GUITAR OVERDRIVE PEDALS EXPLAINED

Once upon a time all electric guitar amplifiers were used within their operational limits (not overdriven) to produce essentially quite 'clean' sounding tones. Indeed the whole idea of the electric guitar pickup and valve guitar amplifier was simply to amplify the sound of the guitar in a big band setting as loudly and cleanly as possible to hold up to the acoustic volume of the drums and brass instruments used in the music of the 1920s-1940s. Getting the sounds both clean and without feedback led to amplifier development and also to the semi-acoustic and solid body electric guitars being invented.

However during the 1950s in the USA a new wave of music came along that threw out many of the of the old rules. The young post WWII generation had money in their pockets, a postive can do attitude and the new sounds coming out the radio were coined as being 'rock'n'roll'.

One of the earliest 'distorted' guitar sounds on a released recording is considered to be Rocket 88 by Ike Turner which apparently occured due to the amplifier suffering accidental damage before a gig leading to a sound which everyone loved and which was then carried over to the record.

Youtube Video: Ike Turner 'Rocket 88' 1951

No longer was it necessary to have a clean guitar sound to be cool, in fact quite the opposite became true, and it was realised that the guitar signal would similarly clip and therefore be distorted if the amplifier was turned up beyond it's ability to reproduce a signal cleanly.

Chuck Berry is perhaps one of the best known purveyors of the early overdriven valve guitar amplifier route to clipping distortion using valve amplifiers smaller than would be required to produce sounds at band level cleanly.

Youtube Video: Chuck Berry 'Johnny B. Goode' Live 1958

In so far as overdriving a valve guitar amplifier is concerned, that was pretty much it. You took a master voume valve amplifier, turned all the knobs up until the signal was no longer produced cleanly, and hope that the amplfiier didn't 'malfunction'!

Youtube Video: Marty McFly overloads his friend 'Doc' Brown's home-brew amplifier in the Hollywood Blockbuster 'Back to the Future' 1985. The ultimate in 'cranked' experiences?

We would be technically and morally remiss at this point having looked at the 'clean' amps being pushed 'too hard' to stay clean type of overdrive by 'cranking', to miss the biggest change agent of all with regard to tube amplifier overdrive... Jim Marshall. More to follow, but for now...

Youtube Video "The Story Of The Marshall Amp"

Decades of tube amplifier design led to more and more valve distortion being made available in the preamp sections of these amplifiers, and to seperate controls being used for preamp and power amp sections allowing for the preamp tubes to be pushed into clipping whilst keeping the output volume lower.

The thing is that valve amplifiers are expensive to make plus what happens when you want a clean tone for some of your song and and overdriven tone for some of it? You could use two amplifiers at twice the expense using an AB box with a transformer isolated output to avoid ground loops, you could use a more expensive channel switching valve amplifier once they had become available, but there was another option... and in time the overdrive pedal was one of them!

Here we should point out that there are 'overdrive' pedals, 'treble boost' pedals, 'fuzz pedals' and 'distortion' pedals all of which are designed to create a more 'distorted' guitar signal however we are interested here specificially in 'overdrive' pedals.

So in essence an overdrive pedal is intended to sound like an overdriven valve guitar amplifier being pushed beyond its ability to offer clean sounds by exceeding its headroom due to having been turned up loud or as we guitarist like to describe it 'cranked' or to help an amp designed to do this 'get there' quicker.

Such pedals do two things to achieve this:

They can boost the guitar pickup signal volume to assist with clipping the 'front end' preamp tube section of a valve amplifier and as a result perhaps also assist with exceeding the clean headroom of the output section valves.
They can contain circuitry that mimics the sound of overdriven valves via clipping and compression.
They may also offer some tone control via equalisation of the signal either fixed much like treble boosters, or variable.

Boss OD-1 1977

The first really effective overdrive pedal to gain some notoriety was the Boss OD-1 released in 1977 with asymmetric clipping that was more tone true than the later much more famous green overdrive we talk about next, however if you look about you won't find it mentioned that much as it didn't make it as a pedal celebrity by attatchment to a human celebrity, but it is well respected by those in the know nonetheless.

Ibanez (licensed from Nishin Onpa Company 'Maxon') Tube Screamer 1979

The first pedal considered to satisfactorily mimic the overdriven tube amp sound and also really hit the pedal celebrity charts was the TS-808 'Tube Screamer' designed by S Tamura of Maxon (Nishin Onpa Company) Japan and made available commercially by licencees Ibanez in 1979.

The TS-808 pedal design has gone through many changes and reissues but the main thing to note is the generally preferred JRC4558 Op Amp of many of early versions being the most coveted.

Notable TS-808 circuit users include Trey Anastasio, Joe Bonamassa, Eric Johnson, John Mayer, Brad Paisley, Steve Vai, and Stevie Ray Vaughan. The TS-9 incarnation boasts The Edge (U2) as a huge fan.

These pedals have also been used to great effect to tighten up high gain valve amp tones in the metal genre.

If you only get one overdrive pedal either by Maxon (Nishin Onpa Company), Ibanez, or a clone, then this is the standard circuit by which all the others tend to be judged although of course not everyone feels the same way about them, and many, especially the TS9 were made in varieties that sounded just plain bad.

For serious OCD information on this 'most likely to get stomped into oblivion pedal' check out Analog Man's Tube Screamer History

B.K. Butler Tube Driver

One other very well known classic 'holy grail' overdrive pedal is the B.K. Butler Tube Driver containing as it does an actual 12AX7 preamp type valve. This pedal is also one of the best ways known to mankind to make a solid state amplifier sound like a tube amplifier.

Notable Tube Driver user include Eric Johnson for his 'violin' lead tone, Joe Satriani who surfed with the alien using one, and Dave Gilmour (Pink Floyd) around the 'Division Bell' era, Billy Gibbons (ZZ Top), Kenny Wayne Shepherd, and Richie Krieger (Doors).

Summary:

So to get overdrive with a valve amp then, we have determined that you can crank it or stomp it or do both and see what happens! So long as you don't blow it then it's all good!

There are dozens of different 'overdrive' pedals now available to help produce more clipping, sustain and volume through the amplifiers they get plugged into and we suggest that you experiment and decide for yourself what sounds best to you with your own guitar and amps.

Other pages in the section: Guitar Delay Pedals Explained