VCO Calibrator Build Thread

[kjackman]

Building the MFOS VCO calibrator, to... well, to calibrate VCOs. Because at the moment, I have no other CV sources to use. No "standards" modules, no VC keyboard, no stylus keyboard, no MIDI-CV interface, nothing. I am literally starting from scratch. It occurred to me that if I built the MFOS VCO first, I would have no way to calibrate it. So here I am.

All the parts are now soldered on to the PCB. I wish I'd done a better job getting the trimpots flush to the board. Whatta pain. I used to do professional electronics rework 20 years ago, but I can't remember my techniques for getting those parts flush. I'll work it out again somehow.

Anyway, this PCB sat 90% completed for weeks, for want of the 200k and 1.5k resistors. They just came in from Mouser today, yay! I measured resistors with my multimeter until I found 5 that came up exactly 200.0 k. Not 199.9, not 200.1. Did the same earlier with the 100k resistors. I had to go through more than I thought I would, to find them. Makes me wonder if the resistor manufacturer creates and measures an entire batch, plucks out most of the really close ones and labels them 0.1%, then the sorta-close ones and labels them 1%, etc. My OCD side worries that my 100k 1% drawer will end up with tons of resistors close to 100k, but not exactly 100k.

The enclosure is being built by a friendly neighbor with a well-stocked garage, shop skillz, and a lot of time on his hands. He helped us with the WSG enclosure a few weeks ago (just an ammo case with holes drilled in it). This one will look just like the one in Ray's picture on his site, with nice pine side boards. Should be ready in a few days. I just have to decide how I want to connect it to the circuit under test and the power rails... and I have to build freaking power rails. Yeah, I don't even have a "real" power supply yet. I have a couple of PowerOnes I got off eBay, but they still need to be configured and a power buss connected. I really am starting from ground zero.

[loydb]

It's a neat little module. I was in the same situation, no CV source to calibrate a VCO, so I combined the calibrator with a mini-kb (see signature for link). I look forward to seeing your build!

[kjackman]

Dude, I saw that one. Wow... Wish I had the talent to do cases that fantastically great. I could probably work my way up to that, eventually, but I'd need:

* tools
* floor space
* knowledge
* skills
* vocabulary (what's a "rabbet?")
* talent
* safety goggles, gotta have those

I'm all about the electronics... give me PCBs and parts and a soldering iron and I'm king of the world. Finding something to put it in... well, I've got a few shoe boxes around

But seriously, one of my goals is developing top quality synthesizer craftsmanship skills, and the enclosure is a big part of that, especially if I want to eventually build & sell expensive, one-of-a-kind boutique synths someday. Sooner or later, I'll have to learn to love working with wood and metal in the workshop.

So you can be darn sure I'll be watching your build threads very closely! Keep using tons of pics and explain every step - how and why!

[loydb]

Thanks! "Rabbet" is woodworker talk for a groove on the edge of a board that looks like an "L" when viewed end-on.

For low-volume woodworking, you can get a small set of hand tools (good saw, some chisels, a block plane, etc.) and use pre-surfaced (already sanded uniformly both sides) lumber and you can go to town.