The following alignment steps involve sending 1 kHz tone from the
console at Dolby level. In many studios this will be the normal studio
line level (for example, 0 VU).
1. Remove the Model 363 from the signal path by pressing the
Bypass button for each channel.
2. Align the recorder to "in-house" standards, and check that
the recording and console meters agree, or bear a known
fixed relationship.
3. Restore the Model 363 unit to the signal path by releasing
the Bypass buttons and set the SR/off/A switches on each
channel to the center off position.
B: RECORD ALIGNMENT
4. Press Set-up button, and set the rec/play switches on the
Model 363 to the rec position (red LEDs on).
5. Send a 1 kHz test tone at Dolby level (e.g., 0 VU) from the
console to the Model 363.
6. Place the recorder in record, line in, or E-to-E.
7. Adjust the rec in trimmers for Dolby level on the
calibration displays (equal brightness of the green LEDs).
8. Adjust the rec out trimmers on the Model 363 for the
correct reading (e.g., 0 VU) on the tape recorder meters.
As a quick check, you may switch the Model 363 in and out
of Bypass at this point and make sure the tape recorder
meters don't change.
C. PLAYBACK ALIGNMENT
9. Switch console meters to read the return signal from the
tape recorder.
10. Set the rec/play switches on the Model 363 to play (green
LEDs on) and adjust the play in trimmers for Dolby level
on the calibration displays (equal brightness of the green
LEDs).
11. Adjust play out trimmers on the Model 363 for Dolby level
(e.g., 0 VU) on the console meters. As a quick check, you
may switch the Model 363 in and out of Bypass at this
point and make sure the console meters don't change.
12. Release the Set-up button, and make sure the unit is out
of Bypass.
The alignment is now complete.
D: PREPARING FOR A RECORDING
13. Select A or SR on the individual 3-position switches as
appropriate.
14. Record a section of Dolby tone or noise on tape by putting
the recorder into record and pressing the Set-up button on
the Model 363 unit. (Remember that Dolby noise is recorded
on tape at -15 dB below Dolby level (e.g., 0 VU), and so
will read low on console and recorder meters. However,
this level difference is automatically compensated in the
Model 363 calibration display when Set-up is selected.)
Under these conditions, when using Dolby SR, the Cat. No.
300 or the Cat. No. 350 modules will go into the Auto
Compare mode. Auto Compare provides the user with an
accurate audible verification that both the tape recorder
frequency response and the calibration levels are set
properly regardless of the indication shown on the tape
recorder meters and Dolby calibration displays. Listen for
level differences between the pink noise signal coming
from the output of the tape and internal Dolby noise
generator in the Auto Compare mode. The two LEDs on the
front of the Cat. No. 300 and Cat. No. 350 modules
indicate whether the monitors are receiving the internal
reference signal (red LED) or the Dolby noise from the
tape recorder (green LED). The alignment procedure is
correct when the levels between the tape reference levels
audibly match.
Note: Dolby level on tape will now have a fixed flux level
which may be compared with the magnetic reference tape
used for the recorder alignment: e.g., "Dolby Level is +4
dB above 185 nWb/m."
15. It is possible that the level of Dolby noise or Dolby
tone recorded on the tape in this last step will produce a
slightly different reading on the calibration display from
that observed in step (10) above. This is due to the
tolerance of many parts of the complete audio chain, the
accuracy to which the recorder calibration adjustments can
be made (particularly if automatic setting of these
controls is used), and the agreement between meters or
displays in the console, recorder and the Model 363. If a
small difference is observed (as evidenced by the two
green LEDs on the Model 363 not being equally bright), we
recommend that the rec out trimmers on the Model 363 be
slightly adjusted to compensate for this build-up of
tolerances.
