Such headphones are no longer available except at a high price as antiques. With this impedance, the loading on the crystal set was low enough that the set could achieve reasonably narrow bandwidth. Traditionally, crystal sets were connected to headphones having an impedance of around 4,000 ohms. Where line outputs will easily drive a 10K ohm input, there are situations where the input to the headphone amplifier needs to be larger. Also hum and noise may be heard in the phones which is not noticeable on speakers. However, such amplifiers are relatively large and cumbersome for use with phones. You could use an amplifier that is intended to drive a speaker. Also, there may be distortion due to the heavy load on the output. If you plug headphones into a line output, you’ll hear something, but there won’t be enough power to properly drive the phones. Portable devices such as CD players, DVD players, or cassette tape players already have a low impedance output and don’t need extra amplification. This includes a CD deck, DVD deck, cassette tape deck, computer output, and any other device with line outputs. Devices with line outputs require an amplifier to drive the headphones. Though some Mylar headphones are very expensive, they can be found for as little as $5. Modern Mylar diaphragm headphones have an impedance of about 100 ohms. When do we need a headphone amplifier? There are situations where a low output impedance to the headphones is required. In the case of a power amplifier, the signal must be enlarged much more enough to power a loudspeaker. In the case of a pre-amplifier, the signal must be amplified enough to be accepted by a power amplifier. The purpose of an amplifier is to receive a small electrical signal and enlarge or amplify it. This article discusses three different versions of headphone amps to fit your particular application: a stereo amp controlled by the power line a battery-operated mono amp for a crystal set and a battery-operated amp for a ceramic cartridge.Ī headphone amp is a relatively low-powered amplifier that raises the low voltage audio signal from a source device (be it a turntable, PC, or smartphone) to a sufficient level such that it can be converted (or transduced) into sound waves by the speakers inside your headphones. There are situations where a low output impedance to headphones is required.