SynthFrog » AVRSynth

AVR Synth RE-re-packaged

aris — Mon, 19 Jan 2009 21:54:00 +0000

Went today to the electronics shop to get some cheap stuff for the yusynth and saw this box for 6 euros. From what you can see, I got it. It is relatively small with a panel area of 15×9cm.

So I went on to repackage my avrSynth16 I had build sometime ago.

There was a failed attempt to house the synth inside a FIRA drawer from IKEA but the design had some flaws (And it was way to big to have it around).

The first step was to make a 15×9cm layout in inkscape and make objects that were the size of the underside of the components I would use. So I could layout the knobs and switches knowing that they’ll fit. Purple were the knobs, cyan were the switches.

I made the holes with my newly aquired tools that I mentioned in earlier posts (the step drill that is) and had the panel ready for sticking the graphics.

Since the step drill went up to 12mm diameter, the midi socket hole that needed 15mm diameter, got a little help from my old (t)rusty reamer. (I always had that tool! It belonged to my father from what I vaguely remember)

The simple design is always the best. Made in inkscape. (Super drawing program, open source!)

The time of the knob transplant was stressful. A few wires came loose. (The design is not so clean from what you can see)

So it was obvious that it would end like this.. A big spaghetti bundle.

The hardest job was to fit the boards inside the box. It took a lot of careful squeezing and pulling/pushing wires inside the box. This was done while the synth was playing from a sequencer. It kinda reminded me of some brain surgeries you see on TV where the patient is placed on the bed with an open head, and the doctors have electrodes touching his brains to see what is the problem. When the synth stopped responding I stopped pushing!!

You can see that the panel has a slight bulge at the center..

And now the publicity shots!

AVRSynth board update

aris — Tue, 11 Nov 2008 07:30:00 +0000

This is a first step towards completing the board. The odd part is that one of the ICs is soldered on the bottom side. This was a clever thought Collin had as it reduces bridges to 5 total from at least 15. As I realized yesterday, I had put no values to most of the components, so tonight, an updated version of the board will be placed online with the values written.

Not all R2R resistors are in place as I ran out of them. So it might be finished tonight. The thing is that soldering resistor ladders is SOOOO BOOOOORRIIINNGGGG!! I should have used a resistor array.

Another thing I should mention is that the board can work with both AVRSyn 16 and AVRSyn 32 firmwares and processors. So I placed a female pinheader in the place of the crystal and I can test both of them before commiting to AVRSyn 32 and it’s 16MHz crystal

Hope to have updates soon….

AVRSynth 32 PCB

aris — Mon, 10 Nov 2008 10:32:00 +0000

Collin Mel and myself , have designed a PCB layout for AVRSynth, instead of doing it on perfboard. It hasn’t been proofed and debugged yet but I am on the process. If you feel adventurous and/or lucky, you can download the eagle files from here
and try yourself!. Please do tell me about possible bugs you may encounter.

I exposed the photosensitive board covered with a transparency with the PCB layout printed on. I used two transparencies, one stacked on top of the other for extra opaqueness. Still there is a little UV light going through, you may see it on the photos as the copper is a little spotty. No electrical flaws though, but I think, another layer would do a better job.
I developed the exposed board with a solution of 1 teaspoon of pipe cleaner (branded TUB.O.FLO locally) but which contains NaOH. When developed, I etched it using a 14% HCl solution (also a cleaning product) and dropped in it a small cup of concentrated Peroxide. (Named localy “Peridrol”). If interested I can delve in much more detail on the etching process. Just be ware of the fumes and liquids, so work in a well ventilated area, stay AWAY from children (you and the chemicals) and store them out of their reach. These chemicals are highly toxic and caustic and I don’t want to be held responsible for any misusage of the components.

This is how it looks while ethcing.. Beware of them bubbles. They stink and for a reason. DO NOT inhale close to them.

