Shure SR105 User Manual

SR105

Power

Amplifier

OPERATION AND

Manufactured by

SHURE BROTHERS

222

Hartrey Avenue

Evanston, Illinois

SERVICE

INC.

60204

U.S.A.

MANUAL

27A888

1979,

(SJ)

Shure Brothers Inc.

(95B652)

WARNING

To reduce the risk of fire or electric shock, do not expose this appliance to rain or extreme moisture.

Printed in U.S.A.

SR105

Power Amplifier

SPECIFICATIONS

The following specifications apply to both SR105A and SR105B Power Amplifiers except where noted. The SR105A Power Amplifier provides both direct-coupled speaker output and transformer-coupled, constant-voltage, 70-volt output. The SRlO5B Power Amplifier is equipped for direct-coupled speaker output only.

Amplifier Type All silicon transistor power

Power Output

Voltage Gain

Sensitivity Frequency Response

Input Impedance

Total Harmonic

Distortion

Hum and Noise

Output Clipping Level. . 28.3 Vrms min. at 1 kHz (4-ohm

Load lmpedance:

Direct-Coupled

Speaker Output

70-Volt Output*

Model

SR105A

"Model

SR105B

.......

.200 watts rms continuous to

.........

...........

....

.39 kilohms &30%, balanced or

........

only. only.

.2% max. at 1 kHz, 200W (4-ohm

......

.80 dB below rated output (less than

.4 ohms or greater (4 ohms min.)

...

.I50 watts max. (33 ohms min.)

amplifier 4-ohm load

100 watts rms continuous to

8-ohm load

150 watts rms continuous to

70-volt line (33-ohm load)*

27 22 dB (4-ohm load at 1 kHz)

e3.5 dB (33-ohm load at 1 kHz

across 70-volt output)'

1.2 volts nominal (full rated output)

.5 dB, 20-20,000 Hz (typical)

*2 dB, 50-15,000 Hz (typical,

70-volt output)"

unbalanced*

25 kilohms

unbalanced*

load, 28.3 Vrms output)

3% max. at 1 kHz,

load, 70.7 Vrms output)*

2.8 output with Volume Control at

load)

&30%, balanced or

150W (33-ohm

mV at direct-coupled speaker

Load Regulation:

Di rect-Coupled

Speaker Output

70-Volt Output*

Phasing..

Power Supply

Temperature Range:

Operating Storage

Dimensions Weight:

SR105A

SR105B Finish Installation

Certifications

...........

........

.........

...........

.........

...........

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

..........

........

. .

Less than 1 dB from no-load to 4-

ohm load at 200 watts rms output

....

Less than 2 dB from no-load to

ohm load at 150 watts rms output

Pin 3 and phone jack tips of in-

puts in phase with speaker output phone jack tips, and 28V and 70V terminals

120 volts, 50/60 Hz ac only. Power

consumption: 40 watts max. (20 watts typical) with no signal, 450 watts with

watts output; 500 watts maximum

-7' to 43OC (20' to 1 10°F)

-34' to 74OC (-30' to 165OF)

.I78 mm x 483 mm x 270 mm

(7 in. H x 19 in.

15.66 kg (34 Ib 8 oz)

12.23 kg (27 Ib) Matte black Equipped for standard 19" (483

mm) rack mounting; may be operated in optional ing Case

Listed by Underwriters' Labora-

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

kHz signal and 200

x 10% in.

A105A Carry-

33-

SR105

SPECIFICATIONS

(Curves

Power Amplifier

shown

are

typical)

OUTPUT POWER (WATTS)

TOTAL HARMONIC DISTORTION VS. OUTPUT POWER TO 4-OHM LOAD AT 50 HZ, 1 KHZ ONLY)

10 KHz (DIRECT OUTPUT

LOAD RESISTANCE, OHMS

OUTPUT POWER (WATTS)

TOTAL HARMONIC DISTORTION VS. OUTPUT POWER (VARIOUS LOADS) AT (70V OUTPUT ONLY)*

KHz AND CONSTANT 70.7V OUTPUT

FREQUENCY

OUTPUT POWER VS. FREQUENCY AT 1% MONIC DISTORTION TO 4-OHM LOAD (DIRECT OUTPUT ONLY)

(Hz1

TOTAL HAR-

OUTPUT POWER (WATTS)

TOTAL HARMONIC DISTORTION VS. OUTPUT POWER TO 150-WATT (33-OHM) LOAD AT 1 KHz FOR INCREASING OUTPUT VOLTAGES (70V OUTPUT ONLY)*

'Model

SRIO~A

only.

