Monday, 4 February 2019

Microcontrollers & Synths

This page is an index relating to microcontrollers (MCU - microcontroller unit) and how they relate to synthesizers.
It will grow over time so keep coming back

I'm seeing  these chips time and again when building synths.

They usually take the form of a single IC that contains these basic parts:
1. CPU - a microprocessor (4-bit or more)
2. non-volatile flash memory --- this holds the program to be run.
3. RAM - random access memory (volatile memory for data storage)
4. EEPROM - Electrically erasable programmable read-only memory 
    used for non volatile storage of program data
5. GPIO pins - General purpose in/out pins - used to interface with switches, LEDs etc etc.
    These can be configured to be either inputs or outputs.

Microcontrollers are basically tiny computers.
They perform things one step at a time and use a clock to trigger each step.
The clock is an oscillator (usually 1MHz to 20Mhz).

The GPIOs are very flexible ... can be ins or outs because they are controlled with software not hardware
unlike CMOS for example where the pins have a fixed function.
They are limited only by the speed and memory of the chip ( and the ability of the programmer)

Microcontrollers are also able to bridge the divide between digital and analog. So we can use them in the
world of analog synths.

There are plenty of examples of the use of microcontrollers in synthesizers.

Intel produced the 4004 in 1971 Arguably, this was the world's first microprocessor.
This led to the famous 8080 CPU and then the IBM PC's 8088, 80286, 486 etc.

The Buchla Series 300 system was introduced around 1973. It was a marriage of Series 200 modules and a computer system comprising an 8080 eight-bit CPU, a floppy disk drive, video monitor, interfaces to the synth modules, and a music language called Patch IV (developed specifically) for the system.

Buchla 360 - octal signal source

Motorola  produced the 6800 in 1974. It's a 8-bit microprocessor
    Some of the synthesizers using the 6800 & its variants were:
    The 6800 was used in the Fairlight CMI series II. The IIx used the later 6809.
    The Fairlight series III used the 6809 & 68000
    Ensoniq EPS-16 (68000),
    Oberheim Xpander, Oberheim Matrix, ( 6809)
    PPG Wave 2.x , PPG Waverterm A (6809)
    Ensoniq SDP-1  , Ensoniq ESQ1, Ensoniq SQ80 (6809)
    Quasar M8 (6800)

Fairlight IIx

 Texas Instruments produced the TMC0281 Speech Synthesizer in 1978.
 The TMC0281 was the world's first single-chip speech synthesizer.

Zilog  made the Z80 microprocessor in 1976.
This was used in many home computers of the early 1980s  like the Dick Smith System 80 which was my first computer.  

Synthesizers that used the Z80 include: Roland Jupiter 8, Sequential Circuits Prophet 5 & 10,
      Sequential Circuits Prophet 600, Roland MC4, E-mu 4060, Roland MSQ700, Oberheim OB-8,
      MemoryMoog, Emulator I and II, Akai 2700, E-mu SP-1200, E-mu Drumulator,
      Sequential Circuits Drumtraks.

Microchip Technology  introduced the PIC 16C84 Microcontroller in 1993.
      The PIC 16C84 used a new type of memory called EEPROM
      (electrically erasable programmable read-only memory).
      You will find this type of memory used in lots of drum machines from the 90's

These are some of the most common microprocessors used in modern synths. (It's by no means a full list).

Arduino

+ Snazzy Fx Ardcore
   I believe its powered by an Arduino Uno
+ Circuit Abbey Euroduino module.
 


Atmel (AVR, ARM, Arduino, ATtiny, ATmega, ATxmega, AT89, AT90, AT91)
+  Mutable Instrument
      Branches (ATMEGA88PA), Grids (ATMEGA328P), Edges (ATXMEGA32A4U)
      Shruthi - ATMega644p , CVpal
+  ADDAC -  VCC (Voltage Controlled Computer) Atmega2560
+ Elby AVR synth (AT90S8535)
+ Modular Synthesis AVR synth ATMEGA32
+ Bastl Grandpa - Atmega328-PU
+ Buchla Format - Sputnik 244 (ATtiny88 & 84)
+ Buchla Format - 204r ATtiny84A
+ Buchla Format -227r (rev2) ATTINY84A

+ Monome Teletype AVR 32 (32-bit)
ATMEGA88PA

Seeeduino.
+  meng qi voltage memory
Seeeduino V4.2

STM32 
+ Mutable Instruments
     Tides, Peaks, Streams, Yarns, Braids, Frames (STM32F103CBT6)
     Clouds, Elements STM32F405RGT6
+ Owl modular - STM32F4
+ PER|FORMER sequencer STM32F405RGT6
+ Buchla Format - 248r MaRF & 218r
+ DAFM synth - STM32
+ Axoloti -  168MHz STM32F427 microcontroller
STM32


