Shure SR101 Series 2 Operation And Service Manual

SRlOl

Series 2 Audio Console

OPERATION AND SERVICE MANUAL

Manufactured

by

SHURE BROTHERS INC.

222

Hartrey Avenue

Evanston, Illinois

60204

U.S.A.

Copyright 1979, Shure Brothers Inc.
27A1171

(SD)

(95E652)

Printed

in

U.S.A.

SR101 Series 2 Audio Console

SPECIFICATIONS

Equipment Type
Number of

lnput Channels

.

Power Output

. . .

.

Voltage Gain*

Program

. . . .

.

. . . .

All silicon transistor mixerlpre-

Hum and Noise

amplifier (20 Hz-20 kHz)

.

.....

8

.

. . . .

+19

dBm (program line level)

.73

k3 dB MIC input to LlNE

LEVEL out

. . . . .

.

-

125 dBV (equivalent input hum

and noise at full gain)

-

68 dBm output noise (MASTER

Volume Control down)

-

50 dBm output noise (one
channel Volume Control and
MASTER Volume Control up)

50

k3 dB AUX input to LlNE

LEVEL out

Signal to Noise Ratio

23 t3d~

MIC

input

to

MIC

LEVEL

(20 Hz-20 kHz)

.

.

. .

.Typically 81 dB at maximum out-

out

put with one channel Volume
Control and MASTER Volume

Monitor

. .

. . . .

. . .

.78 13 dB MIC input via PRO-

Control at 10 (approximately

GRAM MONITOR to LlNE

60 dB gain)

LEVEL out

65

k3 dB MIC input via PRO-

lnput Attenuation

. . . .

GRAM MONITOR to PHONES
out Input Clipping Level

87

23 dB MIC input via one chan-

at

kHz:

nel MONITOR to LINE LEVEL

MIC Input

. . . .

. .

out

Link

.

. . .

. . . . . . .

.

.38 _t3 dB MIC input to LlNK OUT

(with 600-ohm termination)

30

22

dB LlNK IN to LlNE LEVEL

out

Accessory

. .

. .

. . .

.48 t2 dB MIC input to ACCES-

SORY output (via pins

1-8lIN-

PUTS)

AUX Input

. . . .

. .

43 i.3 dB MIC inputs to ACCES-

SORY output (via pin

91PRO-

GRAM)

Frequency Response

. .

.

13 dB, 20 Hz-20 kHz (150-ohm

source; 600-ohm load)

lnput Sensitivity

. .

. .

. . .

0.4 mV max. for f 4 dBm program
output

Distortion

.

. . . . . . . . .

.

.

Noise

THD less than

1%

at +12 dBm,

Input Common

30 Hz -20 kHz; IM distortion

Mode

Rejection

. . .

.

less than 1% at t12 dBm

.

.O-30 dB (10 dB steps)

.

,315 mV (INPUT ATTEN at 0; Ch.

Volume at 2)

17.5

mV (INPUT ATTEN at 0; Ch.

Volume at 14)

10V (INPUT ATTEN at -30; Ch.

Volume at 2)

0.56V (INPUT ATTEN at -30; Ch.
Volume at 14)

.

.3.15V (INPUT ATTEN at 0; Ch.

Volume at 2)

0.18V (INPUT ATTEN at 0; Ch.
Volume at 14)

IOOV (INPUT ATTEN at -30; Ch.

Volume at 2)

5.6V (INPUT ATTEN at -30; Ch.
Volume at 14)

(300 Hz-20 kHz)

. .

. .

.

-

128 dBV(equiva1ent input noise

LOW-~requency

at full gain)

Equalization

. . .

. . .

-

78 dBm output noise (MASTER

Volume Control down)

-

53 dBm output noise (one

Hig h-Frequency

channel Volume Control and Equalization

. . .

. . .

MASTER Volume Control up)

100 dB min. at 100 Hz (balanced

inputs)

-;I3 dB at 100 Hz with respect to
0 (flat) setting

k12 dB at 10 kHz with respect to

0 (flat) setting

'Measurement conditions: MIC input through

150

ohms, AUX input through

33

kilohms LlNK IN through

600

ohms PROGRAM LlNE LEVEL and MONITOR

LlNE

LEVEL

terminated In

600

O~~~.'PROGRAM MIC LEVEL terminated in

150

ohms. MONITOR PHONES terminated in 8 ohms: MASTER Volume. Channel
~olur;le and MONITOR Controls full up; all other controls and switches 0 or off.

SR101 Series 2 Audio Console

SPECIFICATIONS

...

Feedback Filter VU Meter Calibration

$4 dBm (1.23 Vrms) at 1 kHz to

.......

Frequencies

.I30 Hz; 800 Hz; 2 kHz; 5 kHz

600-ohm load (METER

SENSI-

Tone Oscillator

........

1 kHz; less than 1% distortion;

variable level

lnput Impedance

at 1 kHz:

Microphone

.....

.1.2 kilohms balanced (for use

with 25- to 600-ohm'

micro-

Auxiliary

(Channels

7

phones)

........

and 8). .I70 kilohms unbalanced

.......

Link Input .35 kilohms unbalanced

Output Impedances:

Program

.........

Balanced line level: 120 ohms

actual (for use with 600-ohm
lines)

Microphone level: 0.5 ohms actual

(for use with 25- to 600-ohm in­puts)

Monitor

.........

.Unbalanced line level: 600 ohms

actual (for use with 600-ohm or
high-impedance phones, or
600-ohm lines)

Headphones: 3 ohms

actual (for
use with 4- to 16-ohm head­phones)

ACCESSORY AUX LEVEL

(unbal­anced) pins 1-811NPUTS: 33
ohms

actual (for use with 3-

kilohm

or greater loads); pin 91

PROGRAM: 600 ohms actual

Link Output

......

.600 ohms (actual)

Monitor System

.......

Headphone andlor 600-ohm line

output; individual and mixed
channel select or program; pre­and post-link monitoring

Reverberation

System

.............

Spring type with individual chan-

nel

intensity controls and high-

and low-frequency equalization

Link Jack System

......

External signal conditioning out-

putlinput;

high-level auxiliary
amplifier and tape recorder
signal output;

multiple Console
connection (mix bus); remote
master volume

control

TlVlTY ~ontrol'in

CAL position)
[22 dB-range METER SENSI­TIVITY

Control in full clockwise
position provides 0 VU reading
of -18

dBm (0.1 Vrms) on 600­ohm load]

....

Phasing (polarity).

.AUX LEVEL input and LINK IN

tips and pin 3 of INPUT con-

nectors in phase with pin 9 of

ACCESSORY OUTPUT; tips of

LlNK OUT, PROGRAM LlNE
LEVEL, and MONITOR LlNE
LEVEL outputs; tip of PHONES
jack; and pin 3 of PROGRAM
LlNE and MIC LEVEL outputs.
(PHASE Switch in 0" position.)
Pins 1-8 of ACCESSORY OUT­PUT out of phase with the
above.

.........

Phase Switch Output polarity-reversing switch

(0°, 180°) (reverses phase of all
program outputs)

30 Vdc Bus

..........

