MATRIXSYNTH: Upgrades To Pete McBennett's DIY Synth

Wednesday, December 02, 2020

Upgrades To Pete McBennett's DIY Synth

Pete McBennett

"Hi everyone, here is a demo of the new features of my code and filter. My Arduino code now has a low bass range that is toggled with what used to be the high F key. (See time stamp 0:07 and 0:32) I found it convenient to use that key for switching up and down. I have also added a sustain toggle switch which holds the current note until the next key is pressed. (See time stamp 0:15 and 0:44) Very useful. The sustain switch uses pin A7 on a Nano.

Here is the new schematic with the added sustain switch:

Here is the new code with octave toggle and sustain switch:

I also modified my filter slightly to add a switch for manual control of the filter sweep. (See time stamp 0:59) Sorta like my old LDR synths but controlled with the cutoff frequency knob. And in the process of experimenting, I discovered that Q2 is not necessary. The LM358 buffer stage has plenty of capability to drive the LED's directly, Q2 was a leftover from an early design. This is an easy mod for those who may have already built the filter. Oh yeah, this filter does not have a built in auto trigger like the other one, but any square wave LFO will work if fed into the trigger input.

Here is the schematic for the modified filter:"

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