Summary of Contents for North Coast Synthesis MSK 009
- Page 1 MSK 009 Coiler Multi-Mode Filter and Rectifier North Coast Synthesis Ltd. Matthew Skala November 24, 2020...
- Page 2 Documentation for the MSK 009 Copyright © 2018, 2019, 2020 Matthew Skala This documentation is free: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 3.
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Page 3: Table Of Contents
Contents General notes Controls and connections ......... TUNE knob . - Page 4 Patch ideas Circuit explanation Two-pole state-variable intuition ........Integrators .
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Page 5: General Notes
General notes This manual documents the MSK 009 Coiler Multi- Mode Filter and Rectifier, which is a module for use in a Eurorack modular synthesizer. The mod- ule contains a voltage-controlled two-pole state vari- able filter implemented using inductors (coils, hence... -
Page 6: In Inputs
Patching the MSK 009’s output into some other mod- produce the control value for the filter core. ule’s output should be harmless to the MSK 009, but Both CV inputs can accept voltages anywhere be- doing that is not recommended because it is possible tween the module’s power rails ( 12V to +12V) with-... -
Page 7: Voltage Modification
and 25mA from the -12V supply. Placing an unusu- unpacking the ZIP file you may need to do some re- ally heavy load on the outputs (for instance, with so- configuration of the library paths stored inside the called passive modules) can increase the power supply project files, in order to allow the symbols and foot- current beyond those levels. - Page 8 2mm front panel 2× 1.6mm PCBs 13mm 11mm stand- stand- off off 18mm clearance for mated power connector ≈46mm depth Figure 2: Assembled module, side view.
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Page 9: Safety And Other Warnings
Safety and other warnings Ask an adult to help you. Some lead-free solder alloys produce joints that North Coast Synthesis Ltd. does not offer war- look “cold” (i.e. defective) even when they are cor- ranties or technical support on anything we did not rectly made. -
Page 10: Bill Of Materials
Bill of materials Value/Part No. ′′ 33pF radial ceramic, 0.2 lead spacing ′′ 100pF radial ceramic, 0.2 lead spacing ′′ C2, C3 6800pF film, 0.2 lead spacing C6–C11 0.1µF axial ceramic ′′ C4, C5 10µF radial aluminum electrolytic, 0.1 lead spacing 1N4148 or 1N914;... - Page 11 Value/Part No. LM13700 dual operational transconductance amp U1, U2 TL074 quad JFET-input op amp Fixed resistors should be 1% metal film throughout. RoHS-certified zinc-plated steel hardware is recom- mended, not stainless steel because of galvanic-corrosion incompatibility with aluminum parts. Newer kits may include TL074B op amps instead of TL074, to make offset nulling easier. Also needed: solder and related supplies, PCB, panel, knobs, a cable tie, Eurorack power cable, etc.
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Page 12: Building Board 2 12 Preliminaries
These capacitors act as filters for the power supplies to the op amp and OTA chips. An MSK 009 kit should include six of these capaci- tors, and only four are used on this board; save the remaining two for use on Board 1. - Page 13 Value/Part No. ′′ C2, C3 6800pF film, 0.2 lead spacing C8–C11 0.1µF axial ceramic ′′ C4, C5 10µF radial aluminum electrolytic, 0.1 lead spacing D2, D3 1N5818 or SB130; Schottky rectifier L1, L2 22mH EPCOS 5% axial ferrite choke, B82144A2226J ′′...
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Page 14: Semiconductors
Install the four 27kΩ (red-violet-black-red) resis- the board have a corresponding stripe and the diodes tors R21, R26, R31, and R36. These are feedback should be installed with their stripes matching the resistors for the integrators (R26 and R36), and set markings on the board. -
Page 15: Electrolytic And Film Capacitors
you insert the chip, you must insert it so the chip pad for the positive (long) lead. matches the markings on the board, not the turned- around socket. Install the 16-pin DIP socket for the OTA (opera- tional transconductance amplifier) chip U3. This chip contains two current-controlled amplifiers, which, by means of a frequency-dependent control current, tune the filter core to the desired frequency. -
Page 16: Eurorack Power Connector
The inductors are delicate, especially in the area where the leads attach to the bodies, because the windings that connect to the leads are made of very fine wire. The ferrite core material is also somewhat brittile. It is important not to bend the leads too close to the bodies. -
Page 17: Building Board 1 17 Preliminaries
Building Board 1 Board 1 has components on both sides, and for best Here are some things to be aware of as a kit results, it is important to install them in the right builder. order. Build Board 2 first, and see the general com- •... - Page 18 Value/Part No. ′′ 33pF radial ceramic, 0.2 lead spacing ′′ 100pF radial ceramic, 0.2 lead spacing C6, C7 0.1µF axial ceramic 1N4148 or 1N914; switching diode D4, D5 1N5230B 4.7V Zener H1, H2 nut for M3 machine screw H3, H4 M3x11 M3 male-female standoff, 11mm body length H7, H8...
