Scott Stites Synth DIY

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Modules

These are modules that I plan to put into my synth. For designs of my own, I'll post schematics. For schematics using designs of others, check out where you can find them on my Synth DIY links page.

11U of Modules

This is an illustration of the compactness/versatility that I am shooting for. There are 10 modules here that (as of 21 November) I've designed front panels for. Rene Schmitz's VCO3, Ken Stone's Wave Multiplier, Ray Wilson's AR EG's, VCA's and LFO's, two different mixers of my own design, and the 291 Core VCF. All of these functions fit in 11U of horizontal space (less than 20 inches).

Module Dimensions

I am a 'kitchen sink' kind of person - I want as much control as possible, and as much firepower per square inch as I can muster, while keeping things ergonomic enough to actually use the thing. Bear in mind, this is coming from a person who has synthesized on breadboards and wads of wire, so my sense of ergonomics has been quite "climatized", so to speak.

For module dimensions, I've settled on the MOTM measurements - 5U high by multiples of 1U wide. However, unlike MOTM, I have also chosen the 3.5 mm connector route. My main reason for this is that I can fit more connectors onto a panel than if I were to use 1/4" connectors.

In my preliminary layouts, this seems to be the way to go (for me anyway) - I can fit an amazing amount of functionality onto a 1U wide panel. Below is rough layout of a 1U module with eight controls and twelve connectors. I've just arranged the pots and connectors on top of a blank 1U panel.

1U Panel

One concept that I am adamant about is that most inputs must have attenuators - I've found that degree of control to be quite necessary for my method of synthesis. In fact, lately I've come to the conclusion that, wherever applicable, I will have inverting attenuators (IE, controls which alter the level from -1 to 0 to 1 in gain)on CV inputs. The rare exceptions to this rule will include dedicated 1V/Octave inputs.

Scott Stites Designs

Dual Mixer 1

Contains two mixers. Each mixer (Mixer A and Mixer B) each has four
inputs. There is an additional output that combines the output of both
mixers so that it can be a single eight input mixer.

Inputs and Input controls:
Each mixer has four inputs. The input controls will be
attenuating/inverting.

DC Offsets and DC Offset Controls:
For each mixer there is an independent DC offset that goes full + or -. On
mixer A, the DC offset is available for patching to some other module
through a switching jack - if a connector is in the jack, then the DC
control will control the output, but the DC will be disconnected from the
mixer. In this manner, it can be used as a separate DC offset source
without offsetting anything that is going through mixer when it is used.

On mixer B, the offset is available through an unswitched jack, so that the
DC offset can be used for some other module as well. With this, even with a
connector in the jack, the DC offset will be applied to mixer B - in this
manner, the mixer offset will follow the DC output, so that one control can
control the offset of the mixer and another module. Another cool function
is that you can derive two DC voltages that move in opposite directions with
a single twist of the offset control by connecting from the Inverted B
output and the Offset B output.

Outputs:
Mixer A and Mixer B each have an inverted and non-inverted output. Both
mixers are mixed together for the A and B output, which is a non-inverting
output.

Schematics

Dual Mixer 1 Page 1 of 2

Dual Mixer 1 Page 2 of 2

Dual Mixer 2

This again is a dual mixer with DC offsets that shares some features with
Dual Mixer 1, but has unique functions, as well. Where Dual Mixer 1 has
four inputs per mixer, this one only has three. Like Dual Mixer 1, it has
an additional output that combines the two mixer outputs, so that it can be
used as a six input mixer. Unlike Dual Mixer 1, it also provides an
inverted version of this output. Additionaly, unlike Dual Mixer 1, this
mixer has an output that subtracts the output of mixer B from the output of
mixer A.

Another major difference from Dual Mixer 1 is that the attenuated/inverted
signals derived from the inputs are supplied on separate connectors. For
mixer A, these outputs are switched, so when a connector is placed in an
output connector, it removes this signal from the mix. In this manner, it
can be used as an attenuator/inverter separate from the mixer function. For
mixer B, the connectors are unswitched, so that a signal can be sent to some
other module (at the inverted/attenuated level of the control) and still be
part of the mix of mixer B.

The DC Controls/Outputs are identical to Dual Mixer 1.

Like Dual Mixer 1, each input can be attenuated and inverted.

Schematics

Dual Mixer 2 Page 1 of 2

Dual Mixer 2 Page 2 of 2

Ray Wilson Designs

Quad Ray Wilson Log/Lin VCA

This module contains four Ray Wilson Log/Lin VCA's - each VCA has a CV
input, a signal input, and a signal output. Each VCA is switchable between
logrithmic or linear response.

Related Links

Music From Outer Space

Quad Ray Wilson AR/AD EG's

This module contains five Ray Wilson AR EG's. This is a very handy little
EG, by the way, quite snappy. When used with a gate signal, the EG acts as
an Attack/Release EG. When used with a trigger signal, the EG acts as an
Attack/Decay EG. Why five of them? Outputs of these puppies can be mixed
together to provide complex EG's - which is basically the way the Buchla
systems work, I believe, for EG's.

