Pixie Attaché
– an EDP WASP clone
ELBY Designs
– Laurie Biddulph
Kariong, NSW 2250, Australia
14 of 18
SECTION IX - The Envelope Generators
The Pixie Attaché has two Envelope Generators:
The VCA-EG (Voltage-Controlled Amplifier) envelope
is used to shape the output amplitude of the Pixie and
involves controls (28), (29) and (30).
The VCF-EG (Voltage-Controlled Filter) envelope is
used to sweep the filters; it involves controls (28), (29)
and (30).
These envelope generators are of the attack-decay-release-
sustain type. Figure 3 shows exactly what is happening with
the envelope.
When a note is played the envelope is triggered and the
amplitude of the envelope increases at a rate determined by
the [ATTACK] control (30). It reaches a peak then decays to a
level determined by the [SUSTAIN] control (28), decaying at a
rate set by the [DECAY] control (29). The envelope amplitude
will remain unchanged until the note is released, after which
the envelope will decay to zero at a rate set by the [DECAY]
control (29). Releasing the note before the SUSTAIN section is
reached will result in a simple ATTACK-DECAY envelope.
Figure 3 - Envelope stages. NOTE: The [DECAY] control defines BOTH falling slopes
In the VCA-EG this envelope defines the output level of the Pixie Attaché.
ACTION:
Set up the controls as in Figure 1 and experiment with the [ATTACK], [DECAY] and
[SUSTAIN] controls.
If the SUSTAIN control is turned fully anti-clockwise, the Envelope Generator can be put
into a repeat mode by turning ON the [REPEAT] switch (18). When a note is played and
held the envelope will rise to a peak level, then decay to zero, and repeat this cycle until the
note is released. The 'rate' of the repeat cycle can be adjusted using the [ATTACK] and
[DECAY] controls (29) (30). See Figure 4
