Dorrough 10-A, Instruction Manual

Page 1: ...uction Manual RELATIVE LOUDNESS TO PEAK MODULATION MODEL 40 B LOUDNESS MONITOR MODEL 40 A 25 22 20 18 16 14 12 10 8 6 4 2 0 2 4 6 8 10 12 14 NORMAL PEAK RANGE NORMAL RANGE PERSISTENCE dB dB dB dB 36 1 6 34 32 30 28 26 24 22 20 18 16 14 12 10 8 6 4 2 0 1 2 3 2 2 5 3 2 4 5 6 3 8 10 12 16 20 25 32 40 50 63 80 100 125 MODULATION MODULATION Also covers Models 10 A B 12 A B 20 A B and 21 A B ...

Page 2: ...rily chosen rise time of 300 µs engineers have developed certain compensations such as riding dialogue 3 to 5 dB below music to control the peak levels in an attempt to attain consistent listening levels The standard broadcast practice is to allow for a crest factor of at least 10 dB to cover the peak excursions of the waveform that the VU meter is too slow to indicate The VU meter was never inten...

Page 3: ... ride levels in a manner such that all program material can be adjusted for equal perceived loudness while protecting the peak of the waveform Now one meter gives you more complete and more usable information than any combination of peak hold VU and PPM indicators The DORROUGH Loudness Monitor integrates on the same scale two ballistics showing the relationship between the average and the peak It ...

Page 4: ...u do not see this action make sure the AC line has power and the Power Switch recessed in the back panel is in the ON up poasition or test the internal 0 25 A fuse for continuity 2 While observing polarity feed a 1000 Hz sine wave at a standard operat ing level i e 10 4 8 etc into the left input as shown in Fig 1 3 Adjust the input level control Fig 1 on the rear panel for an indication of 0 on th...

Page 5: ...a B Type meter is generally used as a discrete monitor to indicate either a left or right channel However for Sum and Difference monitoring repeat steps 3 and 4 previous page and adjust each input level control for a 6 dB indication on the meter scale for an individual channel This action will result in a proper sum of 0 on the B Type meter scale NOTE Different amplitudes and phase angles between ...

Page 6: ...14 12 10 8 6 4 2 0 2 4 6 8 10 12 14 NORMAL PEAK RANGE NORMAL RANGE PERSISTENCE dB dB 16 250 6 50 3 00 PANEL 40A D LOUDNESS MONITOR MODEL 40 A 25 22 20 18 16 14 12 10 8 6 4 2 0 2 4 6 8 10 12 14 NORMAL PEAK RANGE NORMAL RANGE PERSISTENCE dB dB LOUDNESS MONITOR MODEL 40 A 25 22 20 18 16 14 12 10 8 6 4 2 0 2 4 6 8 10 12 14 NORMAL PEAK RANGE NORMAL RANGE PERSISTENCE dB dB Fig 3 Physical specifications ...

Page 7: ...RANCE BEHIND PANEL CUSTOMER S PANEL 8 562 MODEL 12 A B OPENING CUSTOMER S PANEL single console or panel mount meter dual console or panel mount meter MODEL 20 A B OR 21 A B OPENING console or panel mount meter straight lined LED s 7 900 CUSTOMER S PANEL 8 750 METER CLEARANCE BEHIND PANEL 8 560 METER CLEARANCE BEHIND PANEL 2 00 2 50 METER CLEARANCE BEHIND PANEL 2 00 2 50 METER CLEARANCE BEHIND PANE...

Page 8: ... of WINDOW 2 Insert BEZEL through panel and hold in place by hand 3 Slide WINDOW into BEZEL 4 Center the WINDOW and turn the jacking screws clockwise until BEZEL is pulled snug against the panel 5 Secure the PCB mount to the WINDOW at outboard holes with four screws Fig 6 Installation procedure for mounting a panel mount meter Follow the listed steps while referring to the guide numbers in the ill...

Page 9: ...rogram reference is different than that of 4 dB simple adjustments to some other standard can be made by the following the procedure listed in the Field Alignment section Applications DORROUGH Loudness Monitors can be used in a number of applications as shown in Fig 7 through Fig 13 including Telephone Transmission AM Mono Broadcast Analog Digital Tape Saturation Monitor Sum Difference Monitor Ste...

