INDUSTRY SPECIAL How electronics technology changed music forever

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Anyone who was around in the Sixties and Seventies would have witnessed the appearance of a radical new musical genre; electric rock’n’roll. This article looks at how this unprecedented phenomenon depended not only on the artists’ skill and innovation, but also on the electronics technology emerging at the time.

Back in the Sixties, the Rolling Stones, Jimi Hendrix, Eric Clapton, the Who, and other like-minded musicians and bands together created a tremendous new electric rock and roll music genre unlike anything that had previously existed. Although much of this was due to their originality and talent, they could not have achieved their breakthrough without the newly-emerging types of electric musical equipment – guitars, amplifiers, and speakers.

Electric guitars were originally conceived simply as amplified acoustic guitars, but in the hands of the above performers they became something entirely more powerful, exciting, and different. This new genre was heavily influenced if not created by US-born Jimi Hendrix, in an astonishing UK career that lasted only three years before his untimely death. Musicians across blues and rock genres like Bob Dylan, the Rolling Stones, Eric Clapton, Pete Townsend, Kurt Cobain, and equally jazz pianist Herbie Hancock and hip-hop legends like the Beastie Boys, all have one thing in common; they have cited Hendrix as a major influence.

In other words – ‘If Jimi Hendrix is not your favorite guitarist, he is your favorite guitarist's favorite guitarist.’

There were other guitarists in the ‘60s that liked it loud, but none of them had truly embraced the potential of wildly overdriven amplifiers, and practically every other band at the time did their best to avoid feedback. But Hendrix, newly arrived in England in 1966, had noticed a number of guitarists using Marshall equipment, and picked up a selection of amps and speakers from this indigenous British manufacturer. Setting all the controls to maximum (famously known as ‘the Hendrix setting’) provided the trademark tone that, in the words of Jim Marshall himself, made Jimi the greatest ambassador his company ever had.

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Hendrix also made good use of effects, particularly the brand new Vox Cry-Baby Wah-Wah that became his signature effect, providing that legendary introduction to ‘Voodoo Chile’. But it’s the virtuosity and progressive fusion of genres in his soloing that truly blew the world away, and continues to inspire musicians to this day. The solid Blues core of his style was neatly mixed with Rock’n’roll, R&B, Jazz, Soul, American Folk, and British Rock influences, pushing the boundaries of psychedelic rock that no-one had come close to touching¹⁾.

Hendrix was able to make these achievements because guitar and amplifier technology had developed sufficiently to allow him to do so. The roots of all this can be traced back to the 1920s, when the first electric guitars started to appear. They were used in country music and big band, and then early forms of rock’n’roll. Big band musicians in particular had been finding that acoustic guitars were not loud enough to be heard over the many other instruments.

The development of the electric guitar

In response to this problem, various individuals began looking at ways to amplify the guitar’s sound. In 1928, instrument makers Stromberg-Voisinet created the first commercially produced electric guitar, four years after Gibson fitted an electromagnetic device to violas and basses which picked up vibrations from the bridges of the instruments and converted them into electrical signals that could be sent to an amplifier and loudspeaker²⁾. While the Stromberg-Voisinet increased the volume of the guitar, the sound it produced still left much to be desired.

A solution to the lackluster pickup of the day arrived in the early 1930s. As with big band players, Adolph Rickenbacker – a Hawaiian guitar player – was frustrated by the guitar’s low volume compared to that of other instruments in an ensemble. He developed a guitar, which, due to its shape, became known as the ‘Frying Pan’. What was special about this electric guitar (albeit a Hawaiian one) was that, unlike Gibson's creations and the Stromberg-Voisinet, its pickups captured vibrations from the strings themselves.
However, acoustic guitars fitted with pickups like this produced large amounts of feedback and unwanted noise. In response, Les Paul – a notable guitarist - devised the first solid-body electric guitar, called the ‘Log’, in 1939. This, however, was laughed at by Gibson, the premier manufacturer at the time, and the humble Log never went into production.

Things changed in 1950 though, when Leo Fender, a self-taught electronics enthusiast, created the Esquire, the first mass-produced solid-body guitar. Taking note of Fender’s successes, Gibson ate humble pie, introducing its own solid-body model, the Les Paul. By 1954, with the advent of Fender’s three-pickup, solid-body Stratocaster, the three most iconic electric guitars of all time were all released. Music would never be the same again.