FREQUENCY ( H

OUTPUT POWER VS. FREQUENCY AT 1% MONlC DISTORTION TO 33-OHM LOAD (70V OUTPUT ONLY)*

TOTAL HAR-

iii

SR105

Power Amplifier

TABLE OF CONTENTS

Section Page

SPECIFICATIONS ii DESCRIPTION OPERATING INSTRUCTIONS

Functional Identification 3 General Operating Instructions Mounting and Ventilation 4 Thermal Overload Power Requirements 4 Functional Circuit Description 4 Input Connections Output Connections 6

Amplifier-to-Speaker Impedance Matching Output Voltage Meter

Basic Operating Hints 10

SPECIAL OPERATING INSTRUCTIONS

Adding Bridging Connections 11

Adding Headphone Jack to Speaker Connections

SERVICE INSTRUCTIONS

Amplifier Service 12

SRlO5A Amplifiers in a

70-Volt System (Cascaded) 10

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...

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Section Page

Replacement Parts 12 Fuse Replacement 12 Bottom Plate Removal 12

Cover Removal 12

Lamp Replacement 12 Dc Output Balance Adjustment 12 Output Voltage Meter Calibration

Printed Circuit Board Removal 13 Small Signal and Predriver Transistors

Driver Transistors 14 Output Transistors 15

Diodes Diode Bridge Rectifier 15 Checking Transistors and Diodes SR105B Amplifier Conversion for 70-Volt Output Service lllustrations Guarantee Shipping Instructions

PARTS LIST 19 CONDENSED OPERATING INSTRUCTIONS ARCHITECTS' AND

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

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

ENGINEERS' SPECIFICATIONS

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

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....

12 14

15 15

15 17 17 17

27 27

SR105

Power Amplifier

LlST OF ILLUSTRATIONS

Figure Page

1 SR105 Power Amplifier Front Panel 2

2 SR105 Power Amplifier Rear Panel

SR105 Power Amplifier Dimensional

Outline Drawing 4

SR105 Power Amplifier Block Diagram

4 5 Input Connections

Output Power vs

2 Ohms to 32 Ohms

70-Volt Output Power vs

Impedance from 4 Ohms to 100 Ohms

Recommended Wire Gauge vs . Amplifier-to-

Speaker Distance: Direct Output

Recommended Wire Gauge vs . Amplifier-to-

Speaker Distance: 70-Volt Output (SR105A Only)

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

Load lmpedance from

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

Direct Output Load

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

...........

........

.......

...........

5 6

7 7

Figure Page

10 70-Volt System Attenuator

Bridged Amplifier Connections

11 12 Headphone Jack for Speaker Connections

SR105 Power Amplifier Top View, Cover

Removed

SR105 Power Amplifier Bottom View.

Cover Removed

70-Volt Conversion: Added Circuitry

15 16 70-Volt Conversion: Transformer Mounting 17 17 70-Volt Conversion: Internal Wiring 18 18 Main Circuit Board Parts Location Diagram 22 19 Filter Circuit Board Parts Location Diagram 22 20 Transistor Lead Codes 23 21 SR105 Power Amplifier Circuit Diagram 25

(SR105A Model Shown)

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

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

..........

.....

11 11 11

13 14

.....

...........

....

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

.......

SR105

(Shown

Carrying

Power

Amplifier

DESCRIPTION

A105A

Case)

The Shure SR105 Power Amplifier is a high-power amplifier designed for sound reinforcement applications. It is capsble of delivering 200 watts rms to a 4-ohm load, and is available in two models, the SR105A and SR105B. The

SRlO5A Power Amplifier provides both a direct-coupled speaker output and a transformer-coupled constant-voltage, 70-volt output, while the equipped with a direct-coupled speaker output only. In this manual "Amplifier" refers to both models unless otherwise specified.

