2 Channels Stereo Class D 3W Digital Audio Amplifier Mini Board DC 5V Super mini volume: 1.85 x 2.11 cm Excellent noise control. When there is no audio input, you cannot hear any noise even you close to the speaker. Two-channel stereo, single 5V power supply, can directly drive any 4-8 ohms speakers. High output power, good sound quality. Unique non-LC filter Class-D digital power board, can directly use the USB as the power supply.