Chassis Placement and Ventilation Requirements
The Ahuja SSB-120DP public address mixer amplifier is engineered for bench, tabletop, or equipment shelf mounting. The physical chassis dimensions are 420 mm (W) x 135 mm (H) x 295 mm (D) with an approximate net weight of 11.0 kg. Ensure the unit is positioned on a flat, stable, and rigid surface capable of supporting its weight without mechanical deflection.
Maintain at least 50 mm to 100 mm of clear airspace around the side and rear ventilation louvers. Avoid placing heat-generating equipment directly above or beneath the amplifier. Prevent exposure to excessive dust, high ambient humidity, direct sunlight, and liquid ingress to safeguard internal circuitry and transformer assemblies.
Dual Power Supply Wiring (AC Mains and 12V DC Failover)
The amplifier features a dual-supply architecture allowing operation from AC mains or an external DC battery source:
- AC Mains Operation: Connect the integrated AC power cord to a regulated 220–240V AC (50/60 Hz) grounded supply. Full-load AC power consumption is rated at 250VA.
- 12V DC Battery Connection: For uninterrupted public address operation during power outages, wire the rear DC terminal block to a 12V battery system (such as a 12V automotive battery or stationary DC backup bank). Rated DC current draw is 5.5A under peak loading. Ensure correct polarity: connect positive (+) to the red terminal and negative (-) to the black terminal.
- Automatic Changeover: When both AC and DC sources are connected, the amplifier prioritizes AC mains. Upon AC failure, internal circuitry instantly transfers operation to the 12V DC supply without interrupting audio delivery.
Loudspeaker Load Matching and Wiring Topologies
The SSB-120DP provides flexible speaker output options on its rear terminal barrier strip, accommodating both low-impedance voice-coil loads and constant-voltage distributed speaker networks. Do not connect low-impedance and constant-voltage line terminals simultaneously.
- Low-Impedance Connections (4Ω, 8Ω, 16Ω): Connect the common speaker lead to the 'COM' terminal and the positive lead to the matching impedance terminal (4Ω, 8Ω, or 16Ω). Calculate the total series/parallel network impedance precisely to ensure it matches the selected terminal tap. Connecting a net load lower than the terminal rating can overload the power output stage.
- Distributed Line Connections (70V / 100V): For long-distance audio distribution in commercial, industrial, or institutional buildings, connect line-matching transformer (LMT) equipped loudspeakers in parallel between 'COM' and either the '70V' or '100V' tap. The sum of all transformer power tap ratings across the line must not exceed the amplifier's rated output of 120W RMS (with a maximum capacity of 160W RMS).
Input Cabling, Line Outputs, and Media Player Setup
Route all input and auxiliary interconnects prior to energizing the amplifier:
- Microphone Channels (Mic 1–5): Connect dynamic microphones to the front and rear 6.3 mm unbalanced input jacks (rated input sensitivity 0.65mV at 4.7kΩ input impedance).
- Auxiliary Channels (Aux 1 & Aux 2): Feed line-level sources (e.g., CD players, external media receivers, audio mixers) into the Aux input jacks (rated sensitivity 100mV at 470kΩ).
- Line & Preamp Outputs: Use the 1V / 1kΩ Line Out terminal to link additional booster amplifiers when system expansion is required. Use the 200mV / 600Ω Preamp Output to feed audio recording devices or secondary signal processors.
- Digital Media Player: Insert a compatible USB flash drive or SD/MMC storage card loaded with MP3 audio files into the integrated front-panel reader. Operate playback using front-panel keys or the supplied infrared remote control. If using the handheld remote control, install the required cells (they are not included).
Pre-Commissioning and Calibration Procedure
Before applying power, turn all input gain potentiometers (Mic 1–5, Aux 1–2, and Master) fully counter-clockwise. Set Bass and Treble tone controls to their center (neutral) positions.
Turn on the main power switch and verify the AC/DC indicator. Slowly advance the Master control and individual input knobs while speaking into microphones or playing media tracks. Monitor the 5-LED output level array to verify signal presence, ensuring the level meter does not stay permanently saturated in the peak zone. Adjust Bass and Treble controls (providing cut and boost adjustments across the 50 Hz to 15,000 Hz operating range) to achieve speech intelligibility and acoustic balance for the venue.
