Soon, this mini-blog will become a fully-fledged maxi-blog at http://www.glitched.org/diy ! But not yet...I'm still working on the design. Anyway, until then, synth.pen.io is the place to go to see my quick DIY updates.
Follow me for further updates on this DIY-type stuff and my music (d01): http://twitter.com/d01 , http://soundcloud.com/d01
Special Note
Word to the wise: always document your progress on any unfinished projects! I added a couple things on the 4069 OSC, but de-soldered certain connections for experimental purposes. Months later, I've forgotten what connections go where and why I did certain things. It's vexing, but now I have to re-trace my steps. It can be difficult, even with the aid of the schematic. Again: documentation can be extremely helpful! I use pen.io or notepad.cc for for this purpose, as well as for simple sharing.Status: Working On It
http://www.cgs.synth.net/modules/cgs35_syntha_vcf.htmlThe Steiner Synthacon multi-mode filter. Sounds weird! Looks pretty simple. Parts ordered from Newark.com. Here's what the schematic looks like:
Status: Recently Completed!
SSM2164-based dual-VCAhttp://www.sdiy.org/philgallo/mgbvca.html
(Something similar to that.)
This is the schematic from which I worked:
If you're a beginner, it may seem a little confusing, with all those lines going everywhere. That wasn't my problem; I was more perplexed by the "why" of it all. What's the purpose of those .1uF and 10uF caps? The 560pF caps and 500 ohm resistors?
Well, the .1uF and 10uF caps on the power rails are for...power supply de-coupling. Basically, smoothing out the ripples in the current coming from the PSU. Once I learned this, I realized that 50% of the components on the schematic are devoted to de-coupling. Cool. No big deal.
But what of the small cap and resistor attached to the signal inputs? Simple: a lowpass RC filter network. Essentially, this little filter dampens the frequencies above ~20khz--freqs that humans can't hear, but could cause unwanted effects on the VCA. (Calculate your own values for a RC lowpass filter: http://sim.okawa-denshi.jp/en/CRlowkeisan.htm )
All I have to do is connect the inputs and outputs. I'll report back with results!
UPDATE 11012011: After a couple false-starts, it works! Two linear VCAs from one SSM2164 chip! It's really smooth and quiet. Although I like my modules to imbue some sort of "color" to the signal, it's good to have a more surgical-sounding element in the mix.
Look how small it is!
I used tiny wires in a more point-to-point style, this time. I liked the way it worked, but I'm going to be smarter about the front-panel hardware, next time. It's just too messy...but it works!
UPDATE 11252011: The front panel has arrived from frontpanelexpress.com and it's awesome! See the pictures, below.
You may be asking, "what's the WASP filter doing on there?" Well, I decided to combine the panels, to save a bit of dough. Functionally, I perhaps gave up a little, but I figure that I'll be using both the modules in most patches, so it doesn't bother me that they're permanently joined together.
I think the separate panels would have been about $30 and $25, so I saved $15. I wouldn't advise this for someone who has a modular setup that's constantly in flux.
The above shows what FPE sent me, prior to the in-filling.
You can really see the fine detail on the engraving. Very deep, no burrs. FYI, the Front Panel Designer font used for the VCA was "Bold, 7-stroke." I wanted the WASP to be distinct from the VCA, so I used "Helvetica Medium, Outline" for the text.
The final product. I decided to leave the 2164 alone because the bare aluminum offers so much contrast to the anodized face. Of course, the WASP filter had to be yellow; an homage to its forebear. The yellow Davies-clone knobs are questionable; they're a bit too bright for my taste, especially the filter mode switch. It's just a little off. Still, I'm extremely happy with the end product!
The rear. It may seem a little cramped, but that's because...it is. Nothing is touching anything it shouldn't, though!
Status: In The Queue
http://yusynth.net/Modular/EN/ARPVCF/index.html
UPDATE: I have put this one on the back, back, back burner because I never received anything from Bridechamber. I have received a full refund. I'll try again in the future, when the guy is less busy.
