MATRIXSYNTH: New ElectroTechnique TSynth - DIY Teensy Synth

Thursday, June 11, 2020

New ElectroTechnique TSynth - DIY Teensy Synth


ElectroTechnique

Note this is the first post to feature ElectroTechnique.

"TSynth is a DIY synth based on the Teensy 3.6 MCU board. It is six voice polyphonic with two oscillators and very comprehensive control and options. Patch saving and recall, three MIDI in options and USB digital audio. It is open source and the PCB and front panel are now available to buy on Tindie. The intention was that the cost of parts to build this synth are around $99 and it should be a serious instrument. There are many features and full details are on https://electrotechnique.cc

All sounds are directly from TSynth with built-in stereo chorus - Youtube tends to muffle the sound, the bass will go very low. I'm hoping that end users will produce better demos and contribute to the code."


Specs via ElectroTechnique:

Oscillators

Six voice polyphony (last note priority), two oscillators per voice, detunable with +/- 2 octaves range, Sine/ Sample & Hold (like tuned noise)/ Square/ Sawtooth/ Ramp/ PWM/ Var Triangle/ User waveforms and level
Pulse Width/ Var Triangle can be set for each oscillator with PWM by dedicated LFO or from the filter envelope
Pink or white noise level
Dedicated LFO for pitch mod (can be retriggered by note on), Sine/ Triangle/ Sawtooth/ Ramp/ Square/ S&H waveforms
Pitch can be modulated by filter envelope (+/-)
XOR ‘Ring Mod’ (creates lots of harmonics with certain waveforms)
Unison with all twelve oscillators detunable from each other
Polyphonic Glide with variable time

Filter
State variable 12dB filter (SVF) with continuous mix between LP and HP (provides notch filter) and BP
Cutoff freq and resonance

Cutoff can be modulated by dedicated ADSR envelope (+/-), dedicated LFO
LFO has same waveforms as pitch LFO (can be retriggered by note on) and rate can be set to match MIDI clock (tempo) with variable time division (1,3/4,1/2,1/4,1/8…)

Amplifier
Dedicated ADSR envelope
Volume for DAC output
Effect amount and mix - currently for stereo ensemble chorus rate and mix but could be set up to allow choices in programmer

Programmer
160x80 IPS colour display
Encoder with button for data entry, Back button for menu navigation
Save and Recall buttons for storing patches, holding Recall initialises the current patch to match the panel controls. Holding the Save button takes you into a patch deletion page.
The programmer makes the synth very flexible with future possibilities for changing User waveforms, alternative filters, alternative effects with further parameter settings.


MIDI
USB HOST MIDI Class Compliant (direct connection to MIDI controller, no PC needed)
USB Client MIDI In from PC
MIDI In 5 pin DIN

Audio
SGTL5000 Audio Shield 16 bit, 44.1 kHz Stereo out
USB Audio in/out—appears as 16 bit, 44.1 kHz audio interface on PC

Hardware
Teensy 3.6 with SGTL5000 Audio Shield. Two 4067 multiplexers providing 32 channels from the pots into two ADCs. The rest of the pots and switches use remaining pins on Teensy
Enclosure is laser cut acrylic with PCB-base front panel and 3D printed end cheeks

USE
TSynth patch saving and recall works like an analogue polysynth from the late 70s (Prophet 5). When you recall a patch, all the front panel controls will be different values from those saved in the patch. Moving them will cause a jump to the current value.

Back button cancels current mode such as save, recall, delete and rename patches. Holding this for 1s is ‘Panic’, all notes off.

Recall shows list of patches. Use encoder to move through list. Enter button on encoder chooses highlighted patch or press Recall again. Recall also recalls the current patch settings if the panel controls have been altered.

Save will save the current settings to a new patch at the end of the list or you can use the encoder to overwrite an existing patch. Press Save again to save it. If you want to name/rename the patch, press the encoder enter button and use the encoder and enter button to choose an alphanumeric name. Holding Save for 1s will go into a patch deletion mode. Use encoder and enter button to choose and delete patch. Patch numbers will be changed on the SD card to be consecutive again.

Settings is a menu for things not on the front panel such as pitch bend range, mod wheeel range, MIDI channel and can be extended to other global functions. Holding this for 1s will initialise the synth with all the current panel control settings - the synth sounds the same as the controls are set.

KNOWN ISSUES
Occasional digital noises from audio over USB, possibly attributable to the 44117Hz sample rate T3.6 uses. T4 uses 44100Hz and will probably be better. Audio from Audio Board is fine.
Plugging in a MIDI controller may alter current patch settings. Arturia Minilab for example, sends its current panel control settings when plugged in, causing MIDI CC messages to be received by TSynth.
Low cost (sub $10) USB to MIDI converters can have problems handling Clock signals and SysEx, which get mixed up with note on/off and CC messages. Use quality converters made by a known brand name.

2 comments:

  1. Hiya Matrix!
    I think a typo crept in here. Think you meant -post- ?

    "Note this is the first -synth- to feature ElectroTechnique."

    ReplyDelete

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