Limiter Switch; Mode Selector - uher SG 631 Logic Operating Instructions Manual

distortion and leads to playback that sounds too shrill and distorted.
The maximal harmonic distortion permissible is 3% and is reached when
the level meter reads 0 dB with the machine set for full record level
(using DIN reference tape). With the maximal record level above 0 dB,
distortion rises far above 3% and rapidly sinks to 1% or less with the
maximal record level below 0 dB.
Each level registering system is equipped with an illuminated indicator
that functions when the peak limiter is switched in circuit (see also sec.
3.5). Although the function indicators of the peak limiter are signalled
parallel to the level indicators, it is possible that with the limiter in-circuit
its. function indicators may light up at brief signal peaks even if the level
meter does not yet register 0 dB - because the level indicating systems
are slightly sluggish due to the mass that must be moved. When setting
the record level without using the limiter, however, this effect has no
influence upon the quality of the recording as the response time of the
level meter is sufficiently brief. (Even the light exposure meters used in
commercial sound studios are "much" slower than the illuminated
function indicators which operate inertialessly.)
Aside from optical control by means of the record level meter, an
acoustical check may be made during record with the aid of the moni-
tor switch (see sec. 3.7). Even during playback the two separate indi-
cator systems of the level meter register the peak values of the sig-
nals recorded on the tape.
3.5 LIMITER Switch ®
The LIMITER button catches in down-position and switches on the peak-
limiting circuit that, when the record level is too high (pointer in red
field of meter), reduces the record signal to a manageable level for the
40
duration of the overloading. The degree of overloading is shown on the
level meter while the two function indicators, located next to their re-
spective level indicating system, reflect the functioning of the limiter by
lighting up for a relatively long or short period. Optimal record level has
been set when one of the illuminated indicators flickers up only
occasionally. Otherwise the record level must be lowered, using the
appropriate level control. When the limiter switches on and off in rapid
succession due to an incorrect record level setting, it creates a
"pumping" or "breathing" effect that becomes noticeable through a
swelling and receding of the background noise.
Pressing the LIMITER switch ® a second time releases it into its up-
position and switches off the peak level limiting circuit.
3.6 Mode Selector ®
Turning this switch sets the SG 631 LOGIC into MONO, STEREO or
SLIDE operating mode. In quarter-track operation (using Tape Head
Assembly Z 412), switching to MONO 1 position sets the machine for
operation on track 1 or track 4. In half-track operation (using Tape
Head Assembly Z 402) MONO 1 position switches to track 1. Always
use level control © or (3) to set the mono record level that in turn, will
be registered by the upper indicator of the level meter. Similarly, with
the switch in MONO 2 position, track 2 or track 4 will be used in quarter-
track operation and track 2 in half-track operation, with level controls CD
or (3) used for setting the record level. The record level for MONO 2
operation, however, is registered by the lower indicating system of the
level meter. During mono operation the level controls (2) and @ are not
needed and should be faded out.