.Pin 10 on ACCESSORY

AUX

LEVEL connector is regulated
+30

~3.5 Vdc supply; pin 11 is
ground (earth). May be used to
power accessories with up to
50

mA.

Operating Voltage

....

.90-132 Vac, 50160 Hz (SR101)

90-132, 180-250 Vac, 50160 Hz

(SR101-2E)

Power Consumption

...

20 watts max. (Console only). 500

watts max. (SWITCHED A.

C.

receptacle)

Temperature Range:

Operating

..........

-7' to 54OC (20' to 130°F)

Storage

............

-29' to 71°C (-20' to 160°F)

Dimensions

..........

.311 mm x 483 mm x 162 mm

(121/'"

H x 19" W x 6%''

D)

Installation

...........

Equipped for standard 19" rack

mounting

(12%" height); may
be operated in accessory
AlOlA Carrying Case or in cus­tom control center

Weight

..............

.22 Ib (10 kg)

Finish

................

Matte black, with beige write-on

trim strip

Certifications

.........

Listed by Underwriters' Labora-

tories, Inc.; listed by Canadian
Standards Association as certi­fied

(SRIOI only)

iii

SR101 Series 2 Audio Console

TABLE OF CONTENTS

Section Page

SPECIFICATIONS ii
DESCRIPTION

OPERATING INSTRUCTIONS

Functional Identification
General Operating Instructions
Mounting and Ventilation
Power Supply
Functional Circuit Description
Input Channels
Source Cuing 7
Reverberation
Monitor System
Monitor Mixer System
Program Mix Amplifier
Link Jacks
Feedback Filters
Program Output
VU Meter Circuit
Tone Oscillator
Basic Operating Hints

SPECIAL OPERATING INSTRUCTIONS

High-Impedance Microphones
Musical Instruments
Tape Recording
Record Playback
Tape Playback
Talkback Circuit
Additional Mixer Inputs

..............................

.................................

.......................

.................

......................

................................

..................

..............................

1

3
3
4
5
5
7

................................

................................

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..................................

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7
8
8
9
9
9

9
10
10

11

11
11
12

12
12

13

13

Section Page

Additional Console Inputs (Two Consoles)
Redundant Console Set-up (Two Consoles) 15
Stereo Operation 16
Remote Volume Control 17
Telephone Line Surge Protection 17

SERVICE INSTRUCTIONS

Console Service 18
Replacement Parts 18
Fuse Replacement 18
Knob Replacement
ServiceAccess 18
Lamp Replacement 18
Reverberation Assembly
Board Removal
VU Meter Removal
VU Meter Calibration
Volume Control Assembly
Parts Removal
Transistor and Diode Removal
Transistor and Diode Checking
Service Illustrations
Optional Accessories
Guarantee
Shipping Instructions

PARTS
CONDENSED OPERATING INSTRUCTIONS

ARCHITECTS' AND ENGINEERS'

SPECIFICATIONS 47

...................................

LIST

...................................

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........

.......

........

14

18

18
20
20
20
21
22
22
22
22
22
22

23
47

SR101

Figure Page

1 SR101 Audio Console Front Panel ........... 2

SR101 Audio Console Rear Panel

2

SRlO1 Audio Console Dimensional

3

Outline Drawing
SR101 Audio Console Block Diagram

4
5 Monitor Mixer Applications
6 Tone Oscillator Applications
7 Preamplifier-Console Connnections
8 Tape Recording
9 Record Playback 13

Talkbackcircuit

10
11 Carbon Microphone Power Supply
12 Additional Mixer Inputs
13 Additional Inputs: Two Consoles
14 Redundant Consoles
15 Stereo Tape Recording

.........................

..........................

........................

..........................

....................

......................

...................

Series 2 Audio Console

LlST

............

................

...............

OF

ILLUSTRATIONS

........

.........

..........

..........

Figure Page

...................

..................

.....................

..............

...............

.............

..............

..................

.................

...........

.........................

....................

....................

....................

...................

2
5

6

9
10
11
12

13
13
14
15
16
17

16 Remote Volume Control 17
17 Printed Circuit Board and Parts Location 19
18 Volume Control Assembly
19 Board 1: Preamplifier
20 Board 2A: Channel Equalizer
21 Board
22 Board 3: Program Mix Amplifier
23 Board 4: Reverb Mix Amplifier
24 Board 5: Program Output

25

26 Board 7: Reverb Spring Amplifier
27 Board 8: Monitor
28 Board 9: Power Supply
29 Board
30 Transistor Lead Codes
31
32 Circuit Diagram

28: Reverb Equalizer

Board 6: Feedback Filters

0: Program Mute

SR101-2E Power Supply

........................

.....

21

33
34
34
35
35

36

37

37

38

38

39

41

42

.4 4-45

SRIOI Series 2 Audio Console

DESCRIPTION

(Shown

in

AIOIA

Carrying Case

with

AlOlB

Panel Lamp)

The Shure Model SR101 series 2 Audio Console is a
solid-state, eight-channel microphone mixer-preamplifier
that enables the operator to mix as many as eight micro­phones with individual control over volume, reverberation,
and high- and low-frequency equalization. The Series 2
Consoles have rear-panel provisions for connection to up
to eight Shure

SR110 Professional Monitor Mixers. The
SR110 is a self-contained, eight-channel, line level mixer
designed to provide a separate stage monitor mix that
follows the program mix levels. In addition, it may be used
in multi-track recording as a recording mix panel. The Con­sole has two outputs: a program output and a monitor out­put. In addition, channels

7

and 8 contain switch-selectable
input connectors for .use with auxiliary high-level sources
or high-impedance microphones. Master volume controls
regulate program and monitor outputs. Program and mon­itor switches permit the operator to select the input signals
to be routed to each of the two outputs.

The program output has both a 600-ohm, balanced, line
level output and a low-impedance, balanced, microphone
output. The monitor has two outputs: a 600-ohm unbal­anced output and an 8-ohm balanced headphone output.
Four switch-selectable feedback filters are included in the
program output, and a pair of link jacks facilitate connec­tion to an additional audio console, mixer, or external
equipment such as compressors, limiters or equalizers.

The Console contains a VU meter with adjustable sensi­tivity to indicate program output level. A built-in 1 kHz

tone oscillator facilitates synchronization of all meters in
the system. An optional panel lamp accessory may be con­nected to the front panel lamp connector for illumination
of controls. Accessory equipment drawing up to 500 watts
may be connected to the rear-panel switched ac receptacle.
A front-panel trim strip provides space for pencilled nota­tions.

The regulated power supply is designed to operate over
a wide range of input voltages, permitting the use of ex­tremely long ac extension cables without performance
degradation.

The solid-state components in the

SR101 Audio Con­sole are protected against damage as a possible result
of open-circuit or short-circuit conditions on the inputs
or outputs. All components are conservatively rated and
are operated well within their respective ratings to assure

long life and trouble-free performance.

The Console is supplied with rack-mounting screws and

spare fuses (the

SRlOI-2E comes with a detachable line

cord).

The Console is Underwriters' Laboratories,

Inc., listed,
and is listed by the Canadian Standards Association as
certified

(SRI 01 only).

