I approached the forum before with an idea I had with an audio relay matrix. Audio goes in one end of the board, is routed through a 32x32 matrix of relays and returns to an output at the other end. After some help from some forum members I had a design that worked pretty well on a breadboard small scale. I had to work out some kinks and have reworked the design to a modular design of 8x8 cards. Each card has four edge connectors which will each plug in to a backplane to route signals from card to card.
I’m attaching the schematic and board I’m working on now. I am using latching relays so that digital signals can be limited to pulses which should cut down on issues with noise reaching audio signals.
The backplane cards will have 4 db25 connectors to input audio and 4 db25 connectors for audio output. The backplane will house an atmega328p and shift registers to source and sink the relay current.
I just need some reassurance on the design maybe some help on what sort of grounding might be best for this circuit. I was thinking of using a star ground to the chassis. I would have a ground pour at the db25 connectors which would then connect to the star ground, keeping it isolated from the power section.
hopefully this makes sense, I know the schematic is not finished but is a start to show where the audio and digital paths will be located