Building the AMORE Starter Kit

This is the AMORE Starter Kit with the Minikorg VCF board in operation.

To get started with AMORE modules you should first build the AMORE Starter Kit. This is a set of circuit boards that contain all you need to test and run an AMORE module. It can be used as service equipment but it can also be used as the basis for a standalone synth. The Starter Kit consists of three circuit boards: The first is cut up in four parts for mounting potentiometers and jacks. In addition to this, there is a motherboard with power supply and the standard connector for the AMORE module. Finally there is a board containing a full blown VCO and a simple LFO. This board is mainly intended as a signal generator when working on modules like filters and VCAs but could also be used as a sound- and modulation source in a standalone synth. This board is optional, if you don't need the functionality.

You use the Starter Kit for testing and troubleshooting your new AMORE modules. As the Starter Kit is already tested, you can rule out errors in the pot/switch wiring, and such, when your module isn’t working. This simplifies the process of getting the boards functional. You also use the Starter Kit for trimming/calibrating the boards. When all modules are built, you use the Starter Kit for calibrating/servicing existing modules. It’s much easier to take a board out of the synth and put it in the slot on the Starter Kit for service than to put the entire synth on the workbench. In addition, you can use the Starter Kit with a board of your choice as a full blown module to your modular synthesizer. This is a great way to try out a new module and hear how it sound together with existing modules. You can take even the Starter Kit plus an AMORE module of your choice with you to a studio or somewhere else, as it is a small, portable unit that is self-contained.
The Starter kit replaces the exerciser, that I described earlier.

The motherboard

The Starter Kit is based around a kind of motherboard (PCB1) that contains the power supply and the standard AMORE connector. On this board the output jacks and the inputs potentiometers are mounted directly. In addition there are solder connections for the needed switches. There are switches for the two switch functions on the AMORE modules. In addition there is a three way switch for each signal input that selects between DC, AC and overdrive mode for that input. The latter doubles the gain to test the headroom/overdrive characteristics of the module. All the CV and modulation amount potentiometers plus the rest of the jacks are mounted on four separate daughterboards (PCB3 – PCB6). These boards are connected to the motherboard with connectors made from header strips.
The power supply on this board delivers highly stabilized -15, +15 and +10 volts at up to circa 1 ampère each. So this board can supply an entire medium-sized synth and not just the Starter Kit. In addition there is circuitry for generation of -1 volts and debouncing for the gate button, whick outputs a gate signal on a separate jack. This is useful for testing envelope generators and similar functions. There is an unused op-amp buffer that I used for buffering a 15 turn potentiometer which is used for precision CVs during testing and servicing modules. The board has connections for an output selector switch (optional) that makes it easy to monitor the different outputs.
You need three separate transformer windings to power the motherboards. Most transformers have two separate windings so you need one such transformer with 18 volts per winding and one transformer with one 15 volt winding. The power rating on the transformers depend on how many modules you want to power with the power supply. For just the Starter Kit, around 10 VA per winding should be enough. Best is to use at least 20 VA per winding, so you can use the power supply up to it's current limit.

The pot/jack board

This board is supposed to be cut up in four ”slices” after etching and drilling. The slices are used as follows:

PCB3: Contains the six pots for the modulation. For each pot there is an op-amp circuit that allows the modulation to go both positive and negative.
PCB4: Contains the six pots for fixed CV.
PCB5: Contains the six modulation jacks plus the two signal input jacks.
PCB6: Contains the headphone amplifier plus jacks for headphones, line out, external input and gate signal output.

The signal generator board

To be able to test AMORE boards like filters and VCAs, you need a signal generator that delivers waveforms with the correct amplitude etc. This board (PCB2) contains a full blown VCO, which is a clone of the VCO in the ARP 2600. This VCO delivers sawtooth, pulse and triangle waves on separate jacks. There are inputs and amount knobs for frequency modulation and pulse width modulation. There is also a switch that changes the VCO frequency range from audio to LFO so you can use it for modulation, just like on the ARP 2600. But in addition, there is also a separate non-voltage controlled LFO which outputs triangle and square waves on separate jacks. This LFO has it's own rate knob.
The signal generator board is fully self-contained, with all potentiometers and jacks on-board. It only needs an external power supply and there is a dedicated connector for this on the motherboard. You could even use this board as a VCO/LFO board in a standalone synth. Built according to the description it does not feature temperature compensation, however. If you require this, you could substitute the 2 kohm resistor with a 2 kohm tempco resistor and put this in thermal contact with the PNP/NPN transistor pair nearby.

