Nagra PORTABLE ANALOGUE AUDIO TAPE RECORDER Instruction Manual - page 33

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 disc. The signal-to-noise ratio of the 

modern disc is excellent, but it is important that the noise level of the tape should not 

be transferred. If a compression is decided upon, it should be done at the time of the 

original recording, otherwise an increase of the pianissimo will also increase the sound 

level of the tape noise. It is difficult to use the complete dynamic range of the recorder 

without the risk of exceeding the maximum level when a  fortissimo is produced. For 

this reason, it is prudent to work simultaneously with two or three tape recorders in 

parallel, but whose input sensitivities are varied by a few decibels. The tape which has 

been recorded at the highest level, but without the maximum level having been 

exceeded, will be the one used for playback. Also, it will be possible to choose, during 

editing, certain passages from tape No 1 and others from tape No 2 etc. 

B) 

Recordings intended for radio transmission. The compression should be done at the 

time of recording. For reporting ect., the use of an automatic level control can be of 

interest. It gives a tendency to always obtain the maximum level, that is, it compresses 

to a large degree. 

C) 

Recording intended for radio transmission to be reworked in a studio. In this case, two 

methods are possible. The signal-to-noise ratio of the Nagra 4.2 is greater than that of 

the radio transmission; therefore it is not essential to use the complete dynamic range 

of the Nagra. It is possible, to adjust the sensitivity in such a way that the fortissimo 

reaches 0 dB. As the maximum level of the Nagra is +4 dB, there is, therefore, a safety 

margin. The compression can be done according to the needs in the studio whilst 

working on the final recording. 

D) 

Cinema and Television, where the sound is always edited during the final mixing. The 

important thing is to preserve the maximum amount of sound information. The very 

large dynamic range of the Nagra 4.2 allows the fortissimo to be recorded at a level 

below the maximum, avoiding accidental distortion due to a burst of sound. In many 

cases, it may even be desirable to work on automatic level control, but this decision 

depends on the circumstances, and those who have to make the decision need no 

advice. The problem of microphone and preamplifier noise should be considered. Very 

often, the background noise of the recording is not dominated by that of the tape, but 

by that of the microphone. In these cases, it is useless to increase the sensitivity 

during recording. The general level will be greater but so will that of the noise level. 

Nothing is gained in information, but the risk of saturation by a loud sound will be 

uselessly increased. 

The "point above which it is useless to go" is around the 80 dB mark on the 

potentiometer scales. This can be easily verified: replace the microphone by a 

resistance equal to the nominal impedance of the microphone to ensure that ambient 

noise does not upset the measurement. Record and playback simultaneously ("Line 

and Phones" switch on "Tape"), listen with good headphones and increase the 

microphone sensitivity. Even with the potentiometer in the extreme left hand position a 

noise will be heard. Turn the potentiometer clockwise. Up to 90 dB on the scale, the 

noise level will hardly vary. As from 80 dB, the noise of the resistance replacing the 

microphone and of the preamplifier becomes dominant. This point varies according to 

the quality of the tape used. With a poor tape it can be 78 dB, whereas with an 

excellent tape 82  dB. It is also to be supposed that the playback will be made on a 

Nagra 4.2 or on a machine with similar performance. If an ordinary machine should be