Synovatron’s A-100 Modular in a Halford Tool Case

A Doepfer A-100 modular synth fashioned in a customized Halfords Engineers Tool Case. Awesome work by Synovatron.
Synovatron's A100 in Halford Tool Case

Tone’s Analog Synthesizer Projects and Products: Modular in a tool case.

DroneGoat: The BRAINRING!

DroneGoat is a tasty little blogspot blog covering analog synthesis and some DIY projects (among other things). There’s lots of great stuff here but I found this to be particularly awesome. An analog ring modulator built into a Brain water bottle.  Reminds me of my Alpo-Can ring modulator except this appears to process inputs and not simply modulate internally generated square waves.

DroneGoat: The BRAINRING!.

DroneGoat Brain Ring Modulator

MIDI Ironing Board

The title says it all. This is way past old news but it’s still a gem. This photo comes by way of Flickr but it was taken at the first (as in 2007) “handmade music” event at Etsy Labs in Brooklyn NY, sponsored by, MAKE Magazine, and Create Digital Music.

ASMO – the Tweakarium

Stu Smith under the project heading ASMO has built this beautiful hand-made custom MAX MSP controller for Chris Cousin.  Click the image to see the entire Flickr set.  From the ASMO blog:

He works with self made instruments custom built from the modified circuits of electronic toys, keyboards and other discarded gadgets. His work explores the sonic landscape of ‘circuit bent’ instruments and their integration into existing modular synthesizer systems. He writes and performs with the groups Threep and The Buoys and has performed at concerts and festivals across the UK, Europe and New York.

You can see more of ASMO’s work here:

Audio Test & Development Box

I frequently work on projects in the living room in front of the TV while sitting on the couch soldering away hunched over a disarray of wires, parts, wires, speakers, cords, breadboards, and tools. Whenever I want to work from the couch I have to go into the studio and make 15 trips up and down the stairs, cables, toolbox, parts boxes, soldering iron, etc. It’s always a major hassle. Then, when I’ve finally completed mocking something up on the breadboard and I want to test it I need speakers, headphones, a sound source and I have to connect it all with alligator clips. It’s really inefficient and makes me less apt to start a project because all I can think about is the huge mess it’s going to make.

So I decided to put everything I need into one self contained box; an audio test and development box. Below is a description of the parts and procedure I used to put it together. If you’re in a similar situation hopefully this will give you some inspiration to come up with a solution that works for you.

If you want to see all the project photos in high resolution you can find them on Flickr here: Audio Test Box Images

Initially I needed to build a box. I looked through all my scrap wood and it was all ¾” plywood which would be way to heavy. The smaller pieces were odd shaped and unusable. I looked at everything from cookie tins to shoeboxes and didn’t like anything I was coming up with. I checked Wal-Mart for something I could get cheap and hack into what I needed but I didn’t find anything there. Then I went to Hobby Lobby because I remembered they had some project boxes for putting flower displays in. After looking through the whole store though I found the perfect box. It’s a miniature “child’s desk” with a top that lifts up. It was exactly what I was looking for, I just didn’t know it. Best of all, it was only $15. You can find them here: Wooden Child’s Lap Desk

What I wanted was a box which had a variable DC power supply, an AC jack, an amplifier, speakers, an audio source, an AC outlet for the soldering iron, a place to put some tools or parts, a quick way to hook up audio ins/outs and DC voltage, and room for multiple breadboards.

Most of it I was able to find around the house. Here are the guts from a pair of old busted up (but functional) computer speakers. These had been lying around for years. But even if I didn’t have them I see them all the time at Goodwill for a couple of bucks. It was a bit of a pain to crack these open. Most of them are manufactured so you can’t service them so you have to break the seal on the plastic to get to the guts. I just used a screwdriver and pried the crap out of it until it snapped. Dirty but easy.

