Ribbon microphones are also known for their high fidelity. They contain a thin ribbon made of a aluminum, duraluminum, or nanofilm, which is suspended in a magnetic field. Incoming sound waves make the ribbon vibrate, generating voltage proportional to the velocity of the vibration. This voltage is transmitted as an electrical signal. While early ribbon microphones required a transformer to increase the output voltage, modern ribbon mics have improved magnets that provide a stronger signal – in some cases even stronger than dynamic microphones. Though ribbon mics have been largely replaced by condensers, several models are still manufactured and used today.