The Q-Tron is an envelope controlled filter that uses the same opto-electronic design as the famed Mutron III. Since the Q-Tron is Electro-Harmonix's first new product in 15 years, they wanted it to have several new features that update the old Mutron box. You still get all that drippy, vowel-like auto wah-wah effect but now with a better frequency response and a lower noise floor.

Q-Tron's features and controls are: switchable up/down filter drive switch; variable filter peak control; hi/lo range control; selectable low pass, high pass, band pass and a mix of BP and Dry combined filters; variable gain with overload indicator; switchable boost; and both effect and direct outputs.