A monophonic, non modular, analog synth combined with an 8-step analog looper

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The monophonic synth

• The VCO : can generate square, triangle and sine waves, one selectable
• classical VCF, VCA, ADSR
• Mute switch
• VC/Gate input :
  • pitch : 1V/octave, 8 octave, either linear (1 half-pitch = 1V/12), either exponential (see also https://www.allaboutcircuits.com/projects/diy-synth-series-vco/)
  • velocity : 100% at 5V, either linear scale, or exponential
  • gate : V-trigger at >2.5V

The 8-step analog looper

• bpm range : typical (see a metronom)
• one led/step
• each step :
  • enabled/disabled (switch + led)
  • pitch (pot)
  • velocity (pot)
• CV/Gate output :
  • 1V/octave, linear
  • Velocity : linear scale
• Input port (enabling input disable sequencer):
  • 1V/octave, linear
  • Velocity : linear scale
  • gate : V-trigger at > 2.5V

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Usefull ICs

ICs to procure, inspired by https://www.reddit.com/r/synthdiy/comments/r986bb/what_are_your_must_have_ics/

OpAmp ICs:

Code name	Description
LM324	Low power quad op amps link
LM358	Low power dual op amps link
LM386	Audio power amplifier link
LM13700	Dual Operational Transconductance Amplifiers With Linearizing Diodes and Buffers
NE5532	Dual low noise op amps link
TL072	Dual low noise op amps JFET (link)[https://www.gotronic.fr/art-tl072-10637.htm]
TL074	Quad op amps JFET (link)[https://www.gotronic.fr/art-tl074-10638.htm]

Comparator ICs:

Code name	Description
LM311	Voltage comparator link
LM339	Low power quad voltage comparators link
LM393	Low power dual voltage comparators link

Logic ICs:

Code name	Description
CD4093	Quad NAND Schmitt trigger
CD40106	Hex Schmitt-Trigger Inverters

Misc ICs:

Code name	Description
NE555	Timer link
NE556	Double timer link
PT2399	Echo audio processor
LM3914	Led bar dot display driver link
TL431	Precision shunt regulator (link)[https://www.gotronic.fr/art-tl431clp-10644.htm]

Transistors:

Code name	Description
2N3904	NPN general purpose transistor
2N3906	PNP general purpose transistor
BC550	NPN low noise transistor
BC560	PNP low noise transistor
2N7000	MOSFET N-channel, 60V, 2A
J111	JFET N-channel
J112	JFET N-channel

[sporniket]

• From square wave, get triangular wave through integrator.
• From triangular wave, get sine wave through integrator.
• From square wave, get sawtooth wave with that kind of circuit

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An ADSR envelop generator : http://www.muzines.co.uk/articles/adsr-envelope-generator/3251

⇒ operational diagramm :

⇒ schematics, (includes a PSU plugged to mains power) :

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Other adsr envelop generator :

• https://www.n8synth.co.uk/diy-eurorack/envelope-generator/
• https://electro-music.com/forum/topic-31473.html&postorder=asc
• https://www.schmitzbits.de/adsr.html

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An example of VCA, to get the part that attenuates the sound coming from the oscillator according to the envelop generator