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Page 19: Decoupling Capacitors
Decoupling capacitors limiting resistors to protect the audio outputs, and The two axial ceramic 0.1µF decoupling capacitors other modules, in case of short circuits or bad patch- C6 and C7 are shown on the board by a special sym- ing. bol without their reference designators. -
Page 20: Semiconductors
level during oscillation. Do not confuse this resistor Install the two 220kΩ (red-red-black-orange) re- with the 220kΩ resistors, which have a similar colour sistors R5 and R8. The first, R5, controls the scale code. of the main tuning knob; the second, R8, contols the reference current for the exponential converter. -
Page 21: Compensation Capacitors
Install the switching diode D1, bearing in mind to correct (only one pin to desolder instead of all of the notes above. This diode is used in the full- them). wave rectifier to switch between inverting and non- inverting modes. Compensation capacitors Install the 33pF radial ceramic capacitor C12. -
Page 22: Board To Board Connectors
If you have built a North Coast Synthesis Leapfrog Filter you will recognize the similar design; the Coiler, however, omits the thermistor used in the Leapfrog. -
Page 23: Final Assembly
ploded assembly diagram on page if further clari- Do not overtighten any of this hardware, and be fication is needed. careful, if you are using wrenches or pliers, to avoid Place (do not solder yet) the seven phone jack scratching the panel. Wrapping the tool jaws with sockets J1 through J7 in their footprints. - Page 24 Your module is complete.
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Page 25: Adjustment And Testing
DC offset and control feedthrough, ing bits of narrow-gauge wire to get into the contacts and since the MSK 009 was never meant to be a “well- on the cable if necessary) to make sure there are no behaved”... -
Page 26: Troubleshooting
counterclockwise (knob pointer around eight o’clock). range. Be sure that the output offset adjustment, Apply power. described above, has been done; excessive DC offset Measure the DC voltage on the HP output and may inhibit oscillation. However, if you want abso- adjust R20 to bring this voltage as near zero as you lutely the most oscillation possible, you may find that reasonably can. - Page 27 to ground plane nearby, and cutting the extra away with a sharp knife was enough to fix the problem. Bad amplitude (including no amplitude) or DC offset in oscillation, combined with funny response to large-amplitude signals on the rectifier input: this combination of issues suggests that one of the Zener diodes was swapped with the nearly identical-looking switching diode.
- Page 28 Patch ideas Here’s a classic subtractive patch. The pitch CV from Deluxe subtractive voice with stereo effect. There the MIDI interface drives both the VCO and the main are two oscillators (in this case, Intellijel Dixie II CV input of the Coiler VCF. Since the tracking is not modules), which could be tuned to near-unison or a exactly 1V/octave, timbre will change depending on musical interval.
- Page 29 The Coiler can be used as an oscillator just by With the tuning set low and audio patched into turning the resonance knob all the way up. It will not the rectifier, the Coiler’s low-pass output functions track 1V/octave, but for drones with manual control, as a simple envelope follower.
- Page 30 Circuit explanation The MSK 009 Coiler VCF is a conventional two-pole Now, consider the frequency response of a two- state-variable design with a twist, or rather a cou- pole Butterworth high-pass filter. There is some ple of coils. The general theory of similar filters with curvature in the graph around the cutoff, but sig-...
- Page 31 only 3dB, due to the curvature of the high-pass re- Adding in the band-pass response as well can fill sponse in the vicinity of the cutoff frequency. in that notch; but because the peak of the bandpass Now suppose we attach another integrator to the is 3dB down, it’s necessary to put in a bit of gain;...
- Page 32 In particular, the EPCOS ferrite bobbin induc- perfections are supposed to give different sounds. The tors used in the Coiler VCF behave very much as the MSK 009 instead makes its main innovation in the in- following circuit made from ideal components would tegrator circuit.
- Page 33 Figure 3: One integrator in the filter core. itor and 27kΩ resistor. At high audio frequencies, U2C and its feedback resistor do that while allowing when the inductor is really providing inductance, the the OTA output to stay at 0V. capacitor has low impedance and the feedback loop Immediately before the current to voltage con- looks like a resistor;...
- Page 34 Figure 4: Input mixer and rectifier. there is one trimmer on each integrator, and the idea themselves have limited frequency range, but maybe is to average them out. The exact consequences of not limited enough; the 33pF capacitor kills the gain adding or subtracting an offset at this point in the in the ultrasonic range and makes sure parasitic os- circuit are complicated;...
- Page 35 cuits at several other points but found they had the most reliable and pleasant-sounding effects here. The rectifier section, shown again below, is an un- usual one. Note that unlike most op-amp precision full-wave rectifiers, this uses only one op amp and one diode.
- Page 36 U1C, on the CV1 input with its 100kΩ input resis- of exponential converter is used in other applications, tor, to 18mV per volt of control voltage input. That it is common practice to apply temperature compen- is (approximately) the right amount to apply to the sation in the front-end amplifier as well, often by re- base of a silicon transistor to double the collector cur- placing the feedback resistor with a carefully chosen...
- Page 37 Mechanical drawings On the following pages you will find: • the schematic diagram for the module; • a mock-up of what the completed module looks like from the front panel; • the top-side silk screen art showing component placement; • the bottom-side silk screen art showing compo- nent placement (note this drawing is mirrored, and shows what you actually see looking at the board, not the X-ray view used in other Kicad...
- Page 39 MSK 009 coiler multi fw rect mode filter NORTH COAST...