Shure SR-107 Service manual

222 HARTREY AVE.. EVANSTON. IL. 60204 U.S.A.

AREA CODE 312/866.2200 CABLE: SHUREMICRO

TWX:

910-231-0048 TELEX: 72.4381

OPERATION AND SERVICE MANUAL

MODEL SR107

AUDIO EQUALIZER

I

The Shure SR107 Audio Equalizer is a compact, versa­tile unit designed to provide adjustment of tonal balance
on an octave-by-octave basis across the audio frequency
range. The
for the purposes of feedback control in live performances,
playback equalization (correcting for equipment response
and/or room acoustics in prerecorded performances), and
improvement in the sound quality of live performances.
Equipment response correction includes the elimination
of such problems as transducer incompatibility, overload
at low frequencies (rumble), tape hiss and disc surface

noise. The
device, designed primarily for installation between the
audio console or mixer and the power amplifier of the
sound system.

SR107 is used in sound system applications

SR107 is a balanced input and output line level

DESCRIPTION

The SR107 has ten octave band, minimum phase, com-

bining type filters centered on
from 31 Hz to 16 kHz. Each filter is adjustable for ap-

proximately 15 dB of boost or attenuation. The equalized
output is adjustable over a

gain of up to 20 dB may be introduced to compensate for

low input signals. A peak-responding overload
emitting diode (LED) is provided on the front panel. The
SR107 contains both professional three-pin and phone
jack input and output connectors, and a phone jack
auxiliary output.

The

SR107 is designed for maximum simplicity of op­eration and maintenance. All components are of the high­est quality and are operated well within their respective
ratings to assure maximum reliability under normal use
conditions.

The

SR107 and SR107-2E are identical except that the

SR107 operates from 108-132 Vac, 50/60 Hz and the
SR107-2E operates from either 105-125 or 210-250 Vac,
50/60 Hz (switch-selectable). The SR107-2E is supplied
with a detachable ac line cord (without power plug). The
SR107 (only) is listed by Underwriters' Laboratories, Inc.,
and is listed by Canadian Standards Association as

certified.

All

SR107 units are supplied with four rack-mounting
screws for mounting in standard 19-inch (483 mm) audio
equipment racks or in optional Shure

Carrying Cases. An optional protective cover, Shure
Model A107A, is also available.

t

International

Organization

for

Standardization

ISO? preferred frequencies

215 dB range, and overall

light-

A30A or A105A

SPECIFICATIONS

Equipment Type
Voltage Gain:

GAlN Control
at UNITY

GAlN Control
at +20 dB

LEVEL Control

Frequency Response
Signal to Noise Ratio

(20 Hz-20 kHz) .Typically 99 dB at maximum out-

Output Noise,

Maximum
(300 HZ-20
at LINE OUTPUT) -84 dBV (63 pV)

Output Hum and Noise,

Maximum
(20 HZ-20

at LINE OUTPUT)

lnput Common Mode

Rejection

Clipping Level

(30 HZ-20

Input

'See

Page

2

.......

kHz

kHz

.........

kHz):

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

*

.....

.All transistor inductorless active

equalizer

.O

dB LINE INPUT to LINE OUT­PUT

-27

dB LlNE INPUT to AUX

OUTPUT

-50 dB LlNE INPUT to MIC
OUTPUT

.......

+20 dB LINE INPUT to LINE

OUTPUT

-7 dB LlNE INPUT
PUT

-30 dB LlNE INPUT

OUTPUT

...

.Provides additional gain adjust-

ment of k15 dB over values
given above, EQUALIZER IN

mode only.

.

.%2 dB from 30 Hz to 20 kHz,

EQUALIZER IN or BYPASS

.....

put with Filter Controls and
LEVEL Control at zero and

GAlN Control at UNITY in

EQUALIZER IN mode.

...

-

69 dBV (0.50 mV), LEVEL Con­trol at

-

-91

Switch in BYPASS

...

-

83 dBV (71 pV)

-

67 dBV (0.56 mV), LEVEL Con­trol at +15, Filter Controls at

-15

-88

Switch in BYPASS

.90 dB minimum at 100 Hz

+18 dBm minimum (+15.8 dBV,

6.2V) GAlN Control at UNITY

-2

0.62V) GAlN Control at + 20dB

+15, Filter Controls at

15

dBV (28 pV), EQUALIZER

dBV (40 pV), EQUALIZER

dBm minimum (-4.2 dBV,

to AUX OUT-

to MIC

Copyright

27Al089

1979,

(SF)

Shure

Brothers

Inc.

Printed

in

U.S.A.

I

FIGURE

Output

Overload Indicator
Input Impedance

Output Impedance: mum

MIC OUTPUT
LINE OUTPUT
AUX OUTPUT

Distortion: Weight .3.5 kg

lntermodulation

Harmonic

Phase

Equalization Filters:

Center
Frequencies

Characteristics

...........

.......

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

+18 dBm minimum (+15.8 dBV,

-10.2

-34.2

....

Illuminates 3 dB 21.5 dB before

.....

.70 kilohms actual, balanced Hz; 6 watts maximum

....

.I

...

.I15 ohms actual, balanced (for

...

.630 ohms actual, unbalanced Storage -29°C to 71°C (-2O0Fto 160°F)

..

.0.25% max. at 12.2 dBm (3.2V)

.I% max. total harmonic distor-

Pin 3 and tip contacts of

.....

.Octave spaced from 31 Hz to 16

..

.15.5 f 2 dB boost or attenuation

6.5

6.2V) at LINE OUTPUT
dBV minimum (0.31V) at

AUX OUTPUT Filters are minimum phase,

dBV minimum (19.5 mV)

at MIC OUTPUT ly isolated.
output clipping occurs

bridging (for use with line lev­el source, 10 kilohms or less.)

ohm actual, balanced (for use
with 25- to 600-ohm inputs)

use with 600-ohm lines)

(for use with auxiliary circuits

of 600 ohms or more

ance)

(LINE OUTPUT) with a 60 Hz Installation
and 7.0 kHz input at a

tion at 12.2
OUTPUT), 30 Hz-20 kHz with

Filter Controls at +15, GAIN Certifications .Listed by Underwriters' Labora­Control +20 dB and LEVEL tories, Inc.; listed by Canadian
Control at +15

INPUT Connectors are in

phase
OUTPUT and tip contacts of

LlNE and AUX OUTPUT Con-

nectors

kHz. Accurate to within

of labeled value

at center frequency

t2 dB at maximum boost or
attenuation at one-half octave
above or below center fre­quency

dBm (3.2V) (LINE

with

pin

1.

4:l ratio

of

MIC/L'NE

SR107 FRONT PANEL

imped-

LINE

t10%

2

Operating Voltage

and Power

Accessory Power
Temperature

Operating

34

.........

SR107: 120 Vac t lo%, 50/60
SR107-2E: 105-125 or 210-250

...a

-31 Vdc open circuit, 27 Vdc at

........

5

Typical filter frequency re­sponse characteristics are
shown in Figures 5A and

combining type and electrical-

Vac, 50/60 Hz; 6 watts maxi-

10

-7°C to 57°C (20°F to 135°F)

..........

Dimensions

.........

.44.4 mm height x 483 mm width

x 218 mm depth (1-314 in. x
19 in. x 8-9/16 in.) (Figure 3)

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

Finish

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

..........

Matte black

.Equipped for standard 19 in.

(483 mm) audio rack mount-

ing; may be operated in op­tional
Case (with other equipment)

........

Standards Association as cer­tified (SR107 only)

*

Measurement conditions unless otherwise specified: Operating voltage
60

Hz

(SR107). 230V 60
tion (~~107-2i). LI~E INPUT 7 volt at 1
OUTPUT
nated in
control at zero;

and

A'UX

150 ohms;

OPERATING INSTRUCTIONS

I

I

TO reduce the risk of fire or electric shock, do not

I

I

expose this appliance to rain or extreme moisture.