 Teensy
 + Ornament and Crime (Teesny 3.2)
 + 16n Faderbank (Teensy 3.2)
 + Radio Music / chord organ (Teensy 3.2 with internal DAC as the audio output)
 + Temps Utile (Teesny 3.2)
 + Malekko Varigate8+ ???
 + Orgone Accumulator
 + TELEX Teletype
 + Euroshield from 1010music

Teensy is a brand of microcontroller development boards created by PJRC and designed by the co-owner, Paul Stoffregen.  Arduino +  32 bit ARM-based microcontrollers = maximum I/O capabilities

Teensy 3.2


PIC (MIcrochip)

Microchip has created its own family of MCUs and baptized them as dsPICs.
The name PIC initially referred to Peripheral Interface Controller
They are also known as digital signal PI controllers.
Early models of PIC had read-only memory (ROM) or field-programmable EPROM for program storage
All current models use flash memory  

The device families: 
+ PIC10 and PIC12 - 12 bit
+ PIC 16 - 14 bit
+ PIC 17 & 18 (21bit)
+ PIC 24
+ dsPIC - released in 2001
    (PIC24 devices are designed as general purpose microcontrollers. 
     dsPIC devices include digital signal processing - DSP - capabilities  in addition.)
 + PIC 32

Silabs (Silicon Labs)

+ Buchla 259e, 260e, and 261e use a C8051Fxxx (Model 120 ??)

---------------------------------------------------------

Useful Links
+ AVR synth video
+ Snazzy Effects ArdCore -Installation Demo
+ Microcontroller... What you need to program a MCU 
+ Microcontrollers... Programmers


Please let me know if there are any mistakes or omissions.

To be continued .........................

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Sunday, 3 February 2019

Statues - NLC - Build notes

These are my build notes for the Nonlinearcircuits Statues Module.
Its in eurorack format.

The name comes from the children's game Musical Statues also known as Red Light Green Light.
This is a 1 to 8 multiplexor/multiplexer….with a thru and hold circuit attached to each output.
The active output is chosen by whichever combination of the x00, 0x0 & 00x inputs is high.

The multiplexer IC can be either a DG408 or DG508 (DIP package)

You can put any signal into these, crossing 1V will send it high. In the demo video, I used the /2, /4 & /8 outputs from a Divide & Conquer which gives it a regular 1-8 count.

Using any old signals will give a more random effect but patterns will still emerge.
IN is the signal getting processed. This module can be used to process CV and/or audio signals.
-----------------------------------


A movie quote? ... Inn't he scrummy? ..

I think this is from . from Ideal ..a British dark comedy television series originally broadcast on TV channel BBC Three, ..... He is known for the line 'Inn't he scrummy?' He often talks to Moz ... He isn't particularly clever, though he is somewhat crafty.
Back to the build..........

-------------------------
S1JL Power diodes are for Reverse voltage protection -Mouser Part No: 821-S1JL. Any similar rectifier with at least 1A rating should be okay, such as 1N4001, 1N4002, 1N4004. Get these sizes; SOD-123 or sub-SMA (DO-214 is a bit too big, so avoid).




Which multiplexer to use? the DG408 or DG508?....
The DG stands for Double-Gate .... its a CMOS chip..... ie there are 2 gates in the one device.

"Multigate transistors are one of the several strategies being developed by CMOS semiconductor manufacturers to create ever-smaller microprocessors and memory cells, colloquially referred to as extending Moore's law."

The DG408 is an 8 channel single-ended analog multiplexer designed to connect one of eight inputs to a common output as determined by a 3-bit binary address.
https://au.mouser.com/ProductDetail/Renesas-Intersil/DG408DJZ?qs=sGAEpiMZZMutXGli8Ay4kA%2fBPd2gF8jLzm9LT6sd4BM%3d

The DG 508 is a Multiplexer Switch ICs 8:1 CMOS Mid Voltage MUX
 https://au.mouser.com/ProductDetail/Maxim-Integrated/DG509ADJ%2b?qs=%2fha2pyFaduielkf44kdqC6FI6vY%2fkDwFpufrTM%252bGuAk%3d


I chose this one & it works.








---------------------------------------

Specs

HP: 8

Inputs

xOO: first bit of a 0-7 number
OxO: second bit of a 0-7 number
OOX: third bit of a 0-7 number
IN: cv/audio signal

If xOO = 1, OxO = 0 and OOx = 1, you have the binary number 101. Converted in decimal : 5, so the output 6 is selected (you have 1 to 8 channels).

