Tony of Oakley Sound keeps updating his modules.  See here for his latest description of the famous ADSR-VCA.

Though I already had four of the earlier revision 2 ADSR/VCA, two with full voltage control, I wanted to upgrade and replace my dual rev 2 ADSR/VCA module with a couple of these rev 4.  There is little difference in the main circuit between rev 2 and rev 4.  The latter adds a looping ability and a switch to control the mode.

NORMAL – Works normally, with the envelope started by the Gate signal.

GATED – Looping will occur only when the Gate is high.

LOOP – The module’s output it will loop continuously in AD mode. The Gate input has no effect in Loop mode.

The rev 4 also provides an independent envelope output, labelled ADSR, good for controlling something simultaneously when also using the VCA feature.  The inverted output from the rev 2 panel is lost, although the rev 4 board can be built to support that as an option.

Bridechamber makes a nice panel for the new rev 4 board, and that’s what I’ve used.

Construction is straight-forward.  As with all Oakley modules, the panel is affixed to the PC board assembly by means of pot brackets.  The rev 4 boards use small Alpha pots that I ordered from Small Bear Electronics, since Mouser does not list the version with PC pins.

I always solder wires from the board to the panel jacks, it’s so simple.  Oakley sells a small PC board to mount the jacks, with a ribbon cable header, if you want to do it that way.

From the Oakley website:

The OMS-410 is a companion module to the MOTM-410 triple resonant filter module. It adds powerful new features to the superb Synthtech module. No component changes are needed to the MOTM module, and the two modules are connected together by two removable connectors hidden behind the front panels.

The OMS-410 allows you to add these new features to your MOTM-410

1. You can add three individual CV inputs to control each vactrol element of the MOTM-410. Each input is sent through a reversible attenuator, with a control knob on the front panel. This allows incredible tonal sweeps and modulations to be created. Its like having three separate voltage controlled filters in one module.
2. The MOTM-410′s two internal VC-LFOs can now be accessed from the front panel. The OMS module shapes the LFO’s outputs to give smooth sinewaves. Two separate VCAs allow these LFO waveforms to be level controlled individually or together. You can now use the MOTM-410 as a twin VC-LFO, whilst still using the MOTM-410 as filter module.

Modifications:

• Housed in a Stooge panel
• Three panel switches added for mode control
• Two of the reversible attenuators can be switched to apply to a MOTM-410 filter, or to be used as a separate VCA with the LFO output jacks.
• The third reversible attenuator can be applied to the third 410 filter, or can be used as an input for VC of the level of VCA 1/LFO 1 output.

SIMPLIFIED SCHEMATIC FOR USE WITH BLOCK DIAGRAM

OMS 410 BLOCK DIAGRAM

From the Oakley website:

This is a very popular dual purpose module. Not only does it feature the classic four stage envelope generator, but it also has a high quality VCA onboard.

This highly useful circuit implementation hardwires the ADSR generator to the control input of the VCA. The signal at the VCA’s other input, the IN socket, will then be multiplied by the ADSR waveform. You can use any signal into this input, audio or CV. If you use CV, then the ADSR output level will be governed by the level of the CV. If you use audio, then the ADSR waveform will control the volume of that audio signal.

A typical use would have the IN socket being driven by the velocity CV from a midi-CV convertor. Thus the harder you hit the keys, the greater the ADSR output level. If you use this to control a filter sweep, this can create brilliantly effective touch sensitivity to your patch.

The circuit is configured so that if nothing is plugged into the IN socket, the module will behave as a traditional ADSR module. The output will rise to +5V at the attack peak.

The ADSR is operated by a gate signal, but can be triggered by slow rising CVs too, due to the built in schmitt trigger function. No additional ‘trig’ input is required.

The ADSR/VCA module is built on one PCB called the VC-ADSR board. Although the 1U panel design does not imply a voltage controlled design, the internal electronics are all voltage controllable. This allows blisteringly fast minimum attack and decay times. And yet, the controls with their true exponential response allow you to adjust the times with ease.

Also on this module is an LED. This gives a visual indication of the output level of the internal ADSR waveform.

Specifications:

The following times are for the unit in standard mode. Multiply all quoted times by 5.5 to get the times produced when in ‘extended’ range.

