Monday, June 30, 2014

MIDI2VC, finished basic functionality

I've now added support for Pitch Bend to the MIDI2VC, which means the project is basically finished. The updated project is here.
 A demo video, with pitch bend, is below:
I thought about experimenting with the sleep mode of the PIC, to see if I can get the circuit a bit more efficient (probably not, since there is a linear regular on it...) My thought was that the PIC could go into sleep mode when it's waiting for an UART character. Seems though, that this function needs to receive a 0x0000 word to get out of sleep mode, and since I don't control the MIDI-device attached, I probably can't get that. Maybe there's a work around, we'll see....
Otherwise, it's time to start working on the MIDI2VC+.

Thursday, June 12, 2014

Synthesizer chopping sound

The chopping sound in the release phase I wrote about in the last post was actually from the DAC going to the lowest key. I coded this a while ago when I wanted to play without having an attack and release envelope. Now this is messing upp the release phase, so I removed the feature to let the DAC voltage level stay on the last played note. Sounds nice!

Tuesday, June 10, 2014

Actual synth sound + Attack and Release

Attack and Release

The last module for my simple synthesizer was an attack and release envelope generator to be driven by the gate out port of the MIDI2VC and connected to the VCA. I saw some designs that I thought where to complicated for now, so I made up my own very simple circuit:
Simple attack and release envelope generator
It's based on a comparator that source or drain current to C1. Right now it's half working. On the release I get an oscillation that sounds like a low frequency humping. Possibly this is caused by the emitter follower on the output. I'll look into it soon. I may also increase C1 to get a longer envelope.

Actual synth sound

So, this is what the synth looks like right now:
Messy analogue synthesizer

And this is what it sounds like:

Now I want to build some better synthesizer modules :)