The following accessories are specifically designed for

use with the

SRlOl Series 2 Audio Console:

AlOlA Carrying Case
A101 B Panel Lamp Accessory
SR110 Professional Monitor Mixer

FIGURE 1. SRlOl SERIES 2 AUDIO CONSOLE FRONT PANEL

36

25

26

(SR101

-

29

2E

Only)

30

34

32

3

3

35

37

FIGURE

2

(SR101 - 2E

2.

SRlOl SERIES 2 AUDIO CONSOLE REAR PANEL

Only)

SR101

Series 2 Audio Console

OPERATING INSTRUCTIONS

FUNCTIONAL IDENTIFICATION (Refer to Figures 1 and
2, Page 2.)
NOTE: All push-button switches are "on" when in (de­pressed) and "off" when out (released). Input attenuator
switches are calibrated in decibels; all other front panel
controls are numbered for reference only.

1. lndividual Channel Volume Slide Controls (Eight)

-

Control volume and input clipping level of each chan­nel separately.

2. REVERB INTENSITY Rotary Controls (Eight)

-

Con-

trol reverb level for each channel.

3. Master REVERB Push-Button Switch -Turns on (or
off) amount of reverb preset by channel REVERB IN-

TENSITY controls.

4. REVERB FREQuency

EQualizer-LOW Rotary Control

-

Adjusts low-frequency reverb signal equalization.

5.

lndividual Channel FREQuency EQualizer-LOW Rotary

Controls (Eight)

-

Adjust low-frequency signal equal-

ization for each channel.

6. REVERB FREQuency

EQualizer-Hlgh Rotary Control

-

Adjusts high-frequency reverb signal equalization.

7. lndividual Channel FREQuency

EQualization-Hlgh Ro-

tary Control (Eight)

-

Adjusts high-frequency signal

equalization for each channel.

8. PHONES Output Jack

-

Provides for connection of

stereo or monophonic headphones for monitoring.

9. Panel LAMP Accessory Connector

-

Provides con­nection for optional panel lamp accessory to illumi­nate front panel.

10. MONITOR Level Rotary Control

-

Controls volume
level to PHONES Jack (8) and MONITOR OUTPUT/
LlNE LEVEL Jack (30).

11. PROGRAM MONITOR Push-Button Switch

-

Con­nects total program output (all channels and reverb)
to PHONES Jack (8) and MONITOR

OUTPUT/LINE

LEVEL Jack (30).

12. lndividual Channel MONITOR Push-Button Switches
(Eight)

-

Connect individual channel outputs (with-

out reverb) to PHONES Jack (8) and MONITOR

OUT-

PUT/LINE

LEVEL Jack (30) when PROGRAM MON-

ITOR Switch (11) is off.

13. lndividual Channel PROGRAM Push-Button Switches
(Eight)

-

Connect individual channel inputs to pro-

gram output.

14. lndividual Channel INPUT

ATTENuator Rotary

Switches (Eight)

-

Provide choice of input signal at­tenuation for each channel. Dual switches on chan­nels

7

and 8 also select low-impedance (MIC) or high-

impedance (AUX) input connections.

15. FEEDBACK FILTERS Push-Button Switches (Four)

-

Provide for elimination of acoustic feedback in four
most probable audio frequency ranges.

16. TONE

Oscillator LEVEL SwitchIRotary Control

-

Turns on and adjusts level of 1

kHz

tone generated

internally for set-up purposes.

17. True VU Meter

-

Indicates volume level of program

output. (Meets all current standards for VU Meters).

18. METER SENSITIVITY Rotary Control

-

Adjusts VU
meter sensitivity for wide ranges of program level
indication.

19.

POWER ON-OFF Toggle Switch - Applies ac power
to power supply and SWITCHED A.C. Receptacle (23).

20. MASTER Volume Slide Control

-

Adjusts level of total

program output.

21. Ac Grounded Line Cord

-

Connects ac power source

to Console power supply

(SRlO1 only).

22.

3AG-3/16A SLO-BLO Ac Fuse - Protects Console ac
input line against overload

(SRlOl only).

23. SWITCHED A. C. Grounded Receptacle

-

Provides up
to 500 watts of switched ac power to accessory equip­ment

iSR101 only).

24.

PROGRAM OUTPUTSIMICrophone LEVEL 3-Pin Con­nector

-

Provides low-impedance microphone-level

program output.

25. PROGRAM

OUTPUTS/LINE LEVEL Phone Jacks

(Two)

-

Provide balanced or unbalanced output con-

nections to power amplifier.

26. PROGRAM

OUTPUTS/PHASE Slide Switch - Re-

verses phase (polarity) of

LlNE LEVEL and MIC LEVEL

program outputs with respect to inputs.

27. PROGRAM

OUTPUTSILINE LEVEL 3-Pin Connector

-

Provides balanced output connection to power

amplifier.

28. LlNK IN Phone Jack- Provides input connection for
external equipment (compressor, limiter, equalizer,
etc.).

29. MONITOR

OUTPUTIPOST LINK-PRE LlNK Slide

Switch

-

Selects program monitoring either before or

after external equipment connection to LlNK Jacks (28,

31).

30. MONITOR

OUTPUTILINE LEVEL Phone Jack - Pro-

vides monitor output connection to power amplifier.

31. LlNK OUT Phone Jack

-

Provides output connection

for external equipment, or mix bus to add Consoles.

32.

INPUTS/AUX. LEVEL Phone Jacks (Two) - Provide
for connection of high-impedance sources to channel

7

or 8 inputs.

33. INPUTS/ MICROPHONE LEVEL 3-Pin Jacks (Eight)

-

Provide for balanced connection of low-impedance
sources to channels 1 through 8 inputs.

34. ACCESSORY AUX LEVEL

1 I-Pin Connector-Provides

output connection to Shure

SR110 Monitor Mixer.

35. AC (MAINS) POWER 3-Pin Connector-Connects ac
power cable to Console power supply

(SRlOl-2E only).

36. VOLTAGE SELECTOR Slide Switch-Selects oper­ating voltage range of 90 to 132 or 180 to 250

Vac,

50/60

Hz (SRIOI-2E only).

37. 180-250V 0.1

AT/90-132V 0.2AT Ac Fuse-Protects

Console ac input line against overload

(SR101-2E

only).

GENERAL OPERATING INSTRUCTIONS

WARNING

Voltages in this equipment are hazardous to life. Make
all input and output connections with ac power dis­connected. Refer servicing to qualified service per­sonnel.

1. Using hardware provided, install Console securely in
standard

19" (483 mm) rack or optional AlOIA Carry­ing Case prior to making electrical connections. For
custom installations, see mounting template supplied
with Console. If desired, connect

AlOlB Panel Lamp

Accessory to LAMP Connector (9).

3

2. Set all front-panel switches to off (out) and all con­trols to

0. Set rear-panel PHASE Switch (26) to 0'.

3. Connect desired PROGRAM OUTPUT/LINE LEVEL
Connector

(25,27) to power amplifier input connect-

ing cable. (NOTE: Shure

SR105 Power Amplifiers
are supplied with audio connecting cables.) If Console
output is to be fed to another mixer or tape recorder
microphone input, use PROGRAM

OUTPUT/MIC
LEVEL Connector (24). If desired, connect mono­phonic or stereo headphones to front-panel PHONES
Jack (8). Connect speakers to power amplifier.