The Basic VCO module is plugged into the AMORE connector and ready to be used.

The Starter Kit back panel. The top row of jacks is for the signal gerenator board. The next row are the modulation inputs and signal inputs to the AMORE board. The third row is the gate out, external in, line out and headphone output on PCB 6. The jacks to the left of the heatsink are the AMORE outputs on the motherboard. Below is a ground jack and the jack for the optional 15 turn CV knob. The DB-9 connectors are for connecting expansion units like the AMORE Exerciser and currently only carry the supply voltages.
To the right of the heatsink there are the three fuse holders and banana jacks for all the supply voltages.

Schematics general

Schematics power supply

Schematics signal generator board

Circuit board layout motherboard

Circuit board layout pot/jack boards

Circuit board layout signal generator board

Component placement motherboard

Component placement pot/jack boards

Component placement signal generator board

Front panel layout

Construction

Because the boards contain both panel mounted components (potentiometers) and rear panel mounted jacks, it is best to find or construct a box with the correct depth. There are solder pads for two different kinds of potentiometers. The large holes fit many different types, whereas the small holes fit certain potentiometers from Alps and some other manufacturers. The required depth of the box will depend on the potentiometers used. I used Alps pots with a 1 mm shim on the pots. For this, the correct depth of the box was 103 mm. If you have a slightly deeper box, you can compensate with thicker shims.
The motherboard must be mounted 15 mm to the right of the other boards, to give room for the AMORE module in the connector. It makes sense to mount the boards above each other, with the signal generator board on top. I recommend 25 mm spacing between the boards. There will be a total of four tiers and below the motherboard there needs to be room for the transformers and the mains wiring. I mounted all the mains components, including the mains socket and switch on the bottom plate. The secondary windings from the transformers are connected to the rest of the circuits with a multipole connector (6 poles needed), so I can easily remove the mains unit for servicing. Don't forget to add fuse holders in series with the transformer windings. Use 2 A quick blow fuses for transformers over 20 VA per winding. The power supply has short circuit protection that folds back the current to 500 mA if the load exceeds around 1,2 A. Note that if the chosen transformer can't deliver 1,2 A, you should change the current limiting circuit accordingly. In that case you'll have to consult the datasheet for the 723 voltage regulator IC.

As usual, begin with mounting wire links and then small parts like resistors etc. The power transistors should be mounted on a heatsink on the back of the box. Don't forget to use insulators between the transistors and the heatsink. It is best to solder the power transistors to the board after they are mounted on the heatsink and both the board and the heatsink are mounted in the box.
The motherboard should be supported in the connector end and not just hanging in the pots and jacks. Otherwise the latter will be strained when you plug in and pull out the AMORE modules. Drill holes in the motherboard for support studs where the etched markings are.

The signal generator board can be supported by the potentiometers and jacks, as there is nothing straining it. If you want the jacks in a different place, you can saw the board apart in the area where there are no components or traces. There are etched pads for connectors between the jack part and the rest of the board. These are only used if you cut the board in two pieces. This module uses the CA3046 transistor array, which can be somewhat difficult to find but is in fact still available from specialist suppliers. One of them is Das Musikding in Germany. They are not expensive, so buy some extra for future modules while you're ordering!

Bill of materials

You should have access to the parts in the general bill of materials.
In addition, you need the following parts:

NE5532 Dual op-amp (1)
LM723 Voltage regulator IC (3)
TIP3055 Power transistor (3)
1N5406 Power diode (12)
LED (3)
100 kohm lin potentiometers (6)
50 kohm lin potentiometers (2)
10 kohm lin potentiometers (8)
100 kohm log potentiometers (1)
50 kohm log potentiometers (2)
5 kohm log potentiometers (1)
Rotary switch (1)
SPDT toggle switch (2)
1-0-1 sinle pole toggle switch (2)
SPDT pushbutton switch (1)
3,5 mm stereo jack for circuit boards (23)
Banana jacks (5)
Male DB-9 connector (2)
Single row circuit board connectors (2.54 mm pitch), male
Single row circuit board connectors (2.54 mm pitch), female
2 x 20 pin circuit board connector (2.54 mm pitch), female (1)
Knobs for potentiometers (20)
Knob for rotary switch (1)
Heat sink
Insulating washers for power transistors
Thermal compound
Mains transformer 2 x 18 V 50 VA (1)
Mains transformer 2 x 15 V 30 VA (1)
Fuse holder (3)
2 A quick blow fuse (3)
Mains switch (1)
Mains inlet (1)
Veroboard (stripboard)
Suitable insulated wire
Suitable case, screws, nuts etc.