• Minimum attack time: 0.75mS
• Maximum attack time: 12 seconds
• Minimum Decay/release time: 1.8mS to fall from 90% to 10% of initial value.
• Maximum decay/release time: 15 seconds to fall from 90% to 10% of initial value.
• Normalised output voltage: Attack peak at 5V from OUT+
• Gate input to activate ADSR: >3V

Modifications:

• Range switch added.
• Front-Panel-Express MOTM style panel

From the Oakley website:

This is a dual purpose module in a 2U width panel. Not only does it feature the classic four stage envelope generator with full voltage control, but it also has a high quality VCA onboard.

This highly useful circuit implementation hardwires the ADSR generator to the control input of the VCA. The signal at the VCA’s other input, the IN socket, will then be multiplied by the ADSR waveform. You can use any signal into this input, audio or CV. If you use CV, then the ADSR output level will be governed by the level of the CV. If you use audio, then the ADSR waveform will control the volume of that audio signal.

A typical use would have the IN socket being driven by the velocity CV from a midi-CV convertor. Thus the harder you hit the keys, the greater the ADSR output level. If you use this to control a filter sweep, this can create brilliantly effective touch sensitivity to your patch.

The circuit is configured so that if nothing is plugged into the IN socket, the module will behave as a traditional ADSR module. The output will rise to +5V at the attack peak.

The ADSR is operated by a gate signal, but can be triggered by slow rising CVs too, due to the built in schmitt trigger function. No additional ‘trig’ input is required.

This design features blisteringly fast minimum attack and decay times. And yet, the controls with their true exponential response allow you to adjust the times with ease.

Each CV input is controlled by a dedicated pot. This pot acts as a reversible attenuator, so that the gain of the input is anything from -1 to +1. This means that any inputted CVs can subtract or add to the times, or level, set by the ADSR pots. With any input knob set to its middle position, then that CV channel is effectively turned off.

Also on the module is an LED. This gives a visual indication of the output level of the internal ADSR waveform.

Modifications:

Input CV normalling, so that with one CV into the Attack CV input this CV is also connected to the Decay and Release CV inputs when those have nothing plugged into them. Release CV is normalled from the Decay CV, as part of this scheme.

Front-Panel-Express MOTM style panel

Little LFO

This is an updated version of the low frequency oscillator on the classic analogue synthesiser, the Korg MS-20. It features two output waveforms, triangle and square. But, the design also incorporates a ‘Shape’ control that affects the rise and fall times of the triangle waveform. Therefore, you can get sawtooth and reverse sawtooth from the triangle output by using the Shape control.

The Little LFO uses an integrated dual SPDT FET switch to enhance the Korg design. It also allows the use of waveform synchronisation. This is where the output waveform is reset back to zero when a SYNC pulse arrives from another module. A range switch may be fitted to allow even lower frequencies to be made.

Little EG

(Note: The Little EG is no longer available from Oakley. The following text is from the original Little EG manual written by Tony Allgood.)

This is a simple but effective envelope generator module primarily designed for use in modular synthesisers.The envelope generator or EG for short, generates a rising and falling voltage at its output when triggered by a gate signal. The speed of the rise in output voltage is determined by the Attack control. The speed of the fall of the output voltage is determined by the Decay or Release controls. The output of an EG is traditionally patched to the VCA control voltage input, to control the volume of the note when the keyboard is pressed; or to the VCF, where it dynamically alters the harmonic structure of the sound throughout the duration of the note played. There are three basic analogue EG types available: attack-decay (AD), attack-release (AR), and attack-decay-sustain-release (ADSR). The AD type produces a rising voltage in the attack phase. This rises exponentially from zero until a predetermined value is reached. The decay phase then starts where the output voltage falls back to zero. If the gate is removed during the attack phase, the decay is prematurely started and the voltage output will fall without the peak ever being attained. Two pots are required for the control of an AD type EG. The AR type produces a rising voltage in the attack phase, again rising exponentially, to the sustain level. The voltage will then remain at this level for as long as the gate is held high. When the gate is removed, the output will fall back to zero. This is the final release stage. Again, only two pots are needed for an AR-EG.

The Oakley Little EG is able to produce AD and AR simultaneously. The unit can be wired up to have two pots, so that attack and decay/release phases are controlled together for the both types of EG output.