4. Connect one or more low-impedance microphones to
rear-panel

INPUTS/MICROPHONE LEVEL Connector
(33). Any high-quality dynamic, ribbon or condenser
low-impedance microphone may be used. Connect
high-impedance microphones or auxiliary high-level
sources to

INPUTS/AUX. LEVEL Connectors (32) in
channels 7 or 8 only. If AUX. LEVEL Connectors are
used, set corresponding front-panel

MIC/AUX (INPUT

ATTEN) Switch (14) to AUX.

5. If external signal-processing equipment such as an
equalizer, compressor or limiter is to be used, con­nect Console

LlNK OUT Connector (31) to external

equipment input and Console

LlNK IN Connector (28)

to external equipment output. (See Link Jacks, Page

8,

for detailed information.)

6.

SR101: Connect ac line cord (21) to grounded 90- to
132-volt,

50/60 Hz ac source.

Line cord

is

a 2.44m (8-ft.), 3-conductor cord with
3-pin grounding plug. If extension cords are required,
use high-quality, rubber-jacketed cable with 18 gauge
or larger wire.
SRlOl-2E: Obtain suitable &pin male ac connector
and attach to line cord: brown lead to "hot" or "live"
terminal,

blue lead to neutral terminal, and green/
yellow lead to ground or earth terminal. (Connector
should be installed by qualified service personnel.)

Select proper operating voltage (90-132V or

180-

250V)

using VOLTAGE SELECTOR Switch (36). Note
that switch positions are marked 115 and 220 volts.
Make certain proper fuse is installed in fuseholder
(37):

O.1AT with switch set to 220, or 0.2AT with

switch set to 115. Insert female end of line cord into

chassis power connector (35) and connect male plug
to 3-wire grounded ac power receptacle providing
proper operating voltage.

7. Turn on front-panel POWER Switch (19) and allow
one to two minutes

warmup time. This warmup time
allows the supply voltages to stabilize and capacitors
to charge to provide optimum performance. Depress

PROGRAM Switch (13) for channel to be used. (IM­PORTANT: No program output will result if this switch
is not depressed!) Set INPUT

ATTEN Control (14) for

that channel initially to

0 for normal or PA use, to -10
for instrumental music, or to -20 or -30 for "hard"
rock music. For AUX. INPUT sources (channels 7 and

8), set INPUT ATTEN Control initially to -20 or -30.

8.

Set MASTER Volume Control (20) to 7. Set METER
SENSITIVITY Control (18) to CAL position. Have some­one sing or talk into microphone and raise channel
Volume Control (1) to achieve desired sound level. If
VU Meter (17) reads too low at proper sound level, in­crease METER SENSITIVITY Control until normal me­ter movement

-

operation in black area of scale with

occasional peak excursions into red area

-

is ob-

tained. If meter still reads low, reduce power amplifier
volume level and increase channel volume level. For
single microphone set-up, if meter indicates exces­sively high level ("pinning" or "pegging" needle),
decrease channel Volume Control to obtain good
meter reading and increase power amplifier volume
level or input sensitivity to obtain proper sound level.

In multiple microphone set-up, it may be necessary

to
decrease MASTER Volume Control in order to main­tain channel Volume Control setting. Ideally, channel
Volume Control should remain approximately at mid-

range (7-9) to facilitate increases or decreases in con-

trol setting due to program change; INPUT

ATTEN
Control (14) adjustment will aid in maintaining this set­ting. If feedback occurs below desired sound level,

consult section on Feedback

Filters

(Page 8).

9. Set HI and LO FREQ EQ Controls (7,5) for channel in
use. Vertical position

(0) indicates "flat" frequency re-

sponse. Clockwise

(+)

settings increase high-fre-

quency (treble) or low-frequency (bass) equalization

and counterclockwise

(-)

settings decrease fre­quency equalization. Note that these controls also
affect feedback; readjustment of Feedback Filters (15)
may be necessary.

10. If reverberation is desired, depress REVERB Switch
(3) and adjust REVERB INTENSITY Control (2) to

desired level for channel in use. Recommended set­tings are: speech

-

0, vocals - 3-6, instruments

-

5-10. Adjust HI and LO REVERB FREQ EQ Controls

(6,4) for desired frequency equalization.

11. To monitor channel in use, depress MONITOR Switch

(12) for that channel. Monitor output is available at
front-panel PHONES Jack (8) and rear-panel MONI­TOR

OUTPUT/LINE LEVEL Jack (30). Adjust MONI-

TOR Control (10) for comfortable listening level. Note

that any or all channels may be monitored whether or

not PROGRAM Switch (13) for that channel is de-

pressed; merely depress MONITOR Switch for desired
channel. When total program output monitoring is de­sired, depress PROGRAM MONITOR Switch (11). Note
too that only those channels with PROGRAM Switch
(13) depressed will be heard while monitoring with
PROGRAM MONITOR Switch depressed.

12. NOTE: During temporary shutdown (break, intermis­sion), it is not necessary to turn off Console power. It

is designed to operate continuously, and optimum per­formance is maintained after internal voltages are al­lowed to stabilize. Also, do not turn off all microphones.

Leave the master or announcer's microphone on (PRO­GRAM Switch depressed) so that

if

the Console is left
unattended, announcements may be made, and the
Console operator will be alerted that the next perform­ance is about to begin.

MOUNTING AND VENTILATION

The Shure

SR101 Audio Console may be operated in a
standard 19" (483 mm) audio equipment rack, in a Shure
AlOlA Carrying Case, or custom-mounted in a table- or

desk-type control center. Four rack-mounting screws are
provided with the Console. These screws may also be used
if the Console is to be custom-mounted in a metal-top con­trol center.

A custom-mounting template is supplied with the Con­sole. Cutting dimensions and drill hole locations are given,
as are clearances for insertion and ventilation. The

dimen-

sions given should be followed to provide adequate cable
clearance (see Figure 3, Page 5).

In either rack- or custom-mounted installations, consider
rear-panel access before installation is made. Although
most installations will not require frequent access, it should
be remembered that input and output changes, and some

switch movements, will necessitate rear-panel access. Rear

panels are most easily reached in standard audio racks or
in custom installations having bottom access, such as an

open desk or a lower control center access panel.

,

.

NOTE: CLEARANCE DIMENSIONS

I

SHOWN. SEE MOUNTING
TEMPLATE.

I
I

I

I

*

NOT INCLUDING CONNECTOR/CABLE CLEARANCE

DEPTH.

I

-

--

-

FIGURE

3.

SRlOl AUDIO CONSOLE

DIMENSIONAL OUTLINE DRAWING

POWER SUPPLY

SR101: The SR101 regulated power supply is designed to
operate from 90 to 132 volts ac,

50/60 Hz without adjust­ments, allowing the Console to meet all specifications over
this wide range of ac input voltages. A three-conductor,
grounded line cord (21) supplies ac power to the Console
through the front-panel POWER ON-OFF Switch (19). The
Console consumes 20 watts maximum (0.2 amperes) and
the ac line input is protected by a

3/16-ampere slo-blo fuse

(22) and a wired-in

3/10-ampere slo-blo fuse in series. A
wired-in 1-ampere slo-blo fuse protects the 5.6-volt second­ary winding (indicator lamp) of the power transformer.

