drifting…
The prototype is making noise and I’m tuning it to musical notes. Unfortunately the drift of various components is to high to maintain a stable tuning :( For example my 440hz A tuning:
The ppm (temperature stability) of the XR2206 is 20ppm/C, fine. The ppm of the DAC is 0.16ppm/C, even better. The ppm of the digital potentiometer (mcp42100) is 800ppm/C! That number explanes the variation in tuning. Off to find a solution!