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3.22 Stroboscope Discs 50 Hz @ and 60 Hz @
The 50 Hz stroboscope disc is incorporated into the tape tension sen-
sor of the supply reel while the 60 Hz disc is on the sensor of the
take-up reel. Under artificial light and at a mains frequency of 50 Hz,
the line segments on the left stroboscope disc will appear to be standing
still if tape motion is at the exact speed of 7
will seem to rotate slowly if the tape speed is slightly inaccurate. The
same holds true for the stroboscope disc on the right tape tension
sensor (of the take-up reel) at 60 Hz and under artificial light.
The stroboscope is a highly precise indicator that permits recognition
of the very least deviation from the nominal tape speed. Very slight
stroboscopic deviations are, therefore, of no practical significance.
When the stroboscope seems to turn anti-clockwise, tape speed is toe
high; when it seems to turn clockwise, the speed is low.
3.23 Find Speed Ajuster (7Vz ips) / Pitch Control @
When the tape speed selector set to 19 cm/s, this control may be used
to adjust the speed by approximately +4%. The pitch of the recording will
thus also be altered by ±4%. In general, it is necessary and advisable to
alter the tape speed only when playing tapes recorded on other machines
or when, for example, the pitch of a recording made with your SG 631
must be adjusted to that of a musical instrument. As a matter of prin-
ciple, of course, recordings on your SG 631 should be made at the
nominal speed. Consequently, after altering the tape speed, do not for-
get to reset the speed to exactly 19 cm/s (7
scope to assure accuracy. Fine speed adjustment should be made only
after the machine has warmed up (allow at least 10 minutes after switch-
ing the power on) so that any slight drift during the warming-up period
44
may be taken into consideration. With the fine control in "0" position,
fc
the 7
German DIN standard 45500.
3.24 Reel-Size Switch
When using reels up to 7" in size, press this pushbutton into its
lower, locking position. The green function indicator "5-7" will light up.
If two IOV2" reels are used, the switch should be set to "IOV2". It will
then be in its up-position and the green function indicator "IOV2" will
light up. (Always use two reels of the same size!)
4. Record Operation for True Audio
Enthusiasts
4.1 Input and Output Connections
2.1, 2.5 and 2.6 (or 2.11 and 2.12). If, while seeking the correct setting
for maximal record level of an input source connected to the RADIO
input, it is found that the level controls (3) and 0 must be kept just
barely opened in the lowest part of the scale range, check whether con-
necting the input source to the PHONO input would lead to better
recording conditions. Contact assignment and input impedances would
have to be taken into consideration, and a crossover adapter (pin 1 is
cross-connected with pin 3, pin 4 with pin 5), obtainable from your audio
dealer, would have to be inserted into the PHONO socket. The proce-
dure is conversely similar when input sources are connected to the
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