CAUTION

These fuses should not be replaced with any

other size or type of fuse.

Accessory equipment may be connected to the

rear-

panel SWITCHED A.C.

Receptacle (23). The accessory

equipment may consume up to 500 watts maximum, which

provides for use with high-power amplifiers such as the

Shure

SR105. Note that the receptacle is switched but not
fused; all accessory equipment used with the Console
should contain its own fuse.

SR101-2E: The SR101-2E regulated power supply is de­signed to operate from either 90 to 132 volts ac or 180 to
250 volts ac,

50/60 Hz, as selected by the rear-panel VOLT­AGE SELECTOR Switch (36). A three-conductor, grounded
line cord supplies ac power to the Console through the
front-panel POWER ON-OFF Switch (19). The

SR101-2E
line cord does not have a connector on the power source
end of the cord. Obtain a suitable three-pin male ac con­nector and install it on the line cord: brown to "hot" or
"live" terminal, blue lead to neutral terminal, and green/

yellow lead to ground or earth terminal. (Connector should
be installed by qualified service personnel.) The ac line is

protected by a 0.1-ampere Slo-Blo fuse (for 180- to 250-volt

operation) or a 0.2-ampere Slo-Blo fuse (for 90- to 132-volt
operation). Wired-in

3/10- and 1-ampere fuses protect the

ac line and power transformer 5.6-volt secondary winding,

respectively.
FUNCTIONAL CIRCUIT DESCRIPTION

(See Figure 4, Page 6)

Each 3-pin professional audio input Microphone Con­nector (33) feeds its own low-impedance lnput Transformer,
which provides a gain increase of 23 dB. Channels

7

and 8
also contain switchable AUX LEVEL phone jacks (32) which
accept high-impedance microphones or other inputs. The

lnput Transformers (and, on channels

7

and 8, the AUX-

MIC Switch) are fed to 0-30 dB INPUT ATTEN Controls (14)

and then to the Preamplifier, which provides a

A6 to $30
dB gain increase. The amount of gain provided by the Pre­amplifier (6 to 30 dB) is controlled by the Channel Volume
Control

(I), providing an increase in input clipping level as
gain is reduced. The Preamplifier circuits contain the in­dividual Channel Volume Controls and feed the individual
Channel Equalizer (HI and LO FREQ EQ) Controls

(73)
which decrease the signal approximately 2 dB when set to
the 0, or "flat," setting.

The Equalizer outputs go to the Program and Monitor
circuits, and to the ACCESSORY AUX LEVEL Connector
(34) for interconnection with

SR110 Monitor Mixers. The
Channel Equalizer outputs going to the Program circuits
go first to the individual channel PROGRAM Switch

(13),

and subsequently to the Reverb circuits and individual
channel REVERB INTENSITY Controls (2). When reverb is
not used, the REVERB INTENSITY Control is set to 0, and
the channel output is sent directly to the Program Mix
Amplifier. When reverb is employed

-

REVERB Switch (3)

depressed

-

the REVERB INTENSITY Control feeds the
Reverb Intensity Mix Amplifier, Reverb Equalizer, Reverb
Driver and Differential Amplifiers, Reverb Output Mix Amp­lifier, and then into the Program Mix Amplifier. Note that as

the control is increased the amount of non-reverb ("dry")

signal sent to the Program Mix Amplifier is reduced, while

the signal sent to the Reverb lntensity Mix Amplifier is

increased.

The Channel Equalizer output to the Monitor input, con-

trolled for each channel by a MONITOR Switch

(12), is fed

to the Monitor Mix Amplifier, which changes the input by

+3 to -13 dB. The Amplifier output goes to the PROGRAM

MONITOR Switch (1

I), where it may be selected to continue

through the MONITOR Level Control

(lo), +40 dB Monitor

Amplifier, and to the rear-panel MONITOR

OUTPUT/LINE

LEVEL jack (30) and front-panel PHONES jack (8).

The Program Mix Amplifier goes to both the PRE LlNK

side of the POST

LINK/PRE LlNK Switch (29) for routing to
the Monitor circuits, and through a 560-ohm resistor to the
LlNK jacks

(28,31). When accessory equipment is not con­nected to the LlNK jacks, the jacks are bypassed and the
program signal is fed to the POST LlNK side of the POST
LINK/PRE LINK Switch for monitoring, and to the MASTER
Volume Control (20). Note that the PRE

LINK/POST LlNK
Switch output to the Monitor circuits is also routed to the
ACCESSORY AUX LEVEL Connector (34).

The output of the MASTER Volume Control, after feeding

a

0 dB gain Amplifier, is sent through a bank of four select-

able FEEDBACK FILTERS

(15), which provide attenuation
at 130, 800, 2000 and 5000 Hz for feedback control. The
FEEDBACK FILTERS output goes to a

+6 to +31 dB
Amplifier, also controlled by the MASTER Volume Control,
through a

180' PHASE Switch (26), and into the Program

NOTE

(

TYPICAL OF CHANNELS 1-8

l

1

lMlCROPHONE LEVEL

200

HIGH

X~~~

1+23 dB1

mn

-

RESISTOR

I

n:

-

0-30 dB CHANNEL

,

INPUT

-

ITTEN

TONE

OSC

LEVEL

/

f

-

VOLUME - CHANNEL

(SECTION

/I

I

,

CHANNEL REVERB

VOLUME

(SECTION

/

-2

dB REVERB

A)

EWALIZER

P

0) (SECTION A)

I

pimq

OUT

-

4-

IN (SECTION 0)

FEEDBACK

FILTERS]

-

-

INTENSITY

/

I

I

I

INTENSITY

/

f

-

f

(SECTION

NOTES: I. AUX. LEVEL INPUT AND AUX-MIC SWITCH

ON CHANNELS

7

AND 8 ONLY.

FlGUR,E

4.

[PHASE]

m-

MASTER

VOLUME

.

8)

MON

-

LEVEL

/

1-10 dB1

SRlOl SERIES 2 CONSOLE BLOCK DIAGRAM

PROGRAM OUTPUTS

LEVEL

Output Transformer. The Transformer feeds three LlNE

LEVEL Output Connectors (25,27) and a MIC LEVEL Out­put Connector

(24), which is at

50

dB below line level. The

+6

to $-31 dB Amplifier also feeds the METER SENSITIV­ITY Control (18), which goes to a +22 dB Meter Amplifier,
and then to the VU Meter (17).

The Console also contains a 1

kHz Tone Generator for
use in set-up and checkout. The Generator is activated and
controlled by the TONE OSC LEVEL

SwitchIControl (16),

and the control output is fed to the Program Mix Amplifier.

A detailed description of the Console circuits and con­trols and their uses is provided in the following paragraphs
of this section.

INPUT CHANNELS

Eight professional, three-pin, audio MICROPHONE
LEVEL lnput Connectors (33) are provided on the upper
rear panel of the Console. The Console is designed to oper­ate with high-quality, low-impedance dynamic, ribbon or
condenser microphones. Two additional AUX. LEVEL In­put Connectors (32) are provided for channels

7

and

8.

