Jeannie is an 8-voice polyphonic open source synthesizer with 24dB Ladder Filter and 12dB State Variable Multimode Filter
Jeannie is an 8-voice polyphonic open source synthesizer kit with digital sound synthesis and digital filters based on a fast ARM Cortex-M7 processor with 1MByte Ram. For sound generation, the user has a variety of classic and band-limited waveforms at his disposal. A pool of 15 waveform banks with 63 different waveforms each offer plenty of space for sound experiments. A waveshaper with different characteristics provides for gentle to vicious sounding distortions. To tame the waveforms, there is a digital 12dB multimode filter with fade function from low-pass to highpass and a band-pass function. In addition, there is a 24dB LP ladder filter. A 24Bit DSP effect module with adjustable parameters rounds off the sound synthesis. An integrated polyphonic 16-step sequencer provides for the playfulness of the small synthesizer. A total of 2048 sound patchesfrom 15 banks can be loaded and stored via an integrated SD card. A color 1.8 inch TFT display allows a clear menu structure and easy operation of the synthesizer. The parameters are entered via four rotary knobs below the display and an encoder for selecting the sound programmes and switching to the menu functions. In addition, there are six buttons for operating special synthesizer functions.
• DIY 8-voice polyphonic synthesizer
• ARM Cortex-M7 processor 720MHz with 1MByte Ram
• two digital oscillators per voice
• 15 waveform banks with a total of 945 waveforms
• 12 standard waveforms, some of which are band-limited
• Noise generator (white and pink noise)
• Oscillator Modulation (XOR, XMOD, MOD, AND, PHA, FM)
• Waveshaper with different curve shapes
• 2 LFOs with 6 different waveforms and fade in / fade out function
• 2 ADSR generators 0.3ms – 12s with positive and negative control
• 1 PWM LFO from 0.04Hz - 25Hz
• Digital 12dB multimode filter with resonance and fade function (LP/HP/BP)
• Digital 24dB low pass ladder filter with resonance
• 24Bit DSP effect module with 15 effects and adjustable parameters
• Polyphonic 16 step sequencer
• SD cards for loading and saving the sound programs max. 2048
• Colored 1.8 inch display with a resolution of 160x128 pixels
• Volume control
• Boost function for improved bass reproduction
• Stereo audio output jack 6.3mm
• 4 potentiometers for parameter input
• Encoder for menu control and sound selection
• 6 function keys
• Midi In and Midi Out / Midi True
• USB 2.0 midi interface
• Simple firmware update via USB
• External power pack 12V DC / 1000mA
• and power switch
For a while I have been using Teensy 3 and 4 in MIDI controller projects, and have recently been thinking about adding a basic synth on board so that the controller can also stand alone as a musical instrument. So I’m quite interested to see synth designs like yours which are based on Teensy. I previously experimented with the Teensy Audio Library and managed to get some nice sounds. On the base 600MHz Teensy 4.1 the Moog Ladder filter seemed to use quite a lot of CPU, with a couple of oscillators it was around 10% CPU if I recall correctly. Overclocking is obviously one way around this problem.
How do you find the performance of the Moog Ladder versus the State Variable filter?
I notice that you used an external effects DSP. Is this purely for performance reasons, or is there some other advantage of the SPIN-FV1 over software effects running on the Teensy?
Hello Stewart. Thank you for your interest. In the Jeannie I have integrated both filter types. In the System menu you can select Ladder or State Variable Filter. The CPU performance with 8 voices is between 65-75% depending on the sound patch. The memory utilization is around 85%.
Additional audio effects would overload the Teensy 4.1 processor. For this reason we used an external effect DSP (Spin Semiconductor FV-1). This DSP offers up to 15 programmable effects.
I really love these DIY-things. Buying Zynthian Kit was a great improvement for my creativity. And now this Jeannie Synth really pushes my GAS!!! The many features and sounds are amazing. One question: How long does it take to boot up?
Sorry, one more question: I really hate menu diving. I had a Roland MC 101 and I couldn’t work with it because some simple function were hidden very deep in endless sub menus.
I am also owner of a 1010music Blackbox and of course Zynthian Kit, were on both the workflow is very comfortable without deeper menus.
How is Jeannie working? Is everything quite quickly accessible? Compared to Zynthian/Blackbox?
UPDATE: I read the f***ing manual of Jeannie and recognize it is a clear and simple menu structure for easy and quick access. Am I right?
I built Jeannie last weekend and she sounds absolutely amazing!!
Yes, it was lots of soldering but the manual explaines every step very well and the result is more than worth it.
A big advantage is the impressive quick access to all sound configurations like oscillators, waveshapes, filters, FX, envelope, etc… You walk to every parameter adjustment in seconds. The developers really know how to design an absolutely efficient user interface.
For everybody with some soldering experience who is interested in building a really advanced Synthesizer by its own should have a look at TubeOhms Jeannie Kit.
From the program page you can jump to the menu pages by pressing the DATA controller.
If you press it again, you return to the program page. Via the Shift key
reach the submenu (SUB menu). Press the Shift key repeatedly to get there
either to a 2nd submenu (if available) or to the previous menu page. A scroll up
other menu pages is also possible within the submenus.
Improved filter sweep at cutoff. There were always jumps (staircase effects) when turning the cutoff control, especially at lower frequencies. This is due to the low resolution of the cutoff controller and the midi CC’s (7 bit). To reduce this effect, I programmed a low-pass filter in front of the filter’s internal control input. The Midi CC 74 for the cutoff also runs over this.