Outputs

The output selected by the x00, 0x0 and 00x inputs is fed the input signal (thru). When the selected output is changed the signal is held at whatever voltage it happens to be (ranges from approx -11V to 11V) (hold)



Links:
+ https://www.nonlinearcircuits.com/modules/p/statues
+ BOM

 + DIY index
+ All about CMOS

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You can find more NLC builds here.
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Friday, 1 February 2019

hARMONIC experiments

Playing around with the Verbos 262v


I'm surprised how many vactrols it uses.


Apologies for the poor sound on this instagram video, but it does sound really amazing.
I'll do a proper recording one of these days.

It started me wondering how many other "harmonic" related VCO modules there are out there.
Not may I think.
In Euro the The Verbos Harmonic Oscillator (HO), the Mutable instruments Plaits & Braids and the Make noise Telharmonic were some modules I could find. The HO looks related to the Buchla 148, 262v.
Do let me know if you know of any other modules that you think fall into this category.
The old Hammond organ with its drawbars is an example of this type of synthesis (additive synthesis).
In the software world Native Instruments Razor is a good example.
This brings up the topic of additive vs subtractive synthesis.
and begs the question why are there so few Synth modules that do additive synthesis?

The other euro module that I think can be loosley added to this list is the Make Noise Echophon.



The Echophon's depth control of the pitch shifter can be used to roughly approximate the harmonic series of the imputed  audio .. these are the frequencies that are multiples of the fundamental. To do this the large black pitch control knob must be set to max.

Every musical sound has these harmonics. A sine wave has only the fundamental or first harmonic, a saw tooth contains all harmonics in inverse proportion to their number. A square wave has all the odd harmonics in the same ratio, etc etc.
So with the Echophon, we can for example, just use a sine wave which has only the fundamental harmonic, and then add more harmonics by turning the depth control knob (the blue one).

Maybe this is use of pitch shifting modules to obtain spectral shifting is worth further investigation.
I understand that shifting the pitch of signal components retains their harmonic relationships.
----------------------------------------------------------------

Other modules worth exploring are clock dividers & multipliers .
Eurorack modules in this category include the SSSR Labs VC Divider, the 4MS Atoner, the quad clock distributor, the RCD (rotating clock divider) and SCM (shuffling clock multiplier). Use audio-rate input sources instead of LFOs with the clock dividers & multipliers to get harmonically related outputs.

The Doepfer A-137 is worth a look at.



The basic idea of a wave multiplier is to multiply the waveform of an incoming signal (e.g. triangle/saw/sine from a VCO) within one period of the waveform. This leads to additional harmonics of the incoming signal. The period and consequently the pitch of the signals remains unchanged.
The A-137 works as a kind of "inverse low pass filter", i.e. it adds a lot of harmonics to a signal that contains none or only a few harmonics (e.g. sine or triangle waveform). In contrast to that a low pass filter (e.g. A-120) removes harmonics from a signal that contains a lot of harmonics (e.g. saw or rectangle waveform).
 -------------------------
Ladik make a Harmonic Generator in 8 HP
The H-020
 ------------------------

A little bit  more off this topic, but still  loosley related are filter bank style modules.
I think the Verbos Bark Filter, and the Frap Tools Fumana are worth investigating.
The Bark/Fumana seem to be inspired by the Buchla 296/295/294.
Also worth a google are the 4MS Spectral Multiband Resonator (SMR) and the Serge Resonant Equalizer.

Re the Buchla 294/295/296, the Verbos Bark, the Fumana, the 4MS SMR and the Serge Res Eq. ... maybe they can be better described as "spectral processors"..... they are much much more than fixed-filter banks.
 
 The 294 comb filter is on the extreme left.

 The 295 filter

The first two, the Buchla 294 & 295, Don called comb filters, but their evolution into the amazing 296 seems plain to see.

The 296, the Fumana and the Bark are 16-band filter/spectral analyzers. Amazing tilt-like controls, you can address odd and even bands. They also have a row of envelope followers -- one per band.


Mark Verbos has chosen to use the "Bark scale".
It is named after Heinrich Barkhausen who proposed the first subjective measurements of loudness.
The scale ranges from 1 to 24 and corresponds to the first 24 critical bands of hearing.

 The Frap Tools Fumana - Dual16 Band Spectral Editor

The outward style of each of these modules is very similar ... the upper section provides access to each filter's main output at the chosen fixed frequencies.

