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DOCUMENTS:

Current version: 1.1

Schematic

BOM

Names

Values

BOM Power Regulation

FUNCTION:

This module divides the incoming signal. It contains two sets of dividers. The first one divides by 2 (1 octave), 4 (2 octaves), and 8 (3 octaves) and mixes these sub-octaves in the output (Octave Mix 1, 2, and 3). This whole mix can also be shifted with the top Octave Selector switch.

The second divider divides by 3, 5, 7, 9, 11, or 15 and mixes this signal into the output. This signal can also be shifted using the bottom Octave Selector switch.

Quoting from the Synthasystem manual:

This module contains two sets of frequency dividers. one set divides by 2, 4, and 8 (1, 2, and 3 octaves) and mixes these sub octaves in the output with the octave mix pots. This whole mixture can be shifted in octaves by the octave selector switch.

The second divider can divide by 3, 5, 7, 9, 11, or 15 according to the setting of the Divider Switch and also mix this with the output through the mix pot. This divider can also be shifted in octaves with the octave select switch.

In the second divider, illustrated in the second table below, dividing by 3 shifts the input tone down by an octave and a perfect fifth, dividing by 5 shifts by 2 octaves and a major third, dividing by 7 shifts 2 octaves and a minor seventh, dividing by 9 shifts 3 octaves and a major second, dividing by 11 shifts by 3 octaves and an augmented fourth, and dividing by 15 shifts by 3 octaves and a major seventh. Add on octave to each of the above for each position of the selector switch. for example, with the selector in position 2 and the divider switch in position 9, the total shift is 4 octaves and a major second, etc.

A signal fed into the SIG IN jack comes out of two SIG OUT jacks in parallel after being divided. Overall output level can be adjusted with the output level pot. All the output signals from the divider are square waves and thus can also be used as control voltages to an oscillator to create very interesting sequential effects. Even staircase waves can be generated by the proper setting of the octave mix pots.

This module can be used as a trigger divider by feeding recurring triggers into the Trigger Input jack and taking the resulting divided triggers out of the Trigger Out jack. the triggers are produced by a voltage level threshold circuit on the mixed waveforms. different divide patterns for triggers can be produced with certain mixtures of the octave pots and mix pots. A table of divides is given on the next page for both halves of the divider.

USE:

Inputs/Outputs:

There are two inputs:

1. Signal. This is the signal to divide. A square wave works best, but you can always be creative. This input is summed with…
2. Trigger. This is an input for a trigger pulse train. The PCB accommodates either an S-Trigger or V-Trigger. Refer to the schematic for details.

There are two outputs:

1. Signal. This is the mix of the divided input signal / trigger. It is a pulse train.
2. Trigger Out. The module produces a trigger pulse at each output pulse. This can also be wired to be an S-Trigger or Voltage-Trigger. See the schematic for details.

Knobs:

This module has five knobs (pots):

1. Three Octave Mix controls.  All signals / triggers which are input are divided by 2, 4, and 8. The Octave Mix knobs determine how much of the divide by 2 (1 octave), 4 (2 octaves), and 8 (3 octaves) mix is added to the output.
2. One Mix knob. The signal /trigger is also divided by 3, 5, 7, 9, 11, or 15 (see “Switches” below). This control determines how much of this divided signal is mixed with the output signal.
3. One Out knob. This controls the overall output level of the mixed divided signal.

Switches:

This module has three switches:

1. Top row Octave Select. This switch divides the mixed signal / trigger which is divided by 2, 4, and 8 by 1, 2, 3, or 4 octaves. For example, when the Octave Select switch is set to 1, the signal is divided by 2, 4, and 8. when it is set to 2, it is divided by 4, 8, and 16. Three, it is divided by 8, 16, and 32. Four, it is divided by 16, 32, and 64. See the table below.
2. Bottom row Octave Select. This switch is equivalent to the other Octave Select, but it acts on the signal path which is divided by 3, 5, 7, 9, 11, or 15. See the table below.