The Amplifier is of rugged construction and is conserva-

tively designed to provide reliable operation at high power levels with minimum distortion and phase shift. Used in conjunction with a suitable mixer-preamplifier or audio console such as the Shure Model quality, high-power, sound reinforcement system may be assembled for use with a variety of speaker systems. Sev-

SR105 Power Amplifiers may be interconnected (de-

eral scribed under Operating Instructions) to provide greater

power output for large installations and redundant opera-

tion. The basic direct-coupled speaker output capabilities of the Amplifier are well suited to the source-oriented speaker systems used in theatres, auditoriums, stadiums, ballrooms, and convention halls, in short, wherever maximum coverage with reserve power is required. The addi-

SR105B Power Amplifier is

SRI05A and SRlOSB

SR101, a versatile, high-

tional 70-volt output feature of the makes it equally adaptable to source-oriented or distributed speaker systems such as those used for background music or announcements in industrial buildings, institutions or public places.

An Output Voltage Meter in the Amplifier facilitates ad-

justment and output level monitoring.

Silicon transistors and similar solid-state devices are used throughout the Amplifier. Short-circuit and thermal overload protection are design features which eliminate the need for special installation or operation precautions. All components are of the highest quality and are operated well within their respective ratings to assure maximum reliability under normal use conditions.

The Shure

1.8m

sory package consisting of four rack-mounting screws, one Volume Control Cover, one Power On-Off Switch Cover, and one spare 5-ampere fuse.

The Underwriters' Laboratories, Inc., and are listed by Canadian Standards Association as certified.

The signed specifically for use with the

SR105 Power Amplifier is supplied with one

ft) audio input connecting cable and an acces-

SR105A and SRIO5B Power Amplifiers are listed by

A105A Portable Carrying Case accessory is de-

SR105A Power Amplifier

SR105 Power Amplifier.

FIGURE 1. SR105 POWER AMPLIFIER FRONT PANEL

FIGURE

SR105 POWER AMPLIFIER REAR PANEL

(SR105A MODEL SHOWN)

SR105

Power Amplifier

OPERATING INSTRUCTIONS

FUNCTIONAL IDENTIFICATION (Refer to Figures 1 and 2, Page 2).

1. OUTPUT VOLTAGE Meter put voltage in percentage of maximum voltage.

2. VOLUME

3. THERMAL OVERLOAD Indicator Lamp Amplifier shutdown due to excessive heat sink temperature.

4. POWER ON-OFF Switch fier.

5. BALANCED BRIDGING anced bridging, high-impedance input connection.

3AGl5A Ac Line Fuse - Protects Amplifier ac input

6. line aaainst overload.

7. Ac Line Cord

supply.

8. DIRECT OUTPUT Jacks (Four) - Provide for output

connection to

9. DIRECT OUTPUT

connection to

10. 70V-OFF Switch 70-volt output transformer for use with distributed speaker systems.

11. 70V OUTPUT Terminal Strip

Provides for output connection to 70-volt distributed

speaker systems.

12. SPARE FUSE

power

13. UNBALANCED PARALLELED

put Jacks (Two) - Provide unbalanced (one side

grounded) input connections for use with

pedance sources.

70-Volt Output Cover Plate (SRIOSB Amplifier only)

14. Covers pre-drilled and marked area where Switch (10) and Terminal Strip (11) are located.

GENERAL OPERATING INSTRUCTIONS

Control - Controls Amplifier output level.

Connects ac power to Amplifier power

direct-coupled speaker systems.

Terminal Strip - Provides for output

direct-coupled speaker systems.

