A tape head is a type of transducer used in tape recorders to convert electrical signals to magnetic fluctuations and vice versa. The electromagnetic arrangement of a tape head is generally similar for all types, though the physical design varies considerably depending on the application - for example video recorders use rotating heads which implement a helical scan, whereas most audio recorders have fixed heads. A head consists of a core of magnetic material arranged into a doughnut shape or toroid, into which a very narrow gap has been let (an air gap or other insulating material).

This gap causes the magnetic flux to spill out of the material at that point, which is where the tape is made to run. The flux thus magnetises the tape at that point. A coil of wire wrapped around the core opposite the gap interfaces to the electrical side of the apparatus; thus either supplying a signal in the case of recording, or being fed to an amplifier in the case of playback.

The basic head design is fully reversible - a variable magnetic field at the gap will induce an electric current in the coil, and an electric current in the coil will induce a magnetic field in the core and hence in the tape drawn across the gap. While a head is reversible in principle, and very often in practice, there are desirable characteristics that differ between the playback and recording phases. One of these is the impedance of the coil - playback preferring a high impedance, and recording a low one.

In the very best tape recorders, separate heads are used to avoid compromising these desirable characteristics. Having separate heads for recording and playback has other advantages, such as off-tape monitoring during recording, etc. The width of the head gap is also critical - the narrower the gap, the better the head will be - a narrow gap gives much better transcription in the magnetic domain (the magnetic flux density is higher, and hence will give stronger recording for a given signal, or greater signal pickup for a given tape).

A narrow gap also permits higher frequency signals to be recorded for a given tape speed. The desirability for a narrow gap means that most practical heads are made by forming a narrow V-shaped groove in the back face of the core, and grinding away the front face until the V-groove is just breached. In this way, gaps of the order of micrometres are achievable.

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