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For my electrical engineering senior design project, I decided on designing a analog music synthesizer with MIDI control. I have to admit, this was what I wanted to do since high school and was my ultimate goal as a musician, artist, DIY person, and engineer. This project, in the end, will combine all of my knowledge into one nice little package that I get to show off to friends, family, and faculty and is to be completed by the end of this year.

The first image is the Alesis Q25 MIDI keyboard I purchased to test with.

The second, third, and fourth images are of one of the initial synth implementations.

The initial design features two voltage-controlled pulse oscillators (VCOs) scaled at one volt per octave. MIDI control is done with a PIC microcontroller that receives data and outputs it to a digital to analog converter (DAC). The voltage from the DAC is used as a control voltage (CV) for the oscillators. Velocity has not been implemented in this version and the last note played is always heard at output.

The fifth image is our current revision. It features the addition of a voltage-controlled amplifier (VCA). With this version, we now have a MIDI-controlled monophonic synthesizer. It is not in the video.

I'll add another video of the most recent revision as soon as I get back into the lab.

Tuning is an issue in the upper octaves, as demonstrated in the video, but will be fixed soon. The video demonstrates the operation of the one volt per octave scaling and MIDI control with the keyboard. Please post any comments about my project or ideas of what should be added in future revisions. Thanks! :D

Update (8.25.2015)

Sorry everyone, I never got around to documenting

<p>Hey. I know this instructable was a while ago... I'm a high school student building analog synths. I'm really interested in your midi to cv converter. I know you said it was a PIC chip, but may I ask what the chip was specifically?</p>
It has been a long time since I've worked on the project. I never got around to properly documenting the information so I can't tell you the exact chip at the moment.<br> <br> The code I ran was very simple. The PIC microcontroller only checked for &quot;note on&quot; and &quot;note off&quot; messages and stored the information in memory and then output the current note to a DAC and was then scaled as necessary via an amplifier.<br> <br> My suggestion if you're new would be to stick to an easy to program microcontroller with enough outputs, as needed, and a &quot;universal asynchronous receiver/transmitter&quot;. Read up on the MIDI specification. Some of the interfacing can be found here:&nbsp;<a href="http://www.midi.org/techspecs/electrispec.php" rel="nofollow">http://www.midi.org/techspecs/electrispec.php</a>
Hey. How this project is going ? <br> <br>can you give us an update ?
It's coming along. I might be able to get another video, but the sounds coming from the synth won't be what they're supposed to be. I sort of killed some of my integrated circuits... I'll have to buy new ones. :[

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Bio: Hi! I'm a bachelor of science in electrical engineering trying to get by. Music and audio are my main interests, but just about anything ... More »
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