Modifications:

• Added range switch for LFO.
• Omitted LFO pulse output to save panel space.
• Used a toggle switch to select between AD/AR envelope shapes to save panel space.
• Front-Panel-Express Panel.

Note the unusual location for LEDs and toggle switches to the lower right of the pots. This works for Oakley modules because of their orientation on the back of the panel.

From the Oakley website:

The Superladder is a voltage controlled transistor ladder filter. Cut-off frequency and resonance are both voltage controlable.

The VCF may be built as a 1U filter core or as a complete 3U filter system. Although the 1U module can be used as a filter module on its own, it is expected that users will make use of external mixers to control CV and audio levels going into the filter.

The Superladder VCF module has a variable shape output. It incorporates a feature first seen on the Oakley Orbital prototypes. The SLOPE pot gives you an output that can be varied from one pole (-6db) to four pole (-24db), with band pass in the middle. And that’s band pass with Moog ladder warmth.

The audio output is ‘Q compensated’. This means that the output volume will not drop significantly when you turn up the resonance pot. This design uses two inbuilt VCAs to achieve voltage controlled resonance without the hassle. A beautiful sound.

Modifications:

I made a custom 2U Front-Panel-Express Panel for this filter. It includes audio-taper pots for a two-input signal mixer, plus separate attenuator pots for the exponential and linear CV inputs. The panel wiring is neat and tidy with the board mounted by pot brackets.

From the Oakley website:

The classic four stage OTA based phaser. Wonderfully lush and smooth, it is similar in sound to the phaser used by Jean Michel Jarre on Oxygene and Equinoxe albums.

The unit includes a useful internal low frequency oscillator with accompanying bicolour LED. The centre frequency of the phase shifter can also be controlled by an external control voltage, thus allowing envelope generators to be used to sweep the phaser to create filter type effects.

Freq: Controls the frequency of the two notches created by the phase shift network.

Emphasis: Accentuates the feedback signal within the phaser to create a deeper effect.

Depth: A simple attenuator to adjust the level of the internal LFO or incoming CV.

LFO Rate: adjusts the speed of the LFO.

The internal LFO produces a triangle wave output which is also available from a front panel socket. This allows you to use the internal LFO for other modulation purposes. The LFO signal is automatically routed to the modulation depth pot when no jack is inserted in the CV input. Two Equinoxe units can be used for stereo phase panning.

Modifications:

• One Issue 1 and one Issue 2 Equinoxe are housed together in a custom Stooge panel.
• Omitted the LFO LEDs.

From the Oakley website:

Up to three inputs, either CV or audio, can be summed or mixed together. Each control knob can be set so that the gain of the input is anything from -1 to +1. This means that not only can inputs be added together, but can subtract as well. With each input knob set to its middle position, then none or very little of the input signal will reach the output. You can thus use this to attenuate, or invert, CV or audio signals around your modular.

The MultiMix ‘Stooge’ version features a clever combination of three output sockets to achieve a variety of uses. Insert into the OUT1 jack and you will find a controlled version of the signal going into IN1. But if you don’t utilise the OUT1 jack, then its output will automatically be summed with IN3 to form a mixed output at OUT3/MIX. Likewise, not using OUT2 will make its output join with the IN3 signal too. So you can use this module as a standard mixer if you don’t use the OUT1 and OUT2 sockets.

Moreover, IN2 is normal-connected from whatever is plugged into IN1, and IN3 from IN2, making it simple to use the MultiMix as a distributor. Plug one signal into IN1 and take three outputs, each with individual level and inversion control.

Modifications:

• Stooge panel normalling of inputs and outputs
• Omitted the LED

Panel photo by Scott Juskiw
Also see Scott Juskiw’s Multimix modification page.

From the Synthtech website:

The MOTM-820 is used to add slew to an input. The most common use would be to add portamento to a control voltage feeding a VCO. Check out the features:

• Independent voltage control of both rise (UP) and fall (DOWN) times
• Times variable from 500us to 5 minutes
• Ganged UP/DOWN control to emulate standard portamento effects
• A SHAPE control that varies the glide slopes from Linear to Log

From the Oakley website:

The OMS-820 is a companion module to the MOTM-820 voltage controlled lag processor. It adds powerful new features to the superb Synthtech module.

