This is the circuit diagram of USB Powered Stereo Computer Speakers, or it is widely known as PC Multimedia Speakers. The circuit adopts single-chip microcomputer design, low-voltage power supply, compatible with computer USB power supply, simple heat dissipation, low price, high flexibility, and wide temperature range.
The heart of the circuit is the IC TDA2822M. The IC is actually a monolithic type in an 8-pin mini-DIP (dual in-line package). It is designed for use as a dual audio power amplifier in battery powered sound players. The TDA2822M features very low quiescent current, low crossover distortion, a DC supply voltage as low as 1.8 V, and a minimum output power of approximately 450 mW/channel using a 4-ohm speaker at a 5-V DC input.
An ideal power amplifier can basically be described as a circuit that can deliver audio power to an external load without creating a lot of signal distortion or drawing extreme quiescent current.
The circuit is powered by a 5V DC power source available from the computer’s USB port. When the power switch S1 is turned to the “on” position, the 5V power supply extends to the circuit, and the red LED1 of the power indicator lights up immediately. Resistor R1 is actually a current surge limiter, and capacitors C1 and C4 act as snubbers.
How a USB Powered Stereo Computer Speaker Circuit Works
The operation of the circuit is very simple. The audio signal from the computer audio port or the headphone port feeds the amplifier circuit through R2 and C2 (for the left channel) and R3 and C3 (for the right channel). Potentiometer VR1 is used as a volume control for the left (L) channel, while potentiometer VR2 is used to control the volume of the right (R) channel. Pin 7 of TDA2822M receives the sound signal of the left channel, and pin 6 receives the signal of the right channel through VR1 and VR2 respectively. The amplified signals that drive the left and right speakers are obtained at pin 1 and pin 3 of IC1 respectively. Components R5 and C8, and R6 and C10 form a classic zobel network.
Build a stereo computer speaker circuit on a medium sized generic PCB and house it in a suitable enclosure. It is indeed recommended to use the socket of IC TDA2822M. External connections should be made using properly shielded wires to improve results.