Those are not the types of transformers I’m talking about. You use signal transformers to isolate inputs / outputs, like these: https://cinemag.biz/mic_input/

Those are not the types of transformers I’m talking about. You use signal transformers to isolate inputs / outputs, like these: https://cinemag.biz/mic_input/mic_input.php https://cinemag.biz/mic_input/mic_input.php https://cinemag.biz/line_input/line_input.php https://cinemag.biz/line_input/line_input.php They’re directly in the signal path of a preamp, and when overdriven, change the sound.