Three years ago, before I got into modular synths, this was the first module I wanted. I've always loved the ARP filter sound and this seemed perfect. In 2009, I didn't know anything about modular synthesizers and what to start with or even what format to go with (eventually, I chose Eurorack). I asked Mr. Deyo, of Bridechamber.com, to help me with some of the preliminaries, and he filled me in.
So, here we are, three years later and I'm purchasing the 4072 filter kit from Bridechamber! Well, that should be past-tense; I ordered it about 15 days ago and still haven't gotten a shipping notification.
Anyway, I can't wait to get these parts.
PT2399-based delay:
There are many flavors of the circuit based around this delay chip. I like this approach because it includes a soft-clipper before the input to create a warmer sound:
http://www.uni-bonn.de/~uzs159/pt2399.html
UPDATE: Looks like BugBrand has used a similar circuit:
http://matrixsynth.blogspot.com/2011/04/bugbrand-pt-delay-overview-demo.html
UPDATE: Debating whether to build this one or not. I mean, it's "just" a delay and I already have some really capable models in the Virus TI Snow ("tape" style) and Monomachine (dirty digital).
Status: Complete!
CMOS (CD4069)-based VCO:
It's completely functional, I just need to calibrate it to 1V/oct. The PWM sounds really cool, but the saw is pedestrian. I could easily build another copy on the same board, which is what I'll probably do next.
UPDATE 03282011: Now working on the second voice. I hope I have enough room and the required components!
UPDATE 03292011: Second voice almost complete. This will be much more compact. Hope to get most of it done, today!
UPDATE 04062011: Complete! Well, all I have to do is glue the two transistors together and put some heat sink compound on them (er, reverse that), but I'm considering this done.
Look at the difference between the two VCO layouts! I really went freeform with the second one (left) because I misjudged how much space I had left on the board.
Now, that's a disorganized rat's nest! I really have to figure out how to solder in an orderly manner. Still, you can't argue with the results: it works!
UPDATE 04122011: The tracking on this oscillator is pretty bad. I can't get any more than a couple octaves out of it. Disappointing, but this is still a very usable and cool sounding modulation osc. Eric Archer (ericarcher.net) states that this is probably due to not using matched transistor pairs. Yep, that's probably it. Plus, I didn't really do a great job of sticking the trannies together. They're sort of off-axis.
I did read something on Thomas Henry's site about the quality of certain manufacturers' 4046 chips. I wonder if this goes for the 4069 CMOS chips as well. To test this theory, I bought a few 4069s from various manufacturers. I'll report back.
Update 04262011: Well, the chips from the different manufacturers didn't make a lick of difference. The only thing that really matters is the matched complementary transistors (NPN + PNP). I probably won't want to put forth the effort to make a matching device, so this may be the end of the road for the VCO (but I'm still very happy with it!)
Here are a couple sound samples, from my soundcloud:
http://snd.sc/fcil4E
EDIT: Ok, just one sound clip. I didn't like the others. More, soon.
Status: Complete (But Waiting for Panels)
1) EDP Wasp Clone Filter, Layout by FonikUPDATE 11012011: I have designed a dual-panel which pairs the dual-VCA and WASP modules. Ok, it might not be the most logical choice, but I'll be using those modules in nearly every patch. Plus, it saved me like $10. Anyway, it's 14HP wide and black. I should get it from frontpanelexpress.com, this week!
2) PIC-based Voltage Controlled ADSR and 3) LFO from http://electricdruid.net/
The VCADSR was the first project I did completely from scratch, starting with translating the schematic to the board. I even added a 2x gain stage with an inverted output! I made one mistake where two of the capacitors are 10x the recommended value, but it seems to work well.
The VCLFO looks pretty strange because I went a little overboard and attempted to use a diode array chip to protect the PIC from transient over-voltage exposure. It turns out that it was unnecessary and the PIC was more robust than expected.