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"meModular" Modular DIY Synth
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author "meModular" Modular DIY Synth
rolfdegen
Hallo friends of Modular Synths thumbs up

My name is Rolf from Wuppertal in germany. I love electronic music (J.M.Jarre, Mike Oldfield, Vangelis) and electronic components. My last "small" project was a digital sample synthesizer called "Degenerator". I worked on it for six years. But it was a lot of fun and I learned a lot (see Link).But now I want a little bit relax and develop smaller things

Degenerator


Link: https://www.sequencer.de/synthesizer/threads/avr-synthesizer-wave-1-de -generator.87599/page-21
Link: https://www.tubeohm.com/de-generator.html
Youtube: https://www.youtube.com/user/rolfdegen1806/

Modular synthesizers have been an exciting topic in recent years. They are versatile expandable and inexpensive to build. For starters, I opted for a small system. It should consist of a VCO, VCF, VCA and an Envelope Generator. I would like to build some modules myself.
This year was a Nice mudular happening "Happy Knobbing" in Fischbach germany. Link: https://www.youtube.com/watch?time_continue=267&v=dKY-H7VmwNI

I have already started with an sweet little case from Dieter Doepfer.


Link: http://www.doepfer.de/home_e.htm

The power supply is not very big, but has enough power reserves for some modules. Its +5V +12V and -12V and DC current up to 360mA.

In my next review i start building an Oscillator. On Sequencer.de I post everything in German. Link: https://www.sequencer.de/synthesizer/threads/memodular-modularer-diy-s ynth.148901/

Best regards from Germany. Rolf
rolfdegen
Hallo..

My first DIY Modul is an VCO (Voltage Controlled Oscillator). The basis is a CEM3340-G from Curtis. These chips were built in the 80s in many synthesizers. Because of digitization in music electronics, the chips were no longer in demand and disappeared from the market. In recent years, the demand for analog synthesizers has grown again and the chips have been re-produced.

In my first step i build a triangle and sine out for my VCO. The triangle output of the CEM3340-G is not symmetrical. For the symmetrical adjustment of the triangle output, I have provided a trimmer R28.
The trimmers R33 and R27 are used to set the sinusoidal shape and symmetry.

VCO


Sine sweep: https://drive.google.com/open?id=1z_BxgFnUachjezBpC2MiINbbsz35n0bq

spectrum analysis


Sine waveform


Development environment


In the next step I will expand my oscillator. FM, AM, an additional SubOszillator and much more ..

Greetings from germany. Rolf
rolfdegen
Hey friends ..

My second Curtis Chip CEM3340-G from Portugal has arrived. He probably had a longer journey behind and now gets a new nice home.




Greetings Rolf
jorg
Rolf, there is a competing re-issue of the 3340 (and many other CEM chips, as well as some "inspired-by-CEM" chips)

http://www.alfarzpp.lv/eng/sc/AS3340.pdf
rolfdegen
Hi jorg

I have tested the AS3340. I would like to use this chip but it is not temperature stable. See here:

Link: https://www.muffwiggler.com/forum/viewtopic.php?t=211256
Youtube: https://www.youtube.com/watch?v=NYHd-r7GKzc
Boofin Moonrocks
Excited to see you starting to develop some modules! I followed the degenerator development for a number of years (haven't gotten a chance to build it yet though).
rolfdegen
Thanks cool
tobb
rolfdegen wrote:
Hi jorg

I have tested the AS3340. I would like to use this chip but it is not temperature stable. See here:

Link: https://www.muffwiggler.com/forum/viewtopic.php?t=211256
Youtube: https://www.youtube.com/watch?v=NYHd-r7GKzc


Total crap indeed!
rolfdegen
Did you have an AS3340 with the same temperature problem?
I'm looking for someone who can confirm that!
guest
the warm up time on the AS3340 does not suprise me, what does suprise me is that you are not seeing any warm up time for the CEM3340. did you test them both the same way (both from a completely cold start - circuit and powersupply off for an hour or more)?
rolfdegen
Yes. I tested both in the same circuit. You can see it in the videos. The recording starts before switching on the supply voltage.

AS3340 Video: https://youtu.be/NYHd-r7GKzc

CEM3340 Video: https://www.youtube.com/watch?v=dyJD9JxCbrM

Greetings Rolf
guest
just to verify: the powersupply was off for an hour before both test? or was on for an hour before both tests? the chip is just one area of drift, the powersupply, and all other components on the board also drift. i ask, as my CEM3340 definitely took a bit to warm up.
rolfdegen
I measured at a room temperature of about 29 ° C. The case was open. The power supply is a switching power supply +12 -12 + 5V from Doepfer (Recom RAC10-12DA). ± 0.02% / ° C typ.

rolfdegen
Hello..

I have corrected some minor errors in the schematic and adjusted the frequency setting on the Coarse and Fine controls. The frequency on the Coarse control can now be adjusted over 12 octaves.
With a CV control voltage of 0.00V this corresponds to a frequency of 0.30Hz - 6500Hz. You can set + - 2 semitones on the Fine knob.

Small note: The housing of the potentiometers should be connected to ground (GND) in the circuit, as they cause small disturbances in the signal when touching.





The next step is now the construction of the 2nd oscillator and the modulation control.

Greeting Rolf
rolfdegen
Today I ordered small colored TFT displays for my VCO. Through a menu you can set different oscillator functions.

0,96 Zoll TFT Display


Link: https://www.amazon.de/dp/B076PFHPVM/ref=pe_3044161_185740101_TE_item_i mage
rolfdegen
Hello..

Today I was busy again and put the design of the VCO front panel into practice.
Above display with encoder for setting the oscillator functions eg Hard- u. Soft Sync, Modulation, LFO, Sub-Osc, Octave and many more.
In the middle the controls for Coarse u. Fine Tune and pulse width. Below inputs and outputs.



Greetings from germany. Rolf
rolfdegen
Hello friends..

The TFT display is working now. It is controlled by an Atmega328P in I2C (TWI) mode. A corresponding library for the display controller SSD1306 is available in the internet (see link). I think the looking at colors of poti knobs and tft display is really well.

Link: https://www.arduinolibraries.info/libraries/ssd1306


meModular VCO



A small problem occurred while operating the display. The display causes interference on the + 5V power supply which are also audible in the oscillator. To avoid the interference, a small filter consisting of a coil and capacitor must be connected in front of the + 5V power supply of the display.

Greetings from germany. Rolf
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