Posted: Wed Jan 24, 2007 2:00 pm Post subject: Home Brew Analog Modular Synthesizer
I've pondered building a analog modular synthesizer for a long time, and after buying a digital-analog synthesizer (EDIT: oops I meant synth, I have a sequencer too though) a few years ago, I recently found out how to print and etch circuit boards, so I motivated to it right away.
This was after a few weeks ago I built a guitar heavy-fuzz pedal on a breadboard, and it actually worked, I have a fair understanding of circuitry logic, and it brought my confidence back up on the matter.
I have ordered much of the parts for the entire synthesizer, and already owned resistor and capacitor kits
I made the bipolar 12V+ 12V- psu from a schematic and got it to work properly, this after plugging it in with three capacitors in backwards. They began to swell and leak, and luckily, I had only plugged it in for a moment. The capacitors were hot, angry, and did not calm down until I discharged them. Hopefully I won't need new ones, they still hold a charge. Hazardous.... I have read of exploding caps....
It worked Thats a start
The next part needed is the VCO voltage controlled oscillator, if I can get this to work, ultra-cool sounds are not too far away.
I got impatient the other day, and started constructing it by hand.
I got some pcb drill bits on ebay, unfortunalely I have also broken several attempting to use them in a dremel
Sadly, things often do not work out right, and one side of the pcb I got on ebay is too thick for the etchant to remove properly, so while waiting on it to etch, my circuit got over-exposed and is too broken up to use. At least I know the next one will come from a laser printer
I have needed one of these far too long...
Last edited by super dank on Mon Jan 29, 2007 9:38 am; edited 2 times in total
Thanks, this is about to look so easy that anyone can do it. I was stunned to find out how easy this can be done at home, as I thought for years that I would have to send off for a professional printed board if I wanted one. I may get back into programming PIC16F EEPROM chips. I got into it about a year ago when I found that assembly programming skills I had learned in dos are almost the exact same as with programming the eeproms, except the PIC16F's have only one file buffer F, as compared to the file buffers AX, BX, CX, and DX with x86 machines, so programming a PIC is very linear
I ordered some Press N Peel sheets from Techniks
The Press N Peel sheet did not feed right the first time, but I haven't had a problem since.
Pressed without steam for 5-15 minutes, I'm not sure which works better, I just leave it for a while. When it cools, the sheet tries to peel away at the edges, I leave a few sheets of paper over it until it is cool.
I had seen alot of people recommend Press N Peel on the net, but it is expensive, about $1 USD per sheet, however, after using this product, I would say that it's worth every cent.
There may be a couple of breaks in your traces, but they are easily fixed with a permanent marker if you are using ferric chloride
I don't know it yet, but the card on the right is the wrong one. I made the one I wanted a bit later.
There are two ways I have learned to do the etching with in-expensive solutions. There are other ways of doing it by UV exposure, but I haven't looked into it much.
Ferric Chloride is nasty stuff. It stains anything and everything you get it on, and if you make the solution yourself by mixing reagent with water, you must do it outside, it produces chlorine gas, but once it's mixed, you can bring it indoors.
I kept running out and bought some that hasn't been mixed with water. It boils when you mix it, just be careful outdoors.
The other way you can do it is two parts 3% bathroom H2O2 / water and one part 20% Muriatic Acid (hydrochloric acid) HCL. This is also nasty stuff, but it etches faster, it does not stain as bad, and it is by far the cheapest solution.
I prefer the Ferric Chloride. It stains, it takes longer to etch, it doesn't last long, and it is hazardous to the environment (all my waste is jarred up, I don't know where to take it yet), but I like the Ferric Chloride better for one simple reason, if your Press N Peel traces break, you can fix them with marker, and the ferric chloride won't etch it. The 1X(20%HCL) / 2X(3%H2O2) will eat through your marker traces.
Alcohol/Ethanol will only remove the permanent marker, but Acetone takes the Press N Peel right off
No more broken bits....
