Operating Instructions

SR105 Power Amplifier

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

1.OUTPUT VOLTAGE Meter - lndicates Amplifier out- put voltage in percentage of maximum voltage.

2.VOLUME Control - Controls Amplifier output level.

3.THERMAL OVERLOAD Indicator Lamp - lndicates Amplifier shutdown due to excessive heat sink temper- ature.

4.POWER ON-OFF Switch - Applies ac power to Ampli- fier.

5.BALANCED BRIDGING lnput Jack - Provides for bal- anced bridging, high-impedance input connection.

6.3AGl5A Ac Line Fuse - Protects Amplifier ac input line aaainst- overload.

7.Ac Line Cord - Connects ac power to Amplifier power supply.

8.DIRECT OUTPUT Jacks (Four) - Provide for output connection to direct-coupled speaker systems.

9.DIRECT OUTPUT Terminal Strip - Provides for output connection to direct-coupled speaker systems.

10.70V-OFF Switch (SRIO5A Amplifier only) - Activates

70-volt output transformer for use with distributed speaker systems.

11.70V OUTPUT Terminal Strip (SRI05A Amplifier only) - Provides for output connection to 70-volt distributed speaker systems.

12.SPARE FUSE Fuseholder- Holds spare 3AG-5A power supply fuse.

13.UNBALANCED PARALLELED HlGH IMPEDANCE In- put Jacks (Two) - Provide unbalanced (one side grounded) input connections for use with high-im- pedance sources.

14.70-Volt Output Cover Plate (SRIOSB Amplifier only) - Covers pre-drilled and marked area where Switch (10) and Terminal Strip (11) are located.

GENERAL OPERATING INSTRUCTIONS

W A R N I N G

Voltages in this equipment are hazardous to life. Make all input and output connections with ac power dis- connected. Refer servicing to qualified service per- sonnel.

DIRECT SPEAKER OUTPUT OPERATION (MODEL SRIO5A and SR105B AMPLIFIERS)

1.Install Amplifier before making electrical connections. Using hardware supplied, secure Amplifier in rack or carrying case, allowing at least 51 mm (2 in.) above and behind case for ventilation. Use forced-air cooling for multiple-amplifier installations.

2.Set Switches (4,lO) to OFF and VOLUME Control (2) to 0.

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

CAUTION

In multiple speaker installations, be sure not to ex- ceed maximum power rating of any speaker.

4.Connect audio console or microphone mixer output to Amplifier UNBALANCED PARALLELED HlGH IMPE- DANCE lnput Jack (13) (standard phone jack). For in- terconnections up to 15m (50 ft), use single-conduc- tor, shielded, low-capacitance cable. For intercon- nections longer than 50 ft, use 600-ohm balanced line into Amplifier BALANCED BRIDGING lnput Jack (5) (professional, 3-pin, female audio connector).

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

6.Connect line cord (7) to grounded 120 Vac & l o % , 50/60 Hz source capable of supplying 450 watts.

7.With VOLUME Control (2) set at 0, turn front-panel POWER Switch (4) on. Adjust VOLUME Control to de- sired amplifier operating level.

CONSTANT-VOLTAGE 70-VOLT SPEAKER OUTPUT (MODEL SR105A AMPLIFIER ONLY)

1.Connect auxiliary equipment as for direct speaker op- eration in steps 1, 2, 4, 5 and 6 above.

2.Connect required speakers to 70V OUTPUT Terminals

(11)and, if necessary, DIRECT OUTPUT Connectors (8,9). Total speaker impedance should be as close to 33 ohms as possible. Be careful not to exceed Amplifier 150-watt power output capability. (See Output Con- nections, Page 6.)

3.Connect audio console or microphone mixer output to Amplifier UNBALANCED PARALLELED HlGH IMPE- DANCE Input Jack (13) (standard phone jack). For in- terconnections up to 15m (50 ft), use single-conduc- tor, shielded, low-capacitance cable. For intercon- nections longer than 50 ft, use 600-ohm balanced line into Amplifier BALANCED BRIDGING lnput Jack (5) (professional,3-pin, female audio connector).

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

5.Connect line cord (7) to grounded 120 Vac *lo%, 50160 Hz source.

6. With VOLUME Control (2) set at 0, turn front-panel POWER Switch (4) on. Adjust VOLUME Control to de- sired amplifier operating level.