Music From Outer Space. MFOS, as it is known to it’s fans. Ray Wilson’s stunning contribution to the immortal pile of stuff we all leave behind when we pass away. Ray has passed on, and as I shed a single tear of sadness at the loss, I am comforted to know that perhaps he is now an electron somewhere, doing work for the universe as he moves from valence to valence and atom to atom. We all miss Ray Wilson.
Ray is one of my heros: he fell in love with electronics and through reading Electronotes, a magazine dedicated to DIY synthesizers, he taught himself to think like an engineer and design like an artist. He has created a more or less new modular system. He’s done kits by the ton. He contributed a great deal to my early enthusiasm and excitement about both electronics and electronic music. I was honored and surprised when Ben Mandberg gave me the kit he’d had sitting in his closet for 6 years. I received it earlier this month. What a PCB!! She’s monstrous!
+/-300 resistors, over 100 caps, lots of IC’s, and filters galore (twelve in all!)
I will populate the board with the BOM provided by my homie Ben. It’s a mix of ceramic TDK capacitors and nice film caps, milled IC sockets, Kayama 5% carbon resistors (all but 4 in the circuit,) 1N914 diodes instead of 1N4148s, and some pretty generic unmatched (as far as I can tell) PNP/NPN transistors. The ICs are a mixed bunch: Operational Transconductance Amplifiers (OTAs) from National Semiconductor, Farnell made LM324s, and the ubiquitous TL072 from Texas Instruments too. The CD40106 Hex Inverting Schmidt Trigger IC is from TI also. TI used to make oil field hardware- until they invested in this new fangled “sillycon” in the 60s. Now they are “King Shit of Fuck Mountain,” to quote Bob Odenkirk from Mr. Show.
One of the ssoftware utilities Ray used in the design process was actually software from TI called “Texas Instruments FilterPro.” I plan to explore this software when I design new expansion PCBs for the MFOS vocoder. He also used Webbench Filter Designer. I plan to do some expansion boards with 4-12 channels each after I modify the output mixer bus with individual volume knobs and outputs for each band. Thankfully, Ray anticipated this, and gave the ability to tap into and out of critical busses on the PCB quite easily. I’ll need that software I’m sure, though, as filters are all math! I’m looking forward to playing with some new tools.
I did my least frequent components on the BOM first, starting with resistors as they were the shortest in height. I actually did the small signal diodes first as they were the shortest, but there was no method necessary. They were all the same. The BOM had been ordered with no customer part number in the Customer Part# field for Mouser, so I had to look at the spreadsheet BOM for placing each part of each value. If the CP# field had been filled in for some of the parts, I could have placed them without going back n forth from the BOM. Many parts though wouldn’t have had room in the field for all the designators though, so it’s a moot point. So all the resistors that were only used once were first. Then the resistor values only used twice. And so forth. This meant that by the end I was able to confidently put the most numerous part into the PCB without looking at each resistor designator because I knew that there was only one value left and that any open resistor pads had to be for that value.
I then did the IC sockets, anchoring one pin at a time to make sure the whole thing was flat against the PCB before soldering. And so on up in ascending order of height, so caps, then transistors, and finally trimpots. Something like that, more or less. I like to pretend I’m logical and methodical when I assemble stuff. Yeah, right. Like anyone really is. Plus, ya want to know when I’m least logical and careful? When I’m excited. And be warned, people, I am really excited so I did rush a lil bit to get ‘er soldered up. So it looks a little home-made, but hey, I stuffed and soldered it in under 6 hours.
Some of the capacitor selection here on the PCB looks to me to be pretty arbitrary, but I’m just gonna get ‘er goin and make modifications later. Ben may not have gotten film caps consistently for the filters on the PCB so some might be ceramic- oh well. If need be, I’ll change some caps later. I’m so fucking grateful to Ben Mandberg, who is a true homie, for the gift. Any caps he bought are just fine by me!
I’ll get into the details of what capacitors do what, which filter strips on the PCB are what bands, how the filters work from an electrical point of view, and how Ray designed this magnificent device to work in another post. Then, with any luck, we will do some serious modification. Along the lines of the Moog Vocoder and some of the Kraftwerk vocoders: possibly modular I/O for each band, possibly potentiometers to control the volume of each band fed to the output mixer bus, and in the end, let’s face it, probably both. God help me, it’s gonna get comically complicated. I was born a circuit bender, I’ll die a circuit bender. Or was that a Snake Handler? Don’t matter. Below is a pic of what it looks like before I solder and cut all the leads from a big ass PCB like this. You can see it’s not super precise or technical. I just bend the leads enough for them not to fall out when I flip the PCB. Then I bend em back a little when I solder them. I makes them easier to cut and less likely to short to another lead during solder application.
It’s time for me to get mad mathematical as I delve into the world of analog filters and frequency manipulation. That will all be upcoming. So will be a post on the chassis, finished unit, some more stuff about power supplies for bi-polar circuits.