The DC power supply I used was one I had purchased a couple of years ago for a project. It’s a Meanwell Switching Power Supply that I picked up at Fry’s. Fry’s is one of the last few national stores that still carry electronic components. It’s convenient if you need something right away… just hop in the car and get what you need… but be prepared to pay a premium. Anyway, this is the power supply:   Meanwell Switching DC power Supply I’ve used this power supply dozens of times and it’s great. AC in, DC V+ and V- out with a neutral earth ground. The voltage is adjustable from 10 to 15V DC which covers just about anything I’ll ever do.

Skipping ahead, I started drilling and cutting openings for the parts. Depending on what you’re using for parts and a box you might have to do something different but this worked well for what I was doing. The two speakers in the bac and the AC cord jack on the front right corner so I could comfortably plug it in. I used two tools to cut the holes. The circles were cut with a Dremel tool and the rectangular hole I used a chisel. The wood on this Hobby Lobby box was really soft so chiseling out a hole only took about 10 minutes. One word on chisels… never use them for anything other than wood, store them safely, and keep them oiled. Nothing worse than a fucked up chisel.

The speakers fit perfectly in the back corners of the box. I really couldn’t have built something better than what I bought at Hobby Lobby. And like I said, the wood was really soft so I was able to screw in the speakers directly into the wood using the screws used in the original plastic enclosure. This was much easier than sifting through bins of spare parts finding something to fit. Screwing in the AC jack was equally simple.

Next I installed the amplifier section of the computer speakers. I wanted to use the original DC power supply that came with the speakers so I wasn’t running it off of the supply I’d be using for a project. I simply screwed in the transformer directly into the wood. Now, this probably isn’t the safest way to go about this. The wires are exposed, and there’s no heat sink so do this at your own risk. Next I needed to attach the amplifier to the box. I didn’t have any standoffs that were the right size and the mounting holes were in awkward positions. I decided to make my own brackets. I frequently make brackets for projects using ½” brass strips. You can find these at pretty much any art supply store or train/model hobby store. They’re cheap, really strong, easy to bend, and easy to cut with a Dremel. A couple cuts, bends, and holes drilled and I was set up. I used mounting screws and nuts to adjust the height and stabilize the front of the circuit board

So when soldering it’s important to keep a wet sponge near by to occasionally wipe the tip. I made my own little portable holder that I’ve used for years now. I love Pillsbury’s Flaky Supreme cinnamon buns. When you’re done baking them you slather on that super sugary frosting and they’re delicious. I keep the plastic containers that the frosting comes in and wash it out, cut two plain old sponges in circles and plop them in the plastic container. Add water. It’s just the right size and stays wet for a day or so. Only problem is that it slips and slides all over the place which can be a hassle.

So, to keep the sponge from sliding all over the place and keep it at arms length I chiseled out a circular depression in the top of the box which the plastic container can rest in. Again, the wood is soft on these boxes so it didn’t take long at all. Just took a little patience so that I didn’t slip and chisel out a huge piece of wood.

Next I wanted a built in outlet for my soldering iron so I didn’t need to keep an extra power strip handy just to use one outlet. I went to home depot and bought a wall jack with only one outlet. In this instance I bought a safety outlet. I figured since I’m mounting the outlet directly to wood, with no switch, or fuse the least I could do is get a safety outlet. I’d suggest putting in a power switch and fuse if you try this. Chiseling out this hole took a bit longer and the wood needed to be notched out so the outlet would sit correctly. Also, because of limited space on the side panel I had to trim off the ends of the mounting brackets (not shown in this picture). The Dremel saves the day again.

Skipping ahead, here’s the AC wired up. I stripped out the heavy gauge wire from an old busted power strip and trimmed it to size. I added some heat shrink tube for color coding. The wires on the end of the AC input jack needed to be soldered but on the other ends I crimped on some spade tongues so I could connect/disconnect the wires quickly and easily if needed. I did this for all the AC lines. The wiring is pretty simple. White and black or the power inputs and the center is ground. I go from the input to the outlet to the power supply. Not visible in this picture is the AC power going to the amplifier in a similar fashion.

