(4) The application of bias current is not an amplitude modulation process as the bias
frequency does not enter the recording or playback process. Since the wavelengths of the bias
frequencies are small, they are not picked up by the playback head.
(5) During playback, the magnetized surface of the tape passes over the gap of the reproduce
head which causes magnetic lines of force to be induced into the core of the head, thus generating a
voltage. This playback voltage is proportional to the rate of change and is therefore, dependent upon
frequency.
(6) Equalization maintains a uniform frequency response in both recording and reproducing
circuits. The playback circuit takes care of low frequency equalization and the record circuits take care
of high frequency equalization. The recording equalization compensates for record head core losses and
self demagnetization of the short wavelength approaching the head gap.
(7) High frequency equalization, sometimes known as preequalization, increases the
amplitude of frequencies above 1000 Hz and obtains a greater signal-to-noise ratio during reproduction.
Low frequency equalization, sometimes known as post-equalization, has an inverse frequency
characteristic to that of the preequalization.
Learning Event 3:
OPERATE REEL-TO-REEL TAPE RECORDER
1.
To operate as reel-to-reel tape recorder follow the following steps:
a. (1)
Check output/input connectors.
(2)
Check external sound source.
(3)
Check power cord for defects.
b. Put on and thread tape through record/playback heads.
CAUTION: DO NOT STRETCH TAPE BY PULLING.
c. Select tape speed that optimizes tape to be used.
d. Check equalization position if not automatically selected.
e. Check and position the record/safety override, (if applicable).
f. Check record channels or format (mono or stereo).
g. Input external sound sources (audio console, microphone, or turntable).
h. Set record level at 0db or 100% VU meter from external sound source.
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