The R and D teams in the audio industry have provided us with many different ways to capture sound over the years. Keith Gemmell examines the different formats used for recording, from wax, through analouge tape to digital hard disk.

Recording sound was actually underway as early as 1806 when Thomas Young, an English physician recorded the vibrations from a tuning fork onto a rotating wax drum. But he couldn’t prove conclusively that he’d actually done it because he had no way of hearing the recording back. A Frenchman, Leon Scott de Martinville had the same problem, in 1857, when he recorded fluctuations in air pressure onto soot, also using a rotating drum, a large diaphragm and pig’s hair.

Thomas Edison completed the task, in 1877, when he recorded his voice onto the worlds first recording medium - a strip of paper, coated with paraffin. Later that year he built a phonograph and used a cylinder to record the sound, this time covered in tin foil. In 1887 he updated the whole thing and began using a solid wax cylinder.

The commercial possibilities of such a momentous discovery were enormous and it wasn’t long before Emile Berliner, a US German immigrant, invented the gramophone, in 1888. He used a wax coated disc, which, after the recording, he immersed in acid, to expose the grooves made by the stylus.

Magnetic wire and tape

Although the wax analogue recording process remained much same until around the time of the Second World War, record companies began experimenting with two new formats - magnetic wire and magnetic audio tape. Both formats were developed simultaneously and battled for supremacy. In fact quite a few commercial reel to reel wire recorders and playback devices were on sale in the US in the 1940s. But tape eventually won through.

In both cases the recording principle is the same. A length of magnetic tape (or wire) is sped past a recording head. An electrical signal, captured by a microphone, is fed to the recording head and recorded onto the tape as a magnetic pattern. The tape is then passed over a playback head which converts the changes in the magnetic field back into electrical signals (sound).

Wire recorders like the Webster - Chicago 288 were common in the US, in the 1940s (photo: Tom Albrecht at antiqueradios.com).

By the 1950s professional recordings were made using 1/4” wide tape running at speeds of 15 and 30 ips (inches per second). And because analogue tape can carry multiple tracks in parallel, in perfect synchronisation, it wasn’t long before 2 track stereo superseded mono recording. The natural progression from here was 4 track recording and by the late 1960s, professional recording studios began using 8 and 16 track recorders. The tape size used for these machines increased accordingly, to a width of 2”. In the 1970s, 24 track recording eventually became the standard and recorders such as the Studer A80 and the Otari MTR90 remain a common sight in top flight studios, even today.

The Studer A80, a classic analogue 24 track tape recorder, still used in many recording studios around the world

Why did analogue tape become so popular? Because different instruments could be assigned a track each and mixed down to 2 track stereo. Also, it could be easily spliced and edited. And its disadvantages? Tape hiss, caused by the magnetic particles, was the main problem, particularly at speeds of 15 ips and below. However, in the 70s, various companies tackled the problem using volume compression and expansion. The most successful system was developed by Dolby laboratories. Other flaws included distortion and wow and flutter (pitch variation) but, like hiss, these problems were practically inaudible on high-end machines.

Open reel recorders

Although it’s all digital now, the home recording boom began with the advent of analogue tape machines like the Teac 3340, which in the 70s, offered musicians affordable 4 track open reel recording on 1/4” tape. 8 tracks on 1/2” tape soon followed, with the Tascam 38, but it was Fostex who first squeezed 8 tracks onto 1/4” tape with their revolutionary A8. The race to produce affordable 16 track machines using 1/2” tape began, and soon after, the Fostex B16 and the Tascam MSR16 became a common sight in budget studios around the world. It’s ironic that just as analogue tape recording had reached a state of near perfection it was almost completely abandoned, with the sudden rise of digital technology.

Compact cassette recorders

Also popular in the early days of home recording, the portastudio provided a cheap way of making demos on a 1/8” cassette tape. Tascam developed the concept first and perhaps one of their best machines was the 488 which, remarkably, allowed 8 tracks to be recorded onto a standard cassette tape.

DAT recorders

Whereas analogue recording captures sound as magnetic particles, digital recording converts audio signals into binary code. Pioneered by Sony, DAT (Digital Audio Tape) first appeared in 1987. The technology employed is similar to that used in video recorders. A rotating head is used to record the audio data on to 1/8” magnetic tape, housed in a shell approximately half the size of an ordinary compact audio cassette.

