Nagra PORTABLE ANALOGUE AUDIO TAPE RECORDER Instruction Manual - page 46

Switchable Microphones 

Certain condenser microphones can function as omni-, bi- or unidirectional by means of a simple 

switching. 

Choice between Condenser or Dynamic Microphone s 

Condenser microphones give the best fidelity. In particular their reproduction of transient noises is 

excellent, but they cost more and are less robust than the dynamic microphones. They require a 

power supply either from the Nagra or from an auxiliary device. 

They exist in two types: D.C. polarization and H.F. polarization. The performance and reliability 

depend, in the long run, more on the competence of the manufacturer than on the chosen system. 

Dynamic microphones are reputed to be more robust, but here again, the technological level of the 

manufacturer seems to be more important than the chosen system. The coloration which certain 

moving coil microphones give can be used to advantage.  

5.6. MAXIMUM GAIN OF THE RECORDING CHAIN OR SENSITIVITY OF THE MICROPHONE 

INPUTS 

In general, the Nagra 4.2 is used to record the "master tape", that is to say, the original from which 

copies are made. In consequence the recording level should, in certain cases, be lower than normal 

so that correction can be made during transfer. 

In the case where a loud sound is recorded, the noise level is that of the tape itself, the microphone 

noise level being lower, due to the reduced gain of the recording chain. In these conditions, it may 

be useful to use a high recording level so that the signal-to-noise ratio is as high as possible. In the 

case where the sound level is very low, the gain has to be increased to a point where the 

microphone/preamplifier combination noise level becomes greater than the tape noise level. Under 

these conditions, no advantage is obtained by recording at a high level. 

If the sound to be recorded is at a still lower level, it is better to adjust the gain to the point where 

the noise from the microphone clearly predominates, and under record the tape. In any case, an 

increase of gain will not improve the signal-to-noise ratio, whereas the inconveniences of high level 

recording will subsist: distortion and a reduced safety margin in the case of a sudden increase of 

sound level. 

For these reasons, the sensitivity of the microphone preamplifiers has been limited under normal 

conditions to 0.2 mV into 200 Ohm to enable a recording to be made at 0 dB. 

However, there exist applications where a Nagra must be used to obtain a tape recorded at nominal 

level to avoid having to adjust the playback level. In these cases, it is probably better to use a higher 

gain, and there are available increased gain preamplifiers. They are recognized by the figure 

following the letter X in the code, which indicates the number of decibels by which the gain has 

been increased. 

Nagra 4.2 Preamplifiers 

There are three types of microphone preamplifiers: 

a) 

plug-in preamplifiers which are fixed inside the Nagra 4.2, but are easily 

interchangeable. 

b) 

cable preamplifiers which are placed close to the microphone and which feed a plug-in 

preamplifier designed for condenser microphones. 

c) 

auxiliary preamplifiers which transform the line input into a third microphone input. 

These accessories are placed between cable connecting input No 3 and  the 

microphone.