Input

There are two main parts in input board. A MCP6002 op-amp chip is applied to amplified the input signal because the output of a guitar is very low. Then the signal is sent to MCP3202 12 bits ADC chip to be transformed into digital signal and then sent to the Raspberry Pi from the SPI bus. A potentiometer is applied to change the load of the op-amp as a gain knob so that the input amplitude can be changed. A 6.35mm Stereo jack is used as the input jack however we just use one channel of it so there is no stereo sound.(Only the guitars with pizeo systems need stereo hardware)

https://github.com/LemonRepublica/RPI_AMP/blob/master/resource/Circuit/input_all.pdf

Output

The propose of output board is to transform the impulse from the PWM to playable signal by the MCP6002 op-amp. Then send the signal to another 6.35mm Stereo jack to ready to be sent into speaker. It is like the power-amp of guitar amps.

https://github.com/LemonRepublica/RPI_AMP/blob/master/resource/Circuit/output_all.pdf

Power

The power board is aim at remove the possible noise from the power output of raspberry pi. Some analog low-pass filters are applied. There is also a voltage dividing circuit to provide the 1.6v reference voltage for the input amplified circuit. https://github.com/LemonRepublica/RPI_AMP/blob/master/resource/Circuit/power_all.pdf

#Build your PCBs! If you are interest in building your own RPI_AMP, the EAGLE PCB file is here: https://github.com/LemonRepublica/RPI_AMP/blob/master/resource/hardware