The Leapfrog VCF does not actually go "ribbet," at least not without some effort. But after being told by one friend I showed it to that most people don't want to make real music on their modulars but just want something that goes "uuuuuuuuuuuLAAAAAAAAAAAAARGH" (which, let's face it, is true), I've added a demo highlighting that. Uulargh? Yeah, we've got this.
You've probably noticed that although resistors and capacitors come in many different values, some of which seem like they could be randomly chosen, there's nonetheless some sort of logic to it. You'll see power-of-ten sizes like 1kΩ, 10kΩ, 100kΩ and it's understandable that those would be "round" numbers it might be convenient to use and manufacture... but for instance there also seems to be something special about the number 47, so you see many resistor values like 4.7kΩ, 47kΩ, 470kΩ, and capacitors like 0.47µF and 470pF. Why 47? Why not 46 or 48 - especially when 47 is a prime number and 48 has many small divisors, which would seem more useful? Here are some notes on the commonly-used numbers and where they come from.
The panel contractor says they dispatched the first production batch of MSK 007 Leapfrog VCF panels to me on Friday, and those are the last remaining physical items needed before I can launch the module; so I'm still hopeful that I can aim for a launch by the end of the month. That means I need to finish up the last few documentation items; one of them is a description of the exponential converter temperature compensation circuit, and that's an interesting enough item to be worth a Web log posting of its own.
I've spent most of this week working on the third prototype for the Leapfrog VCF. I'm hoping to have this available for sale by the end of the month - maybe in time to have some kind of spooky Halloween tie-in for the launch.
This week I'm planning to order the prototype boards for the Leapfrog Filter, and it makes a good opportunity to go through some common questions beginners ask about shopping for PCBs. When you go to buy PCB production services you're typically hit with a form asking you to select which features you want, and it's not always clear what the consequences of the different answers may be. In this entry I go through some of those options, and give some other notes on shopping for PCBs.