The pickups used on these solid body guitars did not pick up audible sounds; instead, they were entirely electric, or to be more accurate, magnetic. Such pickups comprised a bar magnet wrapped with as many as 7000 turns of fine electrical wire. The guitar’s vibrating steel strings produce a corresponding waveform in the magnet’s magnetic field, which in turn induces a varying current in the wire coil.
The circuitry within the electric guitar body is quite simple, with the pickup signal being sent to the amplifier and then on to loudspeakers. In fact, the amplifier can be considered as part of the guitar. However, the guitar electronics does have some functionality. A simple low-pass filter allows the guitarist to adjust tone by turning a knob on the face of the guitar. This is linked to a variable resistor in the low-pass filter. A second variable resistor controls the amplitude, or volume, of the signal sent to the amplifier. Many electric guitars have two or three different pickups located at different points on the body. Each pickup will have a distinctive sound, and multiple pickups can be paired, either in-phase or out, to produce additional variations³⁾.

The guitar amplifier

A stereo amplifier in a hi-fi system is designed to be transparent; the aim is always to reproduce and amplify sound with as little distortion as possible. However, this does not suit rock guitarists at all – they love distortion!

The origins of distortion in guitar music are varied, with many different claims around the first documented use. It’s widely accepted that the first uses of slight distortion were from the earliest guitar amplifiers available being pushed to their limits. Blues artists such as Elmore James and Buddy Guy tried to match the raw power of their vocal performances with similar styles when playing, and in the early 50’s the sound could be heard on tracks like ‘Maybellene’ by Chuck Berry. Guitarist Link Wray also began to modify the valves in his amplifier and poke holes into the speaker cone to get similar sounds⁴⁾.

In 1961 Country artist Marty Robbins had a track called ‘Don’t Worry’. During recording of the track, the bassist was plugged directly into the mixing desk, however there was a problem with the channel which caused it to distort and create an intense, distorted fuzz effect. There are similar stories of experimentation with distorted sounds, and in 1964 Ray Davies of The Kinks supposedly took a knitting needle or razorblade to the speaker cone and cut it to get that distorted sound!

Marshall Amplification is now one of the largest guitar amplifier manufacturers in the world, but it was started as a small London shop selling drums and related kit in 1960, by its founder Jim Marshall. Musicians including Pete Townsend of the Who and Ritchie Blackmore of Deep Purple pushed him to supply amplifiers as well as drums. They also said that, although the Fender Bassman came close, no existing amplifier delivered exactly the sound they were looking for.

By 1962, Marshall and his colleagues had developed five protypes that they rejected as unsuitable. Number six, though, delivered the ‘Marshall sound’ that they had been seeking – and they sold 23 on the first day of sale. It differed in several key aspects from the Bassman design on which it had been based. It used American military-surplus 5681 power valves, a relative of the 6L6 beam power tube – a type of vacuum tube (US) or thermionic valve (UK) – that offered significant performance improvements over power pentodes. It was introduced by Radio Corporation of America in April 1936 and marketed for applications as a power amplifier for audio frequencies⁵⁾. The valves are still commercially available today.

However, these valves could supply 50 W output power, which was more than could be handled by a single loudspeaker at the time. As a solution, Marshall assembled four Celestion 12” speakers into a separate closed-back cabinet, as against the Fender unit which integrated both amplifier and speakers into a single open cabinet.

Other crucial differences included the use of higher-gain ECC83 valves throughout the preamplifier, and the introduction of a capacitor/resistor filter after the volume control. These circuit changes gave the amp more gain so that it broke into overdrive sooner on the volume control than the Bassman, and boosted the treble frequencies. These factors allowed the amplifier to deliver the thicker, heavier, highly distorted sound sought after by rock guitarists.
This new amplifier came to be named as the JTM 45, after Jim, his son Terry Marshall, and the maximum wattage of the amplifier. Jimi Hendrix, Eric Clapton, and other blues rock-based bands from the late 1960s such as Free used Marshall stacks both in the studio and live on stage making them among the most sought after and most popular amplifiers in the industry.

