by Paddy Kingsland
Sound International December 1978
The synthesiser section of the Avatar is based on the very popular Arp Odyssey, and the layout of the controls and facilities available are almost identical. The fundamental difference is that the keyboard is replaced by a special pickup which, when fitted to your existing guitar, supplies the necessary information to control the synthesiser.
The `hexaphonic' pickup is really six separate pickups, one for each string on the guitar and, considering this, it is very compact. There are two versions available, with different spacing of the pole-pieces, to suit different makes of guitar. The pole-pieces must be centered exactly beneath each string, and as bending strings will alter their position the pickup is placed as close to the bridge as possible, where movement of this sort is at a minimum. For best results solid guitars should be used, as they have better acoustic separation between strings than acoustic and semi-acoustic models.
Fitting my pickup to a Fender Telecaster proved to be quite difficult, as the plate which holds the bridge saddles and existing bottom pickup had to be sawn in two and filed down to provide a slot. A curved piece of spring steel is placed between the pickup and the body of the guitar so that the height of the pickup can be adjusted by tightening or loosening the fixing screws.
The Avatar must have an absolutely clean signal from each string or it won't reproduce the pitch of notes correctly. The makers advise the use of heavy gauge strings, which should be renewed before they go dead; to maintain a clean sound and accurate intonation — out of tune notes show up much more on certain synthesiser sounds than on straight guitar sounds.
With the benefit of hindsight, I would have had an Arp agent fit the pickup, and at the same time correct fret buzzes and adjust the action of the guitar. Probably the best way is to take your guitar to a dealer and ask to see the pickup, so that any problems with fitting will be immediately apparent. The six wires (plus earth) from the pickup are terminated in a neat connector screwed to the guitar. I would prefer a more flexible type of lead to connect the guitar to the Avatar than the one supplied. Sensibly the input connector and the jacks for pedals and footswitches are situated at the front of the Avatar; all other connections are at the rear.
The six outputs from the pickup are fed to a multiplexer, which selects the strongest signal and switches it to the pitch extractor (pitch to voltage converter). This supplies a voltage capable of controlling the pitch of the oscillators in the synthesiser. Pulses are also derived to trigger the envelope generators each time a string is plucked.
The synthesiser is monophonic - capable of playing one note at a time. If you play a run using several different strings, the multiplexer switches to each new string as it is plucked and supplies only that information to the pitch extractor. If you play a chord, the note which is loudest is selected, and the synthesiser finds that pitch. Six switches decide which strings trigger the synthesiser, and so it's possible for instance to select only the bottom E-string, and play chords while listening to the normal audio output of the guitar. The synthesiser then reinforces the bass notes. This can be very effective if the oscillators are tuned an octave below the normal pitch of the string.
The audio output of the hexaphonic pickup is available in mono or stereo modes, with the E, A and D strings on one side and the G, B and E strings on the other when in stereo. The sound produced is very bright and toppy; I prefer the guts of the Telecaster bottom pickup. However, by switching to 'Hex Fuzz' you can get what Arp call 'clean fuzz', a very useful innovation. The outputs from the hexaphonic pickup are fed to six separate fuzz devices, the outputs of which are mixed together. The resulting sound is free of the usual intermodulation between strings, and is a very exciting noise.
A wide range of wah-wah effects can be obtained by feeding the pickup (with or without Hex Fuzz) through the voltage controlled filter. This can be controlled by a variety of devices, including a foot pedal, a low frequency oscillator, a sample and hold device (which gives a 'controlled random' effect) and the envelope follower. The envelope follower provides a voltage which mirrors the envelopes of the notes played on the guitar; usually a hard transient as the string is plucked, followed by a slow die-away. By playing alternately loud and soft strokes you can vary the amount of wah-wah produced, and get very interesting rhythm patterns. On melody lines, by carefully setting up the filter to shape the notes, it's possible to get very near to the sort of sounds synthesisers are best known for — without using any oscillators just the audio output from the guitar! The envelope follower's output can also be inverted to provide a sort of backward tape effect on each note.
The synthesiser section is, as I said earlier, more or less an Arp Odyssey without the keyboard. The sound sources available are two voltage controlled oscillators, each with square wave or sawtooth waveforms, and a noise generator (useful for wind effects and suchlike). These sounds are selectable by means of switches to the inputs of the three channel mixer. The output of the mixer is permanently routed via the VCF to the VCA. In the final stage, two faders are used to mix the synthesiser output signal with the straight guitar output (clean or Hex Fuzz). A muting device is provided, before the output sockets, so that the system can be switched on and off by a footswitch, meaning that you can have your guitar set up in the normal way using the standard pickups and switch the Avatar in when special effects are required.
