I’m trying to develop a Teensy based Eurorack module. I’ve posted various incarnations of it on here before. I’m having trouble with the circuit that sends modular level audio to the Teensy
Here is my circuit design which is intended to take Eurorack modular audio (-5V…5V), and convert it to the range (0V…1.2V), for the Teensy 3.6 ADC. The first op-amp is in an inverting summing op-amp configuration. 5V is added to the input, putting it in the range of 0V…10V, and the op-amp reduces this to the range (-1.2V…0V), the second op-amp, inverts this signal at unity gain, giving a signal from (0V…1.2V). The circuit appears to work, but it is very noisy. There is a LOT of background noise coming from somewhere. I’ve tried adding capacitors across the feed back resistors, but that doesn’t change much. Can anyone tell me if there’s a fundamental mistake with my schematic? I’ve been scratching my head for days now. All help much appreciated!