Trimming

There are five trimmers on the signal generator board:

Saw offset
Adjust this so that the VCO sawtooth wave is symmetric around 0 volts.

Tri adjust
Adjust this to make the triangle waveform look as good as possible.

Tri offset
Adjust this so that the VCO sawtooth wave is symmetric around 0 volts. Note that adjusting the offset will change the waveform so you will have to readjust these two settings for the triangle wave until both the waveform and the offset is OK.

Freq trim
Adjust this so that the VCO has a frequency range of approximately 20 Hz to 20 kHz when turning the frequency knob all the way.

Scale
This will only have to be adjusted if the VCO is supposed to track 1 octave/volt. For use as a test tone generator this is normally not necessary. If you require this, you will have to connect a voltage of exactly 1, 2, 3, 4, 5 volts etc. to the KOV input and check that the frequency doubles for every volt.

Skill level required: LOW

There isn't anything particularly difficult on this board.

I mounted the mains transformers, socket and switch on the bottom plate. The secondary windings are connected to the motherboard via the connector between the transformers. This way, the mains part can easily be removed for access to the underside of the motherboard.

The motherboard is mounted to the rear panel and the power transistor legs are shaped so they fit in the holes and the transistors have good contact with the heat sink (black surface in the picture). The transistors are screwed to the heatsink (holes drilled and tapped in advance).

This is the underside of the motherboard. The power transistors are about to be soldered.

The motherboard has been removed from the box. The power transistors are now soldered.

The motherboard seen from the back.

Here the wires for connecting the motherboard to the transformers, the fuse holders and the banana jacks on the back panel have been soldered.

The studs that support the motherboard on both sides of the AMORE connector can be seen here (below the motherboard).

The front panel switches have been connected to the motherboard. Note that the final version of the motherboard has some improvements which don't appear on this prototype.

Here the boards for the modulation pots (PCB3) and jacks (PCB5) have been mounted. Note the plugs and wires that connect them to the motherboard. I solder small strips of Veroboard on the female connectors, to solder the wires to.

A close-up of the plugs. The required length is sawed from a longer connector. Note the small piece of Veroboard (three rows of holes) soldered on top of the connector. The wires are soldered to the other end of the Veroboard.

The signal generator board is the last one to be mounted.

The signal generator board seen fron the front.

Here all boards can be seen from the left end of the unit. The circuits on the Veroboard to the right in this prototype have been integrated on the motherboard in the final version. The pot below the Veroboard is a 15 turn type that is used for generating precision CVs. There is an unused op-amp buffer on the motherboard that can be used to buffer the voltage from the pot. An extra jack has to be added to the back panel if you want to add this feature.

The other end with no module in the AMORE connector.

Front panel construction

The Starter Kit uses my new method for making front panels. As you have seen from the pictures above, the pots and switches are mounted on aluminum plate that is a part of the case structure. For the actual front panel, there must be some kind of spacer, to conceal the nuts and threads on the pots and switches. The actual front panel is then made of clear polycarbonate plastic and the graphics is on a photo paper printout behind the clear plastic. The advantage with this design is that you can fairly easily change/upgare the graphics (just replace the printout) and the clear plastic protects the graphics.
As you can see in the pictures, I used wood for the spacer layer. With the switches and pots I use, this layer should be 8 mm thick and that's a standard wood dimension.

Here the wood spacers are in place. As you can see, they are screwed to the aluminum case with countersunk screws.

The clear plastic and the graphics printout are fixed with very small wood screws. You can see them along the edges and there is one between ”mudulation 3” and ”modulation 4” too.

A closeup of the finished panel.

The AMORE standard connector on the motherboard