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Posts: 181
Joined: February 2, 2002
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After a lot of experimentation with motor isolation and some trouble with static electricity, I have the new SOTA motor installed. When I first ran it, I was getting constant popping sounds in the speakers from about every 5 to as long as 30 seconds. After some discussions with Christian at Sota and Kent at Pass Labs, I realized that I was probably getting static discharge due to the belt movement. When I did the conversion, I neglected to reestablish the plinth ground that had been tied to AC ground for the old motor. So I ran a wire from both the plinth ground screw and a screw from the bottom of the motor to a bolt I attached to the aluminum cover plate on the bottom, and from there another wire from a second new ground screw to the phono preamp ground. Problem solved. The other issue I had a hard time dealing with was transmitted noise through the solid aluminum plinth top plate to the tonearm, despite this motor being quieter than the Hurst. It certainly vibrates much less in my hand. The best solution I came up with was to mount the motor on rubber isolation standoffs I purchased from McMaster-Carr. I ordered standoffs in a couple of different durometer hardnesses to experiment with. With medium hard ones, noise was drastically reduced at 45 rpm, but not content with that, I tried the soft ones which yielded barely detectable noise picked up through my mechanics stethosocope even on the plinth right next to the motor. Very cool, indeed. However, it does bother me that the soft mounts have considerable shear flex, so I may try the harder ones and test both with Analog Magic to see which gives the better w/f readings. It's not lost on me that I've been fighting this fixed motor design and have essentially replicated a SAMA, but without the mass loading from the motor pod. But the results I'm hearing are very impressive. I have not heard such rock solid imaging and fine detail from this table before. The attached wow and flutter measurements were made with Analog Magic's 33 1/3 test disk. I did three trials, each with one belt and one with two belts. I tested having no standoffs and motor tightly fastened to plinth, use of medium hardness standoffs and finally with soft standoffs. Analog Magic computes 8 or 9 wow and flutter measurements in track 3. I recorded 8 and took the average. The conclusion is that 2 belts are definitely better than one. And surprisingly, the medium hardness standoffs gave the best reading at .073, with no standoffs in second place with .077, which I thought would have been the best option, and in third place, the soft standoffs at .079. I probably can't hear the difference between these readings, so I will probably use the soft standoffs which gives the lowest transmitted noise.
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