Top Row Octave      Mix 1   Mix 2   Mix 3

1                                 2         4         8
2                                 4         8        16
3                                 8        16       32
4                               16        32       64

Bottom Row Octave    3    5    7    9    11   15

1                                   3    5    7   9    11   15
2                                   6   10  14  18  22   30
3                                 12   20  28  36  44   60
4                                 24   40  56  72  88 120

GENERAL CONNECTIONS:

Connect an incoming trigger pulse train or AC signal to the input. Set the divide switches and the mix to get the output you want.

COMPONENT SELECTION:

See the Component Notes page for more information.

Resistors:

This module was originally built with carbon core, 5% resistors with one or two 1% metal film resistors. So, you have a wide range of options here. I recommend using 1% tolerance, metal film resistors everywhere, but the critical resistors are R37 and R38, input summing resistors. These should ideally be hand matched or purchased to 0.1% tolerance to insure consistent response between the inputs.

Capacitors:

There are probably a billion different ceramic capacitors at a place like Mouser. Pick a capacitor that can fit the hole easily, typically 0.1 inch on centers.

Pick good quality electrolytics where designated.

Inductors:

None

ICs:

None

Transistors:

The original used 2N5172 NPN and 2N5138 PNP transistors. These are still available, but I could only find a “PN5138” which I think is the same transistor. In any event, you can use any standard NPN or PNP transistors and they should work.

Diodes:

Nothing special, 1N4148s are fine.

Pots:

Your choice for your panel. If you use the panel I laid out, the holes and spacing will work for the Alpha 12 and 16mm pots. You can probably use nicer BTI, Bourns, etc. 9mm pots with “pot chiclets”

Trimmers:

None

Jacks:

For the panel I laid out, a good 3.5mm or 1/8 inch jack will work. I use the Switchcraft 42A Tini-Jax true 1/8 inch jack. These are switched jacks and they work with 1/8 inch plugs and 3.5 mm plugs.

Switches:

I’m using an Electroswitch C5P0112N-A Mouser number is: 690-C5P0112N-A for the Octave Select rotary switches. It can be set to any number of throws from 1 to 12.

I’m also using an Electroswitch C5P0206N-A, Mouser 690-C5P0206N-A for the 3, 5, 7, 9, 11, 15 divide switch. It has two poles and 6 throws, just right and it matches the feel of the other rotary switches.

I’m sure there are probably better feeling rotary switches. Get those that you like if you have a preference.

BUILD NOTES:

Soldering:

I assume you know the basics of soldering. I like to insert the low lying parts first, like resistors, diodes, etc. After these, I install the IC sockets. Next capacitors, transistors, connectors. Use a good solder, either an organic flux, which you should wash regularly, or a no-wash flux.

Take a break every so often, wash off the flux if you are using a flux which required cleaning. Double and triple check orientations, pins, and solder joints.

Power Supply Regulation/Filtering:

This PCB requires the Power/Regulation daughter board. I did it this way to allow this PCB to be parallel to the front panel which allows it to mount in shallow cabinets.

See this page for details on this module.

The Frequency divider just needs +12 volts. You do not need to add the additional filtering components or any of the negative supply components. For the +12 volts, if you are using a 12 volt main supply, just install the ferrite bead, 10uF electrolytic, 0.1u ceramic, and the 1n4001 diode.

If you have a +15 volt main supply, install the LM317 regulator and associated components and trim it to +12 volts.

COMPONENT PLACEMENT:

Mounting:

This PCB has four holes to allow flexible mounting configurations. The FPE Euro panel is setup to allow this PCB to be mounted parallel to the panel using some 3/4 to 1 inch (typical) standoffs. The mounting holes are connected to ground. The Power Regulation PCB will mount to this PCB using standoffs.

Calibration:

None

PANEL NOTES:

There is nothing too special. I suggest using connectors on the flying wires from the jacks and pots to the PCB.

The mounting holes and spacing are setup for Alpha 16 mm or 12 mm pots. The jack holes are 0.25 inch in diameter.