Page 10: ... Saturation Monitor This interconnect drawing shows an example of monitoring tape saturation by comparing pre and post tape signal levels Once saturation is reached the post tape readings will no longer track increases in pre tape signal levels NOTE This example assumes the tape deck is aligned for unity gain Although a B Type DORROUGH Loudness Monitor is preferred an A Type is acceptable AUDIO FE...

Page 11: ...t Applications An A Type DORROUGH Loudness Monitor can be utilized to verify phase integrity of signal pairs feeding a bank of power amplifiers In addition a B Type DORROUGH Loudness Monitor can be used with bridging resistors to monitor the outputs for any power amplifier failure STL OR CUTTING SYSTEM RIGHT STEREO FEED R L LEFT R L SUM DIFF LOUDNESS MONITOR MODEL 40 A 25 22 20 18 16 14 12 10 8 6 ...

Page 12: ...put of the precision rectifier feeds a split to the PEAK and PERSISTENCE cir cuits Since the desired display is to be logarithmic the signals are fed to corre sponding linear logarithmic converters The outputs of these converters feed the display drivers The driver for the PEAK display is configured as a dot while the driver for the PERSISTENCE display is configured as a bargraph Each of the 40 LE...

Page 13: ...o the meter s left input termi nals see Fig 1 2 Feed a 1000 Hz sine wave at a reference level of 0 dB into the meter 3 Adjust the left input gain control VR 13 so that DS 1 is off and DS 2 3 4 are on 4 Adjust the input signal to 25 dB 5 Adjust the low PERSISTENCE level control VR 44 so only the first LED 25 dB on meter scale at the bottom of the PERSISTENCE scale is illuminated 6 Adjust the low PE...

Page 14: ...14 After both channels have been aligned follow the procedure for setting up the operating level as described in the Initial Set Up section see Installation Once you have completed this procedure re assemble the meter and place the unit back in service Fig 15 Simplified view of key alignment components on Model 40 A 40 B circuit boards VR44 VR48 VR49 VR46 DS2 DS3 DS1 R18 DS4 VR14 VR13 25 dB A 14 d...

Page 15: ... PERSISTENCE level control VR 48 so that the bargraph illuminates LEDs up to and including the 6 dB LED 9 Adjust the high PEAK level control VR 49 until the 6 dB LED brightens NOTE This indicates that both the PEAK and the PERSISTENCE drivers are both providing current to this LED 10 Increase input signal to 14 dB and observe that the 3 dB LED illumi nates NOTE The 3dB LED should indicate drive fr...

Page 16: ...m the factory as a replacement for the standard Power Supply Board for use with a customer s power supply VR49 VR48 VR44 VR46 VR14 VR13 R L L L R R POWER SUPPLY BOARD INTERFACE BOARD CUSTOMER S POWER SUPPLY VR49 VR48 VR44 VR46 VR14 VR13 R L L L R R 15 15 5 DS1 DS2 DS3 DS4 R18 VR49 VR48 VR44 VR46 VR14 VR13 R L SIGNAL BOARD LED DRIVER BOARD 25 dB A 36 dB B 14 dB A 3 dB B 5 dB A 6 dB B 11 dB B 0 dB A...

Page 17: ... A 14 dB A 3 dB B 5 dB A 6 dB B 11 dB B 0 dB A VR49 VR48 VR44 VR46 VR14 VR13 R L VR49 VR48 VR44 VR46 VR14 VR13 R L Fig 17 Simplified view of key alignment components on Model 12 A 12 B circuit boards Refer to Fig 5 and Fig 6 for specific panel mounting instructions Check with the factory on availabilty of an optional Interface Board as a replacement for the standard Power Supply Board for use with...

Page 18: ...BOARD DS2 DS1 DS3 DS4 11 dB B Fig 18 Simplified view of key alignment components on horizontal Model 20 A 20 B or vertical Model 21 A 20 B circuit boards Refer to Fig 5 and Fig 6 for specific panel mounting instructions Check with factory on availabilty of an optional Interface Board as a replacement for the standard Power Supply Board for use with a customer s power supply ...

Page 19: ...18 NOTES ...