect this is pure imagination. I heard nothing but good notes out of this thing. And I have had other turntables on hand to make A/B comparisons with. Both belt drive and idler drive types.
*( but mostly that review he wrote on the Grand Prix Monaco direct drive turntable)
I digress. The early listening session was useful as a shake-down run to see what parts fell off...metaphorically and physically. No metaphors were hurt and nothing physical fell off so I decided my next part of the project would be to focus on another plinth design. Besides, and in the meantime, I had given away my 'early listening' plinth to another SP10 mkII owner in need of one.
Something different. Idea of it not sorted. 'Drew many sketches. Wasted entire summer of 2013 making drawings I would not use. Then, late August, I took a break and thought about other projects. A couple of weeks later, a new idea for the SP10 comes. This one.....
The Mule. Initially I thought of it as a "test mule". I wanted it to be as reasonably light as it might be while retaining structural rigidity. Then, I thought, I'd use it to test for noise generation. The idea being that any noise being generated by the motor unit would not be damped, and therefore masked, by a high mass plinth. Another consideration was that I wanted to keep the turntable's footprint as small in area as I could. A third consideration was to minimize the visual effect one gets when mounting a 9 inch tonearm next to one of these rather large motor chassis. This turntable was originally designed for 10 inch effective length arms. And a 9 inch arm just seems rather small and proportionately wrong when parked next to it. So, I thought I could mitigate the visual distraction by reducing as much of the supporting structure as possible. A minimal plinth. That way the first thing you see when looking at it is the motor chassis and the arm. That was the intent, anyway.
The build was detailed and tedious, but not particularly difficult. Numerous cutouts of 1/2 inch thick baltic birch multi-ply. Stacked precisely via dowel pins and glued together with hide glue. The resultant structure has proven to be exceptionally rigid. The sound quality I hear out of this build exceeded my expectations. Very notable is the exceptional bass reproduction I get with this assembly. This is the best turntable/plinth/arm/cart setup I have heard in this room at reproducing bass. I would not have anticipated it. Deep, tight, well textured and accurate bass. Also, energy levels have exceeded, by a large margin, what I had heard from the previous higher mass plinth. It sounds quicker, sharper, more forward and more energetic. Detail reproduction is reference level to my ears. The best sounding turntable I've had in this room. Period! *
* Not the best I ever heard, just the best I've owned. And I'm not yet done with it.
Fiddling with the bearing: link for the gory details
When I did get around to taking the bearing apart I found little to worry about. Visible evidence of having been run, but no measurable evidence of wear. Of some interest to me was the thrust pad that appears stuck onto the very end of the bearing shaft. At first I couldn't figure out how this was assembled. Were there internal parts to it, or was it a...simple snap-on cap.
It turns out it was the latter. Matsushita used what appears to be nylatron as a thrust cap material to ride over a fixed and immovable bearing ball. The bushing sleeves in the housing are bronze, but not of the porous type. Given this there is a maintenance factor with this bearing. Periodically oil should be fed into the lubrication orifice at the top of the motor housing.
Getting back to the thrust of it. I thought to try different thrust cap materials and also thrust ball materials to see if I could measure or hear any difference between them. I did this by machining several thrust caps out of different materials.
I checked these different cap materials for wear by playing the SP10 for a week with each cap, then disassemble and inspect for the size of the wear dimple in the center of each cap. Nylon (not pictured) fared the worst. The rest were about even and wore less. I measured the player each time for noise and recorded my results. No significant difference in noise levels between these materials. I heard no difference in sound quality. Ultimately, I decided to go with either of the Torlon choices. This simply because it is a more modern material that appears to wear very well.
Then there was this
About lube: I'm using straight 20 wt turbine oil, like in a Thorens.
History of the deck is unknown. No documentation of any service history. The PCB's appear to have original solders intact. Note that the unit operates without flaw!
Hey, I've got the SP10 mkII standing over a Minus-K platform. Cool, huh!
However good the SP10 mkII is ordinarily, it is a bit better when standing over a true isolation stand like the Minus-K. 1/2hz isolation in all directions. The earth moves. The floor shakes. The walls vibrate. And the SP10 on top of the Minus-K remains completely undisturbed.
Those are my notes to this date. 5/6/2014