Cassette tape speed adjustment

of

definite

using

complain

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be

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using

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3 of them made on the same batch of tape and on the same machine but more than 15 years ago. As they are all stored in the same environment they could theoretically all have chemically degraded/stretched to the same degree. I'm trying to find some process that gives an independent verification that does not require a know good machine. eg quartz controlled (so low tens ppm) f-meter coupled strobe fed to rotating capstan if diameter/s of the spindles are manufactured to specific dimensions of precisely known tolerances. Perhaps 1.9 +/- 0.002 mm and 2.4 +/- 0.002mm say, no such data found googling. I can only measure to +/-0.02 mm and no slip gauges for absolute calibration. +/-2 in 200 or so, is not accurate enough

"N_Cook" wrote in news:hft7vv$nsr$ snipped-for-privacy@news.eternal-september.org:

Suggestion:

Google for guitar tuning meter

There are meters available for ~20 bux and even some 'on line' meters.

Record a known good 'string note' frequency and use it for your standard. Should get you close enough for any audiophile's ears

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bz    	73 de N5BZ k

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an 
infinite set.

round.

a

parts

dips

You are assuming that if the capstan rotates at the correct RPM , that the tape speed will be correct. The proper way to do this is to measure the playback frequency of the tape which gives you the tape speed. Obviuosly, the accuracy of the test tape, the accuracy of the counter, etc all come into play to add errors. The industry standard is to use a wow and flutter meter in conjunction with a test tape. The test tape is recorded at 3000hz on a reel to reel recorder and then loaded into a cassette shell because there is no cassette recorder on earth that can produce a test tape with the

10x or 5x accuracy needed as a standard. Wow and flutter meters are basically frequency meters. They are like guitar tuners, but the output is weighted to breakup the frequency variations into long and short term changes. If you can find a calibrated wow and flutter meter with a test tape, I'm sure the cost will far exceed what your client is willing to pay. The technology is at least 20 years old, and there really isn't a market for anyone to make this equipment available. The bottom line -------- Even if you go through the time and expense to do this right, what good is it if your client's tapes are not recorded at the same precision? You and he will be better off if you add a front panel speed control so that he can dial in the speed to match the tape being played

speed

Konig

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I found a large quantity of salvaged capstans+spindles.

26 off on my mike (rather than callipers before) measure 1.99 +/-0.01 of reading accuracy and 2 nearer 2.00 5 off measure 1.79mm 1 at 2.19mm 9 measure 2.49mm

So I will give a few to my engineer mate and ask him what they measure and the temperature at the time.

The machine in question uses 2.49. Assuming it is actually 2.5mm then doing the maths and strobing with quartz f-meter calibrated strobe then my test tapes are 0.4 percent out from calculation via 15/8 ips etc. spindle rotation speed of 6.05 rev per second with an error of about 0.4 percent , needs longer gate time or repeating more times to bring that accuracy up (rounding errors? so probably longer gate time required than my meter has). If 2.49 diameter then 0.6 percent out

This is becoming bizarre ... Konig strobe test tape. Good enough. End of. If not good enough for your very discerning customer with "perfect pitch", then it is he who is at fault, for believing that the cassette medium is sufficiently good to serve his needs, and you for allowing him to continue believing this ...

Arfa

You should be able to get a very accurate reading of the diameter of the capstan with one of those cheap digital verniers.

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    W
  . | ,. w ,   "Some people are alive only because
   \|/  \|/     it is illegal to kill them."    Perna condita delenda est
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440Hz is the usual reference tone.

--
    W
  . | ,. w ,   "Some people are alive only because
   \|/  \|/     it is illegal to kill them."    Perna condita delenda est
---^----^---------------------------------------------------------------

JSB

calibrated

answer

spindle

The mechanical structure of a digital is the same as a vernier or DTI one . With the same susceptibility for the plate-form arms to deflect from unrelieved manufacturing stresses , let alone abuse. Compared to micrometers which have a more rigid , less internally stressed, rod like basic structure. Just because you can read to greater accuracy does not necessarily mean better measurement in absolute terms

Sure, but you can zero out a digital vernier each time you use it, which helps. And for your purpose one should be plenty accurate enough.

--
    W
  . | ,. w ,   "Some people are alive only because
   \|/  \|/     it is illegal to kill them."    Perna condita delenda est
---^----^---------------------------------------------------------------