Retroaktiv SSH User manual

SSH
COMPLEX SAMPLE & HOLD
OPERATION MANUAL
SQRSAW TRISIN

2
OVERVIEW
SSH
SSH Users Manual
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SQRSAW TRISIN
Figure 1- SSH Front Panel
• : For external sample & hold signal (+8v to -8v)
• : For external trigger signal (3v min, 10v max)
• : For controlling internal clock rate (+5v to -5v)
• : For controlling slew amount (+5v to -5v)
• : For controlling the shape of slew (+5v to -5v)
• : Noise generator output (+5v to -5v)
• : S&H staircase output
• Slewed S&H output
:
• : (3-position) Toggles when slew is active.
• : (2-position) Toggles the symmetry of the
slew shaping circuit.
:
• : Sets rate of internal S&H clock
• (RATE): Aenuates RATE input signal
• : Sets slew amount
• (Slew): Aenuates SLEW input signal
• : Sets the shape of the slewing effect
• (SLOPE): Aenuates SLOPE input signal
• Indicates rate of internal S&H clock
OVERVIEW

3
INTERNAL CLOCKSSH
SSH Users Manual
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Figure 2 - SSH Block Diagram
INTERNAL CLOCK
The built-in clock generator determines the interval at which the sample and hold
generator samples incoming signals. The clock ranges from about .25Hz to 100Hz. The
minimum rate of the clock can be set by the MIN RATE trimmer located on the rear of
the module. The rate of the clock can be controlled with external CV (+5v to -5v signals
recommended.) External CVs can be aenuated using the CV (RATE) knob.
The internal clock is normalized to the S&H trigger input via the TRIG jack. When a
cable is inseed into the TRIG jack, this connection is broken, and the S&H generator
will be clocked by the external trigger signal. External trigger signals should be a pulse
such as those from a typical LFO. (3vpp minimum. Input tolerant of pulses 10vpp)

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SAMPLE & HOLD
SSH
SSH Users Manual
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SAMPLE & HOLD
The sample & hold generator generates a staircase-type waveform by sampling an
input signal (8v to - 8v recommended) at an interval set by the internal sample & hold
clock or an external trigger signal. The input signal is sampled at the positive leading
edge of incoming clock signals. The stepped S&H waveform can be accessed at the
STEP output jack.
The internal white noise generator is normalized to the S&H signal input, which will
generate a random staircase waveform. External signals (8v to -8v) can be sampled by
plugging into the EXT input jack. This will break the normalized connection between
the noise source output and the S&H signal input.
NOISE GENERATOR
The noise circuit is a 5vpp white noise source. This can be accessed at the NOISE output
jack. The noise generator is normalized to the sample & hold input, which generates a
random staircase output waveform.
SLEW LIMITER & WAVESHAPING CIRCUIT
The SSH contains a complex slew limiter circuit which is used to limit the rate at which
the staircase waveform can change. By adding slew, a sharp edged staircase waveform
becomes rounded as the slew effect limits the rate at which the voltage can change.
The slope of the slewing is set by the SLOPE knob. With SLOPE set to fully count-
er-clockwise position, the slope of the slewing effect will be exponential. When set
to center position, the slope will be linear. The slope of the slew can morph between
exponential and linear when set to any position between EXP and LIN. (See figure 3)
Figure 3 - Slope knob function (SYM mode)

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SLEW LIMITER & WAVESHAPING CIRCUITSSH
SSH Users Manual
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Figure 4 - Staircase with no slew applied
Figure 5- Staircase with 30% slew applied, linear slope
Figure 6- Staircase with 30% slew applied, exponential slope

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SLEW LIMITER & WAVESHAPING CIRCUIT
SSH
SSH Users Manual
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Figure 4 shows a staircase waveform from the S&H generator. No slew is applied. Note the
sharp edges of the staircase waveform.
In figure 5, some slew has been applied to the staircase waveform. Since the SLOPE knob is in
the LIN (center) position, the slewing from step to step is linear. Similarly, in figure 6, slew is
applied to the staircase waveform. In this case, the slewing has an exponential (RC) curvature.
In the examples given in figures 4-6, notice that the RISE/FALL switch is in the center position.
The RISE/FALL switch determines when the SLEW is active. In the center position (BOTH), SLEW
is active when the staircase waveform is rising and falling (Always active). It is possible to dis-
able the SLEW effect during rising or falling steps of the staircase waveform. To enable SLEW
only when the staircase is rising, set the switch to RISE. To enable SLEW only when the wave-
form is falling, set the switch for FALL. Figure 7 illustrates the function of the RISE/FALL switch.
Figure 7 - RISE/FALL switch function (Linear slope)

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SLEW LIMITER & WAVESHAPING CIRCUITSSH
SSH Users Manual
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Figure 8 - RISE/FALL switch function (EXP slope)

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SLEW LIMITER & WAVESHAPING CIRCUIT
SSH
SSH Users Manual
retroaktiv
The SYM/ASM switch controls how the SLOPE circuit funtions. When the switch is in top po-
sition (Symmetrical mode), the slope set by the SLOPE and CV knobs will be applied to both
rishing and falling steps of the S&H waveform.
Seing the switch to the boom position (Asymmetrical mode) will change the way the slope
knob functions. In ASM mode, the SLOPE knob will function as shown in figure 9.
Figure 9- Slope knob function (ASM mode)
ASM mode allows the slewed S&H waveform to have a different slew shape on rising steps and
falling steps. Figure 10 illustrates how the slew/slope is applied in ASM mode.

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SLEW LIMITER & WAVESHAPING CIRCUITSSH
SSH Users Manual
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Figure 10- Slope knob function (ASM mode)

10
TRIM PROCEDURE
SSH
SSH Users Manual
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SQRSAW TRISIN
TRIM PROCEDURE
MIN RATE TRIM
• Set front panel knobs as shown in Fig 11. RATE
should be set at minimum.
• Use the MIN RATE trimmer on the PCB to adjust the
minimum rate of the internal clock. Monitor the
rate using the panel LED indicator. If this trimmer
is set too low, the clock LFO will no longer oscillate.
A recommended minimum rate is .25Hz (period of
about 5 seconds.)
SLOPE CIRCUIT TRIM
• It is recommended that an oscilloscope be used to
monitor the SSH output signals when trimming the
SLOPE circuit. This can be done by ear as well, but
it can take more work.
• Set the front panel knobs as shown in figure 11. Set
RATE knob to center position. Monitor the SLEW
output signal at the SLEW test point at the rear of
the SLEW output jack.
• Use the SHAPE trimmer on the PCB to dial in an
exponential waveform, then sweep the SLOPE knob
to center position. Slewing should morph from EXP
to LIN as the SLOPE knob is swept from fully count-
er-clockwise to mid-position. If the trimmer is set
too high, the slew will not be EXP when SLOPE is set
to its minumum. If the trimmer is set too low, the
slew effect will become extreme.
• When satisfied with the range of the slope knob, set
the SYM/ASM switch to ASM position. Turn SLOPE
knob fully clockwise. Monitor the SLEW output and
use the INV trimmer to trim the falling poions of
the SLEW waveform such that they match the EXP
curve set in the previous step.
• Seing SHAPE and INV can be done by ear if the
SLEW output is connected to the pitch CV input of a
VCO. Monitor the pitch and adjust the shape by ear.
Figure 11 - Panel settings for trimming