I

Functional Description (Refer to Figures 1 and 2)

1.

31 Hz to 16 kHz Filter Controls- Provide _+I5 dB

level adjustment at center frequency of each of ten

octave band filters.

Hz

with VOLTAGE SELECTOR Switch in 220V posi-

OUTPUT terminated in 600

GAlN Control at UNITY:

EQUALIZER

Switch set to

WARNING

6

mA, maximum

(7

Ib, 12 oz)

A30A or A105A Carrying

kHz

through 600 ohms. LlNE

ohms, MIC

Filter Controls and LEVEL

IN.

OUTPUT'

58.

I~OV,

termi-

I

I

I

I

I

2

SO/M

w.

6

WLlTS

17

SR107-2E

ONLY

16

FIGURE

15

2.

SR107 REAR PANEL

7

8

9

10

11

12

13

14

EQUALIZER IN/BYPASS Slide Switch - Disables

filters and LEVEL Control in BYPASS position and

returns gain of Equalizer (LINE INPUT to LlNE OUT-

PUT) to value determined by rear-panel GAlN Con­trol.
LEVEL Control -Operative only in EQUALIZER IN
mode. Provides adjustment of Equalizer output level

+I5 dB to compensate for changes in gain re-

of
sulting from Filter adjustments.

-

OVERLOAD LED
dication when peaks in output signal approach
actual clipping level of output amplifier.
POWER
unit.
Power-On lndicator Lamp
being applied to unit.
30 VDC Accessory Power Jacks
open circuit (27 Vdc at 10
equipment.
AUX OUTPUT Phone Jack- Provides unbalanced
low-impedance output for connection to audio con­sole or amplifier-mixer link input.
LlNE OUTPUT Phone Jack
unbalanced line level output to power amplifier.
MIC/LINE Slide Switch - Connects line level or
low-impedance microphone level signal to 3-pin
OUTPUT Connector.
OUTPUT 3-Pin Male Connector
anced output at either line level or low-impedance
microphone level as selected by
May be unbalanced externally.
GAlN Control

from UNITY to +20 dB to accommodate various

input and output requirements. Operates in both
EQUALIZER IN and BYPASS modes.
LlNE INPUT 3-Pin Female Connector
balanced bridging, high-impedance input connec-

tion from audio console or mixer-preamplifier. May
be unbalanced externally.

LlNE INPUT Phone Jack
unbalanced bridging, high-impedance input con-

nection from audio console or mixer-preamplifier.
Ac Grounded Line Cord -Connects unit to ac

power source

VOLTAGE SELECTOR Slide Switch

lection of 105-125 or 210-250

tion
AC (MAINS) POWER 3-Pin Connector
unit to ac (mains) power source via supplied line
cord

General Operating Instructions

The

SR107 Audio Equalizer is primarily intended for
connection in a sound system between the output of an
audio console or mixer-preamplifier and the input to the
power
level input to the Equalizer and utilizes its line level out­put to drive the power amplifier. In a system using a
limiter or compressor between the mixer and power am­plifier, the
limiter or compressor and power amplifier to achieve
best signal-to-noise performance.

Out and Link In jacks of a console or mixer equipped
with these jacks. The
operation at the lower signal levels characteristic of this
location and is equipped with an auxiliary output of ap­propriate level for the Link In connection. In the follow-

amplifier(s). A typical installation provides a line

An alternate location for the

ON/OFF Switch - Controls ac power to

(SR107-2E only).

(SR107-2E only).

SR107 should be connected between the

Provides peak signal visual in-

-

Indicates ac power is

-

Provide 31 Vdc

mA max.) for accessory

-

Provides balanced or

-

Provides bal-

MIC/LINE switch.

-

Provides gain adjustment range

-

Provides

-

Provides balanced or

(SR107 only).

SR107 is between the Link

SR107 can provide satisfactory

-

Vac 50/60

Permits se-

Hz

-

Connects

opera-

ing general operating procedure, variations in connec-

tion for Link operation are indicated where applicable.

1. Using hardware provided, install
Equalizer securely in standard 19 in. (483 mm) rack
or optional
making electrical connections.

2. Connect audio console or mixer-preamplifier line
level output to
or phone jack (13. 14). (For Link use, connect link

output of console or mixer to either

INPUT Connector.)

3. Connect
OUTPUT Connector (9, 11) to power amplifier input.
If 3-pin connector is used, place
in LlNE position. (For Link use, connect

OUTPUT (8) to link input of console or mixer.)

4. Place all Filter Controls (1) and LEVEL Control (3)

in zero position. Move EQUALIZER
Switch (2) to BYPASS. Set GAlN Control (12) to

UNITY. (For Link use, set GAlN Control to

SR107: Connect ac line cord (15) to grounded 108-

5.

132V, 50/60 Hz ac source.
SR107-2E: Move VOLTAGE SELECTOR Switch (16)
to 115V or 220V position as appropriate. Attach
suitable
insert chassis connector into AC (MAINS) POWER
Connector (17). Connect ac line cord to grounded
105-125V or 210-250V, 50/60 Hz ac source.

6. Position speakers in desired operating locations

and aim for uniform coverage of audience area.

Position microphones (if used) as required by per-

formance or application involved. Basic precautions

relative to microphone and speaker locations

should be observed to reduce feedback potential.
Set all tone controls in audio console or mixer to
their zero or flat position. Set output phase switch
(if any) to

7. Apply power to sound system. Place POWER ON/

OFF Switch (5) in ON position. Power-On lndicator
Lamp (6) will go on, indicating operation of unit.

8. Using voice, program material or tone generator

(such as Shure Model
system, increase console or mixer output level until
SR107 OVERLOAD lndicator (4) flickers. Increase
volume control on power amplifier until amplifier
clipping distortion is evident. OVERLOAD lndicator
now indicates onset of clipping in both
power amplifier. NOTE: This step does not apply
to Link operation.

9. Using voice or program material as source, adjust

console or mixer output to provide desired sound

level in room. (For Link use, adjust individual chan­nel volume controls for desired mix and set to level

that will cause only occasional flickering of
OVERLOAD lndicator on peaks of high level pro­gram material.) If microphones are used as sound

source, satisfactory sound level may not be possible

due to feedback. In this case, set volume to stable

point just below feedback level.

10. Operation of
flickers slightly, on only the loudest program peaks,
is recommended. This will maximize signal-to-noise
ratio, but will generally not result in audible distor­tion since lndicator threshold is 3 dB below actual
clipping level.
Operating with OVERLOAD lndicator always off may
result in less than optimum signal-to-noise per-

formance.

A30A or A105A Carrying Case prior to

SR107 LlNE INPUT 3-pin connector

SR107 LlNE OUTPUT phone jack or 3-pin

&pin male power plug to ac line cord and

0" or in-phase condition.

A15TG) for input to sound

SR107 such that OVERLOAD lndicator

SR107 Audio

SR107 LlNE

MIC/LINE Switch

SR107 AUX

IN/BYPASS

$20 dB.)

SR107 and

SR107

If OVERLOAD Indicator is flashing brightly or on
constantly, operating level is too high and will cause
distortion, and may result in less than full power
output from the sound system.

11. Set EQUALIZER Switch to IN position. Adjust Filter
Controls for particular equalization objective. See

procedures for feedback control, and playback and
live performance equalization in following sections.

While adjusting Equalizer Filter Controls, use

LEVEL Control to maintain desired volume in room.
Do not attempt equalization beyond bandwidth
limits of sound system. For best results, keep

number of Filter Controls used to a minimum, and
adjust each control no more than required.

12. After equalization, perform listening check of audi­ence area to be sure that sound quality is satis­factory throughout room.

Mounting and Ventilation

The SR107 Audio Equalizer is designed for rack-mount-

ing in a 483 mm (standard 19 in.) audio equipment rack
and is supplied with the necessary mounting hardware
(see Figure 3).