(SRIO5A Amplifier only) - Activates

Fuseholder- Holds spare 3AG-5A

supply fuse.

lndicates Amplifier out-

lndicates

Applies ac power to Ampli-

lnput Jack - Provides for bal-

(SRI05A Amplifier only)

HlGH IMPEDANCE In-

high-im-

WARNING

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

DIRECT SPEAKER OUTPUT OPERATION (MODEL

1. Install Amplifier before making electrical connections.

SRIO5A and SR105B AMPLIFIERS)

Using hardware supplied, secure carrying case, allowing at least 51 mm and behind case for ventilation. Use forced-air cooling for multiple-amplifier installations.

qualified service per-

Amplifier in rack or

in.) above

2. Set Switches

3. Connect required speakers to Amplifier DIRECT OUTPUT jacks (8) wire size and arranging speaker connections for speaker load impedance as close to 4 ohms as possible. Remove DIRECT OUTPUT Cover (14) and use rightangle phone plugs to connect speakers to Amplifier. When using DIRECT OUTPUT Terminal Strip (9), thread wires through Cover grommet. Replace cover.

(4,lO) to OFF and VOLUME Control (2)

andlor to terminal strip (9), using proper

total

CAUTION

In multiple speaker installations, be sure not to ex-

ceed maximum power rating of any speaker.

4. Connect audio Amplifier UNBALANCED PARALLELED HlGH IMPE-

DANCE terconnections up to 15m (50 ft), use tor, shielded, low-capacitance cable. For interconnections longer than 50 ft, use 600-ohm balanced line into Amplifier BALANCED BRIDGING lnput Jack (5) (professional, 3-pin, female audio connector).

Connect additional power amplifiers or other auxiliary equipment as required to remaining Amplifier input jacks.

6. Connect 50/60 Hz source capable of supplying 450 watts.

With VOLUME Control (2) set at 0, turn front-panel

POWER Switch (4) on. Adjust VOLUME Control to de-

amplifier operating level.

sired

CONSTANT-VOLTAGE 70-VOLT SPEAKER OUTPUT (MODEL

1. Connect

2. Connect required speakers to 70V OUTPUT Terminals

3. Connect audio

4. Turn 70V-OFF Switch (10) to 70V.

SR105A AMPLIFIER ONLY)

eration in steps 1, 2, 4, 5 and 6 above.

(11) and, if necessary, DIRECT OUTPUT Connectors (8,9). Total speaker impedance should be as close to 33 ohms as possible. Be

150-watt power output capability. (See Output Connections, Page 6.)

Amplifier UNBALANCED PARALLELED HlGH IMPEDANCE Input Jack (13) (standard phone jack). For interconnections up to 15m (50 ft), use tor, shielded, low-capacitance cable. For interconnections longer than 50 ft, use 600-ohm balanced line into Amplifier BALANCED BRIDGING lnput Jack (5) (professional, 3-pin, female audio connector).

Connect line cord (7) to grounded 120 Vac *lo%, 50160

With VOLUME Control POWER Switch (4) on. Adjust VOLUME Control to desired amplifier operating level.

console or microphone mixer output to

lnput Jack (13) (standard phone jack). For in-

single-conduc-

line cord (7) to grounded 120 Vac &lo%,

auxiliary equipment as for direct speaker op-

careful not to exceed Amplifier

console or microphone mixer output to

single-conduc-

source.

(2)

set at

turn front-panel

MOUNTING AND VENTILATION

The SR105 Power Amplifier is designed for rack-mounting in a standard 19-inch (483 mm) audio equipment cabinet rack and is supplied with the necessary mounting hardware.

To insure adequate air circulation, a minimum clearance of

51 mm (2 in.) should be provided above and behind the Amplifier (see Figures 3, Page 4). If the cabinet ambient temperature reaches

43OC (llO°F), forced air ventilation should be provided to avoid the possibility of thermal overload (see following section). The Amplifier may be operated

-7"

in an ambient temperature range from

to 43°C (20"

to 110°F) in continuous duty without derating.

The Amplifier may also be operated while mounted in a

A105A Carrying Case.

Shure

NOT INCLUDING CABLE AND LlNE CORD CLEARANCE DEPTH.

