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Hints, Tips and Solutions (Do NOT post requests for help here) If you have any useful general hints and tips for vintage technology repair and restoration, please share them here. PLEASE DO NOT POST REQUESTS FOR HELP HERE!

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Old 18th Dec 2018, 4:37 pm   #21
Heatercathodeshort
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Default Re: Nice Way To Measure Turntable Speed

I have a copy of 'Cockleshell Heroes' Royal Marines School of Music, HMV 78 number B. 10938. It's a fabulous recording but alas it has been recorded 'fast' to get it all onto a 10" 78. If played at around 72 it sound 100% correct.

How accurate were the original recordings I wonder. John.
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Old 21st Dec 2018, 10:33 pm   #22
Nymrod121
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Default Re: Nice Way To Measure Turntable Speed

I've been working on re-modifying a Trio turntable that Nickthedentist passed on to me a while back. A simple modification:

I soldered 233k resistors in parallel to give 16.5k; connecting this combination in series with the servo feedback loop results in the speed being bang on. This was done initially by connecting a ten-turn 20k pot and adjusting it to get a zero-beat when using a 1kHz test tone record track against my smartphone tone generator app set to 1kHz. I disconnected then measured the pot with my Fluke DMM hence the 16.5k value.

The cartridge/stylus combination works perfectly - I set the tracking at 3 grams & tried some of my grandparents' records earlier. At this point - captainpugwash: take a bow, mate

Although very crackly/scratchy, Enrico Caruso singing 'O Sole Mio' is really rather good (especially for a recording that's around 100 years old) - and for me, that's saying something as I've never really been very keen on operatic stuff!

Guy
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Old 24th Dec 2018, 7:05 pm   #23
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Default Re: Nice Way To Measure Turntable Speed

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Originally Posted by Andrew2 View Post
For showing on TV, aren't feature films sped up by 4% in order to match the 25 Hz frame rate? I assume this speeds up the soundtrack as well? I can't say I've ever heard anyone moan about this.
On the other hand I may be talking through my hat.
This is true - however the reverse is not, it is quite easy to spot a 25 fps made for television film running at 24fps, particularly on orchestral music.
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Old 24th Dec 2018, 8:15 pm   #24
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Default Re: Nice Way To Measure Turntable Speed

Yes, a bit flat (low frequency) is easy to spot, a bit sharp (higher) sounds OK. Most sound studios I have met have the vocals "harmoniser" (frequency shifter) set to +1/2 a tone by default.
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Old 28th Dec 2018, 10:41 am   #25
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Default Re: Nice Way To Measure Turntable Speed

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Originally Posted by Boater Sam View Post
Does it really matter? Does a few % of speed inaccuracy ruin the enjoyment of playing records?
Here here.
Use the strobe marks set in the rim or failing that put a piece of sticky tape on the rim and count how many times it passes you in 1 minute.
Simples. No need for elaborate gizmo's that one does not understand the workings of and just have to trust implicitly.
Trust your own eyes and senses, the term K. I. S. S. comes to mind here.

Mike
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Old 28th Dec 2018, 12:59 pm   #26
stevehertz
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Default Re: Nice Way To Measure Turntable Speed

Quote:
Originally Posted by Nymrod121 View Post
I've been working on re-modifying a Trio turntable that Nickthedentist passed on to me a while back. A simple modification:

The cartridge/stylus combination works perfectly - I set the tracking at 3 grams & tried some of my grandparents' records earlier. At this point - captainpugwash: take a bow, mate
Three grams sounds a bit high. Most hifi cartridges run at 1 to 2g, 2.5g maybe. Saying that, I'm sure there are some that need 3g to track. Might be worth checking the cartridge spec; not saying you're wrong, just seems a tad high to me!
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Old 9th Feb 2019, 8:23 pm   #27
rontech
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Default Re: Nice Way To Measure Turntable Speed

Last year I inherited a load of engineering stuff from a friend. Among the measuring gear was a 4 digit mechanical turns counter, as used for lathework.

I would imagine by connecting a flexible drive cable from the turntable spindle the cumulative revolutions would be dispayed. A good stopwatch should then enable an accurate measurement of speed. I imagine the longer the test period used, the greater the accuracy obtained.
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Old 9th Feb 2019, 9:30 pm   #28
Restoration73
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Default Re: Nice Way To Measure Turntable Speed

Smiths made an industrial tachometer (normally in a wooden box with different types of
coupling) that could measure up to 50,000 rpm in 3 ranges. I use mine rarely.

I remember Leonard Bernstein sued Granada when they screened "West Side Story" at
25 fps, as the agreement to show specified the running time.
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Old 10th Feb 2019, 2:08 am   #29
dave walsh
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Default Re: Nice Way To Measure Turntable Speed

Yes I recall that, in audio terms, it's a 4% tonal difference but few people could actually detect that on transmission-you would need perfect pitch-I never noticed! That's why Broadcasters got few complaints. Leonard was either artistically sensitive or an opportunist but I don't think he needed the money really. Maybe Sidney upset him?

Dave
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Old 10th Feb 2019, 1:38 pm   #30
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Default Re: Nice Way To Measure Turntable Speed

After all these posts, maybe a humble old fashioned stroboscope is the best after all!
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