Vintage belt drive turntable upgrade
If you do not have the best,
Make the best of that you have
I always have liked vintage components from the 70-th. The very engineering and manufacturing approach was very different back than, comparing it to the modern one. They didn’t save on quality and quantity of materials, and they didn’t save on high quality machined parts as well. It is especially important for such components as turntables are. As a result, on many vintage belt drive middle-end Hi-Fi tables both a motor and a platter bearing are largely oversized and overpowered. So they may handle a much heavier platter and still work for years and years. I mean 5 to 10 kilograms platters, and sometimes up to 20 kilograms. And a motor still will be able to accelerate a platter to reach its nominal speed in just 3-10 seconds. I was thinking about completing such an upgrade for a long time, so I already had prepared some materials and was hunting on flea markets, garage sales and Goodwill stores in Toronto City area in a hope to find a decent candidate. Suddenly I was lucky enough to get a vintage Micro MR-611 table from a local Goodwill store for a couple of bucks. A wooden cabinet together with the plastic cover were badly scratched, however the turntable itself in perfect condition. It was a middle-end hi-fi belt drive turntable from the year1970-something, with cast chassis, machined platter, VTA adjustable arm from Micro, everything very decently made. The size of Micro MR-611 motor is 3 times larger than that of Thorens turntables of the same period, and a platter bearing assembly also very huge. However, a platter mass was only about 2 kilograms, certainly not enough for such an overpowered motor. This is a hysteresis sinchro motor, and it maintains a very stable speed. Examination with the medical stethoscope has demonstrated a very quiet performance of the motor, platter bearing and drive system. So, Micro MR-611 was a perfect candidate for a DIY upgrade project. Actually, a sonic performance of the original, intact MR-611 didn’t differ seriuosly from the sound of my vintage 1980-something Sony direct drive turntable. I just couldn’t hear the substantial difference despite the Micro brand aura (aura just doesn’t contribute to the sound for me). Actually, Sony was of much more convenience, with its soft-touch operated semi-automatics and auto shut-off. My new vintage Micro design would promise a better sonic performance, so I went to upgrade it.
My upgrade idea was to increase the platter weight up to 5-7 kilograms (I do not like going to extremes). My decision to use additional cylinders on the top of a platter has been based on the vintage Transcriptors turntables design. So, I ordered 6 aluminum alloy cylinders 90mm in diameter, 60mm high; one center cylinder of the same size; a stainless steel spindle extension part; and additional stainless steel cylinder to re-install the arm 60mm higher for the purpose to level the arm with the 60mm taller platter. I also ordered 4 aluminum alloy feet to screw them right into the bottom holes of chassis (threaded holes originally served to connect the chassis to the wooden cabinet). Having all the parts ready, upgrade have taken me just a couple of hours to complete. Here are stages step-by-step:
1. Micro turntable stripped of its cabinet and plastic cover.
2. A platter taken off.
3. Tone arm wires unsoldered, the arm taken off.
4. Six holes drilled through the platter and filed to oval shape.
5. Six cylinders were put on the top of the platter and screwed from the bottom. A tricky part was to balance the platter weight, so the holes in the platter were made oval to allow cylinders to be moved 2mm closer or further from the platter center. The platter bearing oil was replaced with the liquid one, a belt taken off, the turntable installed 45 degrees inclined, with cylinders screwed slightly. A platter was rotated manually and released on order to give the heavier side of it to stop closer to the earth. After several trials a cylinder from the heavy side was moved 1mm closer to the center, and a platter was finally perfectly balanced, finally all screws tightened. After that the bearing oil replaced with the one of the same consistence as before.
6. Four legs screwed into the bottom holes of the chassis.
7. Arm re-installed using a steel cylinder, the arm wires pulled through it and soldered to the proper RCA jacks.
8. A platter installed on the turntable with the belt on.
9. Spindle extension and a center cylinder put on the top of a platter, Micro own rubber top, so the upgraded platter is complete and ready to work.
10. Later I have made kind of a new wooden cabinet.
11. Finally I have ordered a new plastic cover and installed it using Micro own hinges.
Picture 11) A central cylinder installed.
Picture 12) A rubber mat is on its place.
OK, let me tell about the results. The difference in sound was just amazing, and my Sony isn’t any match to upgraded Micro anymore. A sonic performance of Micro MR-611 just went up, into another category, it is rather a Hi-End turntable now, and for sure not a middle-end hi-fi one anymore. Several times I’ve tried to make experiments replacing Micro with Sony in my stereo system, and every time Sony went back to the closet, despite all its handy automatics. It finally stays in a closet, as a reserve table. Sony is a decent table of pretty good quality, and I like how it is built (it is a piece of 1980-th engineering, design based on Sony’s own professional turntables). I just do not like how it sounds anymore…
Another story: a detachable auto shut-off.
So, finally I was satisfied with how my Micro sounds. I tried several phono cartridges, both MM and MC, several phono preamps, and finally I have chosen a vintage Ortofon MM, and a vintage high-output Russian MC cartridge together with the custom made clone of Audio Note tube phono preamp.
Satisfaction with the sound however didn’t compensate dissatisfaction with the convenience: after the two years of semi-automatic turntable use I have become addicted to its automatics. Operating turntable fully manually has appeared to be very annoying. Even worse: it doesn’t help to relax and fully enjoy the music, if you need to hurry to the turntable every 20 minutes to lift the arm. And that scratchy, ugly sound of the last “silent” groove is really abusive for sensitive ear of audiophile. So it isn’t just a matter of convenience, it is also a matter of how to fully relax and fully enjoy the music. Maybe some audiophiles will argue, considering themselves as not been lazy enough to manually stop their turntables. However no mentally healthy audiophile will state that he likes the sound of that “silent” last record groove!
So, I wanted more again, and I couldn’t find it on the market. As a result I started another DIY project. The idea was to create the automatic stop with no any mechanical contact with the arm and turntable, optically operated, with no any interference to the sonic performance of the turntable. And to make it as a completely independent component, able to be adjusted and work with almost any turntable. It seems logical: if other audio devices are divided into different components, why auto stop devices aren’t? You can buy separate arms, separate motor drive units, AC/DC supplies, cables and wires, separate phono pre-amps, and etc. to compose a working turntable. So why automatic stop and auto shut-off components aren’t offered? I’m not considering here purely mechanical arm lift devices, because, IMHO, their mechanical trigger doesn’t meet real hi-fi and Hi-End criteria. So I’ve decided to develop and make one that does. Together with my friend, who is a Hi-End equipment engineer, we developed both mechanics and electronics. In few months a working prototype was ready, and for my surprise it worked perfectly from the first trial. After some improvements several working prototype devices were ready. Finally I’ve filed a patent application for it, because it really contains some new ideas.
I consider my experience of Micro turntable upgrade as a very successful.
A little film about(5.34Mb)
As to the auto shut off devices, I’m accepting orders for making them for you. Contact information: Waltertobin@gmail.com