SR107 may also be operated while mounted in a

The

Shure

A30A or A105A Carrying Case. The A30A has a

panel height capacity of 88.9 mm

(3% in.) for two SR107s
or one SR107 and one other unit of 44.4 mm (1% in.)
height. The

A105A has a panel height of 178 mm (7 in.)

and will accommodate up to four units with panel heights

equal to that of the

SR107.

No special precautions are required for ventilation. The

SR107 may be operated over a temperature range of - 7"

to 57°C (20" to 135°F) in continuous duty without

derating.

Power Supply

The SR107 is furnished with a three-conductor power
cable and three-prong grounded plug (15). Connect the
SR107 to an outlet which supplies 108 to 132 volts ac,
50/60

Hz

power. The maximum power consumption at
120 volts under normal operating conditions is 6 watts
(0.05 amperes at 120 volts).

If extension cords are re-

quired, a high-quality, 18 gauge or larger cord should

be used.

r

18-9/16 IN]

197

mm'

483

443

mrn

I

I9

IN]-

rnm

117

7/16

IN

I

17-314 IN)

1

--

"NOT INCLUDING CABLE/CONNECTOR CLEARIWCE DEPTH

FIGURE

OVERALL DIMENSIONS

The SR107-2E is furnished with a three-conductor de­tachable line cord without a power plug. Obtain a suitable
3-pin male power plug and attach it to the line cord. The
plug should be installed by qualified service personnel.
(Brown lead goes to "hot" or "live" terminal, blue lead
to neutral terminal, and

green/yellow lead to ground or
earth terminal.) Connect the equipment end of the line
cord to the AC (MAINS) POWER Connector (17) on the

rear panel of the SR107-2E. Select the proper operating
voltage (1 15V for 105-125V supply or 220V for 210-250V
supply). Maximum power consumption at either operating
voltage is 6 watts.

A POWER ON-OFF toggle switch (5) on the front panel

controls the application of ac power to the

red indicator lamp (6) indicates the power-on condition.

Functional Circuit Description

Input connections to the SR107 Audio Equalizer are

made through either a three-conductor (stereo type)

a

phone jack (14) or

three-pin female audio connector

(13) (see Figure 4). The connectors are wired in parallel
to provide a balanced line level input with either con­nector. Inserting a two-conductor phone plug into the

phone jack will automatically unbalance the input. The

input signal is passed through a 6 dB
transformer to an attenuator. The attenuator provides an

additional 11 to 26 dB of loss depending upon the setting
of the LEVEL Control (3) described later.

I44

4

mm

11-314 IN)

3.

SR107 and a

stepdown input

FIGURE

4.

SR107 BLOCK DIAGRAM

The next stage is an input amplifier which has a gain
of 14 to 34 dB depending on the setting of the rear panel
GAlN Control (12). The output of the amplifier is fed to

two cascaded differential amplifier stages which com-

prise the equalizer boost and cut circuitry. The individual
active gyrator resonators for 31 Hz, 125 Hz, 500 Hz, 2 kHz

and 8 kHz are connected to the first of the differential
amplifiers and provide control of these frequency bands.

The second amplifier is connected to the 63 Hz, 250 Hz,

4

1 kHz,

kHz, and 16 kHz active resonators for control of

the remaining five frequency bands. Each of the ten

octave-spaced filters is equipped with a front panel Filter
Control (1) which may be adjusted for up to 15 dB boost

or cut relative to its zero or flat position (see Figure 5).
This configuration of minimum-phase networks assures
correct filter characteristic combinations, minimum am-

plitude ripple, and minimum phase shift.

The output of the second Equalizer differential ampli-

fier is fed to the EQUALIZER

IN/BYPASS Switch (2)
which selects the input to the line output stage from
either the equalizer amplifier in the IN position, or from
the output of the input amplifier stage in the BYPASS

position.

(3)

The Equalizer LEVEL Control

of the Equalizer output level over the range of

provides adjustment

215 dB
relative to its zero setting. Reduction in output is accom­plished by attenuating the signal input to the input ampli-

fier. An increase in output is produced by changing the
gain in the output amplifier. The LEVEL Control operates
only when the EQUALIZER

INIBYPASS switch is set to

the IN position.

I

-10

z

U

-5

g

0

P

$

-5

-10

u

20 100 KO0 IOPOO 20,000

FIGURE 5A-

FREWENCY IN HERTZ

Em FILTER AT

7.5 dB

BOOST

OR

CUT

work at the output of the output amplifier. The AUX OUT-

PUT can be used to feed the link input of an audio

console or mixer so equipped.

An LED driver stage connected to the output amplifier

illuminates the front panel OVERLOAD LED (4) when the

audio signal approaches the output clipping level. The

OVERLOAD Indicator operates in both the EQUALIZER
IN and BYPASS modes.

Input and Output Connections

Two LlNE INPUT Connectors are located on the rear

panel of the

SR107. A professional, three-pin female
audio connector (13) provides a balanced connection
from the audio console or mixer-preamplifier. A standard

1/4

in. three-conductor (stereo) phone jack (14) provides
either a balanced or unbalanced input connection de­pending upon the phone plug (three-conductor or

two-

conductor) used.

The gain of the

the back panel

SR107 can be adjusted by means of

GAlN Control from UNITY to +20 dB in
either the EQUALIZER IN or BYPASS modes. The 20 dB
gain capability may be used in hi-fi or Link applications
to maintain desired signal-to-noise performance through

SR107. It also allows the Equalizer to accommodate a

the
variety of normal input and output levels while maintain-

ing an adequate operating signal-to-noise ratio.

Three output connectors are provided on the rear

panel. A professional three-pin male audio OUTPUT con-

a

nector provides

balanced low-impedance output at
either microphone or line level depending upon the
setting of the associated

LlNE OUTPUT Connector is a standard

MIC/LINE Slide Switch. The

1/4

in. three-

conductor (stereo) phone jack which provides a low-

impedance line level output that can be either balanced

a

or unbalanced. The AUX OUTPUT Connector is

1/4

ard

in. two-conductor phone jack providing a low-

stand-

impedance unbalanced output suitable for connection to

a hi-fi power amplifier or the link input of a mixer or
audio console. The LINE, microphone level and AUX out­puts are isolated and may be used simultaneously.

t20

+I5

t10

15

U

H

O

p

-5

u

:

-I0

g

-I5

-20
4

2

20 100 1000 IO.WO 20.000

681

2

4

681

FIGURE50 -EACH FILTER AT MAXIMUM BOOST OR

FREWENCV IN HERTZ

2

4

CUT

681

2

FIGURE 5.

TYPICAL FILTER CHARACTERISTICS

The output amplifier has a gain of 5 to 20 dB depend-

ing on the setting of the LEVEL Control, and is capable

+

of delivering

18 dBm through the output transformer to

a 600-ohm load at either of the balanced LlNE OUTPUT

(9,

Connectors
nector may be switched from balanced line level to

11). The three-pin male OUTPUT Con­low-

impedance microphone level output (50 dB below line

level) by means of the

MIC/LINE Slide Switch (10) which

selects one of two secondary windings on the output

(8)

transformer. The AUX OUTPUT Phone Jack

is sup-

plied with an output signal that is 20 dB below that of the

LlNE OUTPUT. This is obtained from an attenuator net-

APPLICATIONS

The primary applications for the SR107 Audio Equal-

izer are as follows:

1. Feedback Control -Adjustment of sound system
frequency response to provide maximum gain be­fore feedback and improved sound quality in a
variety of live performance situations. The

is equally adaptable to feedback control functions
in either a house sound system or stage monitor
(foldback) system.

2. Playback Equalization -Adjustment of audio play-

back system frequency response to compensate for
any variations in electrical or acoustical response
that may alter the natural sound of the recorded

material.

3.

