So what has the Old Crow been up to lately? As getting crOwBX boards made for the euro and vintage replacement editions is largely a wait for the factories game I decided to do a project I had in mind for a long time, prompted by obtaining one of Dan Alich's awesome DuinoKits. "This aluminum case would make for a great little synthesizer enclosure," I thought to myself. "I think it is finally time."
Time for Crowminius. My take on the minimoog built as a single board synthesizer that fits into a DuinoKit case. Every control and jack found on the mini is likewise found on Crowminius. MIDI, dual LFOs dedicated to oscillator PWM, the Power Supply That Does Not Suck(tm). All here.
The circuit board is 8.5" x 11" (216mm x 280mm), the size of the DuinoKit Essentials PC board the aluminum case of which settled the form factor goal for the Crowminius project.
The green things are some 3D-printed shelf clips I made that serve as makeshift pitch/mod levers. I will print better ones meant for this.
There are three LFO LEDs, two are behind the PWM pots (top middle), the 3rd shows the rate of the control osc. and is over by the pitch/mod wheel pots.
The vactrol/LDR is for MIDI modwheel action, which is kind of experimental at the moment.
The A440 reference is not a Wein bridge sine oscillator, but rather is a DDS table-lookup PWM sine tone generated on the MIDI microcontroller.
There will be USB MIDI, once I figure out how to do it. I rigged the hardware as per the V-USB spec but I am not a C programmer by trade. But, eventually.
The power supply will run on a single 12VAC, 250mA wall transformer. The power supply that does not suck mode involves the use of two 12VAC wall transformers so as to provide full-wave rectification.
The DAC is scaled to provide 5 octaves, F1 to F6 over a 4.096-Volt range. The DAC's 2nd channel will operate the filter cutoff for assignable key velocity or whatever.
I did not use ua726s as they are a pain to get and the thought of exposed parts heated to 80C meant someone would get burned. LM3046s are fine; there is a tempco resistor under the three arrays for the VCOs.
The filter resonance pot is in fact a 50K reverse-log type, but I provided for using a linear pot+resistor to cheeseball it.
Yes I will be offering bare boards. They will be $100.00. I have to correct a few cosmetic issues (mostly reversed knob and switch actions) but every part came from Digikey, Jameco, Mouser or Small Bear.
More later.
Crow
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Last edited by oldcrow on Sat Mar 28, 2015 7:41 pm, edited 1 time in total.
Silly question, probably, but is this designed to go behind a panel or sit, umm, naked, as-is? The angle of the photo makes it really difficult to judge the size of certain parts (the big knobs look like they're towering over the Davies 1900s, for example). Also curious what the four patch points are for...
I wasn't thinking of a panel as the board mounts in an aluminum case that has a cover, but if I can devise a method to mount the small switches up higher on solder-in tiers, use pots with longer shafts and relocate a couple jacks some sort of panel could be used. --Crow
home_listening wrote:Nice!
Anyway it can be easily mounted behind a panel (without running wires for the switches and pots?)
I might make an SMT/pre-assembled unit, but that is down the road. I have crOwBX in Euro coming out later this spring so my SMT stuff is dedicated to that right now. --Crow
Adminius wrote:I understand that you're going to make the PCBs available for DIY, but will there be any completely assembled systems available?
Build a Eurorack version of this and you'll be hailed as a synth god (or at least a minor synth deity; "Crow, the god of LFO's").
There are three oscillators, I just tuned them to a major and faded each one up with the on-board mixer knobs. That whole demo is just me flipping switches and twiddling knobs with the other hand on my MIDI master keyboard. The output goes through my mixing desk and into Ableton Live with one loop send/return to my Lexicon reverb.
Crow
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logicgate wrote:Awesome!
You made the chords by multitracking or there's a paraphonic mode?
In fact my case is from DuinoKit, I bought an empty one for this prototype, and will be arranging a bulk purchase.
The four small jacks are external filter CV, external pitch CV, external loudness (footpedal) and a switch trigger input. These four jacks are 3.5mm types in order to fit at all.
--Crow
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monstrinho wrote:Silly question, probably, but is this designed to go behind a panel or sit, umm, naked, as-is? The angle of the photo makes it really difficult to judge the size of certain parts (the big knobs look like they're towering over the Davies 1900s, for example). Also curious what the four patch points are for...
Last edited by oldcrow on Thu Mar 26, 2015 4:38 pm, edited 1 time in total.
This is a whole synth. It is not really set up to act as one voice in a polyphonic like crOwBX is. Of course you can just use four of these and dial in the same patch and use a MIDI key assigner. --Crow
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Dogma wrote:So is it meant to be a voice or a whole synth?
Detuning sounds lovely BTW not too much beating or any really
