Cassette construction
To learn more about cassette tape, let us examine its technical terms and the names of its components. Understanding its construction and how different tapes perform makes the cassette world still more enjoyable!
The basic cassette design developed by Philips is shared worldwide. TDK refined it to the limit, guided by the idea: the cassette shell is part of the deck.
- Shell dimensions: 63.8 × 100.4 mm.
- Thickness: 9 mm; 12 mm in the head-entry area.
- Tape width: 3.81 mm.
- Tape speed: 47.6 mm/s.
How recording works
When recording onto cassette tape, the deck’s recording head converts the audio signal received from the microphone into a magnetic signal. Contact between the recording head and tape coated with magnetic material creates a magnetic recording. Playback reverses the process: the playback head reads the tape’s recorded magnetic signal and converts it into an electrical one. This passes through an amplifier to a loudspeaker and is reproduced as sound.
Characteristics of the different tape positions
Normal / Type I
The basic cassette tape position. During the cassette’s heyday, it ranged from inexpensive economy versions to high-grade models. Gamma iron oxide was the principal magnetic material. These tapes generally delivered powerful low and middle frequencies, but high-grade models such as AR and AR-X could also offer excellent high-frequency performance.
High Position / Type II
Initially called Chrome because its magnetic material was chromium dioxide, this position later became known as High Position with the transition to cobalt-based tapes. Its characteristics include low noise, good high-frequency performance, wide dynamic range and clean sound.
Metal / Type IV
Unlike Normal and High Position, Metal tape uses unoxidized metal as its magnetic material. Its defining feature is exceptionally high recording level: magnetic energy is approximately four times that of High Position. It reproduces powerful bass and lustrous treble at high quality.
Names of cassette components
A cassette generally consists of the following 19 components.
- Variable-pitch screw.
- DB sheet.
- Erase-protection tab.
- Rib preventing shell deformation.
- Guide post.
- Side A shell section.
- Dust-proof leader tape.
- Non-Binding guide roller.
- Guide pin.
- Dual-spring pressure pad.
- Shield plate.
- Hub.
- Triangle Ball.
- Transparent window.
- M-shaped rib.
- Side B shell section.
- Spindle pin.
- Screw hole.
- Double clamp.
Cassette glossary
Explanations used to be printed on the back of cassette packaging. Perhaps many people used the tapes without understanding them? Belatedly, let us explain what those words meant.
Magnetic material
In a cassette, this is the substance applied to the tape’s surface for magnetic recording. Tape color differed according to the magnetic material: Normal was usually reddish-brown or dark brown, High Position completely black or blackish-brown, and Metal a glossy dark gray.
Maximum recording level (MOL)
MOL abbreviates Maximum Output Level. A higher recording level can preserve sound at better quality, but excessive levels cause distortion. MOL expresses the recording limit: the level at which output-signal distortion reaches 3%. It is also called the practical maximum recording level.
Bias noise
This is the hissing noise heard when playing a recorded tape. It is also called hiss noise.
Dynamic range
The range from the loudest to the quietest sound that can be recorded and reproduced; in other words, the interval between bias noise and MOL. It represents the amount of information in the signal. A wider range allows clearer reproduction: loud sounds remain undistorted, while quiet ones do not disappear into noise. Tapes with a wide range were therefore considered high quality.
Frequency response
The frequency range a cassette tape can record and reproduce, also indicating its capabilities. Early Normal cassettes covered roughly 60-10,000 Hz. The arrival of Metal tapes made it possible to reach 20,000 Hz reliably.