This is basically the “hello world” of DSP on an FPGA. I’m including source code, but no schematics, since it’s all on a prototyping board. I’m using a Digilent Nexys2 board with two of their periphial boards (PMOD’s), a 12 bit SPI ADC, and a 16 it I2S ADC. The audio can take two paths depending on switch positions, either ADC -> DAC, or ADC -> FIR Low Pass Filter -> DAC. The audio is coming from my computer in analog form, so this music has seen a lot of conversions before it leaves the speakers. But it still sounds pretty good.