These standard quarter-inch phone jacks allow connection
to auxiliary high-level sources or high-impedance micro­phones. Switches on the channels 7 and

8

INPUT ATTEN
Control (14) allow the user to select between either the
low-impedance microphone input (MIC), or the

high-im­pedance auxiliary input (AUX). Each low-impedance micro­phone input is connected to a low-impedance, balanced­input transformer, the output of which is connected to a
0-30 dB input attenuator. On channels 7 and

8,

the outputs
of the low-impedance microphone transformer and the
AUX. LEVEL lnput Jack (32) terminate in the AUX-MIC
Switch. The output of this switch goes to the 0-30 dB INPUT
ATTEN Switch (14). Note that the AUX-MIC Switch has
two detented positions; no output will be obtained when
the switch is between detent positions. The MIC-AUX
Switch grounds the unselected input to reduce crosstalk.
This should be considered when connecting inputs to this
channel. A

I-kilohm isolation resistor is provided in the

AUX input circuit. When the AUX input is not selected, this

resistor is grounded, placing the

I-kilohm load on the AUX
input. If the source connected to this input is also bridged
to feed other inputs, an additional isolation resistor may be
required.

The INPUT

ATTEN (14) four-position switch provides

input attenuations of 0, 10, 20, or 30 dB. This switch allows
the user to compensate for the differences in levels due to
different sources, such as close talking or distant micro­phone placement, and to compensate for high output levels
from condenser microphones.

The Channel Volume Control (1) is a dual control: one
section, in a feedback circuit, sets the gain of the preampli­fier, and the second section is a preamplifier output

attenu-

ator.

This circuit configuration increases the preamplifier
input clipping level as the Volume Control is reduced to
lower settings. Ideally, the control should operate in the

middle range, between 7 and

9.

This can generally be ac-

complished by proper INPUT

ATTEN Control (14) setting.

The output of the Channel Volume Control (1) feeds the

equalizer circuit. Individual HI and LO FREQ EQ controls

(7,5)

allow the user to shape the sound of each input
channel without affecting the other channels on the Con­sole. The HI FREQ controls provide up to 13 dB of boost
or cut at 10 kHz with a 1 kHz hinge point. The LO FREQ
controls provide up to 13 dB of boost or cut at 100 Hz with

a 1 kHz hinge point. Control settings with plus

(+)

markings

indicate boost, and minus

(-)

markings denote cut. A 0

setting provides a normal or "flat" frequency response.

The output of the equalizer feeds the channel PROGRAM

and MONITOR Switches

(13,12). The PROGRAM Switch

selects the channels to be connected to the program out-

put. The MONITOR switches select the channels to be con­nected to the monitor output. The two switches are inde­pendent and have no effect on each other.

SOURCE CUING

Microphones, tape recorders, or other sources may be
preset, or cued, during a performance in the following
manner. With

headphones connected to the front-panel

PHONES Jack (8) or rear-panel

MONITOR

LlNE LEVEL
Jack (30) (high-impedance headphones only), depress the
PROGRAM MONITOR Switch (11) and a PROGRAM Switch
(13) for a channel that has program material at the proper
level on it. Adjust the MONITOR Level Control (10) until an
adequate audio level is heard in the headphones. Release
the PROGRAM MONITOR Switch and PROGRAM Switch
for that channel, and depress the MONITOR Switch (12) for
the channel being cued. With the MONITOR Level Control
previously set, raise the channel Volume Control (1) until
the same audio level heard in the other PROGRAM channel
has been reached.

With the channel PROGRAM Switch (13) released and

the channel MONITOR Switch (12) depressed, the source

will be heard on the headphones and not on the program
channel. This allows the Console operator to cue up tapes,
check out microphones, etc., without interfering with the
program. When the channel is to be activated, depress the
channel PROGRAM Switch.

It is most important to have a good knowledge of micro­phone placement and the performer's microphone tech­nique when cuing a microphone. Always begin cuing in the

new microphone at the lowest estimated volume setting. If
volume level correction is necessary, slowly raise the Vol-

ume Control

(1)

level. If a change in the INPUT ATTEN
(14) setting is required, wait until the vocalist takes a
breath or the instrumentalist takes a rest to balance out the

volume and attenuation levels to the required degree. Note
that minor changes in volume during a performance per-

ceptible to the Console operator are rarely noticed by the
audience. However, if the channel level is set too high when
the channel is turned on, the sound may "blast" the audi­ence, or cause acoustic feedback, or both. Either condition
will prove embarrassing to the Console operator.

REVERBERATION

The SR101 Audio Console contains a built-in electro­mechanical spring-type reverberation device utilizing four
coil springs in two transmission paths. Reverberation is ac­complished by driving the input ends of the springs in a

torsional mode and transferring the torsional movement

back into an electrical signal which exhibits time delay with
a long decay time at the opposite ends of the springs. Since

the reverberation device is electromechanical in nature, it

is sensitive to mechanical shock.

The Console is designed to provide a foundation of "dry,"

or non-reverb, signal on the total output, no matter how the
channel REVERB INTENSITY Controls (2) are set. Of great

importance, too, is the fact that reverb intensity can be

increased without increasing overall gain.

In most units

which employ artificial reverberation, the total gain

in-

creases as the intensity of the reverberant signal is in­creased. This generally leads to acoustic feedback. How­ever, the

SR101 Audio Console reverb mixing system
reduces the "dry" signal as the reverb signal is increased;
this provides an almost constant gain and reduces the

possibility of feedback as reverb is added.

The following controls are pertinent to reverb operation.

The output of the PROGRAM Switch (13) feeds the channel

REVERB INTENSITY Controls (2). These are dual controls:

one section controls the amount of "dry" signal fed to the

program mix amplifier, and the other controls the amount

of signal fed to the reverb mix amplifier. As each REVERB

INTENSITY Control is increased, the amount of signal to
the program mix amplifier is reduced and the amount of
signal to the reverb mix amplifier is increased. As stated

above, this action keeps the same approximate overall

volume level to avoid feedback problems. The REVERB

INTENSITY Control is generally used at settings of

0 for

speech, 3-6 for vocals, and 5-10 for instruments.

The reverb mix amplifier combines the output of all chan­nel REVERB INTENSITY Controls
sending it to the REVERB FREQ EQ Controls

(2), mixing the signal and

(6,4). The
output of the reverb equalizer circuit drives the reverbation
system. The separate REVERB FREQ EQ-HI and -LO Con­trols affect the reverb signal only. These reverb controls
modify the reverberant signals in essentially the same way
the channel equalization controls modify both "dry" and
reverb signals. The REVERB FREQ EQ Controls allow the

user to change the reverberant sound to compensate for
the reverberation in each room in which the Console is
used. In a

"boomy" (low-frequency resonant) room, de-

crease the REVERB FREQ EQ-LO Control or increase the

REVERB FREQ-HI Control, or do both until the proper
equalized reverb sound is achieved.