This is the finished PCB, without any components on it. I will post photos of the component mounting process and hope it works the first time

When this is finished, a core midibox module will take care of the midi messages that are needed to have access to the AVRSynth32 functions that are not available through it’s pots. (such as cutoff, resonance, ADSR params etc.)

AVRSynth 16 Panel

aris — Mon, 10 Nov 2008 09:24:00 +0000

The AVRSynth has officially its panel. Drilled on a 3mm aluminum sheet sized at 27×21cm (almost an A4). It was a little difficult to correctly align the holes when drilling them because the drill bit had a tendency to drift off and walk away. The result was a random offset of each hole at about 1mm (in random directions that is.).

Nevertheless, a panel I had made earlier was printed on photographic paper. To align these two, I punched small holes at the centers of the knob positions and turned it facing down (the paper) so I could see through the aluminum holes that it was all aligned (or at least there were no big offsets). I glued it with simple roll on glue and transfered the buttons and knobs from the cardboard panel they were on, to the aluminum one. Now it is a little mess underneath the panel but nevertheless everything works as planed.

I passed it’s output through MC-909 effects and it sounds wonderful. Even raw, it sounds pretty nice. I might make a demo with sounds coming out of the AVRSynth 16.

The svg file for the panel layout is here

Stay tuned for updates on the AVRSynth 32 + midibox project.

A family photo (extra members not shown

An AVRSynth 16 layout

aris — Thu, 06 Nov 2008 21:15:00 +0000

I made a layout to be printed on photopaper and be glued on an aluminum panel. I can’t process the aluminum sheet by myself so I resort to glueing photopapers allover the place. So,
this is it, it has 8 knobs, 16 switches and volume/power and it will be ready with pots on sometime in this week.

You can find the original svg (made with inkscape) at the file repository here

AVR Synth part 5 (final)

aris — Thu, 23 Oct 2008 11:44:00 +0000

The connections are simple now.

It got a little wiry but it plays alright.. The following sample is a single note (until the end where I start to improvise
The loop is made by the envelope only (decay time)

The original site of JAREK ZIEMBICKI is here
There is this other guy named krüe who modified a little the hardware (used an atmega 32 instead of atmega16 and a 16MHz osc instead of 8MHz) and added a lots of features. Source code included! here

A note. I found that the code on Jarek’s site didn’t work with my atmega16 so I got the hex file off here where they also sell ready made boards.

My sample is here

AVR Synth part 4

aris — Thu, 23 Oct 2008 11:37:00 +0000

The switch multiplexer.. lots of diodes

and cables

AVR Synth part 3

aris — Thu, 23 Oct 2008 11:35:00 +0000

midi interface (a little deviation from schematics here since I didn’t have a P900 or 4N25 optocoupler at hand and used a 6N138/9)
The (typical) power supply. 5v with 7805

AVR Synth Part 2

aris — Thu, 23 Oct 2008 11:34:00 +0000

This is the Digital to analog converter. It uses lots of 1% resistors. The schematic mentioned that for the most significant parts, 0.1% resistors should be used but I didn’t use such. It really has no effect on sound (at least for me that I didn’t expect anything special).

Again, a little attention to the schematic, can save you from a lot of bugs later…

AVR Synth Part 1

aris — Thu, 23 Oct 2008 11:30:00 +0000

I decided to make JAREK ZIEMBICKI’s AVRSYN. But there were only the schematics and no board layout so I had to make my own. So I started laying it out on eagle but I got on a deadlock due to the fact that I didn’t want to make a double sided board. I would etch it myself and double sided boards are a BIG pain in the but (vias and such, alignment etc). So I made it on a perfboard. But before that, I decided that it should be made into discrete modules. One for the microchip, one for the D2A (an R2R resistor ladder type) , one for the midi interface, one for the power supply and one for the switch multiplexer.

Here is the main part. I put pin headers to wherever it would connect to another module and got myself a lot of ribbon cable. The AVR is a really simple design. Only the layout makes it complicated. It can be made by anyone (Even I made one!!!).