So here we are, in the dawn of the 1980’s as in-car entertainment prepares to take the next major leap forward – in the form of both the cassette deck and the compact disk also known better as the CD. In 1970, the Advent Corporation combined Dolby B noise reduction system with chromium dioxide (CrO2) tape to create the Advent Model 200, the first high-fidelity cassette deck. Popular on automotive cassette decks, the Dolby B noise reduction system was key to realizing low noise performance on the slow and narrow cassette tapes. It works by applying dynamic range compression to the high frequencies on recording, primarily boosting low-level high-frequency sounds, and corresponding expansion on playback. The CrO2 tape used different bias and equalization settings to reduce the overall noise level and extend the high frequency response.
Cassette decks soon came into widespread use and were designed variously for professional applications, home audio systems, and for mobile use in cars, as well as portable recorders. From the mid-1970s to the late 1990s the cassette deck was the preferred music source for the automobile. Like an 8-track cartridge, it was relatively insensitive to vehicle motion, but it had reduced tape flutter, as well as the obvious advantages of smaller physical size and fast forward/rewind capability.
One of the major drawbacks of the cassette and the cassette player was the need of regular maintenance. The cassette tape is a magnetic medium which is in physical contact with the tape head and other metallic parts of the recorder/player mechanism. Without such maintenance, the high frequency response of the cassette equipment suffers. One problem occurs when iron oxide (or similar) particles from the tape itself become lodged in the playback head. As a result, the tape heads require occasional cleaning to remove such particles.
The early to mid-1980’s saw the introduction of the in-dash compact disc (CD) player. Touted as a digital audio storage medium, the CD itself is a plastic polycarbonate disc, an analog medium that contains digitally encoded data. The data is read out by loading the disc in the player’s mechanism that scans the spiral data track using a laser beam. The tracking control is done by analog servoamplifiers and then the high frequency analog signal read from the disc is digitized, processed and decoded into analog audio and digital control data which is used by the player to position the playback mechanism on the correct track, do the skip and seek functions and display track, time, and index.
Because there is no physical contact between the disc and the laser, the CD player didn’t have the maintenance shortcomings like the popular cassette decks of the time. In-dash CD players use a slot loading method for loading the CD into the player. Unlike the standard CD player of the day, there is no tray that pops out, and a motor is used to assist disc insertion and removal.
As a result of these and other advantages, analog cassette deck sales were expected to decline rapidly with the advent of the compact disc. Interestingly enough, the rapid transition was not realized and CDs and cassettes successfully co-existed for nearly 20 years.
While the growth in availability of the in-dash CD player was limited to mainly the single CD player throughout the 1980’s and into the early 1990’s, a number of upmarket automakers began to offer a version of what was known as the CD changer. Mounted in-dash, the glovebox, center console or even the trunk, these changers usually stored three, six or even 12 CDs for selection and playback.
A CD changer holds multiple Compact Discs, usually in a cartridge, revolving tray or carousel, and allows the user to access (or play) any of them, one at a time. The three main types of CD changes employed by automakers over the years include: external cartridge CD changers that have one or more cartridges the user loads with up to twelve different CDs (depending on manufacturer) inserted into the CD changer. Usually found in the car trunk, the 12-disc CD changer can then remove one CD at a time for playing.
Internal cartridge CD changers are usually in-dash units that work on the same basic principle as external cartridge players, except the cartridge never leaves the CD player. This type of CD player accepts multiple (usually 3 or 6) CDs through a single slot loading system and stores them internally.
A few automakers even used a carousel-type CD changer that consists of a circular platter that holds three or more CDs. Traditional carousel CD players hold three, five, or seven discs on a flat carousel tray. The carousel ejects to allow access to the CDs. Once back inside, the CD changer can rotate the carousel to access all of the CDs.
NEXT TIME: From cassettes and CDs to iPods and streaming music.