I had to drill a number of holes on the lid of the box so I could mount binding posts, switches, and jacks. Because the wood was ½” thick I needed a small hole on one side and a large hole on the other to fit the body of the component. Drilling the small hole is easy. Just choose the size that matches the width of the threaded mount on the component. To make a larger hole that sinks in to the correct depth I use an old trick. Measure the depth you need up the drill bit from the tip and then wrap a bunch of masking tape around the drill. Now drill your larger hole over the smaller hole and only go as deep as the tape. I tend to add a lot of tape so in case I push to hard the tape actually stops the drill so I don’t go all the way through the wood and ruin the hole.

Here I mounted three binding posts across the top of the box for DC power. I simply drill holes and screwed the plastic posts into the holes. The wood is soft so they took really well. I did have to tweak the size a bit with a round wood file but that was minimal. Because you can’t get in under the top of the box it’s necessary to solder the connection wire to the bottom of the binding post before you screw it in. I made sure to use heat shrink given the proximity to the DC & AC power wires.

Here are all the binding posts jacks, and switches installed followed by an image of the underside of the lid. All jacks were wrapped in heat shrink tubing. I tidied up the wire using staples from a staple gun. Instead of using the staple gun though I gently pushed the staples in with needle nose pliers so as not to knick the wires. After I had put this all together and tested it I was having a hell of a time getting the audio out to work right. The wiring wasn’t at all complicated so I had no idea what was wrong. I should have known though… one of my switches I bought at Radio Shack. So besides being completely ripped off by having to pay $3.99 for a $0.20 switch, I also got totally hosed because their parts are worthless shit.

These last two are the finished box (for now). You can clearly see I can fit around four or five breadboards vertically on the top of the lid if need be and all my ins and outs are in easy reach. The lid opens up and provides enough extra space to keep the AC power cable, a soldering iron, the sponges, some solder, needle nose, a pencil, or whatever. On the second picture if you look inside you’ll see a little RCA .mp3 player. I bought this at Wal-Mart for 30 bucks. It’s 2GB mp3 player/flash drive that runs on 1AAA battery. What I’ve done is load up 25 clips of various types of instruments or sounds. Guitars, vocals, drums, bass, synths, full songs, etc. This way when I’m testing an audio circuit I’m working on I can listen to how instrumentation actually sounds running through it. And when I’m done I can grab it and go. I used to have an iPod and lost it… which I was OK with because iTunes irritated the crap out of me. This thing was super cheap, has plenty of storage for what I need, and all you need to do to add .mp3s is drag and drop.

And last but not least, here’s a poorly drawn diagram of the entire operation. I’ve set it up so that either an internal or external audio source can feed the development circuit via the internal .mp3 player or an auxiliary stereo ¼” jack. Just connect the input binding posts to the circuit you’re working on (left, right, gnd). If your not working on a stereo set up I’ve added a mono/stereo switch which merges left and right and sends it to the ‘left’ binding post. Second you can easily hear the impact your circuit has on audio I’ve added a bypass switch so you can toggle between your circuit and direct audio out. Third, when the audio exits your development circuit it feeds into the binding posts on the right which subsequently feed the internal amplifier and speakers. Should you prefer to send the signal out to an external amp (or whatever) you can do so via a second stereo ¼” output jack. If the signal from your development circuit is mono, there is a stereo mono switch that sends the mono signal (connected at the L binding post) and feeds it to both the L & R inputs of the internal amplifier. I’ve tried to draw it out so it makes more sense than I’ve written it here. Of course, if you have questions just leave a comment or email me.

