Preamp Two

Here is my Hi-Fi preamplifier project. In this repository you can find schematics, PCB layouts, CircuitPython code, BoMs, measurements and photos.

Features:

• MDAC volume controller
• 6 way relay based input selector
• High performance design with measurements
• Quality components and modular design
• Completely digitally controlled
• All open source and written in Python

Components and code

The preamplifier is made up of a number of connected components:

• MDAC attenuator (PCB, code): Controls the volume
• Input selector (PCB, code): Selects the input
• Encoder panel (PCB, code): Holds rotary encoder and LED indicator ring
• Power Supply 5V (PCB): Power supply for digital components.
• Power Supply +/- 15V (PCB): Analog Power supply for MDAC attenuator
• Micro controller board (PCB, code): Holds the Itsy Bitsy M4 Express and other connectors
• RCA panel (PCB): For the RCA sockets and connectors

The PCBs and schematics were created in KiCad and the code that runs on the micro controller is CircuitPython.

Enclosure

Diagrams, CAD files and other information can be found here: enclosure

Measurements

THD, S/N ratio and power consumption: measurements

Prototypes and testing

See here for a number of different prototypes. All PCBs were made by OSH Park.

Photos