One-Stop VCO-1 Documentation Download Resource VCO-1 Schematic Page 1 of 2 (PDF Format, 1.05 MB) VCO-1 Schematic Page 2 of 2 (PDF Format, 663 kB) VCO-1 Parts List (PDF Format, 646 kB) VCO-1 PCB Image (PDF Format, 22 kB) VCO-1 PCB Parts Placement Guide (PDF Format, 822 kB) VCO-1 Front Panel Layout (PDF Format, 358 kB) VCO-1 Front Panel Drill Guide (PDF Format, 416 kB) Return to the Main VCO-1 Page On-line Technical Resources The ultimate source of information for building analog synthesizers would certainly have to be Bernie Hutchins' legendary Electronotes. Bernie still offers these documents for sale, and they could not be more highly recommended. Electronotes is literally the bible of Synth DIY. Electronotes Howard Moscowitz's vision of a community of Electronic Music without borders has become reality with his award winning Electro-Music site. Howard has created a phenomenon that simultaneously nurtures, inspires, and promotes the blossoming electro music movement. If you are an electro musician or afficianado, I cannot recommend this forum enough. The Electro-Music forum not only provides resources for composing and enjoying electro music of all types, but also encompasses information on the instruments and use of the instruments used to create this artform. Within Electro-Music is a subforum entitled "Thomas Henry Designs" and it is populated by a number of people who are both enthusiastic and knowledgable about Thomas' designs. Even Thomas himself is known to show up there. This link is for the Thomas Henry forum, but don't hestitate to explore the whole experience that is Electro-Music. 
Magic Smoke Electronics is offering a series of Thomas' publications, including "The Electronic Drum Cookbook" and "Making Music With the 566". In addition to that, Magic Smoke will be offering the TH-201 Mankato Filter, a filter designed by Thomas in the summer of 2004. This filter quite simply blows me away to this day. It was used in the first sound sample on this site - keep an eye on Magic Smoke. When the Mankato comes out - buy it!! You'll see what I mean...... 
Return to the Main VCO-1 Page Finding Parts - The Eternal Quest There are really only two parts in the VCO-1 design that may be moderately, but not overly difficult, to get: The 2K Tempco resistor (R8) and the CA3080 (IC1) which was sadly and misguidedly discontinued by Intersil (apparently, it's not used in any current Cellular Phone or Video Game designs these days). Fortunately the CA3080 is still quite available, and thanks to the remarkable and irreplaceable Ray Wilson, the 2K tempco is a Paypal purchase away. All of the other parts are very common - you can get them at all at the usual suspects: For us in the States, Mouser Digikey, Jameco, Allied. For those of you in Europe, the RS's and Reichelts, etc. For you lucky, lucky Japanese, the Akhibara, etc. For the people down under, it looks like you have some nice places left to find parts. The 2K Tempco (R8) Music From Outer Space. To any Synth DIYer, that's usually 'nuff said. But, I'll expound anyway. I can't even begin to count how many of Ray's designs have found their way into my synthesizer, or how his writings have enhanced my own otherwise feeble attempts at design. If it weren't for Ray, Thomas, Ken Stone and Rene Schmitz, I doubt if I'd be much past installing batteries in a flashlight. Ray Wilson's Music From Outer Space site is one of my greatest inspirations - I firmly believe his Sound Lab music synthesizer design is arguably the single most successful DIY project of all time, and that's not all Ray offers - he's got all sorts of filters, oscillators, yin-yang contemplating dinosaurs, VCAs, wacky sound generators, phase shifters, spacemen and documentation, all magnetically and gravitationally encased in that juggernaut of a site of his "Music From Outer Space". Not only does Ray have all that, but he also makes available the coveted 2K Tempco resistor, without which I'd just fold up shop and call it a day. I'm sure you've been there already, but go again - and enjoy. The link is to the page where he dangles the words "PT146 2K @25C 1% +3500ppm Tempco" hypnotically on your computer screen. 
