Smooth / Stepped (SSG)

From the original SMMS Catalog:
”The SMOOTH & STEPPED FUNCTION GENERATOR (SSG) is a complex multi-functional module to provide various slew and sample functions.

• The Smooth section will place a positive and negative slew (glide) on a changing input voltage for lag effects, voltage controlled portamento, and non-linear, low frequency filtering. With the CYCLE jack patched to the input, the unit will oscillate yielding a voltage controlled triangle wave LFO. A high level into the HOLD input will hold the current output level, whether the unit is oscillating or processing an external control voltage. This is identical to a track-and-hold function. 

• The Stepped function can be used as a sample-and-hold with voltage controlled slew rate limiting. Slew rate limiting limits the size of the step at the output. For example, with a random voltage input and the step size set to a small value, the output is a random voltage that varies only slightly from step to step, gradually covering the entire range of the input voltage. No large changes in the output will be allowed. With the Cycle jack patched to the input and a trigger applied to the Sample input, complex staircase waveforms are generated. 

• The COUPLER is an internal comparator comparing the Smooth and the Stepped outputs. This is useful for generating complex control voltages and for patching a random voltage generator. In fact, the Random Voltage Generator module is a Smooth & Stepped Generator internally patched to function exclusively as such. If random voltages are often used, a Random Voltage Generator is a more space-efficient module; but if seldom used, the Smooth & Stepped Generator can be patched when needed (and can be used for other functions when not used as a random voltage generator). Note that a Noise Source is needed for use of the Smooth & Stepped Generator as a random voltage generator.”
  
  ”The SSG is of course the Smooth and Stepped Generator module. It consists of two sub-modules, the top being the Smooth section, the bottom is the Stepped section. The outputs are tied together with a comparator at the CUPL. jack - this gives a HIGH if the smooth output is greater and a LOW if it isn't. *** CAUTION *** HIGH at CUPL is ~ 10VDC, LOW is ~ -10VDC. This is fine for use as a trigger but be careful when using it as a control voltage.... you won't hurt the Serge but if you're using it to control a VCA for example you may destroy your speakers and bring plaster raining down on your head from shattered walls. The Smooth section is a VC lag processor with some interesting additions: 1. Hold input. When this goes high the output no longer tracks the input but is held at the same level that was present when Hold went high. 2. Cycle. This is similar to GATE on the DSG but not the same thing. It is normally not HIGH but LOW (-10V) The Rate knob determines the rate of lag. At zero rotation the *rate* is low, so that translates to a lot of lag. The Stepped section is a sample-and-hold, also with interesting additions: 1. A rate knob. This determines how big each step is at the Stepped output. Full rotation = bi steps, zero rotation = very tiny steps. 2. Cycle jack. This is also normally LOW (-10V). More on this in another installment. The stepped section can serve as an extremely high quality sample-and-hold --- MOTM's sample and hold claims a droop rate of about 1mv per second - in other words, if you do a single sample driving a VCO at 1 volt per octave, then hold it and just listen without resampling you should be able to hear a VCO's tone drop perceptibly, without any trouble. An informal test I did measured > 10mv droop in 400 seconds on the SSG. Other listening tests bear this out.” -John Papiewski (2001)
  

  Calibration: From Serge kit instructions:

• For this module to work properly, a jumper must be installed between pad S and pad L. (This should have been installed during construction, although if you wish to test the two parts of the Stepped generator individually, it can be left disconnected until you have.)

Patch the CYCLE output of the Smooth Function into the IN jack. Monitor the OUTPUT while turning the RATE knob full clockwise. The pitch should be about 100 Hz, and should go to sub-audio rates (as seen from the LED'S) when the knob is turned down. Check that a control voltage into the VC IN jack will control the rate. Note that this is an attenuating input only, with no inverting processing.

A high level applied to the HOLD input (greater than about 4.5 volts) should stop the Smooth Function from cycling. With the Smooth Function patched to cycle, connect the CYCLE of the Smooth Function into the SAMPLE input of the Stepped Function. Patch the Stepped Function CYCLE to its IN jack. Using the STEPPED OUT to control the pitch of an oscillator, listen for the pitch change motion as the Stepped RATE is turned up. When fully clockwise, a triangular "staircase" waveform will be generated by the Stepped Function Generator. For best audible rate, the Smooth Function should be fairly slow. As the Stepped RATE knob is turned down, the staircase will slow down.

Note: I was unable to get a satisfactory result from the Stepped function using these procedures, instead simply adjusting the trimmer until it worked as expected.

** 4U Modular is a term used for the format most commonly known as “Serge Format” or “Loudest Warning Format”. Out of respect for the ever growing format, 4U Modular is the easiest way to refer to it. More Specifically it refers to the panel height and mounting hole style. 4U Modular will patch up just fine with other 4U "Serge" formats such as "Random Source", but it will not mount in RS boats or Buchla Boats (or power off Buchla power for that matter). An info page about this will be added to the website soon to make this a lot more easy to understand.

DIY Info:
LGE092 Bill of Materials
LGE092 Schematic
LGE092 PCB Layout w/ Designators
LGE092C I/O Board Schematic (Wiring Diagram) (When using unipolar LED’s, install the Smooth and Stepped LEDS in backwards for them to work with more common positive voltages)
LGE092C I/O Board Bill of Materials
LGE092C I/O Board Jumper Modification (The wiper of the Stepped Rate Potentiometer has a missed trace connection to Pin “O” on the I/O PCB. A simple jumper will fix this)
Mechanical Parts BOM generally required for building Low-Gain Electronics Modules

Patch Ideas & Uses: (Compilation of Message Board Posts formatted by Guy D2)

Details:

• PCB Size: 6” x 2”

• Current Draw: TBD

  Assembled Modules are built to order, please be patient when ordering. Use the contact page if you have any questions or requirements!