Most DAT machines use four sampling modes: 32 kHz at 12 bits, and 32 kHz, 44.1 kHz or 48 kHz at 16 bits. Some though can record at 96 kHz and 24 bits. The quality of the sampling depends on the duration of the recording. For example, 32 kHz at 12 bits provides six hours of recording while 96 kHz at 24 bits will provide just 90 minutes on the same length of tape.

DAT tape was commonly used for mastering in pro and semi-pro studios alike during the 80s and 90s. However, the advent of CD-R has led to a gradual decline in sales, although the portable variety remains a firm favourite for location recording.

MDM

Modular Digital Multitracks were directly responsible for the demise of personal open reel multitracks. They are easy to use, require little maintenance and can record 8 tracks of audio onto a cheap video cassette tape. Like DAT recorders, they use a rotating record head. From the early 90s onwards, Alesis and Tascam dominated the market with the ADAT-XT and DA-88 machines respectively. The ADAT machines recorded on S-VHS tape and the DA-88 and its descendants use Hi-8mm tape. They can still be found in many studios today and Tascam’s current flagship model is the DA-98HR. These machines are great for combining old world tape recording with digital editing and sessions are often recorded first on an MDM, transferred to a computer hard disk , for editing, and sometimes returned to the MDM for mixdown.

At the head of the TASCAM DTRS range, the DA-98HR is perhaps the ultimate modular multitrack recorder

Random access recording

Video cassette, of course, is not the only digital recording medium. Much more common these days are the various random access multitracks which record to hard disk and magneto-optical disk. Unlike the tape based digital formats, random access recording allows you to edit tracks. You can also record virtual tracks - several takes perhaps, of a single instrument - and choose the best one afterwards.

DAW

Digital Audio Workstations are probably the most commonly used random access systems used for home recording today. All you need is a reasonably powerful computer, recording and editing software and a sound card. Audio is sent to the sound card’s analogue inputs where it’s converted into a digital signal and recorded on the hard drive. Alternatively, a USB or FireWire interface such as M-Audio’s Omnistudio or Audiophile can be used instead. The advantages of this system are virtually unlimited tracks and digital signal processing (depending on the processing power of your computer), mixing to stereo on the hard drive, graphical faders and waveform editing.

HD

Not everybody likes computers, and for some, a stand alone Hard-Disk recorder is a better option. In the 90s Akai produced the first affordable machines like the DR4 and the DR8. However, due to the fixed hard disk within these machines, backup and storage was slow. Today, hard disk recorders are much more sophisticated. The ADAT HD24, for example, has two hot-swappable media bays which provide convenient access to the recording drives, reducing data backup time to just minutes.

MO

Magneto Optical recorders provide similar features to the hard-disk type. A laser is used to magnetise the disk and read the recorded data. MO disks are slower than hard disks but are reliable and cheap to buy. Otari manufacture a mono machine (popular with the talking book industry) as well as 2 track stereo and 8 track units (both popular in the world of film/video post production and broadcasting).

MD

MiniDisc is another ‘laser-read’ magneto-optical format and two types are available. One for 2 track recording (used in regular consumer MiniDisc machines) and MD data discs, used in multitrack recorders. The main attraction is, of course, the size and portability. However, to fit the data onto such a small disc, the MD format uses a form of data compression (ATRAC) and the sound quality is not as good as a DAT machine.

Tech terms

DAT - Digital Audio Tape, supplied in 1/8” cassette format. Commonly used for 2 track mastering.

MDR - Recordable Minidisc, often used by local radio, to record and play back programs.

DA8 - Digital audio cassette for Tascam’s DTRS modular recorders such as the DA-98HR.

ADAT - Digital audio cassette for Alesis modular recorders.

AAC - Advanced Audio Coding, an audio codec that may well replace the mp3 format. A favourite with the audio industry because it features built-in copyright protection.

MP3Pro - The latest advance in mp3 technology offers stereo compression at half the size of the standard mp3 format.

More information

Recording History - Lot’s information plus a film clip showing a demonstration of the Ediphone, circa 1907.

Copyright 2006 Keith Gemmell