I made the first and realized my error, then made the second, I may end up using both. Theres no telling if either will even work yet I suppose...
Time goes by......
One of my IC's, an old obsolete transistor array, still has not yet arrived, and I have ordered others from another source. I still do not know if this module will work yet. I have ordered an old antique oscilloscope too, so if I have alot of problems, it should help me find some of them.
I decided to make another VCO module that that same site has up for sale/use. It has a two sided pcb, and so I took a shot at making it. I found out the hard way that when you do the second side of the pcb, you should keep the other side raised from the surface with four coins or something. Your first toner patter will try and transfer again.
I drilled a few holes as guide-points, and lined the second side up with them via the light in the room, versus the mounting screw holes.
I have all the parts for this Oscillator, I just need to build it now.
I got 2500 1% variance resistors $4.99 + $20 shipping from Hong Kong What a deal!
I began constructing the second VCO module. This one is the one for sale at musicfromouterspace, I thought perhaps it is more complex than the other VCO, although, the first VCO I printed is dubbed "Updated and Improved" and is not for sale at the site.
This is the second one, the two-sided pcb. I over-fix my traces. I know that they are ok, but when I see a bubble or something, I just solder it all up to feel better : ]
I learned very quickly that organizing all the parts, then putting them all in place, then soldering all at once is the only way to do this in a time-efficient manner. These two cards have taken alot of time to assemble, but I have been taking alot of time to double-check, triple-check, and generally review my work in a tedious manner. I think the second and third VCO won't take as long to make as I will probably work with less care to detail.
Stiff copper hook-up wire seems alot easier to work with than softer wires. It can take more current too.
I have learned over time not to expect things like this to work all the time, and again, this module does not work.
It's often a matter of a simple bug messing everything up, Ill probably look at this one later. This is not actually the module I was originally interested in. All I get is speaker clicks, an obvious sign of Direct Current.
My second order of vintage CA3046 ic's came in the mail. Also my nice camera finally arrived from England (left it there) and I got to take I nice picture of the original vco THAT WORKED
At least something is going right
This is a short audio recording of a Sine, Triangle, Sawtooth, then a Square/Pulse wave with the Pulse Width knob turned from least to greatest, producing that slide. I do not have a voltage outputting keyboard right now, so I used a potentiometer knob to control the input voltage, controlling the sound octave. I only adjusted the pitch once, after the first four beeps.
The idea is for my Access Virus to have a powerful, bulky new friend The synth on my sequencer is terrible, and I need (want) another lead synth
The next part needed besides more oscillators (and faceplates) is a VCF or voltage controlled filter. This is the unit that starts to produce those sounds they used to put in all the 1970's and 1980's horror films. There is actually a program for the computer that emulates an old Moog synth very well, but I have had the opportunity to try it, and if you enable polyphony (disabled) and press more than one key, it sounds like crap. If I had purchased the software ($350) I would have been upset.
I intend to have at least one Moog style filter, if not several. They were among the most rich sounding synthesizers to be found about thirty-five years ago.
I do not have my Oscilloscope yet and cannot yet fine-tune this oscillator.
Joined: 03 Dec 2004 Posts: 1749 Location: Stockholm, Sweden
Posted: Fri Feb 02, 2007 12:32 pm Post subject:
Nothing less than impressive.
Not that I have any clue whatsoever of how it's going to work, but I see there's a lot of work being put into it. _________________ Man, or woman, or both? Grandis spiritus, sanctus diavolos
I made the faceplates out of some good steel and painted them with white primer, after doing it this way, it would probably be far less time consuming to use one panel for everything, but then it wouldn't be modular would it...
I heat-shrinked the resistors that go to the potentiometers inline in the wire because the leads on the resistors kept flexing off.