Click for Hi Res

16 Step Sequncer & Synth: An Update

This is a follow up to my original post on the 16 step sequencer/synth that I posted several months ago. It’s taken some time to get moving on this but I finally ordered up 32 pots to test my design and make sure everything was working. The overall concept is to have a 16 step sequencer where each step allows you the flexibility to adjust the VCO, LFO, envelope, noise generator, and filter on each step. The sequencer will allow you to switch, for example, the VCO from individual control on each step to a global setting. This would hold true for all parameters. The sequencer will step forwards, backwards, and allow you to select how many steps to make (1-16). Each step will have an optional output that bypasses the main output when used. Finally, the sequencer section will have a speed or rate control. I’m still debating if I want to figure out how to make this sync to a midi clock or display a BPM reading. When it’s all finished it will have over 80 dials, 50 switches, and plenty of flashing LEDs for those late evening explorations. Video to follow soon…

Also, I’m getting to the point now where I need to consider what type of enclosure all this will go into. I’m looking for carpenters, machinists, and artists to talk about unique ideas and options. If you interested shoot me an email.

Synth - Sequencer

Here we have 32 pots temporarily wired up on a piece of cardboard. This was the cheapest and most reasonable way to wire up the amount of pots for just a test circuit. I do this frequently when I need a quick mock up for controls. These are 1M linear taper pots and they’re all wired with a common ground and then each one is individually wired to a multiplexer input. I should be able to just take these out of the cardboard and drop them into the finished control panel when it’s completed.

Synth - Sequencer

This is full shot of the prototype prior to some sequencing enhancements. You can clearly see the leads from the pots coming into the 4067 multiplexer. It’s only necessary to run one set of 16 leads to the multiplexer, each additional row of pots can be wired to the previous with only the addition of one unique lead to the control input of the sn76477. A 555 timer is wired as an astable multivibrator for the clock and is sufficiently stable for my purposes. Although difficult to see in the image the sn76477 has a regulated 5V DC output to drive your logic ICs regardless of what your power supply voltage is. The group of black leads with green shrink wrap brings over the 4 bit binary count to the second multiplexer. In this image the binary counter is a 4520B dual binary counter. The original plan was to utilize both counters and a comparator to set the sequence length from 1 to 16 steps. The three switches at the top of the rightmost breadboard are for selecting the mix channels of the sn76477. through a combination of these switches you can include a VCO, LFO, decay, noise generator, and filter as well as bypass the sound completely. Like the pots these will be added for every step in the sequence for tailored sounds on every step of the sequence.

Synth - Sequencer

In this photo you can see some changes have been made. I swapped out the 4520B dual binary counter for two SN74LS193N pre-settable up/down 4 bit binary counters. The output of one counter is wired to the multiplexers and controls the sequence and then flows into the 4063B 4 bit comparator. The second counter is manually stepped manually with a push button switch and also feeds the comparator. Count A > count B a high signal is sent to the master reset of the sequencer counter and the sequence starts over at the beginning (0). The two switches off the side of the leftmost breadboard are required to allow for running the sequence in reverse. They serve two functions 1) to switch both counters from up to down counting and 2) to send a preset to the sequence counter on reset. Normally the counters reset to 0, but when going in reverse you want it to reset to 15 otherwise your sequence gets stuck on 0 indefinitely (due to the comparator condition always being met). Make sense?

Synth - Sequencer

This is just a close up of the hectic wiring going on. I only have yellow and white wire so it makes for a confusing time tracking down and correcting problems. In the left-middle you can see the 555 timer obscured by a couple yellow wires. Currently the frequency of the clock is variable with a duty cycle of 50%. One of the next steps is to include another timer so I can retain adjustable frequency and adjust the duty cycle to something much higher like 90%. This won’t impact the sound but it will make the LEDs flow from step to step smoothly… a totally superficial enhancement. On the lower right is a 3 input multiplexer to handle sending the reset number to the sequencer clock when running in count down mode. Another next step is to add an analog switch to replace my two toggles to switch from count up to count down mode.

Hot Fuzz

Previously I’ve posted on a fuzz box that I made for Paul Digs. Recently Jamie Roberts asked me to build him a custom remake of the old Electroharmonix/Sovtek Bigg Muff fuzz pedals. I was speaking with Paul and the fuzz I made for him didn’t really suit his needs so I decided to design and build two fuzz pedals. Starting with any number of the dozens of Big Muff Schematics available on line I tested the circuit and made a couple small modifications… asymmetrical clipping. I used Eagle Cad to draw up the schematic and generate the gerbers and then sent out the custom boards for manufacturing through Batch PCB. They have an exceptional service and are extremely easy to deal with. I highly recommend them.


