Your Briscati M1 DAC (if you still have it) is asynchronous, hence timing on the computer side makes no difference. I would try to reduce injected electrical noise, by using USB cable without +5V and GND wires and possibly use USB isolator. You could also try quieter, perhaps linear, power supply for your Macbook. All computers have many internal switching regulators, but I believe the main power supply affect it the most (highest power).