DOLBY MODEL 363

CONSOLE LEVEL REFERENCE - Routine in-house alignment
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A:	INITIAL STEPS

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.