That was essentially the most difficult part. Upon receiving the boards back I mocked up the enclosure layout, drilled my holes and then sent out the enclosures for chrome plating. This was expensive, $80+ per enclosure, which was more than half of the entire cost of each pedal but it was worth every penny. They came out stunning. Exceptional knobs, custom silk screening, and pots with 11 detents. Up to 11! Having finished I would only have changed two things. I would have included a power on LED and included a 9v battery clip instead of just a DC power supply. Nearly all parts were sourced from mouser. The only exceptions were the footswitch, jacks, enclosure, and knobs.


Unfortunately I don’t have sound samples but these things squeal and pump out some serious gain. But, as with anything analog with that much gain you get a significant amount of noise. Not really a problem when you’re playing… just when you stop.


You can see the detailed photo set here on Flickr.

AD633 Ring Modulator

This is a Ring Modulator or similar sounding effect box based around the AD633 (Analog Devices Four Quadrant Analog Multiplier). The original design is taken from Roman Sowa. His website has further details on his design and the schematic I used as a starting point. The above photo shows the finished version albeit without knobs. This is mostly because I, despite better judgment, bought pots from Radio Shack, and didn’t want to waste them. As you can see the shafts are just a bit long. No matter; they work.

I made a few modifications. The first was to remove the option to select AC/DC coupling. I felt that I had no need for DC coupling so I hard wired it up AC coupled. Secondly I added some gain on the clean channel. The clean signal was coming through a little light which I personally didn’t like. Lastly, I added a LED meter on the output volume which you can see in this picture. Using a LB1403N I made a level meter which increases as you turn the volume up. This doesn’t actually monitor signal level but the position of the pot. There’s no real purpose other than I like blinking, flashing, pulsating and adjustable lights on all my gear. Who doesn’t? It’s wired through a dual ganged pot with a trim pot to adjust sensitivity. The detailed photos can be seen at the full Flickr photo set.

From a distance the paint job looks OK but as you can see in the first photo there’s definite room for improvement. Wet sanding, Clear Coat, and Polish would definitely help but it’s not a bad first run. The fluorescent paint however had a tendency to get ‘powerdery’ and presented some problems. Check the sound samples below to hear what it sounds like.

Many more photos and comments on the build can be found on Flickr here:
AD633 Ring Modulator

Sound Samples:
Before & After Number 1
Before & After Number 2
Before & After Number 3
Before & After Number 4

DJ Paul Digs Fuzz


This is my second design from scratch that I put together for DJ Paul Diggs. He mentioned to me he wanted to add some fuzz to his Fender Rhodes and this seemed like a great chance to take a stab at an original design. Well, almost original. The distortion circuit is a portion of a larger circuit which I found on the web but unfortunately did not document. The remainder however, the sweepable low pass filter and second tone control I added in myself. Overall this is a pretty versatile sounding fuzz box with a pretty wide range of tones. It utilizes diode clipping so it still can be a little harsh although with the filter and clean/dirty mix you it can be tweaked for a nice sound. This is hopefully only the first version, I’ll be working with Paul to refine the tone and the layout to hopefully make this a perfect compliment to his Rhodes and bring about the sounds of classic rock years gone by like those from Joe Zawinul and the likes of Weather Report… though that’s just my taste, I’d bet it will end up a bit different.

This time I actually took notes and threw together a schematic. I’m hardly an engineer and my understanding of analog circuits is elementary so I welcome suggestions and criticisms from anyone familiar with these types of things. As with the other projects you can see detailed photos on the build at Flickr.

More photos, comments, and the schematic can be found on Flickr here:

Paul’s Fuzz

Sound Samples:

Unfortunately I neglected to sample this box before popping it in the mail. Version II will definitely have samples. That will be better anyway.  Incedentally I’ve repalced this fuzz with a better one.. the Big Muff Mod.