Let's Go Shopping
MonoWave (X)
Reproduced with permission from Paul Maddox
Let's Go Shopping

Envelope Generator's (VCF-EG & VCA-EG)
These are the same as the design in Modulus 8, these are compact (needing only two chips) simple to use and fast.

Again Paul went for simplicity, with a little modification to the scaling , you could use it to generate a CV/GATE output for another 1V/Octave synthesiser.
Two DACs are used, U403 holds the NOTE CV, U402 the Velocity CV and U406 has the GATE signal. When the main CPU writes the NOTE value, the MSB is also the gate value (note data on MIDI is only 7-bits wide).

These again are based on a Modulus edition. The VCA uses a CA3046, this is configured as a Gilbert Multiplier and gives a superb SNR!

No secrets here, its a Moog Ladder clone. Giving 24dB/Octave cut off slope. This was based on TomG's adaptation of it and includes some modifications by Paul.
Wave Generator

Ok, now we start showing some secrets.
Essentially the wavegen is just an EPROM feeding a DAC, nothing more. The secret here is the set of NAND gates on the address lines. What these do is allow you to DROP the resoloution from 256-bytes per cycle to 64-bytes per cycle and hence give you a whole stack more harmonics and aliasing.
Oscillator1 and Oscillator2

Some more secrets now, the oscillators. Again, nothing too radical, The main oscillator is the ATtiny2313 micro, This feeds a 4024 to allow octave selection. This, in turn, feeds a 4040, Q0-Q7 give the 8-bit address needed for the Waveform (Q0 is the clock into the 4040), Q8 gives us the sub oscillator. Also the waveform selection latchs are shown in these drawings. These 16-bits are then fed to the wave-generator circuit.

Nothing too major here, you can see the main CPU, LCD interface, Interface to Buttons and also MIDI. The MIDI interface is fully MMA (http://www.midi.org/) compliant. The LCD has been upgraded to a 2-line display. U203 is the latch used for reading the buttons (to see if they are pressed or not) as this PORT on the CPU is used for other things it needed to have an output enable, the NAND gate ensures that when you want to read it, it latchs the data (positive going edge clock) and then enables the outputs (active low enable), simplifing the interface to the CPU.

Here the ADC schematic is straight from the datasheet. The ADCs are self clocking and the CPU just reads values every so often from the ADCs internal latches.

Front Panel
Needless to say this is the human interface part. A single pcb houses all the switches, pots, LEDs and LCD required to interface with the MonoWave. A matching aluminium front panel is now available to assist constructors with completeing their unit. Both the Front Panel pcb and Front Panel are optional allowing customers to design and construct their own version of the MonoWave(X).

Power Supply
The MonoWave(X) requires an external well regulated +15VDC supply (rear panel marking incorrectly shows 18VDC) rated to 400mA. Internally the MonoWave(X) runs from a +/-12V supply.

Only 3 ribbon cables are required to complete the construction of the MonoWave(X).



Email:  elby-designs@bigpond.com
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