Category Archives: Green Synthesizer

Synthesizer Power Supply

Been a while since my last post; been busy stressing myself over school and trying to actually relax a little with my Winter break. Fall 2010 went well in the end; I was quite worried about two of my classes going into the last few weeks, but I pulled everything around and somehow made a decent finish with three B’s and an A. X-Mas was good, even managed to get a Wii! Of course, I spent the last few days working on getting it soft-modded (fairly easy process at this point in the maturity of the product; relies on some crappy programming in a Lego Indiana Jones game that someone managed to exploit with a modified save file). I slapped together a 2.5″ SATA HDD and an external enclosure that runs it off of USB power, and now I have all the games I want! Thank you, Internets! Now Kim and I just need to find people to come over and play with us! >.<

THE FOLLOWING PICTURES WERE TAKEN WITHOUT ANY CARE AS TO QUALITY! :P


As I mentioned a few months ago, I built a simple power supply into my synthesizer. I also finished putting in all the components on the front panel, which looks nice and spiffy; the rectangles of leftover acrylic that I glued to the edges to hold the panel to the case are still rather hackish (and always will be, because I didn’t give that mechanism any thought when I designed this thing!), but overall, I still think it came out just as well as I had intended it to over 4 years ago. Here is the overview of the internals of the power supply, which was pretty much ripped straight from the MFOS Adjustable 1.5A Bipolar Power Supply, but still required a good bit of my engineering construction know-how:

The placement of the components had to be very carefully scoped out in order to prevent any possible problems with interaction with the electronics above (both physical and electromagnetic) – while this overall project is pretty much mid-fi, I have been trying to spend at least a bit of my time on paying attention to hi-fi aspects like noise reduction and high-quality components. Of course, most of the wiring shown here is done with scraps that I needed an excuse to get rid of anyway, hence all the splicing (although even a lot of that is equally due to needing to move the transformers around after having put what I thought to be “just enough” wire length to keep things neat):

The larger transformer (which is pretty much the only product I actually WANT to buy from Radio Shack) is what is driving the regulator circuitry. I realized that a fan would be nice to have to cool those heatsinks, but discovered that the fan was making a mess of my power rails (even after putting in a huge bypass capacitor), so I took apart a wall-wart and ran it in parallel with the main power transformer to power the fan by itself (I know it is overkill, but it works and people pretty much give these things away!). I made the heatsinks with a good bit of hacksaw work on an old winged heatsink I had in my collection of dumpster-diving goodies from back in High School:

My oscilloscope shows this to be a very clean supply with excellent regulation; I did quite a bit of experimentation to make sure of this because, well, I could. It was fun! :D
On the outside of the case, I had a little geometry fun and hand-drilled about a hundred holes in a pattern for the fan intake:

It is a little noisy (acoustically-speaking, while using the machine), so I think I’m actually going to build a small regulator for the fan and place some thermistors to sense the temperature of the heatsinks and only turn on the fan when they actually need it on. However, it might be better to simply put in a lower-voltage wall-wart supply – the airflow is also good for the rest of the electronics inside.

Panel Layout

After spending a few hours with Gimp, off and on, I have finished laying out the front panel. From afar, it looks kind of cobbled together and asymmetric, but I can live with that; after all, this was all afterthought, since I had originally planned and started drilling the panel two years ago with something more minimal in mind. It was only after I finished laying out the modules and drilling recently that I decided to do something a little more with the front panel design:

I have finals starting next week, and a week’s break before I start a “third semester” course. I’ll use that break to do the rest of this work, because I have a lot of studying and preparing to do for my final exams. Sigh.

On a side note, I do not like Inkscape. The interface is bad, and trying to set it up to work as a one-to-one representation of what I planned to print out failed after multiple attempts at changing various settings. In the end, Gimp did not limit my abilities to do all of this; the only things I wished I could do in Gimp (that I couldn’t do) were: (1) change the ruler guide’s inch divisions (1/10 only? wtf!), and (2) group and hide sets of layers (would have made finding and moving individual items faster).

Panel Progress

I hate wasting time, effort and money, but that doesn’t stop me from doing so. I finished laying out, drilling, sanding, and polishing the rest of the front panel for the synthesizer. I also started labeling it by using Gimp to write out and reverse my text on an overlay for some “clear” (eh, close enough for what I’m doing, but they really should call them “matte”) Avery shipping labels that I bought on a whim. Overall, it was not an easy task, particularly when it came to cutting out and sticking the labels to the back of the panel; the results aren’t that great, but still better than anything that I’ve made before. :P

Unfortunately, I’m seriously contemplating redoing it a different way. I have already traced the holes onto some paper backing and scanned them into the computer; from here, I’m going to get some full-page “clear” printer labels and do pretty much the same thing as before, but to whole groups of component holes that correspond to each individual module. I feel that this tactic will produce the best results, especially considering how crooked a lot of the labels I have on there are right now.

As soon as I have this part of the whole project complete, I am going to get going with the soldering; I’m still waiting for an order on some specialty components that I need for the Delay and the Sample and Hold modules.