The output of the reverberation spring is fed to a dif­ferential amplifier whose output is connected to the RE­VERB Switch (3). This switch turns the reverb system on (in)
and off (out) without affecting the overall level or the RE-

VERB INTENSITY Controls (2). In this manner, the RE­VERB INTENSITY Controls may be preset, and when the
REVERB Switch is depressed, the reverb level is predeter­mined. The reverb signal, after passing through the RE­VERB Switch, is routed to the program mix amplifier and
combined with the "dry" signals from the program
channels.

MONITOR SYSTEM

The output of the individual channel MONITOR Switches

(12) are combined in the monitor mix amplifier. The chan­nels that appear on the monitor system are independent of
the setting of the PROGRAM Switches (13). This feature
allows the signals that do not appear on the program out­put to be fed to the monitor output. This may be useful for
providing a

talkback or for a "click track" signal feed.

The monitor mix amplifier is a passive mix amplifier; its

gain depends on the number of channels selected to be
monitored. This type of mixing means that as channels are
added to the monitor system, the overall apparent level
remains constant while each individual channel contribu­tion is reduced. The output of the monitor mix amplifier
feeds the PROGRAM MONITOR Switch (11). When this
switch is released, the monitor system carries the channels
selected by the individual channel MONITOR Switches
(12). When the PROGRAM MONITOR Switch is depressed,
the monitor system monitors the output of the program mix
amplifier.

It should be noted that the individual channel MONITOR

Switches (12) monitor the channels ahead of the reverb,
and the PROGRAM MONITOR Switch (11) monitors the
entire program after reverb. The output signal from the
PROGRAM MONITOR Switch is fed to the MONITOR Level

Control

(lo), which provides an output signal to drive the
monitor output amplifier. The signal from this amplifier
appears on the MONITOR

OUTPUT/LINE LEVEL Jack (30)

on the rear panel, and also through a headphone matching

(8)

transformer to the PHONES Jack

on the front panel.

These two outputs may be used simultaneously.

(8)

Note that the front-panel PHONES Jack

permits the
use of either monophonic or stereo headphones (4-16 ohms
impedance) without rewiring. High-impedance mono­phonic headphones may be connected to the rear-panel

MONITOR

OUTPUTILINE LEVEL Jack (30).

The purpose of the monitor system is to allow an operator
to use headphones to monitor the program if the PROGRAM
MONITOR Switch (11) is depressed, or to monitor the in­dividual channels. Monitoring the individual channels
allows the operator to determine which microphones are
in use, which are turned off, or which may be malfunction-

ing. Note that it is also possible to use the monitor output to

listen to a microphone or cue a tape that is driving a chan-

7

or 8 AUX. LEVEL lnput Jack (32) without having the

nel
signal on the program output.

The second major use of the monitor system is to pro-

vide on-stage monitoring, or foldback, which allows the

performers to hear themselves, but only gives them a
partial mix. This is useful in a system where all the instru­ments have microphones but the vocalists only want-to hear

themselves and one or two instruments, such as the piano,

to be able to keep in tune. When used in this manner, the

MONITOR

OUTPUT/LINE LEVEL Jack (30) is connected

to the input of an auxiliary power amplifier that is connected

in turn to monitor speakers located on stage.

MONITOR MIXER SYSTEM

The rear-panel ACCESSORY OUTPUT/AUX LEVEL Con-

nector (34) of the

to eight Shure

SR101 provides for interconnection to up

SR110 Professional Monitor Mixers. The out­put of each individual channel after the volume, equal­ization and attenuation channel controls appears on this
connector as do the
and the power supply connections. The

LlNK INPUTIOUTPUT total mix signal

SRI10 is a self­contained, eight-channel, line level mixer designed for use
with the

SRlOl Series 2 or similar equipment. The SR110
can provide a separate stage monitor "mix" that follows
the program "mix" levels coming from the eight channels
of the

SR101. In addition, it may be used in making multi-

track recordings: use two

SRllOs for stereo and four for

quadriphonic.

The

SR110 provides eight high-impedance, unbalanced,
line level inputs to its mixing circuitry, one high-impedance,
unbalanced, line level input to its Output Selector Switch

for monitoring the program mix, and one line level,

600-

ohm, balanced output. Individual channel and master vol-

ume controls are provided, as is a switch to choose be-

tween monitoring the channels in use (Mixed Inputs) and
the total program mix (Program Input). The Mixed Inputs

position takes the signal from each channel frequency

equalization circuit, and the Program lnput position ob-

tains the mixed signal at the PRE

LINK/POST LlNK Switch

(29).

The SR110 has parallel accessory inputloutput male and
female connectors. These connectors permit the connect­ion of additional tandem or "stacked"
application is shown in Figure

5,

SRllOs. A typical

Page 9.

POWER PA

AMPLIFIER SPEAKERS

LEVEL

-

SRllO STAGE

MONITOR

POWER MONITOR

MIXER

AMPLIFIER

SPEAKER

I

SRllO

MONITOR

MIXER

STEREO

RECORDER

MONITOR

FIGURE

5.

SR110 MONITOR MIXER APPLICATIONS

PROGRAM

MIX

AMPLIFIER

The program mix amplifier is an active mixing amplifier

in which gain remains constant independent of the num-

ber of individual channel PROGRAM Switches (13) that are
activated. The output of the program mix amplifier is con­nected through a 560-ohm mixing resistor to the LlNK
Jacks

(28,31).

LlNK JACKS

The LlNK Jacks (28,31) on the rear panel of the Console
enable the user to interconnect more Consoles for addi­tional inputs or add external equipment, such as equalizers,

compressors, or limiters. When connecting two or more
SR101 Audio Consoles together to provide many channel
inputs, connect the LlNK OUT Jacks (31) of all the units
together. It should be noted that the LlNK OUT Jack is
actually a two-way jack; the impedance at this point is
actually 600 ohms and any number of units may be tied
together at this point. The LlNK IN Jack (28) is an input-only
jack and has switching contacts that disconnect the output
of the program mix amplifier from the MASTER Volume
Control (20).

If an equalizer, limiter or compressor is connected to the
Console, the LlNK OUT Jack (31) is connected to the input
of the external unit and the output of the external unit is
connected to the LlNK IN Jack (28).

The signals at the LlNK JACKS are typically at a level 10

dB below line level. These jacks will accommodate signal

levels in the range between -30 to

+I0 dBm. The LlNK IN
input impedance is greater than 20 kilohms and may be
considered a bridging impedance. The output of the LlNK

Jacks feeds the MASTER Volume Control (20) which is a

two-section control similar to those used in the individual

channels. The POST

LINK/PRE LlNK Switch (29) on the
rear panel, in the monitor circuit, allows the operator to
monitor the program before (PRE) or after (POST) the LlNK

Jacks.

FEEDBACK FILTERS

The output signal from the MASTER Volume Control

(20)

attenuator section is sent to the feedback filter circuit at
this point. The FEEDBACK FILTERS (15) are four notch
filters whose center frequencies are 130

Hz,

800

Hz,

2

kHz,

and

5

kHz.

These jil'lers are designed

to

minimize

the

acoustic feedback (speaker howl or squeal) that may occur
through some combination of room acoustics, microphone

and speaker placement, volume increase, or equalization
control boost. Each filter modifies the frequency response
of the program output, with the lowest (130 Hz) filter af­fecting the lowest feedback pitch (howl) and the highest (5
kHz) filter affecting the highest feedback pitch (squeal).
The two center frequency filters affect feedback modes in
the middle ranges of the audio frequency spectrum.

