Noisy Cricket Stereo Amplifier - 1.5W Hookup Guide
Hardware Overview and Assembly
The Noisy Cricket is an easy to use board with three connection sections:
The power section has three connections: VCC, VCC OUT, and GND. VCC and VCC OUT both require a voltage range of 2.4-5.5VDC, but only one connection is required. The pot to control the volume has a built in switch. VCC is on the "input" side of the switch, meaning that the amplifier is off when the pot is turned all the way counter clockwise and turns on when you hear the switch click when turned clockwise. VCC OUT is on the "output" side of the switch, meaning that when power is applied to this pin, the amplifier is on regardless of the switch. The switch is rated for 3A of current, which means that you can connect a 5V audio source to VCC OUT and have both board power on at the same time without having to connect multiple switch to power up all of your electronics.
The input section has three connections: Left-IN, Right-IN, and GND for your audio input. The amplifier's gain is controlled by external resistors as highlighed below:
Out of the box, the resistors are configured to take a headphone output signal from your computer or phone. When cranked to 11, the output will be distorted, but that was done deliberately to make sure you're able to get the full power from the amplifier. In stereo operation, both channels are effectively inverting amplifiers, which allows us to use the following formula to calculate the gain: Av = -Rf / Ri, or Av = - Rpot / 2.2kΩ. In mono operation, one amplifier is 180° out of phase, so the gain becomes Avd = Vout / (Vinl + Vinr) = 2 * (Rf/Ri), or Avd = Rpot / 2.2kΩ.
The output of the Noisy Cricket can be configured as stereo or mono.
In stereo operation, the output has a maximum power output of 300mW/channel (with an 8Ω load). To connect your stereo speakers you'll need to connect each speaker to the left and right output pins, as well as ground as shown below.
To get the full output power from the amplifier you'll need to configure the Noisy Cricket as a mono amplifier. When configured as a mono amplifier, the left and right input channels are combined to drive a single speaker.
To enable mono operation, use solder to short the two pads labeled "ENABLE MONO OUTPUT" on the back of the board. It's also recommended to close the other solder jumper labeled "MONO BASS BOOST". Each output has a 100μF decoupling capacitor that is used for stereo amplification. In mono mode however, the output doesn't need to capacitor and will filter out some of the lower bass frequencies and as a result, the audio will sound more "tinny". The mono bass boost jumper shorts the left output decoupling capacitor which will allow the lower frequencies to pass.
In mono operation, the output has a maximum power output of 1.5W (with a 4Ω load). To connect your speaker you'll need to connect one pin of the speaker to the left output pin, and the other to the mono output pin (but NOT GROUND!) as shown below.