Measuring platter speed.

[whubbard]

Hi Guys,

I've gotten two recommendations for measuring platter speed:

1st: Play a 1000hz test track and measure the output to ground with a frequency meter. If it reads 1000hz, you're good.

2nd: KAB Strobe.

Now buying a frequency meter is going to cost about the same as the KAB strobe, but appears like it could be more accurate. So, whats your opinion on this?

-West

[sq225917]

The frequency measurement will only be as good as the pressing, but it does include stylus drag and does give you a 'number'.

The strobe requires less set-up, but doesn't give you a number and doesn't include stylus drag.

[whubbard]

The frequency measurement will only be as good as the pressing

This is my current test record and I'm assuming it is a pretty fine pressing: Cardas Audio

Stan Ricker seems to have a great reputation.

[Conrad Hoffman]

All those methods will work; how accurate do you want to be? How long are you willing to wait? How close to "primary" standards do you want to be? In the US you'll find the line frequency to be extremely accurate, even over short periods and at any time of day or night. Where you live a neon bulb and standard strobe disk (download my arc template generator that also prints nice locally generated, not image, strobe disks) will get you as close as any tt needs. The fancy strobes are usually a complete waste of time and money in the NE USA. If you really want to double check, find an accurate quartz clock with a second hand that doesn't operate off the line. Check it against WWVB if you're paranoid. Now, using a big black line on the strobe disk, time the platter for 50 or 100 or more revolutions. You can get almost any degree of accuracy you want, if you wait long enough.

[3GGG]

I bought an IR speed /RPM counter on eBay, new for $7 plus $7 postage. You can put three or 4 reflective strips then divide the number by three or four for a more accurate reading. Mine reads 33.3 so I am happy with it (TT and tacho)

[Conrad Hoffman]

More strips + divide = smart!

[3GGG]

Throwing away the strips it came with = dumb = me

[h_a]

If you're only interested to adjust (average) platter speed, you can do the following: put something small and well visible onto the platter, like a piece of rubber.

Start the turntable and count how often it passes a certain point within 3 minutes; target value is 100 times (33.33rpm x 3).

While that does not show you how accurate the platter holds the speed within this time, it's often sufficient as one usually cannot do much to adjust the minor speed deviations anyway (regulated by turntable electronics).

Hannes