N_Cook wrote in message ...
Arfa Daily wrote in message
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"N_Cook" wrote in message
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Ron wrote in message
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N_Cook wrote:
Ron wrote in message
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N_Cook wrote:
Arfa Daily wrote in message
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"N_Cook" wrote in message
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Set up a sig genny and test him out


Much easier to say the test tape is stretched.
Perhaps perfect pitch testing would only work by playing the likes of
JSB
Tocatta and Fugue in D major, not pure tones

How come I cannot google the rpm of an audio cassette capstan? A
calibrated
strobe and tipex mark on the capstan periphery should give a definite
answer
(assuming the spindle is clean and not worn).
It should be determinable from tape speed of 1 7/8 in per sec and
spindle
diameter, that is about 1.9mm, but what should it be to 0.1 percent
accuracy?



The rotational speed of a cassette capstan is not a fixed given. The
diameter of capstans vary from machine to machine, and the correct speed
of
tape transport is then a function of how fast you drive the capstan
round.
The reference in my strobe tape, is indeed the mains. I have been using
this
tape for many many years, and I have file://never// had anyone complain
that the
speed of their machine is off, after I have used it to set one up. Konig
must think that the mains is a good enough reference, otherwise, there
would
be no point in them marketing the tape for the purpose of setting up
speed.
Exception to this. As Ron said, very occasionally, when an owner has
recorded tapes when the machine was running at the 'wrong' speed ...

Arfa

Arfa



I've since found 2 capstan spindles of 2.4mm diameterm so no fixed
specification for cassette tape dynamics.

Another possibility as a test tape - record some constant tone, any f, on
a
few minutes of tape, pull out a long length and pass a magnet over two
parts
a measured distance apart. retract, and then time the interval between
dips
in play mode


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