Live Performance Equalization - Adjustment of
sound system frequency response to provide a
tonal balance appropriate to the performance and
to reduce the tendency for feedback.

The following sections present procedures and recom-

mendations for the use of the

SR107 in each of these

applications. Also included is a section discussing acous-

tic measurement instrumentation and its use with the

SR107.

Feedback Control

In many live performance sound reinforcement applica-

tions, feedback is often the limiting factor in achieving

SR107

satisfactory sound amplification and coverage. The SR107

Audio Equalizer provides the means for selective sup-

pression of those octave frequency bands in the audio

spectrum where feedback is likely to occur. These fre-

quency bands differ from one installation to another

depending upon the acoustics of the room, equipment

used, and speaker and microphone placement. The range

of control of both frequency and amplitude provided in

SR107 is sufficient to accomplish significant feedback

the
suppression without noticeable loss of program material.

Proper adjustment of the Equalizer for feedback control
is a matter of some experimentation; a general procedure
is described here. These procedures for both house and
stage monitor live performance sound reinforcement sys-

tems assume that the system speakers have a consistent

phase relationship and that all microphones used are
also wired for consistent phase operation. If necessary,
the phase of any balanced microphone line equipped
with professional 3-pin connectors can be reversed using

a plug-in Shure Model

House System

1. Refer to General Operating Instructions for initial
connections and setup.

2.

Adjust individual mixer volume control for each per­former's microphone to level slightly below feed­back threshold. If console or mixer is equipped
with output phase reversal switch, set to position
giving highest gain without feedback. If necessary,

reduce setting of master volume control slightly and

return to feedback point for each switch position to
evaluate switch effect. Operation of this switch will
usually affect only low-frequency feedback.

3, Increase LEVEL setting until feedback squeal or

ringing is heard. If feedback appears to be
pitched, one of five mid-to high-frequency Filter
Controls
eliminating feedback. Each Filter Control should be
turned down (counterclockwise) and back to

position slowly to determine which is most effective.
Control which stops feedback with the least rota­tion should be turned down only so far as necessary
to eliminate feedback.

4.

If feedback frequency happens to fall between

bands covered by two adjacent controls, it may be
necessary to turn down both controls slightly to
obtain desired feedback suppression.
If feedback sound first noted in step 3 was

5.
pitched, adjustment procedure should be started
using low-frequency (31 to 500 Hz) Filter Controls.

6. Having eliminated first feedback condition, increase
gain by clockwise rotation of LEVEL Control until
feedback is again noted. Repeat steps 3,
to eliminate new feedback condition. This may re­quire adjustment of different Filter Control or a
further decrease in control or controls previously
turned down.

7. Repeat step
system before feedback is sufficient for perform-

ance involved, (b) feedback becomes a combination

of sounds of various frequencies, or (c) any one

Filter Control has been turned all the way down

(-15). Adjust LEVEL Control to slightly below

point at which final feedback sound occurred.

8.

Conduct voice test using each live microphone in

sequence. As each microphone is used, listen for

ringing. If ringing is noted, attempt to eliminate it
by further decrease in appropriate Filter Control
or slight decrease in LEVEL Control setting.

(1

Al5PR Phase Reverser.

high-

thru 16 kHz) will be most effective in

"0"

low-

4,

and 5

6 until either: (a) volume level of sound

9. Perform critical listening check in audience area

during talk test or live performance to determine if
additional equalization adjustments are necessary
to improve sound quality (boost of frequency bands

1

in the
and intelligibility, etc.). Refer to Live Performance
Equalization for additional information.

Stage Monitor System

In a stage monitor system the

tween the audio console monitor line output (line level)

or the line level output of a monitor mixer and the line

level input of the power amplifier used to drive the stage
monitor loudspeakers. With this exception the initial set­up of the stage monitor system is the same as that given
in General Operating Instructions. The number, type and
arrangement of microphones and speakers should be the

same as used in the performance.

1.

If more than one performer's microphone is in­volved, select lead performer or center stage micro­phone for use in feedback equalization procedure.
NOTE: During this procedure a person must stand
in front of or hold the microphone being equalized
in a manner similar to that of the performer.

2.

Roll off low frequency response of system by ad­justing 31 Hz Filter Control to
125 Hz to -5. This will reduce low frequency noise

pickup without affecting intelligibility.

3. Equalize stage monitor system following House
System procedure, Steps

4. Conduct voice test for each of remaining micro-

phone positions in sequence using same channel
gain setting as for first microphone. (This assumes
that all microphones used have essentially the same
sensitivity and response.) If feedback or ringing is
encountered at any microphone location, try elim-

inating it by adjustment of nearest speaker position
or microphone distance. While performing voice
test, check intelligibility of sound from monitor
speakers. Intelligibility can usually be improved by
boosting frequencies in
vided that the feedback threshold is not affected.

5. Check operation of stage monitor system with all
performer microphones on (preferably with some­one standing in front of or holding each micro­phone) to determine maximum gain settings before
feedback for individual channel and master volume
controls.

6.

Operate stage monitor system and house system
simultaneously at desired volume levels to verify
satisfactory performance. If house system console
or mixer is equipped with output phase reversal
switch, operate switch and check for any improve­ment in gain before feedback in either house or
stage monitor system.

Playback Equalization

SR107 Equalizer may be used to adjust the overall

The
frequency response, octave by octave, of an audio play­back system to compensate for any electrical or acousti­cal response deficiencies of the system and to provide
more natural sound reproduction.

Assuming that good engineering practice has been
followed in selecting and installing the loudspeakers for
uniform sound coverage, it is necessary to subjectively
evaluate the sound quality and to equalize for reasonable
audio spectral balance. While no specific procedure can
be offered for this type of equalization, the following
recommendations should be helpful:

kHz to 4 kHz region to improve presence

SR107 is connected be-

-

15, 63 Hz to

2

through 7.

1

kHz to 4 kHz range, pro-

-

10,

Refer to General Operating lnstructions for connec-

tions and setup.

Use typical program source and program material.
Locate listening position in main audience area so
that what is heard is typical of what most of the

audience will hear. If practical, the

SR107 should

be at this location (temporarily) for ease of ad­justment.
As Filter Control adjustments are made, adjust

LEVEL Control to maintain initial volume level, using

EQUALIZER

INIBYPASS Switch to compare equal­ized to unequalized sound level and quality.
Bass guitar, string bass or kick bass drum sounds
are most affected by 63 Hz and (to a lesser degree)

125 Hz Filter Controls. Avoid excessive boost of
these frequencies or low-frequency overload may

occur.
Power supply hum (60 Hz) and certain types of

turntable rumble may be suppressed using 63 Hz

Filter Control. The 31 Hz Control may also be help­ful for very low frequency turntable sounds.
The

8

kHz Filter Control is most effective in con-

trolling "brightness" of the sound, especially affect-

8

ing speech sibilance and cymbal sounds. The

kHz
and 16 kHz Filter Controls may also be used to
reduce record noise and tape hiss.

Vocal performer sound is affected most by varia­tions in the Filter Controls covering the 1 kHz to

4

kHz range.
If room resonance is encountered where frequen­cies in a certain band are accentuated, some ad-

justment of speaker positions may correct the

condition. If this is not practical, experiment with
attenuation of the octave bands in the suspect fre-

quency region. The low-frequency octaves (32
through 250 Hz) are often affected by room char­acteristics. A typical subjective effect is that of a

"boomy bass" sound.
Use tone controls on the console or mixer (if so

equipped) for broadband adjustment of the high

or low end of the audio spectrum.

Live Performance Equalization

Equalization of a sound reinforcement system for live
entertainment applications is similar to that described in
Playback Equalization except that microphones and per­formers constitute the sound source. Utilize this section

where applicable in live performance equalization.