The late 60’s and early 70’s saw the overdriven guitar sound hit the mainstream and later a more aggressive variant that we now refer to as distortion appeared in heavy metal music. Changing demands and tastes led players to want ever more distortion over the rest of the 20^th century. As the times changed, so did the amplifiers, with Marshall introducing 100 W heads and EL34 power valves.

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Different guitar amplifier types

Combo amplifiers, heads, and stacks: Perhaps the most obvious aspect of a guitar amplifier is whether it is integrated with one or more loudspeakers in a single cabinet (a combo unit), or is built as an amplifier head driving one or more separate speaker cabinets. The latter arrangement is called a stack; a head on top of a single speaker cabinet is called a half stack, while a head atop two cabinets is a full stack.

There are many varieties of speaker combinations used in guitar speaker cabinets, including one 12" speaker, one 15" speaker (this is more common for bass amplifiers than for electric guitar cabinets), two 10" speakers, four 10" speakers, four 12" speakers, or eight 10" speakers. Less commonly, guitar cabinets may contain different sizes of speakers in the same cabinet.⁶⁾

Vacuum tube (or valve) and solid state amplifiers: Vacuum tubes were by far the dominant active electronic components in most guitar amplifier applications until the 1970s when solid-state semiconductors (transistors) started taking over. Transistor amplifiers are less expensive to build and maintain, have reduced heat output weight and, and tend to be more reliable and more shock-resistant. Tubes are fragile and must be replaced and maintained periodically. Additionally, serious problems with the tubes can render an amplifier inoperable until the issue is resolved.

While tube-based circuitry is technologically outdated, tube amps remain popular since many guitarists prefer their sound. Tube enthusiasts believe that tube amps produce a warmer sound and a more natural ‘overdrive’ effect.

Solid-state amplifiers vary in output power, functionality, size, price, and sound quality in a wide range, from practice amplifiers to combos suitable for gigging to professional models intended for session musicians who do studio recording work.

A hybrid amplifier involves one of two combinations of tube and solid-state amplification. It may have a tube power amp fed by a solid-state pre-amp circuit, as in most of the original MusicMan⁷⁾ amplifiers.

Alternatively, a tube preamplifier can feed a solid-state output stage, as in models from Vox⁸⁾. This approach dispenses with the need for an output transformer and easily achieves modern power levels.

Modeling amplifiers: Microprocessor technology allows the use of digital onboard effects in guitar amps to create numerous different sounds and tones that simulate the output of a range of tube amplifiers and different sized speaker cabinets, all using the same amplifier and speaker. These are known as modeling amplifiers, and can be programmed with simulated characteristic tones of different existing amplifier models (and speaker cabinets — even microphone type or placement), or set up to the user's taste. Many amps of this type are also programmable by a desktop or laptop computer through a USB connection.

Modeling amplifiers and stompbox⁹⁾ pedals, rackmount units, and software that models specific amplifiers, speaker cabinets, and microphones can provide a large number of sounds and tones. Players can obtain a reasonable facsimile of the sound of tube amplifiers, vintage combo amplifiers, and huge 8x10” speaker stacks without bringing all that heavy equipment to the studio or stage.

Conclusion

Perhaps earlier musicians – maybe Delta bluesmen like John Lee Hooker or Muddy Waters for example – had visions of a more colorful, multidimensional sound, but could not realize these visions as the electronic technology they needed simply was not yet available. We will never know.

Jimi Hendrix, and the other acts that followed him, were luckier. By the time they arrived, the technology essential to fulfilling their ideas had been developed, or was capable of being developed. And this came to fruition after dialogue between the right musicians and the engineers who could understand and implement the sound they were striving for.

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References

¹⁾Why Was Jimi Hendrix So Important? – Guitar Head (theguitarhead.com)
²⁾The electric spark that changed the guitar forever - BBC Future
³⁾How Electric Guitars Work | HowStuffWorks
⁴⁾Distortion Explained - marshall.com
⁵⁾6L6 - Wikipedia
⁶⁾Guitar amplifier - Wikipedia
⁷⁾Music Man (company) - Wikipedia
⁸⁾Vox (company) - Wikipedia
⁹⁾Stomp box - Wikipedia

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