Quote:
Originally Posted by Formerly YB-2
Has anyone used the Platterspeed app on their cell phone to check the rotational spec's on their HW-40? Would be interested in your results if you have. Thanks.
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I measured the original HW40 which uses the same motor and controller so they should be similar. I measured the platter speed using a RoadRunner tach which is accurate to 3 places right of the decimal point.
The HW40 uses a magnetic ring encoder that produces 160 pulses per rev; the read head synthesizes 8 output pulses for every input pulse so the PPR goes to 1280. It also produces a 2 phase output (quadrature) and the controller can read both data inputs so the effective encoder rate is 2560 PPR. At 33.333 RPM, the platter takes 1.8S for 1 rev, but they read the encoder every second, therefore the count for 33.333 RPM would be a non-integer number (1422.222). The controller can only work with integer counts so the platter speed will be either 33.351 when the count is 1423 and 33.328 when the count is 1422. This is exactly what I measured, with the speed fluctuating between those 2 extremes. That equates to ~0.07% W&F. The software for the controller from Elmo Motion Control showed higher deviations, but the platter mass may smooth out the variations.
I also used a test record with a 3150Hz test track and a Leader W&F meter and measured similar results (0.07%).
I plotted the 3150Hz tone on a polar plot using software written by Scott Wurcer on DIYAudio:
The plot shows 2 revs (blue and orange) and a fixed marker at 3150Hz (Green).