On a side note, for some reason I’m already thinking of what I’m going to work on when I’m done with this project; I’m going to get started on a true modular synthesizer cabinet! The acrylic panels that I got from US Plastic turned out to have an unmentioned blade tolerance of 3/16″, making them pretty much unsuitable for building a new case that would have a chance of being better than the one I already have for this synth. Fortunately, I can still use them to build rack-mounted modules for a true modular system (in so far as I know at this point, that is). ;D

I can always order proper material to rebuild the case once I have some money later in my life.

Synthesizer Update

I decided that it was time to expand the synth; I’m going to add the following modules, albeit in non-standard pieces and configurations: MFOS Multifunction Module, Dual VCA, and Noise Module (I will be making these by hand on perfboard to save some cash on PCBs from MFOS, however). There will probably be others, to be decided sometime in the near future.

Now, to do all of this, I needed to remove all of the hardware from the front panel, as well as all of the foil tape that had been there for about two years now. It took a full night of careful scraping (not careful enough, unfortunately) and scrubbing with various chemicals (Goo Gone is just about as effective as WD-40, by the way; it just happens to smell much better). Now that I was the proud new owner of a very heavily scratched panel, I hit it up with some 220-grit sandpaper, then wet-sanded with 1000-grit and 2000-grit sandpaper, and finished it all off with some toothpaste to give it anmockup almost-polished clarity. In the end, I’m surprised with the results (I was considering ordering some specialized acrylic polishing compound online, but now I think I’ll just stick with toothpaste); here is a close-up with a mockup of how I intend to do the labels:

I will be printing the labels from the computer and cutting them out with a bit more uniformity, as well as being more careful with the foil tape, but that’s the essential idea of how I have been planning to do this all along.
As far as the expansion goes, I’ve got a 1:1 scale layout going on some grid paper that I printed up from here. I hope to use it as a drilling guide, as well, because I’ve now noticed that my original drilled holes do not seem to be all that well lined up; I think that I can do better for the expanded sections:

Something that I’ve decided to be improvised once I have everything ready and mounted back on the panel is how I will be sticking the circuit boards to the front panel. Previously, I had used some metal clips made from an old heatsink and JB-Welded to the foil tape to mount them perpendicular to the panel wherever I could get them to fit in free spaces. It performed horribly and fell apart after a bit of jostling. After some rather ignorant searching for what turned out to be called “mounting brackets”, and discovering that the only place I could find them as small as I needed was from Mouser (from whom I had just received some new solder), I decided to just make them out of something similar. After a bit of searching, I finally found some hardware called “one hole midget straps” (humorously suggestive, no?) at Lowes, for which I just need to straighten out one end and drill a hole through it. I only need about 20 of them, so that’s just an hour or so of work to keep from paying $8.00 shipping from Mouser for $2 worth of product.

On the electrical front, I have not made much progress; I started working on soldering together the sequencer circuitry, but ran into a lack of solder that was remedied with a one-pound spool from Mouser. Seems to be a decent product, and I look forward to using it more in the future.

I have also decided to rebuild the case (other than the front panel) from some new stock acrylic, because the current build is not only the wrong size for the front panel (I cut the pieces and put them together rather hastily), but it is cracked and broken in several places. It just plain looks bad, to be honest. Unfortunately, the pieces I got from US Plastic seem to have been cut to the wrong dimensions; I sent them an email and hope to get a response (and maybe some new boards sent out) on Monday.

Spring Break 2010 – Synthesizer Work!

This past week was my Spring Break – classes are going reasonably well, and I’m really enjoying my Electronics I course; it has rejuvenated my desire to work on my modular synthesizer! So much so, in fact, that I furiously worked on the project which I hadn’t touched for about 2 years (and hadn’t touched for about a year prior to that, either!), and have made a large amount of progress. My Modular Synthesizer is really only semi-modular, in that it it built into a (1′H)x(2′W)x(4″D) rectangular case that I built from 1/8″ thick, florescent green acrylic that I bought from US Plastic about three years ago. I lined the back of the front panel with foil tape to help contrast the plugs and jacks from the innards; being able to see the insides is kind of distracting, as I found out when I first mocked up some pieces of equipment several years ago (plus, it provides a convenient grounding plane).

I chose my first modules and purchased some ready-made PCBs from Ray Wilson about three years ago: a VC-LFO, a VCO, a VCF, and a State-Variable VCF (which he sent to me for free because he somehow lost track of my order and didn’t send it for over a month). I started populating one of the boards back then, but then school got in my way, and I pretty much hadn’t touched them until this past Monday.

This past week, I finished all four modules and have them mounted to the front panel and working! Here is a view of the front panel, upside down and displaying all of its delicious insides:

At this point, I need to get access to an oscilloscope so that I can calibrate the waveforms and get an idea of what voltage ranges I am working with and how steady they are across frequency ranges. I also have to get to work on the sequencer (which all of the components on the right side of the above picture are for), which I have built (for the most part) on a breadboard. I have already started soldering it on a protoboard. I also just remembered that this still exists! I think I made that page during my Junior year of High School.

In other news, I’ve got only about 2 feet of solder left in the one-pound spool that I bought almost 10 years ago; I probably used ~1/4 of the thing over the past week. >.<