Key Digital KD-AMP220 2-Channel Compact Digital Amplifier and Mic Mixer Pre-Amp

Key Digital KD-AMP220: Compact Amplification for Speech and Program Audio

The Key Digital KD-AMP220 is a two-channel Class-D compact amplifier and pre-amp that delivers 20 watts per channel into 4 ohms. Class-D amplification switches its output devices on and off rapidly rather than running them in a lossy linear mode, which lets a full amplifier, microphone mixer, and tone controls share one small, cool-running chassis. That integration replaces a separate mixer and power amp with a single box. For speech reinforcement and background program audio in classrooms, conference rooms, houses of worship, and training spaces, it puts everything a small room needs into one unit.

Flexible Power and Impedance

Output power reaches 20 watts per channel into 4 ohms or 40 watts bridged into 8 ohms, with support for both 4- and 8-ohm speaker loads. Bridging ties the two channels together to drive one speaker line harder, trading stereo output for added power on a single run. Matching the amplifier to a 4- or 8-ohm load lets an integrator use standard commercial or residential speakers without an impedance-matching transformer. This range of power and impedance covers the needs of most small rooms from a single compact unit.

Stereo, Mono, or Bridge Modes

A three-position switch configures the amplifier for stereo, dual-mono, or bridged operation. Stereo feeds a left-right pair, dual-mono sends signals to two separate zones, and bridged combines both channels for one higher-power speaker. Selecting the mode in hardware means the same amplifier adapts to a stereo lectern, two independent audio zones, or a single high-output speaker as the room demands. This flexibility lets one model cover jobs that would otherwise require several different amplifiers.

Built-In Microphone and Line Mixer

A balanced 3-pin microphone input mixes with a balanced 6-pin line input and a 3.5mm stereo line input at the amplifier's output. Balanced inputs carry audio on a differential pair that rejects noise picked up over long cable runs, which matters for a microphone placed far from the rack. Mixing these sources internally means a presenter's voice and program material such as video or music combine automatically without an outboard mixer. That built-in mixing removes an entire component from the signal chain in a speech-and-media room.

Switchable 48V Phantom Power

Switchable 48V phantom power is available on the microphone input to drive condenser and dynamic microphones. Phantom power sends operating voltage up the same balanced cable that carries the audio, energizing the active electronics inside a condenser capsule. Making it switchable lets an integrator enable it only for microphones that need it and leave it off for those that do not. This covers the vast majority of lectern, podium, and gooseneck microphones used for speech reinforcement.

Tone Shaping and Noise Gate

Independent input volume, variable output bass and treble, and a built-in noise gate give the amplifier its room-tuning tools. A noise gate automatically mutes an input when the signal falls below a set threshold, silencing the low-level hiss and hum that would otherwise fill the pauses between phrases. Adjusting tone and gain lets an installer shape the sound to a live space and hold background noise down between words. The payoff is speech that stays crisp and intelligible all the way to the back of the room.

Pre-Amp Output for 70V Systems

A balanced line-level pre-amp output lets the amplifier feed a larger 70V distribution system. A 70V system raises the audio to a higher voltage so many speakers can share long cable runs with minimal loss, the standard approach for whole-building paging and background music. Used this way, the unit becomes the microphone mixer and tone processor ahead of a facility-wide audio system rather than the final amplifier. That dual role lets the same model serve a single room today and a larger distributed system tomorrow.

RS-232 and IR Control, Complete Kit

Front-panel controls, RS-232, and IR each provide command of the amplifier, and an external IR sensor is included for hidden installs. RS-232 and IR let a room's control system or keypad adjust volume and source alongside the rest of the AV equipment, so the amplifier is not an island the user has to reach behind. The unit runs from an external 24V supply and ships with an IR remote, the IR sensor, two L-brackets, a full set of Phoenix connectors, and instructions. Carrying CE and FCC compliance, it arrives ready to mount, wire, and integrate into a controlled room in a single visit.