In most indoor sound system installations, the

SR107

Audio Equalizer is adjusted first for feedback control as

previously described. Additional adjustments may then
be made to improve sound quality. This second level of
adjustment is usually performed during a rehearsal where

the performers and musicians are present and the sound

aspects of the total performance can be evaluated. It is
important to note that this secondary equalization process

can affect the feedback threshold previously achieved

and should therefore be performed with caution.

SR107 was not previously connected to the sound

If the

system, refer to General Operating lnstructions for con-

nection and setup instructions. Preliminary adjustment of

the Equalizer can be made using recorded program

material typical of the live performance.

The recommendations given in Playback Equalization

should be considered along with the following:

1. While judgements of sound quality should be made
in the main audience area, it is advisable to check

a number of locations throughout the area for
significant variations in response. If such are en-

countered, speaker location and aiming should be
reviewed.

2. Any increase in Filter Control setting (clockwise
rotation) previously adjusted for feedback suppres­sion should be done with care. In the case of a
reverberant room where an audience would signifi­cantly increase the sound absorption, this may

be

possible.

3. Intelligibility and presence for vocal performances
may be improved by slight increases of system

response in the

4.

Adjustment of the response of a particular micro-

1

kHz to 4 kHz region.

phone must be made through the use of the console
or mixer tone controls for that particular channel.
If an individual channel exhibits a "hollow" or un­natural sound, the gain of that channel may be
near feedback threshold and should be reduced.

5.

If the room is acoustically "dead" (carpeted, up­holstered seats, acoustic wall treatment), the sound
system output may seem deficient in the lower mid-

range frequency region. In this case, slight boosting
of the frequency bands in the range of
4

kHz is appropriate. If the room is "live" or rever-

1

kHz to

berant, the sound may seem excessively "bright"

8

and some attenuation of the octave bands at

kHz

and 16 kHz may provide a more uniform response.

In outdoor applications, attenuation of both low and
high frequencies may be experienced. Boosting

8

octave bands 125 Hz and below,

kHz, and 16 kHz
may be helpful but must be performed carefully to
avoid excessive amplifier and speaker drive levels.

6. Occasionally a combination of program material
and room resonance produces a

"boomy" sound in

which some low frequencies are accentuated. At-

tenuation of the 63, 125 or 250 Hz Filter Controls
will suppress this characteristic.

Equalization Instrumentation

While the final measure of any equalization effort is a

subjective judgement of the quality of the sound delivered

to the audience, acoustic measurement instrumentation

is available which can be of considerable assistance in
more efficient and consistent equalization procedures.

The equipment consists of a pink noise generator

(equal sound energy per octave), an equalization analyzer

and an omnidirectional analyzer microphone with a

known frequency response. The analyzer generally pro-

vides a display of input signal amplitude versus frequency

1/3

in either octave or

octave bands for the complete

audio spectrum.

In general, equalization analyzer equipment is used to
measure sound system performance instead of perform­ing the subjective evaluations previously discussed. Con­nection, setup and operation of the

SR107 remains the

same. Recommendations regarding various equalization

objectives are also generally applicable. Operation of the

analyzer equipment is in accordance with the manufac-

turer's instructions.

Usually, the analyzer equipment is used first to estab­lish the desired house curve or preferred sound system
response characteristic. For playback equalization, the
analyzer microphone is located in the main audience

area and connected to the equalization analyzer input.
The noise generator is connected to the audio console

or mixer input and the volume adjusted to provide a

sound level sufficiently above the room ambient noise

level. The analyzer should be placed close to the

SR107
so that as Equalizer adjustments are made, the results
are easily observed. Adjustment for a flat response in the

audience area of a large room will usually result in an

overly bright sound. Common practice is to adjust for

3

dB per octave rolloff of the high frequencies starting
at about 1 kHz. Frequency response is then checked in
other locations in the audience area and, if necessary,

the Equalizer is readjusted slightly to improve the aver-

age response for the entire audience area. Final equaliza-

tion adjustments are based on listening tests using
typical program material.

Equalization of a sound reinforcement system using

instrumentation is similar to playback equalization. The
sound system is equalized initially to produce the desired

house curve with all microphones turned off. The individ-

ual microphone volume controls are then increased to
the approximate use settings, slightly below the feed-

back threshold. The

creased slowly while observing the equalization analyzer.
As the feedback threshold is approached the analyzer
will show a prominent increase in amplitude of the fre­quency band where feedback is about to occur. The
appropriate
until the amplitude increase disappears. This process is
continued until the major feedback tendencies have been
suppressed and a reasonable sound volume level is being
produced. A talk or performance test of each open mi­crophone is then conducted and the quality of the sound
produced is sampled by listening in various locations
throughout the audience area. Additional equalization ad­justments are made based on the listening evaluation
and taking care to avoid any significant reduction in the

feedback threshold previously achieved.

Equalization of a stage monitor system using analyzer

equipment is similar to playback or house system equal­ization except measurements and evaluation are confined

to the performer's stage area. The pink noise generator

is connected to the mixer input and the mixer volume
adjusted to provide an output from the monitor speakers

significantly above the ambient noise level. A person is

placed in front of the lead performer's microphone (to

simulate performance conditions) and the analyzer mi-

crophone is placed

sample the sound field in that area. The analyzer micro-

phone output is viewed on the equalization analyzer and

initial response adjustments, such as low frequency
off, are made. The mixer volume control for the per­former's microphone is then set to a stable point slightly

below the feedback threshold. The

is gradually increased until an obvious increase in am-

plitude over a narrow frequency band is noted on the

equalization analyzer. This is the onset of feedback and
the appropriate
the system response in this area. This process is con­tinued until satisfactory gain before feedback and a

desired response is achieved. A voice test of each per­former microphone position is made to determine if a
similar feedback threshold is attainable. Final adjustment
of the
available) is made to improve quality or intelligibility of
the sound presented to the performers.

Connecting a VU Meter

An external VU meter may be connected to the

OUTPUT of the SR107 with a series resistor (see Figure

6). Use a true VU meter (such as
resistor connected as shown. The resistor should be
Yz-watt carbon 5%. With a 600-ohm load zero VU is

$4

dBm.

SR107 Filter Control setting is then reduced

SR107 and/or individual channel tone controls (if

SR107 LEVEL Control is then in-

next to the person at ear level to

roll-

SR107 LEVEL Control

SR107 Filter Control is used to reduce

LlNE

Simpson 1349) and a

3600

TIP WIRE

/

TO LlNE LEVEL

OUTPUT PHONE JACK

I

NO CONNECTION TO SLEEVE REQUIRED.

NOTE

EXTERNAL VU METER

5%

FIGURE

6.

I

I

SERVICE INSTRUCTIONS

Service

SR107 Audio Equalizer uses components of the

The
highest quality, operating well within their respective
ratings to assure long life.

WARNING

Voltages in this equipment are hazardous to life.
Refer servicing to qualified service personnel.

Replacement Parts

Parts that are readily available through local electronic

parts distributors are not shown on the accompanying

Parts List. Their values are shown on the Circuit Diagram

(Figure 11). Commercial parts not readily available and
unique parts are shown on the Parts List and may be
ordered directly from the factory.

The commercial alternates shown on the Parts List are

not necessarily equivalents, but are electrically and me­chanically similar, and may be used in the event that
direct factory replacements are not immediately avail­able. To maintain the highest possible performance and
reliability, Shure factory replacement parts should be
used. When ordering replacement parts, specify the
Shure Replacement Kit Number, description, product
model number and serial number.

Cover Removal

To service components inside the chassis, the pro-

tective top cover must be removed. This is done by
removing eight screws from the top surface and lifting
the cover off.

Fuse Replacement

The Equalizer is provided with a wired-in main power

F1 which is rated at 1/16A, 250V, Slo-Blo for the

fuse

SR107 and 1/8A, 250V, Slo-Blo for the SR107-2E. If re­placement becomes necessary, replace with identical

fuse. Insulating tubing should be used on the fuse leads

and to cover the metal end caps of the fuse.
Knob Replacement

All front panel rotary control knobs are pull-off types

and are interchangeable.

