platter speed, test disk & strobes

[NSNO2021]

Given my insatiable curiosity its a surprise its taken me so long to want to check the speed of my Planar 8. I have the RPM app on my android phone which suggests its in the right area but my ears had already confirmed that. This has not stopped me wanting to know what it truly is and make adjustments if required.

eBay & Amazon have no end of stroboscopic test disks, ranging from £10 to well beyond however the choice of test disks with a strobe light is tiny and far the most part the strobe light is the expensive part of the equation --- that being the case is it possible to accurately calibrate my platters speed with only the test disk or with some other form of light source instead of the strobe light (I have no end of LED lights for camping, fishing, cycling, running etc) plus UV torches for another hobby. Thanks Paul

[Daniel Quinn]

I use a laser tachometer. £18 from China. Its as accurate as it gets.

[Geoff.R.G]

You have a strobe in every room of your house, domestic lighting flickers on and off 100 times per second (Once on the positive half of the wave and once on the negative). A camping LED, driven by a DC supply will be useless.

The accuracy of the UK mains frequency is generally accepted to be very good so a simple strobe disc is really all you need. However, if you have a spare oscilloscope hanging around you could hook up a high quality signal generator set to 1KHz to the X input and play a 1KHz test tone from a test record and put the output on the Y input, the resulting display should be a circle any speed irregularity will be shown up as distortion of the display. Look up lissajous figures on Google.

[NSNO2021]

Cheers Geoff, my mains supply which I have tested over about a week is ok, it tends to dip at peak times to 233/4 but for the rest of the time its usually 237/8. I will look up the your suggestion and report back

[Geoff.R.G]

Cheers Geoff, my mains supply which I have tested over about a week is ok, it tends to dip at peak times to 233/4 but for the rest of the time its usually 237/8. I will look up the your suggestion and report back

The turntable speed is measured using the mains FREQUENCY, the voltage has nothing to do with the way the strobe operates. The suggestion of using an oscilloscope was slightly facetious, but it does work.

[NSNO2021]

Its ok. I should have put my mains voltage comment in the context of once its set, the speed should be relatively stable because of the minimal voltage fluctuations.

[NSNO2021]

I use a laser tachometer. £18 from China. Its as accurate as it gets.

Thanks for that, this sounds very interesting, do you by chance have a link ?

[Hannes-Gregor]

Cheers Geoff, my mains supply which I have tested over about a week is ok, it tends to dip at peak times to 233/4 but for the rest of the time its usually 237/8. I will look up the your suggestion and report back

The turntable speed is measured using the mains FREQUENCY, the voltage has nothing to do with the way the strobe operates. The suggestion of using an oscilloscope was slightly facetious, but it does work.

Geoff is right. You only need a strobe disc. The rest will do a lamp of your choice.

[Daniel Quinn]

Just look on ebay, there are loads to choose from, some more expensive but in the UK.

[Latteman]

Vinyl engine has a free download- I printed it and laminated onto a 7” single.
I then use a strobe app on my phone for 50hz