DIGISELEKTOR

Arduino-driven XR2206 analog synth sequencer

CLANDESTIGN

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Description

A digital version of the all-analog SELEKTOR, the digiselektor is a filtered set of CD4046 VCOs modulated by an arduino and filtered via an AD5206 SPI pot . Display handled by 2x MAX7221 LED drivers, OPA series digitally controlled bandpass filter.

https://www.youtube.com/watch?v=9qVxtVNCpUE

Details

AD5206 outputs directly drive CMOS VCOs in this particular model, CD4046, which works fine at 5V. One leg positive, another ground, wiper to input of VCO. No PWM voltage smoothing required. The bandpass filter modulation also plugs right into the AD5206, for 8 bit bandpass resolution- all 5V operation, single rail.

Discussions

raymondwouter wrote 10/05/2018 at 00:22

Hi guys, I'm getting more and more frustrated, to see all these awesome synth based projects!

I really really love synths all my life and I'm able to design some nice housings for it and also can make a synthesizer housing from aluminum sheet metal, in combined with awesome pcs of solid wood and/or wood veneer, I'm Tig welding aluminum, rvs, can work on a metal and wood Lathe, router/milling etc etc!

That's all very nice, don't you think? The problem is , that I have never learned how to work with electronics and that is what I want the most, making my own PCB's. Design my own modules, sequencer, making the PCB's isn't the problem, you can take a router or a printer and a chemical.

I've already bought myself some DIY synths from MFOS (USA) LushOne (UK), Elby-designs (Australia) and Doepfer (D).

I'm pretty handy, buy also getting older and my brain is forgetting things.

I've ask this question many times, how and where do I start with learning how electronics?

I've already got the book from Ray Wilson, the make series and I love to reed it.

is er someone who knows which other books there are of building synthesizers, how VCO's, VCA's, VCF's, DCO's.etc works, how I can educate myself????

Thanks guys

Kind regards Ray W

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Elliot Williams wrote 06/08/2016 at 15:58

The vocal-range bandpass filter sounds awesome. Very cool. You almost get vowel sounds sometimes.

I get the DAC -> VCO part. How does the filter work? We'll be needing som schematics. :)

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CLANDESTIGN wrote 06/09/2016 at 04:04

Hi Elliot! The Frequency pin on the XR2206 is amenable to having an LDR on it... the other end of the DAC is an SPI digital pot, with the ends at 5V and GND, with the wiper to a biased 2n4401 transistor- the biasing is the hardest part- making sure the LED is totally off, but starts lighting immediately, and has decent contrast at 90% to full brightness- I bias to 2-3 LEDs in parallel, so I have one for indication purposes and one extra for any other channel mixing... In this layout there are also stages before and after the filtering that subtract another set of DAC/VCO, but square only, from the CD4046, which works directly with the voltage output of the SPI digital pot-as-DAC via pin 9...

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