Monday, April 1, 2024

Testing bus mixer

I've spent between 50 and 100 hours laying out the voicecard mainboard lately, but finally I had some time to test the bus mixer.

Everything works as it should:

- 16 switches

- 12 VCAs

- Summing on both wet and dry busses

- Summing of wet AND dry


The only thing to worry about is the switching noise. I get huge peaks (>5V when switching. Some are more prominent than others, so not entirely sure what it is caused by. The peaks are there even when the switch has a 0V input on both channels:

Here is a sceenshot of summing two multiple 5V inputs (the output from the VCAs is 4.5V btw...)


Oh - and I had an initial scare, it looked like we had some capacitance somewhere, and serious crosstalk between busses. Turns out the logic probe ground lead had disconnected itself so the output showed the average of whatever it measured:





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