From f3b9e77212fcc2aeb2533dde6a39f1e6f0e627e9 Mon Sep 17 00:00:00 2001 From: gdorn Date: Fri, 2 Sep 2022 04:10:09 +0000 Subject: [PATCH] Update 'Future Modules' --- Future-Modules.md | 44 +++++++++++++++++++++++++++++++++++--------- 1 file changed, 35 insertions(+), 9 deletions(-) diff --git a/Future-Modules.md b/Future-Modules.md index 968fb39..70d39f5 100644 --- a/Future-Modules.md +++ b/Future-Modules.md @@ -4,28 +4,48 @@ What we build next? Pretty confident we do these in this order next. ## Sequencer -#### MK's 5-step sequencer, expanded to baby 8 +Something to generate CV, in particular for controlling VCO notes. The classic is called a "Baby 8", so called because it's a simple circuit that generates a sequence of 8 voltages controllable by individual knobs. + +#### MK's 5-step sequencer, expanded to 8 (or 10?) * Breadboard MK's 5-note sequencer. * Compare to online 8-note sequencers (baby 8) * Either build online 8-note schematic, or extend MK's 5-note to 8-note. -* padding MK's out to 8 notes means roughly $16-20 in parts, depending on PCB choice -* could also go to 10 steps, but no more (uses a decade counter) +* expanding out to 8 notes means ~$16-20 in parts, depending on PCB choices +* could also go to 10 steps, but limited by decade counter #### Bergman's 10-step sequencer (up to 10) * https://www.eddybergman.com/2022/04/8-step-sequencer-v2.html -* can do up to 10 steps with the hardware to support it -* 10-step mode is ~$16 in parts, depending on which are actually needed -* big board, requiring one 8-pin, one 14-pin and one 16-pin IC -* maybe more stable than MK's? test this -* includes weird 8V linear regulator for the hex inverter - maybe save a bunch of effort and pins by using a single tl074, with two as needed and one as schmitt trigger? +* very similar core to MK's, but using fewer diodes (substituting LEDs in many places) +* might be more stable than MK's, but it's unclear what that means and whether it is true. +* weird usage of a hex inverter, maybe for stability? +* 10-step mode is ~$16-20 in parts, depending on which are actually needed +* big board, requiring one 8-pin, one 14-pin and one 16-pin IC. But 3 panel-mounted UI elements for every step (plus some others), so plenty of room for a big board behind it. +* includes weird 8V linear regulator for the hex inverter; if this can be replaced by an op amp in schmidt inverter mode, maybe both 7808 and hex inverter trigger are unnecessary? +### Alternative: Midi -> CV +We could generate CV some other way for now, such as: +* build a keyboard using one of the two keybeds in storage; decipher key matrix, work out either MC or dumb resistor array to output correct volts for each key. +* build a MIDI->CV module +** [Hagiwo's cheap arduino version](https://www.youtube.com/watch?v=bHiZhLAntNI) and https://github.com/elkayem/midi2cv which it is based on +** https://www.instructables.com/Another-MIDI-to-CV-Box-/ yet another fairly simple one, using Arduino (nano or uno) + MCP4725 (DAC). +** https://hkadesign.org.uk/monotronkb.html for yet another version + +### Alternative: CV from something else +* use a [raspberry pi running a DAW](https://old.reddit.com/r/synthdiy/comments/vbaj43/my_opensource_synthsamplersequencerdawinabox_the/) with a DAC and just use python to send CV; could also do midi-over-usb +* buy a Korg SQ-1, which is what MK uses (and runs about $100 on ebay); Korg lists Trade-Up Music as a vendor? ## VCF #### MK's Diode Ladder VCF * ~$8 in parts, two tl074 op amps and otherwise a bunch of diodes and support +#### Kassutronic's KS-20 +* https://kassu2000.blogspot.com/2019/07/ks-20-filter.html +** uses an LM13700 OTA (operational transconductance amplifier) (~$1.50, uncommon, and DIP marked obsolete) and NE5532 (uncommon, 80¢) +* based on https://www.schmitzbits.de/ms20.html which is an attempted clone of a Korg MS-20. +** that one uses a CA3080 OTA, an expensive and rare chip these days ($3/ea on amazon, maybe fakes) + ## VCA #### MK's VCA @@ -58,7 +78,7 @@ Something to take CV in, round it to the nearest 1/12th of a volt (or whatever, * uses an arduino nano (other options probably fine), two 74HC595 shift registers (accidentally a pile in my collection) and the MCP4922 DAC (others may work). * Probably can build our own based on this and/or Hagiwo's quantizer, if going digital ** https://www.quinie.nl/hagiwo-quantizer-how-does-it-work-a-bit-of-background/ -** https://note.com/solder_state/n/nde97a0516f03 +** https://note.com/solder_state/n/nde97a0516f03 and https://www.youtube.com/watch?v=op_DhPr2goc ** arduino nano clone (atmega 328p), 12-bit dac (mcp4726) and small amounts of supporting hardware #### Microcontroller and smoothed PWM @@ -134,6 +154,12 @@ Everybody needs several VCFs with different behaviors. ** CA3080 High-Performance Operational Transconductance Amplifiers - not a jellybean, so $3/ea for sketchy NOS on amazon ** CA3080 design is ancient; maybe an updated one exists with current ICs? +#### Scrat +* https://modularaddict.com/scrat-configurable-vcf-neutral-labs +* plug in your own components to hear what they do +* J175 jfet (~50¢) and H11F1M ($5!) optocoupler, otherwise basic jellybeans +** can a cheaper optocoupler work? what's it even for? + ## CV Generators #### [Ornament & Crime](https://ornament-and-cri.me/) a highly recommenced "polymorphic CV generator"