Vu Meter Circuit; Tone Oscillator; Figure; Tone Oscillator Applications - Shure SR101 Series 2 Operation And Service Manual

If it becomes necessary to use the MIC LEVEL Output
Connector (24) to feed a high-impedance input, use a
matching transformer such as one of the Shure A95 Series
at the high-impedance input.
The output of the program output amplifier is also fed to
the VU Meter (17) circuit.
VU METER CIRCUIT
To allow a wide range of signals to be handled by the
VU Meter (17), a 22 dB VU Meter amplifier is provided. The
output of the program amplifier is fed to the METER SENSI-
TIVITY Control (18) which in turn feeds the VU Meter ampli-
fier and the Meter. The METER SENSITIVITY Control is
calibrated in its maximum counterclockwise position only.
The calibration of this position is internally adjusted at the
factory for +4 dBm at 0 VU across a 600-ohm load on the
program output. The VU Meter amplifier provides the
proper signal, impedance, and level for proper VU Meter
ballistics and calibration. This amplifier also isolates the
Meter from the program output and eliminates the distortion
normally caused by the nonlinearities of VU Meters.
TONE OSCILLATOR
The Console contains a built-in 1 kHz tone oscillator for
set-up and checkout purposes. The TONE OSC LEVEL Con-
trol a-nd ON-OFF Switch (16) injects the 1 kHz tone into the
program mix amplifier. The tone is processed through the
program channel in the same manner as microphone or
auxiliary input signals, except that the reverb system is
by passed.
When using the tone oscillator, calibrate the Console VU
Meter (17) and proceed as follows: With the METER SEN-
SITIVITY Control (18) set to CAL, increase the MASTER
Volume Control (20) and TONE OSC LEVEL Control (16)
until a 0 VU reading is obtained on the VU Meter. A tone
reference level has now been established. The Console
LlNE LEVEL Output (25,27) is now +4 dBm (1.23 volts) and
the MIC LEVEL Output (24) is approximately 4 millivolts.
These reference signals may be used to set up power ampli-
fiers, tape recorders, or other equipment connected to
these outputs (Figure 6A, Page 10). By adjusting the input
level (or volume) controls on the associated equipment, all
the meters in the audio system can be made to "track."
This allows the Console operator to observe the Console
VU Meter (17) to see if all the equipment is in its proper
operating range. This reference tone may also be used to
check out cables and equipment for proper operation.
To check a microphone cable, connect the cable be-
tween the Console MIC INPUT Jack (33) (any channel) and
the MIC LEVEL Output Jack (24) (refer to Figure 6B, Page
10). Connect headphones to the PHONES Jack (8). Release
the PROGRAM MONITOR Switch ( l l ) , and for the channel
being used, depress the MONITOR Switch (12), release the
PROGRAM Switch (13), and set the FREQ EQ Controls (5,7)
to 0, the channel Volume Control (1) to mid-range, and IN-
PUT ATTEN Switch (14) to 0. An audible tone should be
heard through the headphones as the MONITOR Level
Control (10) is increased.
The same process may be used to check out a Console
channel. With a good microphone cable, make the connec-
tions described above. The tone should be heard clearly
through the headphones. If a channel is suspected of poor
quality, i t can be compared with another channel by con-
necting the microphone cable to the second channel with
all controls set in the same manner as the first. By care-
fully noting the level and quality of tone on each channel,
any significant differences can be established.
To check out an auxiliary channel, perform the process
described above, except connect a phone plug to phone
plug cable between the LlNE LEVEL Output Jack (25) and
the AUX. LEVEL Input Jack (32) for the channel (7 or 8)
being checked (Figure 6C, Page 10). Set the MIC/AUX
Switch (14) to AUX and INPUT ATTEN Switch to -30.
The tone oscillator may also be used to provide a check
of cables and equipment connected to the link output. With
the LINK OUT Jack (31) connected to the input of an ex-
ternal equipment, such as a Shure SE30 Gated Com-
pressor1Mixer which in turn feeds a broadcast line, dis-
connect the program output, either at the back of the Con-
sole, power amplifier or speakers (Figure 6D, Page 10).
Turn the METER SENSITIVITY Control (18) to CAL, set the
MASTER Volume Control (20) to 7, and increase the TONE
OSC LEVEL Control (16) for a 0 VU Meter (17) reading.
Slide the MASTER Volume Control down to 0. Under this
set-up condition, the external equipment may now be cali-
brated or checked out without affecting the program output.
After calibrating the external equipment, turn off the tone
oscillator, and return the MASTER to 7. Reconnect the
power amplifier or speakers.
,
M I C ~
ILINE,
,
LINE^
, ,
SR I01 POWER TAPE
AUDIO CONSOLE AMPLIFIER RECORDER
@
MIC L E V E L
1 )
MIC LEVEL
INPUT JACK OUTPUT JACK
SR l O l
AUDIO CONSOLE
0
LlNE L E V E L
INPUT JACK
AUx. LEVEL
n
OUTPUT JACK
SR
1 0 1
AUDIO CONSOLE
I
PHONES JACK
@
POWER A W L
AUX L E V E L
INPUT JACK
I 1
SR lOl
AUDIO CONSOLE
GATED
1
C0E;:SOR
1
I
MIXER
1
FIGURE
6.
TON'E OSCILLATOR APPLICATIONS