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Analog Tape Recorder Alignment and Performance
Verification
Reproduce Mode
LEVEL function with dBu units, with phase displayed in the upper
right display, is most convenient for most adjustments of the reproduce
section ofanalog tape recorders. Ifthere is any doubt which tone is
being played on the reference tape, the phase display may be
temporarily changed to frequency. Bargraph display mode is also
desirable for most adjustments.
The reproduce level controls ofboth channels may be set for the
specified line level output while playing the reference fluxivity section
ofa reference tape.
The reproduce head azimuth may then be adjusted while playing a
high-frequency section of the reference tape (typically 8 kHz to 16
kHz). Azimuth should be adjusted first for a maximum amplitude
indication on both channels, then finally for an average zero degrees
phase shift between the channels. To obtain a bargraph display of
phase, it will be necessary to select PHASE function (-180/+180
degrees) rather than measuring phase in LEVEL function. AVERAGE
phase display mode is preferable to reduce the visible bobble of phase
measurements at high frequencies.
The reproduce treble level (equalization) controls ofboth channels are
then set to produce flat response at a high frequency, typically 10
kHz-14 kHz. Many reference tapes, especially at the lower tape
speeds, have the frequency response tones recorded at a level lower
than the reference fluxivity level. In such a case, it is convenient to
change the LEVEL units from dBu to dBr and press the “dBr ZERO”
button to establish the zero dBr reference while playing the mid-band
reference frequency (usually 1 kHz) of the frequency response section
oftones. Then, at the chosen high-frequency tone, the treble level
controls may be set for a zero dBr display.
For a final check of the reproduce frequency response, select
EXTERNAL mode in SWEEP mode. EXTERNAL mode will follow an
increasing-frequency or decreasing-frequency sequence of tones on the
reference tape while ignoring any voice announcements between
tones. IfdBr units are used, the mid-frequency (usually 1 kHz)
5
A
pplications
Applications
Analog Tape Recorder Alignment and Performance Verification
5-2
Portable One Plus Access User's Manual
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