FIGURE

DIMENSIONAL OUTLINE DRAWING

SR105 POWER AMPLIFIER

270

-00-518 IN.)-

mm'

THERMAL OVERLOAD

The SR105 Power Amplifier is equipped with thermal sensing switches on the output transistor heat sinks. The thermal switches are set to sh~it off ac power to the Amplifier when a temperature of 90°C (194°F) is attained on the heat sinks; the switches automatically recycle and re-apply power when the

(164°F). A THERMAL OVERLOAD light

heat sink temperature drops to 73°C

(3),

located on the

front panel of the Amplifier, indicates if thermal cycling

has occurred. Thermal cycling may occur if air is not allowed to circulate across the black finned heat sinks and

through the grilles of the Amplifier, or if there is a pro-

longed short-circuit on the output.

POWER REQUIREMENTS

The SR105 Power Amplifier is furnished with a threeconductor power cable and three-prong grounded plug (7). Connect the power cable to an outlet which supplies

~10% volts ac, 50160

120

power. The maximum power consumption at 120 volts under any normal operating condition is 450 watts (3.75 amperes at 120 volts).

Idle power

consumption with no input signal is nominally 20 watts.

If extension cords are required to supply power to the Amplifier, a high quality 18-gauge or larger cord should be used.

(4)

A POWER toggle switch on the front panel

the application of ac power to the Amplifier. The

controls

tamper-

proof cover supplied may be used to eliminate accidental movement of this switch.

Main ac power fusing is provided by a 5-ampere, type

3AG, cartridge-type fuse (6) located on the rear panel. A

spare ac power fuse is supplied for mounting in the clip on the rear panel (12).

Additional protection is provided by wired-in fuses in the main ac power circuit (FI, 8 amperes) and in the ac pilot lamp circuit (F3, 1 ampere). These fuses are located under the chassis.

FUNCTIONAL CIRCUIT DESCRIPTION

(See Figure 4,

Page 5)

The inputs of the

SR105 Power Amplifier consist of two unbalanced (grounded) phone jacks (13) and one balancedbridging, three-pin, female audio connector (5). The balanced-bridging input is wired in parallel to the phone jacks after passing through an isolation transformer. The input signal then passes through the VOLUME Control if the Amplifier is an

SR105A, either passes through a Filter

Assembly and 70V-OFF Switch (10) to the Power Amplifier

circuitry, or bypasses the Filter Assembly and goes directly to the Power Amplifier circuitry. In the

SR105B Amplifier the signal passes directly from the VOLUME Control (2) to the Power Amplifier circuitry.

The Power Amplifier circuitry contains a dc balance ad-

justment to minimize idle power consumption and eliminate

dc offset at the direct-coupled

(28V) output. The balance adjustment is generally only performed when active Power Amplifier circuit components are replaced.

The metering circuit, located at the output of the Power

Amplifier circuit, contains a meter calibration adjustment,

a meter rectifier, and an output meter that indicates percentage of output voltage. NOTE: 100% is the maximum

Amplifier output voltage prior to clipping regardless of load. Maximum power output is obtained with a direct-coupled speaker load impedance of 4 ohms, or a 70-volt output

speaker load of 150 watts (33 ohms), or a combination of direct-coupled and 70-volt loads which results in optimum

loading for maximum power output.

The Power Amplifier circuit output goes to four phone jacks (8) and one two-contact terminal strip (9). In the SR105A Amplifier, the output goes through the 70V-OFF

Switch

(lo), a constant-voltage, 70-volt output transformer,

and a three-contact terminal strip (1 1).

A detailed description of the Amplifier circuits and con-

trols and their uses is provided in the following paragraphs of this section.

INPUT CONNECT IONS

Three LlNE LEVEL INPUTS Connectors are located on

the rear panel of the Amplifier (see Figure 2, Page 2). A

professional, three-pin, female audio connector vides a balanced bridging, high-impedance input connec-

tion. Unbalanced, high-impedance input connections are

1/4"

provided by two standard

phone jacks (13) wired in

parallel.

The Amplifier may be driven to full-rated output by any

audio console, preamplifier or microphone mixer capable of delivering 1.2 volts across a 25-kilohm load.

