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DRM1 Major Drum [Archive]


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No longer in production.
Presenting the DRM1 Major Drum - a fully analogue drum voice synthesiser capable of diverse percussion duties. The DRM1 is a natural development from my Modular work and is made up of several circuit sections which are combined with rhythmic areas very much in mind. But, as we'll see, the parts are not too far removed from their synth roots and, with the DRM1X MD Expander, the sonic palate of the DRM1 can be opened further still. This is also the beginning of a new line of rhythmic systems - a hint of the future can be seen here at MuffWiggler
The main parts of the DRM1 are (check the Block Diagram above):
- Input Conditioner + Decay Generators
- Voltage Controlled Oscillator (VCO)
- White Noise Generator + Voltage Controlled Filter (VCF)
- Output Voltage Controlled Amplifiers (VCA) + Mixer with Saturation
- Expansion Headers

The Input section generates trigger events from 3 sources - the Banana Trigger Input socket which expects positive going gate signals (typical +10V but fine with anything over a few volts - this produces variable dynamics), the Pad/Signal 1/4" Jack socket with Input Drive level control (up to +20dB gain) which accepts drum pad, gate or audio signals, and the Manual Trigger button which generates an internal +10V gate signal. These sources generate four ganged Decay Envelopes which control Bend Frequency and Amplitude of the VCO/VCF sections.

The VCO/Osc side features a Triangle Core Oscillator with 1V/Oct exponential control offering a blend between Triangle and Square waveforms via the Shape dial. The Tune dial covers the entire audio spectrum from around 20 to 20k Hz (the frequency can, though, be driven below or above these limits with external Control Voltages). The operating frequency is a combination of the Tune setting with any modulation from the Bend Depth (positive or inverted via switch) and FM (Frequency Modulation) controls, with the FM control taking its source from either an external Control Voltage (CV // 1V/Oct when turned fully clockwise) or from the internal White Noise source (for generating 'tuned noise').

The VCF side, a State-Variable Multimode filter with 12dB/Oct response and Low/Band/High outputs, takes its source from the internal White Noise Generator (switch to Noise), from the sum of the Input section (switch to Ext), or it can be muted (most useful when the VCF is in self-oscillation). Similar to the VCO side, the VCF covers the full audio spectrum and has similar modulation possibilities, though with the internal switching this time offering modulation from the VCO waveform. The filter is capable of self-oscillation when the Resonance (Q) control is turned to full, producing sine-waves when the VCF input is muted. Coupling this behaviour with modulation from the VCO opens up the possibilities of rich FM sounds. You can even, to some extent at least, process external audio through the filter - it isn't aimed at being the cleanest filtration route, but it can be an interesting extra for experimentation.

Each side has its own VCA with the Level control setting the influence of the respective Amp Decay envelope. The two VCAs are combined along with the Impact Generator signal (the Trigger Output pulse conditioned by a simple Low/High-pass filter) through the output summing circuit. This features a diode soft-clip section to limit the output signal amplitude and offer a great range of sonic versatility - by adjusting the balance of the three Level controls and the Out Drive dial, you can move from soft to gnarly saturation while keeping the amplitude about constant (+4dBU typical).
You will notice that the DRM1 has four banana sockets on the front panel (+ a black grounding socket on the back of the case). The instructions give details of how to successfully interface with these (it isn't too complex!). [I have a small supply of banana to minijack interface cables to sell alongside]

The DRM1 is built with several expansion headers in place on the main circuit board. Some of these, as detailed in the instructions, allow the user to adjust a few areas for standalone operation (HP/LP filter response and VCO Sync), but the main purpose is to open the design up with the DRM1X MD Expander. Adding this breaks out several CV signal outputs from within and adds extra CV modulation control to the VCO and VCF sides.
[The DRM1X should be available as special order from February]

Initially the DRM1 is offered only as a standalone device, but it is designed as a 'module' which can fit into a larger system. The standalone is housed in a custom aluminium enclosure (4.5 x 5.25 x 3.5 inch) with PCB material front and side panels. The case holds a DC/DC converter which converts the 12VDC external supply (minimum 500mA, 2.1mm centre positive) to the bipolar +/-15V internal power. A 90-250VAC worldwide power pack is included with interchangeable plug socket adaptors.

The DRM1 is covered by a 2 year parts warranty.
Price - £260 (+VAT in EU - £312) + shipping
Demo Sounds:
Visit the Soundcloud pages for further details of what you're hearing!

Added on Friday 24 January, 2014.