There are two output sockets: standard guitar jack, and XLR which is useful in studios (as is the level switch which provides a choice of high or low output). This is in addition to the mono and stereo guitar outputs, and an output from the synthesiser section only, all at low level on guitar jacks.
The Avatar also has a ring modulator, two envelope generators, and a sample and hold device. The ring modulator can be used to combine the outputs of the two oscillators, usually to produce bell-like timbres.
The envelope generators are used in conjunction with the VCA and VCF to shape the notes produced by the oscillators. One is adjustable in terms of attack, decay, sustain, release; the other in terms of attack and release only. By having two envelope generators, you can control the VCA with one, while the other controls the filter. This is very useful for horn type sounds and the like where it is possible to achieve a hard attack on the fundamental with the harmonics arriving slightly later. By using the LFO to trigger the envelope generator(s), notes can be repeated a number of times for each single pluck of a string.
The sample and hold device provides voltages which can be used to control the pitch of an oscillator to produce a random series of notes, or a continuous repeated pattern. It is triggered either by plucking the guitar or by pulses from the LFO. It works by sampling the level of an audio source at the instant of each trigger, and producing a voltage related to the level at that instant. The voltage is held until the next trigger, when it samples again to produce a new voltage. This device is very useful indeed for producing anything from jokey computers to haunting `spacey' backgrounds. It can also be used to control the VCF and provide random accents on rhythmic passages played on the guitar.
Although the path of the audio signal is permanently routed through the devices in the synthesiser, the facilities for voltage control of these devices are extremely flexible, as in the Arp Odyssey, using slider controls and option switches.
Piano players using a keyboard synthesiser for the first time will know that a new technique is required; the same applies with the Avatar, if anything more so. It is vital to play cleanly with even plectrum strokes and no buzzes from frets. This means that when playing fast melody lines, using synthesised sounds, certain notes tend to wobble in pitch, especially if, like me, you don't play as cleanly as Chet Atkins! It's possible to mask this effect by using the LFO to provide vibrato or repeating wah-wah, but this tends to make everything sound a bit Mickey Mouse. I hope that Arp will find a way to improve the pitch following characteristics on future models of the Avatar and rectify the instrument's only weak point.
The Avatar, for me, really comes into its own when used to reinforce the straight guitar sound. For instance, the guitar with Hex Fuzz mixed with one oscillator tuned an octave below the guitar and one tuned a fifth above makes a rich exciting sound, especially in stereo. The pitchwobble I talked about earlier is less of a problem on these sounds, as it is masked by the guitar sound. Also, for gliding sounds and note-bending plus vibrato, the guitar is a more convenient way of controlling a synthesiser than a keyboard. Of course, for electronic and `spacey' effects, the Avatar provides a vast range of possibilities, and gives excellent control of pitch and timbre. The only trouble with a guitar is that, unlike a keyboard, it doesn't leave you with one hand free to alter the controls during notes. For this reason, a sustain footswitch is provided which holds the note last played as long as the switch is down. This enables you to hold a bass note, while continuing to play a solo or chord pattern on the guitar. Provision is also made for controlling portamento on a footswitch, and for controlling a variety of functions on a foot pedal. (Incidentally the pedal itself is an optional extra.) I am convinced that to use the instrument effectively, these footswitch techniques have to be mastered, particularly when playing live.
Jacks are provided to interface the Avatar with a keyboard, which I intend to do for use on the sort of runs and melodies which are best played that way. This feature makes the Avatar into a very flexible instrument for home experimental studio set-ups.
I am sure the instrument has enormous possibilities when used imaginatively, but it does need a good deal of practice and experiment to play it effectively, even assuming a knowledge of standard synthesiser techniques. Whether or not you are familiar with synthesisers the instruction manual is excellent and it is accompanied by a cassette, so you can compare the sound you are getting with those on the recording in each of the step by step experiments.
For brochure, floppy demo-disc and address of nearest dealer contact ARP Instruments, 320 Needham Street, Newton, Mass 02167, US. Or, in the UK, their distributors Stateside Electronics, Unit 8, New Road, Ridgewood, Uckfield, Sussex TN22 5SX, England.
*VAT is added at 121% for pickup and leads, 8% for unit.
Paddy Kingsland composes and produces music for radio and television programmes, realises electronic effects and music for films, and has recorded synthesiser records for EMI.