I also got the waveshapes of the square, sine, and triangle in the right proportions. By default, the trimmers were way off, and the audio clip I posted before doesn't have a very good sine wave at all, but thats all better now
My Korg D12 mixer / disk has an excellent tuner and frequency counter built in, and it made it fairly straight-forward tuning the octave scale. If you're scale is off, your keyboard will play notes slightly out of tune. With such a great tuner, and the 1V/oct octaver circuit on breadboard, it was pretty easy.
I photoshopped the faceplates and printed them on laminate. I even added my own function to the oscillator, a max pulse width knob, as the max pulse width before my adjustment was just shy of %50
This is an audio demo of three sine, tri, saw, and square wave, the one posted previously had a mangled sine and triangle wave.
This next audio clip is of the simple configuration below, one square wave being synchronized by a sine wave. There are still no filters yet. The filters along with some envelopes and control voltage LFO's will give this instrument alot more whallop.
Next I will need to either assemble a Minimoog filter, or the PolyDAC pcb and pre-loaded EEPROM I ordered from Australia. The PolyDAC will allow me to generate control voltages with a MIDI signal and allow me to control this synth via any MIDI device, keyboard, sequencer, ect.
Everything is amazing... EXCEPT! You don't know how to solder...
You pull the leads through the holes, bend them a bit outward to secure the part IE=> _\ _ /_
........................................................................................................................................... ~~
The ~~ representing the part, the leads and board should be obvious. You should then clip the leads off the part, and solder it to the board. The solder will actually pull up just covering the entire lead, even the tip.
The solder will form almost a Hershy's Kiss shape on the lead, being slightly concave at the bottom.
For your application it's not so important, but anything industrial, you'd be fired. It prevents corrosion of the lead, as it's completely protected, and also prevents cold solders as it's alot easier to make sure it's a good connection. Because there are no cold solders, you won't need to worry about loose/poor connections screwin up your "music".
I assembled about 90% of the polydac about a month or two ago, as well as a minimoog filter, I got a little bit distracted though by some things I've had to deal with, I will be moving into a new home soon, and I have managed to find an interest in firework pyro-chemistry on top of all this (pyro-chemistry thread coming)
A fairly straight-forward pcb
I wasn't able to find the resistor ladders for the board, and it was at the point when I was supposed to make my own resistor ladders I started to get a bit distracted. My woman stopped taking her meds (for nine months) and has turned into some kind of evil wench.
I'm thinking about looping my gear up tonight and working on my sequence library a bit, in fact, I think I'll drag it down here right now :]
I keep this stuff under my bed, and I hardly ever show it to people, people have bad ideas
When I finish the polydac(if it works), I will probably pick back up on the Synth project, being able to punch the sound out with a keyboard :]
I think I should also give some credit where it is deserved, I was greatly motivated to actually start this project by a web site created by Yves Usson, who took old schematics of classic synth circuits, and from them created new printable circuits with parts currently available. These are all available to the public, and I may not have started this project having not been there. I am still waiting for him to complete the circuit for a fixed filter bank, a very powerful module.
Seriously, I'm reading all of this and saying... WTF ?
This is WAY above my head, man it took me 4 hours to understand the first 5 or so lines of your first post! OK, well not exactly but you get the message.
It's always audiophiles.. they always get into the electrical bits for audio work and soon learn most of electrical engineering through it.
In all frankness, I've never messed with electricity much myself and don't know too much about it-- actually I did, I've forgotten it. I did circuit and workshop studies at A-Level standard so shame on me.
Just recapping PSUs, mods on CPUs/MOSFETs/VRMs and MBs is as far as I've done PC related, but yeah I can use oscilloscopes and make a very simple design PCB, simply because it's very damn simple and anyone can do it.
But that what you've done is WOW in my books. Good on you mate. No way something I could do yet.. well I've never thought about it nor tried it, let alone learn, so no.
How much did you get the oscilloscope for and what time/frequency range does it measure? Can it show 2ms and 10mV readings? Does it have a BNC output/input?
Also where did you get the 20% HCL from? England, US or Sweden? I'm in North England right now and I've been refused any purchase of it.
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OK, well not exactly but you get the message.