With this module you can make the MOTM-820 into a voltage controlled LFO with variable waveshape. Or you use it to make a powerful voltage controlled envelope generator, with manual set and preset modes. You will be amazed by the uses you can find for this module.

1. LFO

When the mode switch is turned to LFO, the output of the MOTM module will oscillate between +5V and -5V. The rise time of the waveform will be set by the UP control and the fall time will set by the DOWN control. The frequency will change according to the settings of both UP and DOWN. You can also change the rise and fall time together with the UP/DOWN control on the MOTM. You can easily make saw, reverse saw, and triangle type waveforms. The LIN/LOG pot on the MOTM will alter the shape of the waveform by introducing the usual non-linearites of the exponential rise and decay.

2. EG mode

When the mode switch is turned to EG, you get a voltage controlled AD/AR generator and more besides. This section has four sub-modes. These are selected by two switches: AD/AR and Gated/Reset.

The envelope generator is triggered by a GATE input.

When in AD (attack-decay) and gated mode, the output of the MOTM-820 will then rise until +5V is reached, whereupon it will fall back to zero. Rise and fall times are governed by the MOTM-820 of course, and fully voltage controlled. Removal of the gate signal will cause the decay phase to start prematurely. Standard A-D EG behaviour.

Switch the unit to AR (attack-release) and gated mode, and the output will rise to +7V or so, and stay there until the gate is released. Standard A-R EG behaviour. The RESET input has NO effect in this mode.

Switch to AD and reset mode. The MOTM output will now rise to a +5V peak when the gate input goes high. It will then fall back to zero automatically. Removing the gate has no effect on the output. This is ‘one shot’ mode. However, the output may be forced to decay prematurely by use of the RESET input. A positive signal of above 1V or so will activate reset.

Switch to AR and reset mode. The MOTM output will rise until +7V is reached whereby it will stay there until the RESET input is activated.

Remember that all rise and fall times are controlled by the pots on the MOTM820 and OMS820. And can be varied from 1mS to well over two minutes.

Four LEDs are included on the front panel. Two of these will indicate the status of the gate and reset inputs. Another will show the EG’s status. A fourth LED, a bicolour type, will give visual indication of the final output signal.

The OMS-820′s two pots pots together with the MOTM’s own pots, control the rise and fall time. This will enable you to set a time of say, 1 sec with the OMS-820′s pots and then introduce a modulation signal. The depth of which is controlled by the MOTM’s pots.

Richard Brewster modifications:

• Front-Panel-Express MOTM style panel combines the MOTM-820 and Oakley OMS-820 modules into a single 2U-wide integrated unit.
• The GATE and RESET pushbuttons were omitted because of panel space.
• Added end-of-cycle comparator PULSE output
• Patching PULSE out back into GATE obtains a new LFO mode that cycles 0 to +5V. This works much like the old Serge Universal Slope Generator.

This rather ambitious project combines the MOTM-101 Noise/Sample and Hold module together with two Oakley Sample and Hold modules to create a triple module.MOTM-101 features:

• White, Pink and Slow noise outputs
• Clocked sample and hold with internal clock
• Vibrato output
• Manual slew control on output

Oakley Sample and Hold features:

• Clocked sample and hold with dual polarity clock inputs
• Manual pot that mixes portion of output back to input to limit step distance
• Manual slew control on output

In order to fit all three modules into one panel the slewing features were omitted, as well as the vibrato output on the 101. Several enhancements to the 101 were made. These include external clock input buffering, an output level LED, a clock-polarity switch. On the Oakley S&H instead of two clock inputs with different polarity, there is one clock input and a polarity switch. The internal clock from the MOTM is normal-connected to the clock inputs of the Oakleys. The output from Oakley #1 normals to the input of Oakley #2, and the output from Oakley #3 normals to the input of the MOTM-101. Thus without any external inputs there is always a new random output voltage on each of the sample and holds with each internal clock tick.

Construction difficulty is high for this one. A corner of the MOTM-101 printed circuit board had to be cut away to provide space for the WHITE noise panel jack. Some of the unused slewing circuitry in the Oakley boards was used for enhancements to the 101. As the photos show, the wiring is dense.

Mine is in a custom Stooge panel. But here is a Front Panel Express file if you really want to try building your own.