Ferrite Beads

Ferrite beads are used on the signal leads to all input

and output connectors except the AUX OUTPUT. Be sure

to replace the ferrite beads wherever they have been

removed during servicing.
Printed Circuit Board Removal

SR107 chassis contains two printed circuit board

The

assemblies, the Amplifier Board and the Equalizer Board

identified as

A1 may be made accessible for servicing by disconnect-

A1 and A2 in Figure 7. The foil side of board

FIGURE 7.

SR107 TOP VIEW, COVER REMOVED

ing the leads from the push-on board terminals S and R,

and removing the four Phillips head screws securing the

board. The rear edge of the board (side nearest the back
panel) can then be raised, tilting the board toward the

front panel until it is in an upright position.

The foil side of board A2 may be made accessible in a
similar manner by disconnecting the lead from the
on board terminal A and removing a total of six Phillips
head screws securing the board.

Replacement board assemblies are supplied with a

number of the interconnecting wires already cut to length
and soldered to board terminals. If either of the two
boards in the

assembly should be examined first to determine which

leads are already soldered in place. Those leads which
are duplicated on the new board assembly should be
soldered at the point of origin and removed from the
chassis along with the board. Note the lead colors and
points of connection before unsoldering to avoid con­fusion when installing the new board. Refer to the Circuit

Diagram, Figure 11 for lead identification.

SR107 are to be replaced, the new board

push-

un-

Transistor, Diode and LED Removal

All transistors and diode rectifiers used in the SR107

are mechanically supported by their leads. When replac­ing these devices, proper lead configurations must be

G

low-

and E,

followed. Minimum soldering heat (preferably with a
wattage soldering iron) should be used to avoid damage
to the device. Transistor lead codes are included in the
Notes to Circuit Diagram (Figure

To replace light-emitting diode (LED) D6, mounted on

the front panel, use a long-nose pliers to remove the

mounting ring from the rear of the LED. Press against
the front-panel projection of the LED lens to force it out
the back through the mounting clip. Disconnect the gray

and orange leads from push-on terminals

respectively, on printed circuit board

8).

A1 and remove the

defective assembly.

To install the new assembly, insert the LED in the
mounting collar in the front panel. Slide the mounting
ring over the leads and push it firmly onto the mounting
collar, securing the LED in the panel.

The Shure replacement LED is supplied with gray and
orange leads attached. Thread the leads through the
grommet in the shield separating the power supply from
the signal circuit components. Connect the gray lead to

G

terminal

and the orange lead to terminal E on board

Al.

Active Component Checking

Defective transistors and diode rectifiers may be lo-

cated by use of a standard ohmmeter such as a

260. Polarity of the ohmmeter must be verified before
these checks are made.

With a known diode orientation, measure the diode
resistance in the forward and reverse directions. The
lowest meter reading will establish the "minus" probe
while the other probe will be "plus." Some ohmmeters
are not polarized in this manner with relation to "volts
plus probe" and "volts minus probe." With the ohm-

meter "plus" probe on the anode end of a diode and the
"minus" probe on the cathode end, the ohmmeter should

read approximately 2000 ohms or less. With the meter

probes reversed, a reading of about 10,000 ohms or more

should be obtained. If either of these conditions is not

met, the diode should be replaced.

To check transistors, the ohmmeter should be set to
the 100- or 1,000-ohm scale. Transistors and diodes must

be removed from the circuit before testing. If all condi-

tions in the following table are met, the transistor may

be considered free of any major defect; if any of the
following conditions are not met, the transistor should be
replaced. See Notes to Circuit Diagram (Figure
transistor lead codes.

Simpson

8)

for

Ohmmeter Connections Ohmmeter Readina resistor between the +30 Vdc sup~lv and the orange

-

~-~~--~-~

"Plus" Lead "Minus" Lead Transistor Transistor

Collector Emitter High High with an ohmmeter; the ohmmeter may damage the LED
Emitter Collector High High or give erroneous readings.
Collector Base
Emitter Base
Base Collector Low High
Base Emitter Low

*

NO^

a

s~gn~f~cant measurement

To check the LED OVERLOAD indicator disconnect the
orange LED lead from terminal E of the amplifier printed
circuit board

--

~

NPN PNP

~igh Low

A1 and connect a 1, 1.5, or 2.2 kilohm as shaded areas in Figures 9 and 10.

Low

*

-

lead (gray lead still grounded).
when power is applied to the Equalizer. If it does not

light

it

should

Service Illustrations

The parts location photo (Figure
with the overall Circuit Diagram (Figure 11) provides
identification of all chassis-mounted assemblies and com­ponents. Reference to the overall Circuit Diagram and

the Printed Circuit Board Parts Location drawings (Fig-

ures 9 and 10) provides the means for quickly locating
board-mounted components. Foil circuit paths are shown

be

replaced.

he

NO~E:

7)

*LED

should light

D~

not

check

used in conjunction

LED^

REPLACEMENT PARTS LIST

Reference

Designation

CHASSIS-MOUNTED PARTS AND ASSEMBLIES

A1

A2

C3

C4

C5

C6

Dl -D5
D6
F1

F1

J1, J4

Replacement

Kit No.

*

-

-

-

-

-

-

RKC21
RKC133

-

-

-

(See

Qty.

-

-

-

-

-

-

4
1

-

-

-

90A2236

90A2239

866628

8611628

86B632

86J628

86A404
90A1989
80A297

80A322

90R2600

Figures 7,

Replacement Kit Consists Of:

Part No.

9, 10

Printed Circuit Board Assembly
(Amplifier)

Printed Circuit Board Assembly
(Equalizer)

Capacitor, Electrolytic,

,F, 15V

400
Capacitor, Electrolytic,

,F, 40V

250
Capacitor, Electrolytic,

1000
Capacitor, Electrolytic,

47 or 50

Silicon Rectifier,
Diode Assembly, Light-Emitting
Fuse, AC, 1

Pigtail
Fuse, AC, 1 /8A, 250V, Slo-Blo,

Pigtail (SR107-2E)
Connector, Phone Jack,

3-Conductor, Open Circuit, LlNE
INPUT and LlNE OUTPUT

and

-

-

Description

,F, 40V

pF,

35V min.

/16A, 250V, Slo-Blo,

(SR107)

11)

100V, 112A

Commercial

Alternate

None

None

Sprague
WH11 D407G016K

CDE BR250-50

Sprague TVA 1316

Sprague
CDE NLW 50-50

Motorola 1
Monsanto MV5023
Littelfuse 31 5.062

Littelfuse 31 5.125

Switchcraft

30D-TE1200;

N4002

128

J2

J3

*

Parts listed as RKC Kits should be ordered by that kit number. Any orders received for piece parts where RKC Kit number is
shown will be shipped in RKC quantities.

10

RKl19P

RK122P

95A482

1

95A198

1

Connector, Female, 3-Pin
Audio, LlNE INPUT

Connector, Male, 3-Pin
Audio, OUTPUT

Switchcraft C3F

Switchcraft C3M

REPLACEMENT PARTS LIST - Continued

Reference

Designation

J 5

J6-J7

J8

L1 -L8

MP1

P L1
R1

R2-R11

R12

SI

S 1

S2

S3

S4

TI

T2
T2
T3

W1

W1

Replacement

Kit No.

RKC68

RKC105

*

-

RKC45

-

-

-

-

A

-

-

A

A

-

-

-

-

-

Qty.

1

1 ea.

-

A

-

1

-

-

-

-

-

-

-

-

-

-

-

A

-

-

Replacement Kit Consists Of:

Part No.

