Nagra PORTABLE ANALOGUE AUDIO TAPE RECORDER Instruction Manual - page 51
On the other hand, for a transmission, which is wholly musical, the range of the
transmitter tends not to be used to its full advantage with a VU meter.
b)
The VU meter has a scale, which is not logarithmic. For the needle to move, it is
necessary that the level exceed -20 dB. This causes the operator to compress greater
than is necessary, that is to increase the level of the pianissimo. This reduces the
quality of a musical transmission while increasing the range. On the other hand, it is
favorable if the listener is in a noisy ambience, such a car or a cinema hall.
CONCLUSIONS
The problem to be resolved is to know if the Nagra should be fitted with a modulometer or a VU
meter. The modulometer allows the use of the full dynamic range of the recorder whether for noise,
speech or music. The balance of the sound can, in any case, be achieved during the transfer.
If a mixed transmission of words and music should be recorded on the Nagra and transmitted as
recorded, the operator can simply modulate the speech to +2 dB or even +4 dB, and the limiter
takes charge of any peaks, and the music to 0 or even -2dB.
The VU meter is only justified for radio corporations where it is standardized because of operational
habit.
REMARKS ON THE CALIBRATION
The term "nominal recording level" is that which is considered as the maximum level by habit. The
word "nominal" has been used and not "maximum" as, in the case of the Nagra 4.2, this level can
be exceeded by 4 dB due to a special recording process.
The indication of 0 dB on the modulometer corresponds to the nominal level. It is not measurable
with a VU meter for the needle will exceed full scale deflection, the sensitivity of the VU meter
having been increased by 10 dB to compensate for the slowness of its response.
Thus a signal of -10 dB, that is 10 dB below nominal level, produces on a VU meter an indication of
0 VU whereas on the modulometer an indication of -10 dB is obtained. The calibration generator of
the Nagra 4.2 gives a signal of about -10 dB. This corresponds to 0 VU on a VU meter.