Each EG has a trigger input, a gate input, and an EG output. Each EG has an
attack time constant control and a decay time constant control.

Related Links

Music From Outer Space

Quad Ray Wilson LFO's

This module contains 4 separate LFO's, each of Ray Wilson's design. LFO's 1
and 2 provide Sine, Square and Triangle outputs each. LFO's 3 and 4 provide
Sine, Square, Ramp, Saw, and Triangle outputs. To be a bit clearer, each of
these LFO's has a shape control which fades between Ramp, Triangle and
Sawtooth.

Each LFO has a high/low frequency range switch.

Related Links

Music From Outer Space

CGSWM, VCO3, Mult

Multiple

My long experience with synthesizing on breadboarded circuits has influenced my design of this multiple - the multiples are in, well, multiples of five, just like on standard breadboards.

This multiple contains three columns of 15 connectors each. The first connector of each lower two groups of five connectors is a switching jack. This allows one to have multiples greater than five connections without sacrificing an extra patch cord. When connection to a switching jack is made, the five connectors above it are disconnected from that section of multiples. So, at maximum, one vertical multiple can handle thirteen connections. The combinations of one column of multiples can be one thirteen connection multiple, one nine connection multiple and one five connection multiple, or three five connection multiples.

Ken Stone CGS Wave Multiplier

Oh, what a beautiful circuit, Ken! This is the Ken Stone CGS Wave Multiplier fitted to my format. The upper portion is the 'Grinder' and the lower portion is the Wave Multiplier itself.

Related Links

Ken Stone CGS

René Schmitz VCO3

René's VCO rocks! I've added some 'kitchen' sink stuff to it, since I need to build a subregulator board for it anyway. This is the tentative plan:

1. Add a divide by two and divide by four suboscillator, adapted from Thomas Henry's design in his book "Making Music with the 566", available at Midwest Analog Products.

2. Add a soft sync comparator sub circuit. Breadboarded successfully. The soft sync function will be disconnected when a connector is inserted into the hard sync jack.

3. Provide an output for the soft sync comparator signal. This is a +5V narrow pulse. To be used as a trigger signal. Can be active even if a connector is inserted into the hard sync jack.

4. Provide a fixed 50% duty cycle square wave derived from suboscillator circuit.

5. Provide a ramp wave (invert the sawtooth).

6. Pump up the voltage of the other waves to 10Vp-p.

7. Provide attenuator/inverters for linear, exp, and PWM CV's.

8. Provide AC coupled Exponential and Linear CV inputs, which will be overidden by a connector placed in the EXP and Lin2 connectors, respectively.

Schematics

KS-01 RS VCO3 Connections/Satellite Brd Power

KS-01 RS VCO3 Satellite Regulators, Soft Sync, Attenuate/Invert

KS-01 RS VCO3 Satellite Brd Sub-Oscillator, Level Amps, Ramp

Related Links

Rene Schmitz Synth DIY

Midwest Analog Products

Dual MS20 Filter

Dual MS20 Block Diagram

Dual René Schmitz Late MS-20 Filter

Rene Schmitz designed an adapation of the MS20 filters found in the later models of the Korg MS20 monosynth. It's a pretty cool filter with some crazy resonance. This is the Kitchen Sink version of the filter.

For starters it's a dual version of the filter that is patch programmable - it is normalled to run either in series or in parallel, depending on if input A only is used (parallel) or input B is used (series) - in that case, the signal runs through filter B then through filter A. If both input A and B are used, then it is configured as two separate filters. Whatever signal is arriving at each respective filter can be attenuated by the signal level controls (Signal A and Signal B).

The CVA1 and CVA2 controls control the CV's going into filter A - they will be attenuating/inverting controls. The CVB1 and CVB2 controls control the CV's going into filter B - again they will be attenuating/inverting controls. Now - the kicker is this: the CVB1 and CVB2 inputs are normalled to the CVA1 and CVA2 inputs. In ths case, the CVB1 and CVB2 controls will attenuate/invert the CVA voltages for filter B. Plugging a connector into CVB1 overrides this for CVB1, and plugging a connector into CVB2 overrides this for CVB2. This arrangement allows one to use common control voltages when in any mode - series, parallel or independent, but still allows the freedom to have independent control over each filter if desired in any mode. If you don't want CVA1 controlling CVB1, you can set the control to 0 if you don't have a connector plugged into CVB1. The same applies for CVA2 and CVB2.

There are three inputs for unattenuated Volts/Octave control (labeled KBD). There is an input for filter A, an input for filter B, and one input that controls both filters. This allows parallel, serial, or independent operation from either a common KBD voltage or two KBD voltages. Plugging a connector into KBD A disconnects it from KBD A/B and plugging a connector into KBD B disconnects it from KBD A/B.

There are three outputs. Output A outputs whatever is coming out of filter A, Output B outputs whatever is coming out of Filter B, and Output A+B outputs the mixed outputs of both filters.

Each filter has a separate resonance control.

Each filter is selectable between high pass or low pass mode.

Related Links

Rene Schmitz Synth DIY