958446

95A226
958226

95A689

80A253

90A2594

80A79
46A057

46A76

46A058

9082600

90D2600

5581 19

55C119

55A116

90C2150

51A263
51 A270
51A235

95A632

90A1888

Connector, Phone Jack,
2-Conductor, Open Circuit,

AUX OUTPUT

DC Receptacle, Red and

Black
Connector, 3-Pin, AC

(MAINS) POWER

Ferrite Bead Ring

Knob Assembly, White, Filter
Controls and LEVEL

Lamp, Indicator
Potentiometer, Center Tapped,

Special Taper,
Potentiometer, Special Taper,

250K, Filter Controls

Potentiometer, Screwdriver
Adjust, Modified Log Taper,
10K, GAIN

Switch, Toggle, SPST, POWER
ON-OFF

Switch, Toggle, SPST, POWER
ON-OFF

Switch, Slide, DPDT,

EQUALIZER IN-BYPASS

Switch, Slide, DPDT,

MIC-LINE

Switch, Slide, DPDT,
VOLTAGE SELECTOR

Transformer and Shield
Assembly, Line Level Input

Transformer, Power
Transformer, Power (SR107-2E)
Transformer, Line and Microphone

Level Output

Line Cord and 3-Conductor

Ac Plug Assembly

Line Cord and 3-Conductor
Ac Female Connector Assembly
(SRl07-2E)

(SR107)

(SRI 07-2E)

Description

(SR107-2E)

20K, LEVEL

(SR107)

(SR107)

(SR107-2E)

Commercial

Alternate

Switchcraft 11

None

None

Stackpole 57-0180;

Ferronics 21-030J
None

Leecraft 36N1311-6
None

None

None

Cutler-Hammer
7501 K13

None

Switchcraft

Switchcraft 46206LR

None

None

None
None

None

Belden 17408

None

46206LR

*

Parts listed as RKC Kits should be ordered by that kit number. Any orders received for piece parts where RKC Kit number is

shown will be shipped in RKC quantities.

REPLACEMENT PARTS LIST

-

Continued

Reference

Designation

AMPLIFIER (BOARD Al)

C101, (2103­C104

C102, C108

C106

C109

Dl 01-Dl 03
Q101, Q103,

Q108-Q110

Q102, Q104,
Q107

Replacement

Kit No.

-

-

-

-

-

-

-

Replacement Kit Consists

*

Qty.

-

-

-

-

-

-

Part No.

86A630

868629

86A646

86F628

86A415
86A350

86A348

Description

Capacitor, Electrolytic,

4.7 or 5
Capacitor, Electrolytic,

22

Capacitor, Electrolytic,
100

Capacitor, Electrolytic,
400

Diode, Silicon, Computer, 75V
Transistor, Silicon, NPN

Transistor, Silicon, Low
Power, PNP

,F, 35V

,F, 35V

,F, 25V

,F,

25V

Of:

Commercial

Alternate

Sprague 30D-TE­1303; CDE NLW-5-50

Sprague
226G050CE10;
Mallory MTV-25CD35

CDE NLW-100-25;

Sprague TE-1211
Sprague TVA-1209

TI or GE 1

Motorola 2N5210

Motorola or
Fairchild

502D-

N4148

2N5087
Q105
Q106

EQUALIZER (BOARD A2)

C201 -C202

C203

C204, C222,
C223

C205

C206

C207, C211

C208, C210

C209, C213

RKC65
RKC66

-

-

-

-

-

-

-

-

1
1

-

-

-

-

-

-

-

-

86A334
86A335

86A630

50XA330A

50XA271A

50WA122

50WA472

50WA183

50WA102

50WA683

Transistor, Silicon, NPN
Transistor, Silicon, PNP

Capacitor, Electrolytic,

4.7 or 5
Capacitor, Mica,

33
Capacitor, Mica,

270
Capacitor, Mylar,

.0012 ,F,
Capacitor, Mylar,

.0047 ,F, &5%, lOOV
Capacitor, Mylar,

.018
Capacitor, Mylar,

.001 ,F, k5%, 10OV
Capacitor, Mylar,

.068 ,F, +5%, 1OOV

pF, 35V

pF, 50V

pF, +5%, 50V

f

5%, lOOV

,F,

+5%, 100V

TI TIS92
TI TIS93

Sprague 30D-TE­1303; CDE NLW-5-50

CDE

ED330J03

CDE ED271 J03

WMC08D12**

CDE

CDE WMC08D47*

CDE MFP-05S18**

CDE WMC08D1*

CDE MFP-05S68*

*

*

*

*

Parts listed as RKC Kits should be ordered by that kit number. Any orders received for piece parts where RKC Kit number is

shown will be shipped in RKC quantities.

*'

Cornell-Dubilier alternate part has

*lo%

tolerance; select to

55%

if

possible.

REPLACEMENT PARTS LIST - Continued

Reference

Designation

C212, C225,
C227

C214, C226

C215

C216

C217

C218, C232

C219

C220

C221

C224

C228

C229-C230

C231

C233

C245

D201
Q2014203,

Q205-(2208,
(2210,
Q216-Q220,
Q226-Q230

(2204, (2209,
Q211 -Q215,

Q221-Q225

Replacement

Kit No.

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

Qty.

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

Replacement

Part No.

50WA103

50WA333

50WA274

50WA224

50WA105

50WA684

50WA505

50XA151A

50XA331A

50WA222

50WA393

50WA154

50WA474

50WA205

86H628

86A415
86A350

86A348

Kit Consists

Description

Capacitor, Mylar,
.01 ,F, +5%, lOOV

Capacitor, Mylar,

,033 ,F, *5%, lOOV
Capacitor, Mylar,

,F,

f

.27

Capacitor, Mylar,

.22
Capacitor, Mylar,

1.0
Capacitor, Mylar,

.68

Capacitor, Mylar,

5.0
Capacitor, Mica,

150
Capacitor, Mica,

330
Capacitor, Mylar,

.0022 ,F, +55,1OOV
Capacitor, Mylar,

.039 ,F, as%,

Capacitor, Mylar,

.15pF,

Capacitor, Mylar,
.47

Capacitor, Mylar,

2.0
Capacitor, Electrolytic,

80

Diode, Silicon, Computer, 75V

Transistor, Silicon, NPN

Transistor, Silicon, Low
Power, PNP

5%, 50V

,F, +5%, 1OOV

,F, +5%, 50V

,F, +5%, 50V

,F, +5%, 1 OOV

pF, +5%, 50V

pF, 15%, 50V

+5%, 1OOV

,F, +5%, 50V

,F, *5%, 50V

,F, 25V

Of:

IOOV

Commercial

Alternate

CDE MFP-05S1*'

CDE MFD-05S33*

CDE MFP-05P27*

CDE MFP-05P22'*

CDE MFP-O5Wl

CDE MFP-05P68'

CDE MFP-05W5**

CDE ED-1 51 J03

CDE ED-331 J03

WMC-08D22*

CDE

CDE MFP-05S39"

CDE MFP-05P15**

CDE MFP-05P47

CDE MFP-05W2**

CDE-N LW-75-25

TI or GE 1

Motorola 2N5210

Motorola or
Fairchild

*

N4148

2N5087

*

*

*

*

*

*

Parts listed as RKC Kits should be ordered by that kit number. Any orders received for piece parts where RKC Kit number is

shown will be shipped

**

Cornell-Dubilier alterhate part has

in

RKC quantities.

*lo%

tolerance; select to

*5%

if possible.

NOTES TO CIRCUIT DIAGRAM

General

Shure part numbers are not shown in the Parts List ac­companying the Circuit Diagram (Figure 11) if parts are
readily available through local electronics parts suppliers.
In these instances, the Circuit Diagram shows only the
reference designation and value of the standard parts.

All capacitor values are shown in microfarads unless
otherwise designated. All non-electrolytic capacitors are
100 working volts dc or more unless otherwise specified.

x

Electrolytic capacitors are shown in microfarads

All resistor values are shown in ohms
sistors are '/!-watt, 10% tolerance unless otherwise

specified.

