The compact audio cassette was invented by Philips in 1962, and is a worldwide standard. It has proven itself to be both practical and durable for home and portable uses.

The audio compact cassette dominated consumer pre-recorded music sales in the 1970's. It consisted of magnetic tape 1/8 inch wide and typically about 430 feet long (C-90 cassette) wound around a small plastic supply reel and threaded across the width of the cassette  onto a take-up reel. Both reels are encased in a protective plastic housing which can fit comfortably in the palm of your hand. The two reels are secured in the plastic housing with just enough room to turn. 

You never have to thread the tape onto the take-up reel because it is fastened rather permanently. On rewind, the tape stays attached to the other reel, unlike a reel to reel tape recorder where the tape is not fastened to the take-up reel. 

The cassette housing has four small round holes in the front which allow a post on the recorder to come all the way through. These holes have two functions. Positioning / securing the cassette in the tape transport and/or capstan tape drive during play / record operations. Some cassette recorders have two capstan drives and use both outer holes for the posts upon which the rubber drive wheels impact the tape to pull the tape forward (or backward). Other recorders use the two inner holes for stabilizing the cassette in the recorder transport, then use one outer hole for a single tape drive. When the cassette is turned over to play the other side, the fourth hole is used for the single capstan to pull the tape forward. 

There are two guide wheels on the outer front edges inside the housing to guide the tape from/to the reels. Some cassettes have a pressure pad in the front center just behind the tape where the play/record head presses on the tape.

On the back edge of the cassette housing are two tabs, which if in place, allow recording on the tape. If the tabs are removed, recording is prevented. If you decide to record on the tape at a later time, after removing the tabs, you can put scotch tape, or the like, over the holes in order to allow recording again. With the tabs removed, a spring loaded metal flange in the recorder is allowed to enter the hole created when the tab is removed, thus switching off recording capability.




The audio cassette was a major step forward, as far as convenience was concerned, from the reel to reel magnetic tape recorder, but some fidelity was sacrificed due to slower tape speed and other factors. Cassettes were much smaller than reel to reel tape and did not require manual threading of the tape. You could put a cassette in your shirt pocket and play your music on the go with hand-held players or while driving in a car. Audio cassettes were the perfect combination of affordable costs, portability, playback versatility, and recording capability.

Audio cassettes have two sides, A and B, which were flipped over to play or record the other side (except in the case of tape decks which could play both sides without flipping). The 1/8 inch tape had 4 tracks, two on each "side" for stereo recording. You can record 30 to 45 minutes per side on a normal cassette. A C-60 cassette would be 30 min. per side and a C-90 would be 45 min. per side while a C-120 would be 60 min. per side. The tape speed was 1 7/8 inches per second.



Most cassettes were sold blank, so people could record music or voice, but many pre-recorded music cassettes were also sold.

Audio cassette players/recorders
Cassette recorders come in a variety of sizes from small hand-held to mid-sized desk-top to full size hi-fi home decks. 

Noise reduction:

In 1970, Dolby noise reduction for cassettes began to address some of the fidelity problems associated with tape recording using the audio cassette format. Dolby B-type both reduced tape hiss and spurred many basic improvements in cassette transports, electronics and tape formulations. Soon the cassette was sounding as good as the LP records of the day, and it went on to become an extremely popular and widespread medium for recorded music. 

As listeners' expectations for high-quality playback have grown, various improvements on the original Dolby B-type system have risen to the challenge. The Dolby C-type and S-type noise reduction systems apply the same principles to even more dramatically reduce tape hiss.

Dolby B-type Noise Reduction

Dolby B-type noise reduction is the original Dolby system designed for consumer tape recorders. It is included in all but the least expensive cassette machines, and is used in the preparation of the vast majority of prerecorded cassettes. It is also incorporated in many stereo VHS videocassette recorded to improve their linear audio tracks and, in a modified form, in Dolby Surround decoders. Dolby B-type provides 10 dB of noise reduction at the higher frequencies where tape hiss predominates.

Dolby C-type Noise Reduction

Dolby C-type noise reduction was developed to improve the cassette medium still further by providing twice the tape hiss reduction (20 dB) of Dolby B-type. It is offered along with Dolby B-type in a variety of mid-range and premium cassette decks and players. Dolby C-type is also used in many professional videocassette recorders.

Dolby S-type Noise Reduction

Introduced in 1990, Dolby S-type is based upon the principles of the professional Dolby SR (Spectral Recording) process. It not only provides still more tape hiss reduction (24 dB), but also reduces low-frequency noise by 10 dB. Thus, it permits recording high-level signals at the frequency extremes more accurately and cleanly. In listening tests conducted during 1995 it compared very favorably with compact disc recordings, with most listeners judging the quality of Dolby S-type encoded tapes as comparable with or in some cases superior to the playback quality of the CD. Dolby S-type is steadily gaining momentum and is being incorporated first in state-of-the-art decks for the most discerning listeners.

Dolby HX Pro

Not a noise reduction system, Dolby HX Pro makes it possible to record loud musical passages with fewer high-frequency losses and less distortion. It is available in better cassette decks and is also widely used by the recording industry to improve the quality of prerecorded cassettes, through its process of reducing the effects of tape saturation. As no encoding of the signal takes place, no playback decoding circuitry is required to realize the benefits of Dolby HX Pro.

What type of cassette tapes are available for consumers?

Magnetic tape in audio cassettes can be made using several different materials for recording sound. First there is the ferric-oxide tape, referred to as 'normal' or Type I tape. Another is the CrO2 or chromium-dioxide tape which is Type II. Lastly, there is the metal tape or Type IV. 

(Type III or Ferric Chrome is no longer available.)