When using the Shure

SR101 Audio Console as the

mixer-preamplifier, connect the cable supplied with the

Amplifier from one of the PROGRAM OUTPUTS Jacks

labeled LlNE LEVEL on the

SR101 to one of the LlNE LEVEL

INPUT Jacks (13) labeled UNBALANCED PARALLELED

HIGH IMPEDANCE on the Amplifier (see Figure 5A, Page

6). If a longer interconnecting cable is desired, a conductor, shielded, low-capacitance cable (such as Belden #8401, 8410, or 8411) should be used.

'Des~gned to mate with Cannon

)

Series, or

equivalent

Ser~es, Sw~tchcraft

connector

(2), and

(5)*

pro-

single-

INPUTS

METER

RECTIFIER

VOLT-

METER

(70)

0''

UNBALANCED

BALANCED BRIDGING

INPUT XFMR

SRIOSA AMPLIFIER ONLY. I

VOLUME

FIGURE

LOW-CUT 70

FILTER

ASSEMBLY

SR105

POWER AMPLIFIER BLOCK DIAGRAM

In applications where the Amplifier is located at a con-

siderable distance from the mixer-preamplifier, electrical

interference or excessive hum pickup may be encountered.

Hum pickup may also be encountered over shorter distances as a result of ground loop conditions between the units. Under these circumstances, a balanced line, such as is

used for low-impedance microphones, should be used for interconnections. A low-capacitance, two-conductor, shielded cable (such as

Belden #8412 or 8422) is recommended. A professional, three-pin, female audio connector is required for

wnnection to the mixer-preamplifier, and a similar three-pin male connector is necessary for connection to the Amplifier (see Figure 5B, Page 6). When wiring these connectors, connect the cable shield to pin 1 in each connector, one of the cable conductors to pin 2, and the other conductor to pin 3 in each connector. For balanced line operation, use the cable as described above to connect the mixer-preamplifier PROGRAM OUTPUTS three-pin connector labeled

LlNE LEVEL to the Amplifier LlNE LEVEL

INPUTS connector labeled BALANCED BRIDGING (5).

Since the two input jacks of the Amplifier are wired in parallel, one jack may be used as an auxiliary, high-level, unbalanced output to feed the signal to another Amplifier (SR105 or similar equipment) or the high-impedance input of a tape recorder. The three-pin input connector (5) is connected through an isolation transformer in parallel with the

two input jacks (13). If not otherwise in use, the three-pin

connector may be used as a balanced, high-level, signal

source for a second Amplifier or other auxiliary equipment

(see Figure

5C, Page 6).

METER ADJUST

I I

I I I I

- - - - - - - - - - - - - -

BALANCE

Additional SR105 Power Amplifiers may be added to the system for a fail-safe type operation where complete redundancy is required. Refer to the section on Bridging Connections (Page 11).

Certain input equipment, such as passive equalizers, step attenuators and matching networks, may require a 600-ohm termination for optimum performance. (This is not required with any Shure products.) When a 600-ohm terminated input is required, a 620-ohm, sistor must be connected to the terminals of the input cable connector (see Figure 5D, Page 6). This resistor must be connected between pins 2 and 3 of the three-pin connector, or between the tip and sleeve terminals of the phone plug. The resistor will fit inside the sleeve of the three-pin connector or phone plug. Be careful not to damage the wires, connections, sleeve or resistor when making this installation.

An occasion may arise where it is desirable or expedient to feed the Amplifier from a 70-volt line. This could be in connection with the expansion of an existing installation, or as a result of efforts to minimize cable runs in a new in-

stallation. An input signal for the Amplifier may be derived from a 70-volt line through the use of an attenuator (see Adding Amplifiers in

operating from a 70-volt line, the VOLUME Control (2) on the Amplifier should be set to the "7" position. With the recommended attenuator, this setting will produce approximately 28.3 volts at the DIRECT OUTPUT terminals 70 volts at the 70V OUTPUT terminals (1 1) when the 70-volt input line is at 70 volts.

- -

-1

70-Volt System, Page 10). When

DIRECT SPEAKER OUTPUTS

XFMR*

5%, %-watt re-

(SRlO5A Amplifier)

(8,9),

+ 23 hidden pages