Transistor lead codes are shown in Figure 8. Accept-

able replacements are shown in the Parts List.

The following ground symbols denote:

Chassis Ground
Circuit Ground

Printed Circuit Board Ground (7

Troubleshooting

A general troubleshooting process is as follows: If the
SR107 is completely "dead," check the ac power source,
fuse and power supply output (30 Vdc at pin V or T of
printed circuit board Al).
on but the output is distorted, low or not present, apply
an input signal as described under Ac Voltage Measure­ments below and determine that the input and output

voltage for each board assembly is correct. If an incor-

rect ac voltage is found at either board output, perform
Dc Voltage Measurements as described below to isolate

the problem area.

AC Voltage Measurements

The numbers within rectangular symbols on the

Circuit Diagram denote the ac voltage at that point under

the following test conditions:

1.

Voltage measured with respect to chassis unless
otherwise indicated.

2. Line Voltage:
50160 Hz with VOLTAGE SELECTOR Switch in 220V

position

3. All front panel Filter Controls at zero except 1 kHz

Control at

Switch set to IN.

4.

Input 1 volt at 1 kHz through 600 ohms. LINE OUT­PUT terminated in 600 ohms. AUX OUTPUT not
loaded.

/f7

1

-

-

If

the Power Indicator Lamp is

120V, 50160 Hz (SR107) or 230V,

(SR107-2E).

-

15. LEVEL Control at zero; EQUALIZER
GAIN Control at UNITY.

(k=1000). Re-

volts.

5. Measurements made with ac VTVM of 1 megohm
or greater input impedance.

(*)

NOTE: Measurements of voltage

Q203 and Q208 made with 22 kilohm isola­tion resistor at tip of VTVM probe.

6. Ac voltage measurements may vary
values shown.

DC Voltage Measurements

The number within elliptical symbols
Circuit Diagram denotes the dc voltage at that point
under the following test conditions:

1. Voltages measured with respect to chassis unless
otherwise indicated.

2. Line voltage:
50160 Hz with VOLTAGE SELECTOR Switch in
220V position

3. No input signal applied.

4.

Dc voltage measurements may vary f 20% from

values shown.

5. Measurements made with VTVM of 10 megohms or
greater input impedance.

NOTE: Measurements of voltage at collector Q208

made with 22 kilohm isolation resistor at

tip of VTVM probe.

Resistance Measurements

With the ac line cord disconnected from the ac source
and the POWER ON-OFF Switch in the OFF position, the
following ohmmeter measurements may be made.

1. Transformers may be checked for continuity of
each winding.

2. To test transistors, diodes or the LED, see Active
Component Checking.

120V, 50160 Hz (SR107) or 230V,

(SR107-2E).

FIGURE

TRANSISTOR LEAD CODES

8.

at collector of

%20% from

0

on the

FIGURE

9.

AMPLIFIER CIRCUIT BOARD

PARTS LOCATION

2236-31680-4

FIGURE

10.

EQUALIZER CIRCUIT BOARD

PARTS LOCATION

IgO

LX)/w

0

WATTS

VAL

HZ

WHT

-

--

POWER

5

I

L

KCD

ICO

IW

X3

VDC

I

2

RED

h

GflN

rf7

FIGURE

11.

--

SR107.2E POWER SUPPLY

-.

SR107 AUDIO EQUALIZER CIRCUIT DIAGRAM

AMPLIFIER

BOARD

(A\)

NOTES

:

I,

SPECIFIED. ALL RESISTORS l/4 WATT,

10%

UNLESS OTHERWISE

EQUALIZER

BOARD

I

(~ai

rt/

CHASSIS GROUND

0

4.

VOLTAGE MEASUREMENTS
PANEL CONTROLS AT

AND
MENTS TO
LINE
A.C. VOLTAGES MEASURED WlTH I VOLT,
THROUGH

D.C.

5.

f

TIP OF PROBE.

REAR

-

I20

VOLTAGES

TAKEN

D.C.

VOLTAGE

PANEL

GAIN

BE

TAKEN USING A

V.A.C.,

60

600a

WlTH

LINE OUTPUT

M~ASURED

22

1-1

TO

BE

CENTER

CONTROL AT FULL

Hz. ALL VOLTAGES SHOWN

KOHM

ROTATION EXCEPT

10

WITH

ISOLATION RESISTOR

.$.

CIRCUIT
GROUND

MADE

MEGOHM VTVM. A.C.

WADW

ZERO

A.C

VOLTAGE

WlTH

ALL FRONT

CCW

RDTATION. ALL

l

KHz

WlTH

SIGNAL

BOARD

I

ARE

INPUT

600n.

APPLIED.

KHz

AT

CONTROL

*20Z

AT -15,

MEASURE-

FIGURE

11.

SR107 AUDIO EQUALIZER CIRCUIT DIAGRAM

The Audio Equalizer shall be a rack-mounted 120-volt,
50/60 Hz line-operated all silicon transistor active audio
frequency equalizer for use as a component of a sound
system to adjust the overall system frequency response.

The Equalizer shall contain a total of ten octave band,
minimum phase, combining type filters extending over
the frequency range of 31 Hz to 16 kHz. Each shall be
adjustable for approximately 15 dB of boost or attenua­tion. The equalized output shall be adjustable over a

215 dB range.

The Equalizer shall include a switch to disconnect the

equalization circuitry and permit operation in a bypass

mode. Gain in either the equalizer in or the bypass mode
shall be adjustable from unity to approximately 20 dB
through the use of a rear-panel control.

The Equalizer shall be equipped with a peak-respond­ing overload indicator to provide a visual indication
approximately 3 dB before output clipping occurs in
either equalizer in or bypass operation. The overload

(LED)

indicator shall be a light-emitting diode

mounted

in the front panel.

*

All specifications apply to Model SR107-2E except for the
operating voltage range which is 105-125 or 210-250 volts,

50/60

Hz

ac for

this

model.

The Equalizer shall have a high-impedance balanced
input suitable for operation from a line level source of 10
kilohms or less. Two parallel-wired

LlNE INPUT connect­ors, a three-pin female professional audio type and a
three-conductor

%-inch phone jack, shall be provided.

Outputs shall include: a three-pin male profesional audio

OUTPUT connector switchable by means of a

MIC/LINE

slide switch to line level or microphone level output, a

LlNE OUTPUT three-conductor %-inch phone jack, and
an AUX OUTPUT two conductor

%-inch phone jack. The
microphone and line level outputs shall be balanced and
low impedance. The auxiliary output shall be unbalanced
and low impedance.

A

POWER ON-OFF Switch and power-on indicator lamp

shall be provided on the front panel.

The Equalizer shall be enclosed in a metal housing de-

signed for rack-mounting in a standard 19-inch (483

mm)
audio equipment rack, or mounting in an accessory
vinyl-covered wood portable case. Overall dimensions
shall be

in width, and 218 mm

44.4.mm (1-3/4 inch) in height, 483 mm
(8-9116 inch) in depth. The weight

shall be no more than 3.5 kg

(7

Ib, 12 oz).

(19

inch)

Any Equalizer not meeting all of the above specifica­tions shall be deemed unacceptable under this specifica­tion. The Audio Equalizer shall be a Shure Model

SR107.

GUARANTEE

This Shure product is guaranteed in normal use to be
free from electrical and mechanical defects for a period
of one year from date of purchase. Please retain proof
of purchase date. This guarantee includes all parts and

labor. This guarantee is in lieu of any and all other
guarantees or warranties, express or implied, and there
shall be no recovery for any consequential or incidental

damages.

SHIPPING INSTRUCTIONS

Carefully repack the unit and return it prepaid to:

Shure Brothers Incorporated

Attention: Service Department

1501 West Shure Drive

Arlington Heights, Illinois 60004

If outside the United States, return the unit to your dealer
or Authorized Shure Service Center for repair. The unit
will be returned to you prepaid.