8 UB-Xa User Manual
Switching on neither (both LEDs o) selects a Triangle waveform.
(26) OSC 1+2 PULSE WIDTH – sets the width of the pulse when the Pulse
wave is selected on either or both VCOs. When fully to the left (CCW) a
square wave is produced where the up and down cycles are equal. Turning
the control further to the right (CW) decreases the amount of the up cycle,
producing a thinner eect. At all levels below the maximum Pulse Width
Modulation will vary the waveform.
Holding the Pulse button (25 or 31) for either Osc 1 or Osc 2 allows the
pulse width control 26 to aect each oscillator separately.
(27) SYNC – causes the wave of oscillator 2 to reset at the same time as that
of oscillator 1; giving a harmonically rich but sometimes glitchy eect,
particularly when used in conjunction with F-env.
(28) F-ENV – allows the lter envelope (see below) to change the pitch
of oscillator 2, producing a distinctive eect as oscillator 2 attempts
to synchronize with oscillator 1. The depth is controlled by the Filter
Modulation control.
(29) OSC 2 FREQUENCY – sets the base frequency of oscillator 2 in semitone
steps over ve octaves. This allows oscillator 2 to be oset against
oscillator 1.
(30) SAW – switches on Sawtooth waveform for oscillator 2 (Saw LED on).
(31) PULSE – switches on Pulse waveform for oscillator 2 (Pulse LED on).
Switching on neither (both LEDs o) selects Triangle waveform.
Filter Section
The lter is the way that the UB-Xa shapes the sound produced by the VCOs to
control their timbre. The UB-Xa has two switchable Low Pass Filters (LPF): a
24 dB/octave 4-pole lter which gives a fuller sound, and a 12 dB/octave 2-pole
which gives a smoother sound.
(32) FREQUENCY – controls the amount of high frequencies that are allowed
through the lter. When the control is fully to the left (CCW) no sound
will pass (subject to modulation – see below). As the frequency control is
turned to the right (CW) an increasing amount of high frequency is passed,
until once the control is fully to the right (CW) there is no ltering at all;
and all frequencies can be heard.
(33) RESONANCE – also known as ‘Q’ or Emphasis, Resonance increases the
prominence of frequencies centered around the position of the Frequency
control. In 2-pole mode the overall patch will get louder; in 4-pole mode
it will reduce in volume. The lter will self-oscillate in either mode,
depending on the Atrophy settings in the Voice menu.
(34) MODULATION – controls the amount of modulation from the Filter
Envelope that is applied to the lter. This control also controls the amount
of Filter Envelope that is applied to oscillator 2 when the F-Env button is
used.
(35) NOISE – allows the output of the Noise Generator to be routed to the lter.
When the control is fully to the left (CCW) no noise will be heard. Turning
the control to the right (CW) increases the amount of noise heard until the
control is fully to the right (CW) where the noise is at its highest level.
(36) OSC 1 – allows the signal from oscillator 1 to be routed to the lter at full
volume.
(37) OSC2 Half – allows the signal from oscillator 2 to be routed to the lter at
approximately half the level of oscillator 1 (- 6 dB).
(38) OSC2 Full – allows the signal from oscillator 2 to be routed to the lter at
the same level as that of oscillator 1.
(39) 4 POLE – when this switch is on (LED lit) the lter is working in 4-pole
mode, as described above. When it is o then 2-pole is used.
(40) TRACK – when this switch is on the keyboard voltage is applied to the
lter, resulting in higher notes sounding brighter, particularly if the
frequency control is set low.
Envelope Section
The UB-Xa has two envelope generators, which allow the patch of the lter
and the amplitude of the Voltage Controlled Amplier to be contoured. Both
Envelope Generators feature four stages of contouring.
Filter Envelope
The Filter Envelope controls the contour of the lter when in use. Its eect will
be more obvious if the frequency control is set low. There are four controls
associated with this Envelope Generator:
(41) ATTACK – controls the time taken for the envelope generator’s level to rise
from zero to maximum. The UB-Xa’s attack is adjustable between 7ms and
13 seconds.
(42) DECAY – controls the time taken for the envelope generator’s level to fall
from maximum to the level set by the Sustain control (see below) once the
Attack stage has nished, and providing that keys are being held. The time
is adjustable between a minimum of 9ms and a maximum of 16.5 seconds.
(43) SUSTAIN- controls the level at which the lter will be held once the Decay
cycle has completed and providing that keys are still being held. There
is no time limit to Sustain. It should be noted that a high Sustain setting
(above 50%) will cause the Decay stage to have little or no eect.
(44) RELEASE – controls the rate at which the envelope generator’s level drops
to zero once keys are released. It should be noted that if Sustain is set to
minimum the Release control will have no eect if keys are held down; but
if keys are released during Attack or Decay then Release will still aect the
lter. Release time can be adjusted between a minimum of 50ms and a
maximum of 20 seconds.
The Filter Envelope also aects the pitch of oscillator 2 when the OSC2
F-Env switch is active.
Loudness Envelope
The Loudness Envelope controls the level of the UB-Xa’s output (subject to the
position of the Volume control). Like the Filter Envelope it has four controls:
(45) ATTACK – controls the time taken for the envelope generator’s level to rise
from zero to maximum. The shorter the attack, the punchier the patch.
The UB-Xa’s attack is adjustable between 7ms and 13 seconds.
(46) DECAY – controls the time taken for the envelope generator’s level to fall
from maximum to the level set by the Sustain control (see below) once
the Attack stage has nished, and providing that keys are being held. As
with Attack the shorter the decay, the punchier the patch. The time is
adjustable between a minimum of 9ms and a maximum of 16.5 seconds.
(47) SUSTAIN – controls the level at which the VCA will be held once the Decay
(32) (33) (34) (35)
(41) (42) (43) (44)
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