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Old 25th February 2004, 03:59 PM   #1
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Default T/T Speed Testing

hi all, some help would be great with this..


could any one suggest any methods to test a turntable with regards to its speed stability, i know later models come equipped with strobe correcting circuitry...

but say you have a simple belt driven t/table....

i have access to a CRO etc, the main thing I wanted to test for was the effect the variation in mains frequency did to this t/table...

any ideas at all wud be appreciated!
Thanks
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Old 26th February 2004, 02:57 AM   #2
BrianL is offline BrianL  United States
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Not difficult. You get a strobe disk, put it on your platter and
then shine a strobe lite on it. The strobes were commonly
available in the "old days". Surely someone's web site
has one. The strobe light can be a neon light assembly plugged
into your 50 or 60 Hz power. (strobe disk, of course, must
be correct for your line/mains frequency) This will give your
a measure of your turntable's speed accuracy, ASSUMING that
your line frequency is correct.

A better method would be a bright LED run off of a stable
frequency source like an HP 3325A (or B) frequency synthesizer.
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Old 26th February 2004, 08:16 AM   #3
peterr is offline peterr  Netherlands
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This thread deals extensively with strobes and strobeflashers.
I have one of the items that dice45 talks about and it works great!
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Old 26th February 2004, 09:19 AM   #4
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Quote:
Surely someone's web site has one
http://www.enjoythemusic.com/freestuff.htm
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Old 27th February 2004, 03:04 PM   #5
sreten is offline sreten  United Kingdom
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Quote:
i have access to a CRO etc, the main thing I wanted to test for was the effect the variation in mains frequency did to this t/table...
Just point out a strobe disk can't do this.

A synchronous motor belt drive turntable using a strobe disk
lit by mains lighting will show no variation whatsover if the
mains frequency varies.

An asynchronous motor turntable will show little effect either.

A turntable not linked to incoming AC frequency, e.g. DC servo
belt drive will show variations on the strobe due to the changing
AC frequency whilst speed is actually constant.
This is why most DC servo's have there own strobe light.

The turntable will either be directly linked to mains frequency
variations or show little to no effect all.

Fortunately for belt drive synchronous turntables mains
frequency (but not quality) is extremely stable - have
you seen the size of a generator rotor ?

The long term stability of mains frequency can be assessed
with an old mains synchronous wall clock with a sweeping
second hand and an accurate reference clock.

sreten.
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Old 27th February 2004, 07:00 PM   #6
EC8010 is offline EC8010  United Kingdom
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A battery LED strobe light shining on a strobe disc is the best. I believe Walrus Systems (London) sell such things if you don't fancy making one yourself.

Alternatively, use a frequency counter to measure a 1kHz tone on a test disc if the test disc is known to be recorded correctly and have a hole exactly in the middle.
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Old 28th February 2004, 07:43 PM   #7
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Quote:
Originally posted by EC8010
A battery LED strobe light shining on a strobe disc is the best. I believe Walrus Systems (London) sell such things if you don't fancy making one yourself.

Alternatively, use a frequency counter to measure a 1kHz tone on a test disc if the test disc is known to be recorded correctly and have a hole exactly in the middle.

hi there, i am really after one of these 1kHz test tone records at the moment, does any one have any idea as to where to get one from ? endless net searched have lead nowhere!

..........
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Old 29th February 2004, 12:45 AM   #8
EC8010 is offline EC8010  United Kingdom
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Hi-Fi News do one.
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Old 29th February 2004, 05:14 PM   #9
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Originally posted by EC8010
Hi-Fi News do one.

oh would that be the 'The HFNRR Test Record HFN001' ?!
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Old 29th February 2004, 10:56 PM   #10
EC8010 is offline EC8010  United Kingdom
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That's the one.
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