The three upper frequency filters have little effect on
voice tonal qualities. The 130 Hz filter, generally used to
eliminate low-frequency room reverberations, causes some
decrease in bass tones. This may be compensated for by
increasing the FREQ EQ-LO Controls (5) slightly for the
individual channels in use.

If feedback is present, locate the one FEEDBACK FILTER

Switch (15) which eliminates it. Then increase the VOLUME

(1) or FREQ EQ Controls (5,7) as desired until another feed­back pitch occurs. Then locate the filter to eliminate the
new feedback mode. IMPORTANT: Up to two FEEDBACK
FILTERS may be used at one time; more than two filters
will reduce overall gain and significantly affect system tonal
quality.

Note that the PHASE Switch

(26), which allows the Con­sole operator to change the output phase, functions to
reduce or eliminate acoustic feedback, too. It is normally
used to obtain maximum gain before feedback, or to obtain
the highest pitched feedback for elimination by the feed­back filters.

PROGRAM OUTPUT

The output signal from the feedback filters drives the
program output amplifier. The gain of this amplifier is con­trolled by one-half of the MASTER Volume Control (20) (the
other half is a preamplifier output attenuator). The output of
the program amplifier is sent to the PHASE Switch (26)
mounted on the rear panel of the Console. This switch
allows the user to change the phase of the program output,
which may be helpful in eliminating or reducing

low-fre­quency acoustic feedback. Generally, this switch is ad­justed to the position which either gives the most gain
before feedback or, if both positions give the same gain
before feedback, use the position that produces the highest

pitch feedback. The program signal, after leaving the
PHASE Switch, is routed to the output transformer which
provides both LlNE LEVEL and MIC LEVEL outputs. The
LlNE LEVEL output is connected to one professional

three-

pin, male, audio output connector (27) and two three-circuit

phone jacks (25). The MIC LEVEL output is a

low-im-

pedance output, 50 dB below the LlNE LEVEL output, and is
connected to a professional three-pin male, audio output
connector (24).

Note that all of the program outputs are balanced with

respect to ground. If a phone plug is used to connect the
mixer line level output to an amplifier or tape recorder and
the phone plug is a two-circuit type, the line outputs will

automatically become unbalanced. If the 3-pin unbalanced

output is used and a phone jack output is

also

to be used,
obtain a stereo phone plug and connect the tip and ring of
the plug only. (The sleeve is a shield and would cause a
ground loop.)

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 SENSI­TIVITY Control (18) which in turn feeds the VU Meter ampli­fier 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 SEN­SITIVITY 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 ampli­fiers, 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 be­tween 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

(ll), 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 IN­PUT

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 connec­tions described above. The tone should be heard clearly
through the headphones. If a channel is suspected of poor
quality, it 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, dis­connect the program output, either at the back of the Con­sole, 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 cali­brated 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.

,

MIC~

ILINE,

,

LINE^

,

,

SR I01 POWER TAPE

AUDIO CONSOLE AMPLIFIER RECORDER

@

MIC LEVEL

1)

MIC LEVEL

INPUT JACK OUTPUT JACK

SR

lOl

AUDIO CONSOLE

0

LlNE LEVEL

INPUT JACK

AUx.

LEVEL

n

OUTPUT JACK

SR

101

AUDIO CONSOLE

I

PHONES JACK

@

POWER AWL

AUX LEVEL

INPUT JACK

I

1

SR lOl

AUDIO CONSOLE

GATED

1

C0E;:SOR

1

I

MIXER

1

FIGURE

6.

TON'E OSCILLATOR APPLICATIONS

BASIC OPERATING HINTS

Should any difficulty be encountered in Console opera-

tion, the problem may often be traced to some simple

source
is offered as a basic guide to problems of this sort.

Symptom: Console is

Check: 1. Check that ac Dower source is "live" and

Symptom:

Check: 1. Check that PROGRAM Switch or Switches

such as an error in interconnection. The following

out)

that Console is plugged in.

2.

Check that POWER ON-OFF Switch (19) is
on.

3. Check to see that rear-panel
SLO-BLO Fuse (22) is good. 2. Check that channel PROGRAM Switch (13)

Console is "dead" (no output, VU Meter lamps

lit) 3. Check that AUX-MIC Switch (14) (channels

(13) are depressed.

"dead" (no output, VU Meter lamps

3AG-3116A Check: 1. Check for defective input cable or source.

Symptom:

2. Check that cable from PROGRAM
PUT/LINE
accidentally been connected to PROGRAM
OUTPUT/MIC LEVEL Connector (24).

3. Check that PHASE Switch (26) is not be­tween positions.

4. Check that external equipment is properly
connected to

One channel is "dead" (other channels

ating properly)

is depressed.

7

and 8 only) is not between positions or in

the wrong position.

LEVEL Connector (27) has not

LINK Jacks (28,31).

OUT-

oper-

SR101 Series 2 Audio Console

SPECIAL OPERATING INSTRUCTIONS

The previous section described normal interconnection The high-impedance cable should be limited to 6.lm
and operation of the SR101 Audio Console; this section (20 ft.). If a long cable length is required, use up to 3.05m
provides information on special set-ups to more fully utilize (10 ft.) of high-impedance, single-conductor, shielded
the capabilities of the Console.

HIGH-IMPEDANCE MICROPHONES

UP to two high-impedance dynamic, ribbon or condenser
microphones (crystal or ceramic microphones are not
recommended) can be used with the
need for line matching transformers simply by using the
AUX. INPUT Jacks (32) on channels
corres~ondincl INPUT ATTEN Switch (14) to AUX. NOTE:

very highoutput produced by s0m.e dondenser micro-

The
phones may be compensated for by proper setting of the

INPUT

the low-impedance MIC LEVEL Input Jacks
matching transformer (Shure A95 Series) must be used.

ATTEN Control.

If a high-impedance microphone is to be used with one of

Console without the

7

or 8 and moving the

(33), a line

cable (Belden
phone and line matching transformer, and add as much

low-impedance, two-conductor, shielded cable
#8412,'
and Console input jack. These precautions will help avoid
high-frequency
hum and noise.

Musical instruments, acoustical
tical-electrified, or electrified, may be amplified through the
Console. For acoustical instruments, place a microphone
close to the instrument strings, sounding board, or mouth.
Adjust equalization, reverb and volume controls as
sary.

#8401, #8410, or #8411) between the micro-

(Belden

or #8422) as necessary between the transformer

signal loss and reduce the possibility of

INSTRUMENTS

(non-electrified), acous-

neces-

3.05

m

(10') MAX.

r

AUX OR HEADPHONE
OUT

PREAMPLIFIER

-

FIGURE

-I

r

A95

LINE

MATCHING

TRANSFORMER

LOW IMPEDANCE

7.

PREAMPLIFIER-CONSOLE CONNECTIONS

PUP

LOW IMPEDANCE HIGH IMPEDANCE

MICROPHONE

CABLE

TO

305 m (1000')

1

MIC LEVEL

INPUT

SR

AUDIO CONSOLE

lOl

11