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DIGIstrobo for Speed and Wow and Flutter Measurement, Thoughts? Experience? Competition? Dubious W&F Method?
post Jun 7 2010, 21:21
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DIGIstrobo: Clock Your Speed. Plus Calculate Your W&F?

Hello again.

I'm gearing up for round two of USB turntable sampling. This time I'm taking on USB DJ turntables. I planning to measure turntable speed, in addition to tracking force.

After some research, the only equipment I've found that fits bill is the DIGIstrobo from an Italian company called hifi4music. Positive Feedback has a nice review.

Does anyone have experience with this type of equipment? Are there similar "digi-tachs" I should consider?

I want to measure the speed out-of-the-box, not adjust it for the proper speed. That is why I'm not looking at traditional strobe discs.

Measures Wow and Flutter?
The manufacturer claims you can measure wow and flutter with it- something I would love to provide.

Here's how it works: While you're taking the speed reading, it keeps track of the lowest and highest speed recorded. Presumably, you arrive at a percentage based on largest deviation from the average speed.

The DIGIstrobo claims to be accurate to "0.05% (or 0.1 rpm)."

Clearly, this is a crude measurement but can you really arrive at even a crude WRMS or WTD figure through this method? Or is it really a speed variance measurement? The review uses the terms interchangeably.

The last time we discussed W&F measurement, I got the impression that the WRMS figure represents a deviation from a test tone, not a direct deviation from the measured speed.

If I come up with a percentage based on the DIGIstrobo method, do I even dare call W&F?
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post Jun 9 2010, 11:11
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This thing is utterly useless for wow&flutter.

The spectrum of turntable w&f, once demodulated, is in the DC to ~200Hz band.

The digistrobe is a mere revolution counter. It gives average speed and, in the best
case, long-term drift. Not even remotely w&f.

If you are not interested in the drift figure, then counting 100 revolutions
against a chronometer is just as good.

If you are interested in w&f then you could use a test record with a known
reference tone, record it, demod it, plot spectrum. But beware, most
test records, and all present-day test records, are not good enough
for this.

For those who thing w&f is not an issue: the measured differences between, say, an SME30
and a Feikert or Origin Live are vast. After registering you can download a lot
of measurements at http://www.milleraudioresearch.com/avtech/index.html

Oh, and the PF review was written by someone who doesn't understand w&f ...

This post has been edited by WernerO: Jun 9 2010, 11:14
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