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2. OPERATION
Use of the Test Record Type QR 2008.
Spot Frequencies.
Sections 1 and 6 of this record are used for checking the response and the
cross-talk of stereophonic pick-ups at high frequencies. In addition, the play-
back losses may be estimated at each recorded frequency, by comparison
between the results obtained on section 1 and on section 6. Practically, a high-
quality pick-up in good condition shows the same sensitivity on both
sections.
When an appreciable loss in sensitivity is noticed on the inner bands relatively
to the outer bands, this may indicate an oversized stylus tip, or a pick-up
tracking with too great a force.
The following are the exact values of the recorded velocity, which have been
determined with an error smaller than o.5 dB on section 1 and 1 dB on
section 6.
Frequency
SecUon 1
Section 6
cm/s. r.m.s.:
cm/s. r.m.s.:
kHz
A
B
A
B
20
0.52
o.51
o.47
0.34
16
0.58
o.57
o.55
o.40
12.5
0.63
0.63
0.57
0.49
10
0.68
0.68
0.60
0.55
Note: Since the frequency response of pick-ups is often irregular from 10 kHz
to 20 kHz, a continuous frequency sweep should be used for detecting all the
peaks with certainty. This can be obtained from the use of the Gliding Fre-
quency Record Type QR 2009 providing a logarithmic sweep (20 Hz to 20kHz
in 50 seconds) in A, B, A+ B, and A- B modulations as described in the
preceding text. The smoothness of pick-up response may then be checked by
simply viewing an output
meter,
or, for more accurate frequency response
determination, use can be made of the automatic recording method outlined
on p's 17-19.
1 kHz Reference Tones.
Section 2 is intended for measuring and adjusting the sensitivity and the
cross-talk of stereophonic pick-ups at 1 kHz. Band 3 may also be used for
monophonic pick-ups. (The other bands would be damaged if tracked by a
monophonic pick-up).
The duration of each band is one minute. The nominal calibration value
given on the label is exact within
.±
o.5 dB and the recorded cross-talk is
more than 40 dB below the modulation level.
100 Hz Tracking Test (Compliance Measurements).
This test is made by means of section 3 in lateral modulation and section 4 in
vertical modulation. It consists in determining the tracking possibilities of the
stylus by tracing bands of increasing modulation amplitude. With a few grams
28
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