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2. OPERATION
Piezoelectric
Fig. 2.12. Different oscilloscope figures of a tracking test with piezo-electric
and electrodynamic pick-ups.
downward force, ordinary high quality pick-ups will not be able to track the
bands of largest amplitude, and the stylus loses contact with the groove. This
results in a distorted output which can be noticed aurally or on an oscillo-
scope. Fig. 2.12. By adjusting the applied force in order to barely track one of
the bands the compliance of the stylus system may be calculated by the follow-
ing formula:
C=~
F
where C is the compliance, A is the peak amplitude in em of the last correctly
tracked
band,
and F is the applied force in dynes (dynes are obtained by
multiplying grams by 981).
The following are the exact values of the recorded amplitude, which differ
slightly from the nominal values, and have been measured within
±
o.5 dB:
Band
Nominal Value
Section 3 (lateral)
Section 4 (vertical)
(em peak)
exact value in em peak
exact value in em peak
1
0.001
0.00086
0.00083
2
0.002
0.0018
0.0018
3
0.003
0.0028
0.0028
4
0.004
0.00376
0.0038
5
0.00·
5
0.0047
0.00495
Tone Arm Resonance.
The logarithmic frequency sweeps of section 5 covering the range 10 Hz-
100 Hz are intended for investigation of the pick-ups at very low frequencies,
allowing the plotting of tone arme resonance curves. Four different stereo-
phonic modulations are available: A, B, A
+
B, and A - B. The A
+
B band
may also be used for monophonic pick-ups.
29
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