The CA3080 OTA (IC1) Intersil certainly didn't earn any brownie points with Synth DIYers when they discontinued both the CA3080 and CA3280. Fortunately, both are still around (apparently there were scads of them made before the bean counters realized they weren't on the BOM of the Playstation 2). Here are a few places they can be found. I'm sure there are other places you can get them before resorting to the 'bay'. In fact, other than playing favorites with Small Bear, and referencing Banzai over in Europe, I'd say you probably won't have a terribly hard time finding the CA3080 (BTW, I'm pretty sure the LM3080 will just as well). If you *do* have problems finding one, I highly suggest joining the Electro-Music forum and start frequenting the DIY forums there - particularly the Thomas Henry Designs forum. As the song goes, there are plenty of "gentle people there", though I doubt there are flowers in their hair, or, for that matter, many probably even don't have that much hair left either. But, they can still probably get you hooked up. First on my list of personal recommendations would be Small Bear Electronics. Steve Daniels, the proprieter, is one stand up guy. Small Bear not only stocks the CA3080 for a price considerably less than the first born other dealers seem to think it's worth, but he has one slobberknocker of a DIY inventory. It's guys like Steve Daniels that make looking for that certain part sooooooo much easier. 
Banzai Effects. I've never done business with Banzai, but I recognize them from Aron's Stompbox Forum, and from that know they're on the up and up. They're in Berlin, so I include them for those of you in Europe. Banzai Effects Monolithic PNP Transistor Pairs (Q5, Q6) As Thomas states in his article, using a pair of matched 2N3906 PNP transistors will yield satisfactory results. Alternately, if one wishes to, one can use a matched transistor pair. There are a couple of advantages to using a matched pair - you need not worry about matching the transistors, and, generally one can get improved results using them. I used the 2SA798 matched PNP pair when I breadboarded the circuit myself.
PNP matched pairs aren't generally terribly ubiquitous, but they can be found. As mentioned, the 2SA798 works quite well. The superior, but vastly more expensive Analog Devices SSM2220 would certainly work quite well. There's a third, slightly more wieldy option, which is the THAT320 dual matched pair, produced by THAT Corp. If I'm not mistaken, I believe the THAT320 would even edge out the SSM2220 in performance, but the THAT320 has two matched pairs in it, so it is a larger package that has two extra transistors you don't really need (unless you're building a dual version of the VCO-1). Still, I must admit I'm intrigued by the THAT320.
As it happens, at least for Americans, the 2SA798 (a discontinued part, I believe) is easily available for a very, very good price through Electronic Surplus. Electronic Surplus One place that has really caught my attention lately is KA Electronics. They stock the THAT transistor pairs as well as other THAT parts (THAT, IMO, is the ultimate in precision devices). They have some other very, very interesting things as well. Here's the link - check'em out! KA Electronics Return to the Main VCO-1 Page Sound Samples If you've already listened to the sample linked in the preface to the main page, then you've already heard the first sample listed here. I'm hoping to produce more samples available, but it's summer and it may be a while before I surface long enough from the other projects to record more. Fortunately Thomas has provided me with a few samples from his archives.
This first sample is quite simple, really. The PWM output of the VCO-1 is sent through my breadboarded Thomas Henry Mankato filter, through reverb and then into my Korg D8 recorder. I'm using my Thomas Henry keyboard to control the VCO and filter frequencies. The pulse width modulation is provided by a Ray Wilson LFO, and there is occasionaly some FM vibrato provided by a second Ray Wilson LFO. The envelope generator used on the filter is a Ray Wilson ADSR envelope generator.
At the time this sample was recorded, I think I'd spent all of three minutes calibrating the VCO. The breadboarded Mankato has been on breadboard since summer 2004 - it's a relic of the days I was beta testing the filter for Thomas.
I don't think anything says analog any better than the VCO-1 through the Mankato. VCO-1 Through Mankato Filter (1.25 MB) Next up is a sample Thomas Henry provided, demonstrating the VCO-1 under MIDI control. Thomas points out each waveform as it's presented. This sample certainly demonstrates the pitch accuracy of the VCO-1! Thomas Henry demonstrating the Waveforms with VCO-1 Under Midi Control (368 kB) The next sample again was provided by Thomas. It was originally recorded to demonstrate the MTS100 MIDI to CV Convertor that Thomas marketed back in the days of Midwest Analog. Where the previous sample hints at the pitch accuracy of the VCO-1, this sample absolutely confirms it - listen to this "homebrew" VCO play right along with a crystal oscillator controlled Casio CZ-1000! Thomas Henry Sample With VCO-1 Under Midi Control, Accompanied by Casio CZ-1000 (905 kB) |
