Product revisions

• 0.1 SMD: prototype for the newer design, with pre-assembled SMD stuff
• 1.0b: Correction of an error on the upper PCB
• 1.0: initial release (superseded)

Front Board Rev. 1.0 contained an error.

The square-shaped pad of D4 (cathode) wass in contact with the trace coming from the second pad of D4 (anode). The consequence was that the two pads were connected together, which then prevented the LED to light up.

(See full documentation)

What is it?

The DM77 is a Eurorack compatible Drum Synthesizer, inspired by the classic Coron DS8, with improved characteristics.

It's not a clone. It's a completely redesigned circuit.

The main advantage over the DS8 is the main oscillator being now capable of tracking 1V/Oct for several octaves. Other improvements are:

• a better noise generator,
• an external audio input (VCA),
• a Eurorack compatible output level
• and the use of the LM13700 chip instead of the CA3080.

The DM77 is equipped with a 1V/Octave Saw Core oscillator and a waveform converter to Triangle (slightly adjustable for more harmonics). A second oscillator can do some interesting Frequency Modulations (FM) for metallic sounds. The release/decay potentiometer allows you to set very short or very long sounds. Choose either Trigger or Gate response with the jumper setting. In Gate position, the DM77 can be used as a handy VCO/Synth Voice. The Sweep setting creates that classic disco drum sound.

Listen to the demo sounds: https://soundcloud.com/dhaillant/dm77-various-sounds

About the SMD branch

The SMD version solves the sourcing problem for the LM13700 and greatly simplifies the build process. The circuits are identical to the classic THT version.

In prototype V0.1, a bodge wire needs to be added at the push button. See documentation.

About the PCB

The current PCB revision is version 1.0b in THT. Stay in tune for potential updates and mods.

About the Front panel

The module is 10HP wide. The front panel is made of PCB material, 1.6 or 2mm thick. It is Matte Black with white or silver silkscreen.

The B-Stock Front panels are either slightly scratched or present some irregularities in the surface finish. They are half the price of the regular front panels.