DX7

Yamaha DX-7

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Released in the '80s this synth quickly became the most popular of all time.

It was the first fully digital synth, employed a revolutionary frequency

modulated algorithm and was priced much lower than the analogue monsters

that preceded it. Philip Glass used it to wide effect for Miami Vice, Prince

had it on many of his albums, Howard Jones produced albums filled with its

library sounds. The whole of the 80's were loaded with this synth, almost to

the point of saturation. There was generally wide use of its library sounds

due to the fact that it was nigh on impossible to programme, only having entry

buttons and the algorithm itself was not exactly intuitive, but also because

the library was exceptional and the voices very playable. The emulation is a

6 operator per voice, and all the parameters are directly accessible to ease

programming.

The original DX had six operators although cheaper models were release with

just 4 operators and a consequently thinner sound. Each operator is a sine

wave oscillator with its own envelope generator for amplification and a few

parameters that adjusted its modulators. It used a number of different

algorithms where operators were mixed together and then used to adjust the

frequency of the next set of operators. The sequence of the operators affected

the net harmonics of the overall sound. Each operator has a seven stage

envelope - 'ramp' to 'level 1', 'ramp' to 'level 2', 'decay' to 'sustain',

and finally 'release' when a key is released. The input gain to the frequency

modulation is controllable, the output gain is also adjustable, and the final

stage operators can be panned left and right.

Each operator has:

Envelope:

Attack: Ramp rate to L1

L1: First target gain level

Attack: Ramp rate from L2 to L2

L2: Second target gain level

Decay: Ramp rate to sustain level

Sustain: Continuous gain level

Release: Key release ramp rate

Tuning:

Tune: +/- 7 semitones

Transpose: 32' to 1' in octave increments

LFO: Low frequency oscillation with no keyboard control

Gain controls:

Touch: Velocity sensitivity of operator.

In gain: Amount of frequency modulation from input

Out gain: Output signal level

IGC: Input gain under Mod control

OGC: Output gain under Mod control

Pan: L/R pan of final stage operators.

Global and Algorithms:

24 different operator staging algorithms

Pitchwheel: Depth of pitch modifier

Glide: Polyphonic portamento

Volume

Tune: Autotune all operators

Memories can be selected with either submitting a 3 digit number on the keypad,

or selecting the orange up/down buttons.

An improvement could be more preset memories with different sounds that can

then be modified, ie, more library sounds. There are some improvements that

could be made to polyphonic mods from key velocity and channel/poly pressure

that would not be difficult to implement.

The addition of triangle of other complex waveforms could be a fun development

effort (if anyone were to want to do it).

The DX still has a prependancy to seg fault, especially when large gains are

applied to input signals. This is due to loose bounds checking that will be

extended in a present release.