Nagra 4.2 Portable Analogue Audio Instructions Manual

The Nagra 4.2 fitted with a QSLI can be used to measure the playback pilot signal. 0.85 V 
corresponds to a meter deflection of 1 V on the scale calibrated from 0 to 2 V and normally used to 
measure the voltage per cell of the batteries. 1.7 V corresponds to full scale deflection. 
PILOT CONNECTORS 
 
On the Nagra 4.2, the pilot playback signal is to be found on the Power Pack connector (48), which 
is a 6 pin Tuchel socket, located on the right-hand side of the recorder.  
Pin No 2 is connected to the...

6.0 BASIC THEORY 
 
CONTROL OF THE INPUT SENSITIVITY (MODULATION),DYNAMIC RANGE, SIGNAL-TO-
NOISE RATIO, DECIBELS 
 
The dynamic range is the ratio between the loudest and softest sound levels. The dynamic range is 
large for a symphony orchestra compared to that of an announcer reading a news bulletin. 
The signal-to-noise ratio is related to the dynamic range. It is important that the softest sound level 
to be recorded is still considerably stronger than the noise. Thus, sound with a large dynamic...

be drowned in the noise of the auditorium. On the other hand, a suspense scene permits the use of 
very low sound levels. 
Generally, for dialogue an effect can be obtained not by the absolute level of the sound but by the 
contrast. A burst of sound will be much more effective if it is preceded by a passage at a moderate 
level. This trick is well known amongst cinema mixers -the level is lowered before a forte. 
 
WHEN SHOULD COMPRESSION BE DONE? 
 
A) Recordings indented to be transferred on to a...

used, not having a sufficiently quiet playback chain, it may be desirable to increase the 
input sensitivity above 80 dB. On the other hand, the problem is completely different if 
the tape produced should be used without reworking. In this case, it is necessary to 
compress according to the needs even if the noise level of the microphone 
considerably exceeds that of the tape. For these applications, there is a special range 
of high gain amplifiers available (see section 5). 
 
5.3. INTERFERENCE 
 
To...

 
MAGNETIC INDUCTION 
 
Certain microphones are sensitive to magnetic fields and they should never be placed close to any 
motor, or transformer etc. The cables being double and twisted, means that voltages induced 
should cancel one another, whether the input is symmetrical or not. It is essential, of course, that 
the microphone should be floating, that is to say, that neither of its output wires should be grounded 
(except in the case where the shielding should be connected to the shielding of the...

MAGNETIC HEADS 
 
There are four tape heads on the NAGRA 4.2, these being ERASE, RECORD, PILOT and 
PLAYBACK (see CONTROLS at the front of this manual for their location). 
Contact between the magnetic head and the tape must be perfect. Some tapes leave deposits on 
the heads. Fortunately, the deposits are clearly visible. A dirty playback head gives a muffled 
sound, lacking high frequencies. If the high frequencies come and go rapidly (one to ten times per 
second), the azimuth needs adjusting. A dirty...

Secondary Maxima 
 
If the misalignment of the azimuth is continued at the same time as observing the playback of a high 
frequency signal, it can be seen that after having passed by a minimum, the signal will increase 
again to pass by another secondary maximum. 
If the principal maximum corresponding to the correct angle applies equally to all frequencies, the 
secondary maximum applies only to one frequency, which is fixed for the particular conditions. If 
this frequency changes, the position of the...

 
High Frequency Pre-emphasis 
 
The signal-to-noise ratio of the magnetic tape is perhaps the least satisfactory of its characteristics. 
Great efforts have been made to improve this defect. It is possible to imagine, for example, a tape 
recorder, which sends to the recording head a current, which is proportional to the input signal, 
independent of the frequency (recording at constant current). 
Experience shows that the tape becomes saturated for a given current in the recording head 
irrespective of...

 
Practical Conclusions 
 
The result is: 
a) It is possible to modify the pre-emphasis, within certain limits, by adjusting the bias 
level but still remaining within the limits of the standards. 
b) To record sounds particularly rich in high frequencies, it is possible that the use of 
tapes, which permit high recording level of the high frequencies, could give better 
results. 
c) It is necessary to determine which link in the chain gives the greatest pre-emphasis. 
If all links pre-emphasize to the...

7.0 CALIBRATION AND CARE 
 
HEIGHT OF THE NEOPILOT HEAD 
 
The middle head of the Nagra 4.2 is used to record and playback the pilot signal. Its azimuth is not 
critical, but its height should be correct. The cam of this head does not vary the angle, but only its 
height. Before adjusting the azimuth, check and adjust (if need be) this head. Adjust the height so 
that the tape is exactly in the middle of the head. The eye is sufficiently accurate for this adjustment. 
 
AZIMUTH ADJUSTMENT OF THE PLAYBACK...