Nagra PORTABLE ANALOGUE AUDIO TAPE RECORDER Instruction Manual page 5

Theory .......................................................................................................................... 36
Variation of the High Frequency Level with Azimuth Error................................................. 36
Secondary Maxima ........................................................................................................ 37
Orientation of the Heads on the Nagra 4.2....................................................................... 37
Bias .............................................................................................................................. 37
Effect of Bias Signal Amplitude on the Recording............................................................. 37
High Frequency Pre-emphasis........................................................................................ 38
Relation between Pre-emphasis and Bias ....................................................................... 38
Practical Conclusions ..................................................................................................... 39
DETERMINATION OF THE BIAS LEVEL ............................................................................ 39
Tape Characteristics ...................................................................................................... 39
General Procedure......................................................................................................... 39
Variation of k ................................................................................................................. 39
7.0 CALIBRATION AND CARE .............................................................................................. 40
HEIGHT OF THE NEOPILOT HEAD................................................................................... 40
AZIMUTH ADJUSTMENT OF THE PLAYBACK HEAD. ........................................................ 40
AZIMUTH ADJUSTMENT OF THE RECORDING HEAD. ..................................................... 40
6.2. MAINTENANCE OF THE MOTOR COMMUTATOR ...................................................... 41
Remedy for Motor Noise................................................................................................. 41
Metalization of the Commutator....................................................................................... 41
Cleaning of the Commutator ........................................................................................... 41
6.3. LUBRICATION............................................................................................................ 42
8.0 MICROPHONES ............................................................................................................. 43
INTRODUCTION ............................................................................................................... 43
5.2. THE MICROPHONES ................................................................................................. 43
MICROPHONE CHARACTERISTICS ................................................................................. 43
Sensitivity...................................................................................................................... 43
Frequency Response ..................................................................................................... 43
Coloration. Transient Reproduction. Reverberation .......................................................... 43
Use at High Sound Levels .............................................................................................. 44
Signal-to-noise Ratio ...................................................................................................... 44
Directional Characteristics .............................................................................................. 44
S C
ECONDARY HARACTERISTICS
PRACTICAL ADVICE ON THE CHOICE OF THE MICROPHONES ...................................... 45
Omni-directional Microphones (pressure) ........................................................................ 45
Bi directional Microphones (velocity) ............................................................................... 45
Switchable Microphones ................................................................................................. 46
Choice between Condenser or Dynamic Microphones ...................................................... 46
5.6. MAXIMUM GAIN OF THE RECORDING CHAIN OR SENSITIVITY OF THE
MICROPHONE INPUTS .................................................................................................... 46
Nagra 4.2 Preamplifiers .................................................................................................. 46
Changing the Plug-in Preamplifiers ................................................................................. 47
Plug-in Preamplifiers ...................................................................................................... 47
"STATIC 5" Code: QPM-3-5............................................................................................ 47
"HIGH LEVEL LINE" Code: QPM-6 ................................................................................. 47
"UNIVERSAL" Code: QPAUT & QPUT ............................................................................ 47
SPECIAL PLUG-IN PREAMPLIFIERS ................................................................................ 48
Filtering Versions of the QPSE........................................................................................ 48
Cable Preamplifiers ........................................................................................................ 48
LOW FREQUENCY ROLL-OFF ATTENUATORS ................................................................ 48
Why Filter? .................................................................................................................... 48
When should Filtering be done? ...................................................................................... 49
Conclusion .................................................................................................................... 49
METERING .......................................................................................................................... 50
MODULOMETER OR V.U. METER .................................................................................... 50
MODULOMETER .............................................................................................................. 50
V.U. METER...................................................................................................................... 50
CONCLUSIONS ................................................................................................................ 51
REMARKS ON THE CALIBRATION ................................................................................... 51
9.0 SPECIFICATIONS .......................................................................................................... 52
R D
ELATED TO IRECTIONAL
C ............................. 45
HARACTERISTICS