Many cassette decks automatically read the tape type (I, II, or IV, also called Normal, CrO2, and Metal, respectively) and adjust the bias. But some decks allow you to fine-tune the bias for individual tapes.

Bias (pre-magnetization) is the magnetic adjustment given to the tape. Bias is the process of putting the audio signal to be recorded on a high-frequency carrier wave. Bias helps to avoid errors in recording. Ferric-oxide tape requires normal (100%) bias, chromium-dioxide tape 150% bias, and metal tape 200% bias. Metal tape has a high intensity capacity and can therefore record more accurately than other types of tape. 

Playback correction (equalization) amplifies high tones more than others. It does this to offset the recording process, where bass frequencies are emphasized.

Cassette recorders for the home:

High quality cassette decks for home use are an integral component of a consumer's music system. A cassette tape is often driven by a DC motor. Better tape decks have three motors: one for recording and playback, and one each for rewind and fast forward. A cassette deck can have up to three heads: one for recording, one for playback, and one for erasing. 

The most important requirement of a deck is for the tape drive to be accurate and constant. The tape transport system must pull the tape past the heads at a constant speed, pressure and angle, to ensure the accuracy of both recording and playback. Otherwise there will be a distortion (also referred to as "wow"). A small rod (called a capstan) is used in the tape drive mechanism to keep the tape taut and moving smoothly.

Having three motors provides better quality by distributing the work of maintaining proper speed and tape pressure more evenly.

Additional cassette deck features include:

• Full Logic: The tape drives are controlled electronically instead of mechanically. This feature is also necessary if the cassette deck is to be operated by remote control. 

   

• Automatic Reverse: Enables the listener to listen to both sides of a tape without having to remove the tape from the player and flip it over. It works by reversing the direction of the motors, and turning the tape head assembly around.

   

• Dual Cassette Decks: These decks have two cassette wells, which allow the user to make copies of tapes.

   

• High-Speed Dubbing: A feature found on double cassette decks. When using this feature, both decks operate at double the normal speed, which cuts recording time in half.

   

• Record Mute: This function allows the person making a recording to delete undesired sections by pressing and holding in the button, producing a non-recorded section.

   

• Blank Skip: Decks equipped with record mute often also have a blank skip feature which automatically winds the blank sections rapidly during playback.

Cassette recorder brand names:

Cassette recorders for home use are made by several electronics companies. The better brands include Nakamichi, Sony, Tascam, Aiwa, Onkyo and Denon. Sony, Panasonic  and Marantz also make portables. The Sony 'Walkman' models have been around for years.

How do I maintain my cassette deck?

Cassette deck maintenance prevents  problems and improves recording and playback sound quality.

Dip a cotton swab in isopropyl alcohol and gently scrub the heads (these are the parts that read the tape).

Dry the heads with the other end of swab.

Use fresh swab when one gets visibly dirty.

Repeat until the swab does not appear to be discolored.

Clean heads after about 30 hours of use or according to the recommendations of the manufacturer.

Commercial head-cleaning fluids contain additives that will cause more harm than benefit.

Use a cotton swab and alcohol.

Clean capstan. Turn on deck to spin capstan (the metal spindle to the right of the tape heads that works with pinch roller to guide tape). Gently move swab up capstan shaft.

Clean pinch roller (the black rubber roller that works with capstan to guide tape). Rotate pinch roller with swab in tape path between capstan and pinch roller.

Clean stationary plastic and metal guideposts.

Clean under reel hubs.

Wipe remainder of tape well with a dry swab.

Some decks have two capstans and pinch rollers. See the information that came with your deck to see where the parts are on your equipment.

Use rubber cleaner on pinch roller if required.

Clean the tape path when you clean the tape heads.

Cassette tape brand names:

The better brands for blank tape include Maxell, TDK, Sony, Fuji.

 

Which blank cassettes should I buy?

Match the tape you choose to both your tape deck and what you're recording (speech, music).

Check your tape deck's owner's manual for the manufacturer's recommendations on which kind of tape to use on your recorder.

Buy "normal bias" Type I tapes for use with portable-recorders.

If you're playing tapes on a personal stereo or low-end car deck, buy Type I tapes unless the playback unit has a switch for "high bias" Type II tapes.

Choose "metal bias" Type IV tapes if playing tapes on a high-end cassette deck and it is recommended in the manual.

Buy Type I tapes for recording speech.

Choose Type I tapes or lower-grade Type II tapes for dubbing from one cassette to another.

Buy Type II or Type IV tapes if recording live music on a deck.

Select higher-grade Type II or Type IV tapes for recording from LP or CD.

Higher-grade tapes within a type are typically distinguished by an "X" or an "S" model number.

Most tape decks automatically set the bias for the type of tape by reading notches on the cassette.

"C" indicates the total number of minutes on the tape.

Type II tapes can record higher frequencies than Type I tapes and have a higher signal-to-noise ratio. Type IV tapes are even better.

Warning: C-120 cassettes use thinner tape, which is more prone to jamming and breaking.

What size is an audio cassette?

The standard audio cassette used for recording music is 4 inches wide, 2 1/2 inches deep and 3/8 inches high.

How much did music cassettes cost?

Pre-recorded music cassettes varied in cost depending upon what year they were sold and popularity but generally cost 8 to 10 dollars during the peak years for not so "hot" music to 13 dollars or more for "hits" or popular artists. After music cassettes faded in favor of CD's, you could buy one for as low as 50 cents each.

How is sound recorded on tape?

In the process of recording, sound waves are converted to an electrical audio signal and sent to a copper wire coil (recording head) in an alternating magnetic field. The magnetic variations are communicated to the tape through a narrow slot. Tiny particles in the tape align themselves with the magnetic lines of force and hold those positions after being removed from the magnetic field.