It has four microphone inputs. All four are LO-Z or low impedance (200-600 ohms) microphone stages. The big advantage of these LO-Z stages is that it allows you to extend the length of mike wire upto 30 meters.

MIC-4 stage is selectable with AUX.-1 & AUX.-2 through a slide switch MIC-4/AUX.-1/AUX.-2. Aux.1 & 2 inputs are to be used to amplify sound of Record Player, TV, Radio, or any Musical Instrument.

All MIKE and AUX. inputs are mixable.

Individual BASS & TREBLE Controls permit shaping of desired tonal quality of Music and Speech.

BASS CONTROL - This is for adjusting low frequency (or thick sounds) response. At ‘FLAT’ position the amplifier will produce full frequency response required for ‘MUSIC’ (use box speakers for Music). When Driver Units are being used, keep this at ‘6’ no. Point. This will protect life of Driver Units as they cannot reproduce low-freq. This position also reduces & eliminates feedback and howling.

TREBLE CONTROL: - At ‘FLAT’ position high frequency (shrill / thin sounds) are fully reproduced. Turning to left will reduce shrillness. Keep at position of your choice.

MASTER CONTROL:- This controls adjustments of overall volumes of program inputs.

1.  GROUNDING: - For safety and humfree operation, the chesis of the set must be grounded. Join one wire from the ‘Earth’ terminal at the back plate to earth of AC outlet, or water pipe etc.  If more equipment like booster amplifier, cassette player are associated with this amplifier, make sure that their chesis are electrically connected with each other.

2.  SIMULTANEOUS AC/DC CONNECTIONS TO ENSURE UNINTERRUPTED SERVICE: - The amplifier can be connected to AC supply and 12V-14V Car battery simultaneously.  In such case the set will draw power from AC mains. The battery power will act as a ‘stand-by’. In case of electric failure or AC voltage dropping down abnormally, the amplifier will start drawing power from the battery to keep the operation uninterrupted. The amplifier will start operating on AC as soon as AC supply is restored. On AC operation, no battery is consumed.  If any supply AC or Battery is available, the Power ‘LED’ on front plate will light up.

3.  MICROPHONES: - Use LO-Z microphones on all four mike stages. All ROXY microphones are LO-Z and match perfectly with this amplifier. Do not use High impedance or HI-Z mikes, as they will produce choking sound. Never blow in microphones. This common practice damages their sensitivity. Speak 1 / 2 / 3 instead while testing. While speaking keep the distance between mike and mouth to app. 10-15 cms.

4.  AC MAINS SUPPLY VOLTAGE IS FATAL, as such do not remove top cover of amplifier, when connected to mains. Also car battery must also be removed or should not be connected, if you want to open cover.

5.  DC FUSE: - For safety, the amplifier is provided with fuse in DC line. If it blows, replace it with one of correct rating 8A. Open top cover by unscrewing screws. A glass fuse shall be seen.

An output signal of 200mV strength is available through this socket. This can be used firstly for connecting a Cassette Recorder for recording the running programme. Connect to Aux. of any tape recorder. Secondly, for connecting another amplifier for combined higher output. For example, after connecting driver unit/speakers on this set, there is a need for additional unit/speakers, take another amplifier (say RSB-80E). Connect one wire from Pre-Amp. Output of RSB-55E and join to Aux-2 of RSB-80E. Now you can put additional driver units / speakers on this 80W set. Keep Master Control of 80W set to full and Aux-2 level to choice.

DIRECT SPEAKER CONNECTIONS: - COM 4W 8W 16W have been provided for direct connection of units / speaker to the amplifier. These taps are recommended to be used if the distance between the amplifier and speakers is short enough (say less than 50m). Use 23/36 or thicker wire for connections.

COM-100V LINE: - This line has been provided for installation when speakers are at a distance from the amplifier. (Read instructions of “Selection of speaker & their Connections”).

IMPORTANT: - From our past experience of 45 years, it has been observed that poor sound quality in Public Address installations & a good majority of defects in amplifiers are due to WRONG SPEAKER CONNECTIONS. It is therefore very important to understand & avoid mistakes in speaker connections. (Study ‘Selection of speakers ..’ sheet attached).

WARNING: - When a set of speakers are to be connected to the amplifier, if on Direct tapping, one COM terminal is to be used everytime. But it is important to use ONLY ONE TERMINAL OUT OF 4W, 8W OR 16 W.  Similarly on  voltage tapping, connect one to COM and other to 100V.   NEVER USE TWO TAPINGS AT A TIME

MONITOR: - The flicking / lighting of the LED on the panel indicates that output from the amplifier is going towards the speakers.

As stated above SELECTION OF SPEAKERS AND THEIR CONNECTIONS TO THE AMPLIFIER is the key to the successful use / operation of the whole Public Address Installation. For guidance, please refer to a separate sheet ‘SELECTION OF SPEAKERS AND THEIR CONNECTIONS’ attached.  Some basic points are briefed as under:-

1.  The output wires coming from Output Speaker Tapings of the amplifier should not short. This is fatal, as firstly it will stop the sound output from the speakers. Secondly, it will seriously damage the amplifier. Its AC fuse or inside DC fuse will be blown off immediately, needing a replacement. As such, please ensure that output wires do not short at

a)  Output terminal strip.
b)  In the connection wires.
c)  At driver unit / speaker end.

2.  Wires used to connect driver units/ speakers on DIRECT SPEAKER tapings should be thick (app. 23x36 size). However, while using 100V line tapping thinner wires can be used.

3.  When a number of speaker / units are to be connected, connect them suitably to make a nett impedance i.e. the nett output of all such speaker / units should be just two wires. One of these has to go to COM terminal & other to 4,8 or 16W. Or alternatively one to COM and other to 100V line. The same is explained with examples in ‘Selection of speaker and their connections’ sheet attached.

4.  For safety of speakers/units, the total nett power handling capacity must be more than that of amplifier.

5.  Connect all speaker/units at the Output FIRST and only after that connect the AC lead to the AC supply outlet or Battery terminal at backplate to Car battery terminals.