The Buchla 294 uses the scale:
<250/ 1K / 4K / >4K

The Buchla 295 uses the scale:
<100/ 200/ 350/ 500/ 700/ 1K/ 1.4K/ 2K/ 3.5K/ >7K

The Buchla 296 uses the scale:
<100/ 150/ 250/ 350/ 500/ 630/ 800/ 1K/ 1.3K/ 1.6K/ 2K/ 2.6K/ 3.5K/ 5K/ 8k/ >10K

The Frap Tools Fumana uses the scale:
 15/ 65/ 90/ 122/ 170/ 230/ 320/ 435/ 600/ 825/ 1.1K/ 1.5K/  2K/ 3K/ 4K/ 5.5K/ 22K

 The Verbos Bark filter uses the scale :
<100/ 300/ 510/ 770/ 1.08K/ 1.48K/ 2K/ 2.7K/ 3.7K/ 5.3/ 7.7K/ >10.5K

The published Bark band edges are given in Hertz as [0, 100, 200, 300, 400, 510, 630, 770, 920, 1080, 1270, 1480, 1720, 2000, 2320, 2700, 3150, 3700, 4400, 5300, 6400, 7700, 9500, 12000, 15500].

So the Verbos Bark uses every second Bark band.
Looks like the Frap Tools has more evenly spaced bands following something like a graphic EQ, whereas the Verbos focuses on frequencies that are more recognised by the ears.
The Fumana might be better for shaping bass sounds as it has 3 bands below 100Hz, but the Bark may be better for singling out harmonics that the human ear can distinguish ???

Quote: Fumana manual.
"Each of the two filter array is based on 16 parallel analog bandpass filters. The main filter bands from 2 to 15 are mainly based on Bessel calculation, while bands 1 and 16 are respectively a lowpass and highpass with a custom method to obtain better musical results. All bands on the main filter array use an 8th order slope (48dB/oct)." 

Links:
+ Top Octave Generators
+ Muffs - DIY Harmonic Osc
 

Sunday, 27 January 2019

Korg Volca Modular

I'm really looking forward to getting my hands on one of the new Korg Volca Modular synthesizers.
I've got quite a few Volcas and even modded some in the past.
I wonder if this is hackable too?

Instead of using 3.5 mm jacks the volca modular uses those tiny patch wires  you see being used on breadboards. The new AE modular  from Tangilbe Waves uses this same system, as do Sound Machines with their NS1nanosynth,  and Bastl Instruments with their Kastle, SoftPop, Bitranger & OMsynth. 
Apart from this being wonderful news for the DIY synth community, it's a great introduction to what is termed West Coast synthesis. (Google Don Buchla & Serge Tcherepnin).

The idea of "West Coast Synthesis" is a really recent construct I think.The term comes from the fact that in the very beginning of synthesizers there was Bob Moog in New York and Don Buchla and Serge Tcherepnin in California --- its really a difference not of geography, but a difference of philosophy. Buchla was I think more interested in making art than in creating a business. It's said he created the interface first, and then the electronics followed.

Usually, its really expensive to enter this world, or you have to be OK with DIY in order to build something like a Serge synth. KORG  looks like it has drawn inspiration from the Buchla Easel in its colour scheme, its signal path & its modules.



I love my old easel because it is so flexible. I hope the new Volca will be just as nimble and
introduce the wider synth community to the joys of the West..

I also don't think Korg have ever made a West Coast style synth before (message me if I'm wrong).

Part of the West Coast philosophy is instead of having standard filters that remove content from the VCOs (subtractive synthesis), it uses wave folders. (Though I don't think I can strictly say this is an additive synth).
Wave folders do exactly that ... they fold oscillator waves in on themselves to generate more harmonic content (above the fundamental).

The volca modular has no envelope generators or VCAs ... instead it has functions ... or function generators and LPGs (Low Pass Gates).... all very Buchla.

East Coast synths use ADSR style envelope generators ....
Here, were have functions or slope generators (if you are into Serge).
Function generators are much more flexible ...you can get many more different envelope shapes
than your standard AD or ADSR envelopes.....& you can loop these too.

For more info on function generators click here:
https://djjondent.blogspot.com/2019/01/the-integrator-circuit-analog-computers.html
But be warned ... it's a bit nerdy
:-)

Saturday, 26 January 2019

SOMA Laboratory - DVINA

SOMA Laboratory, the company behind innovative electronic instruments such as LYRA and PIPE,
is once again breaking new ground & exploring new sonic territories. Soma Laboratory has a new instrument in the pipeline (in addition to the upcoming PULSAR-23 organismic drum machine).

This new instrument is called DVINA. It's such a radical step for Soma, that the company is first seeking feedback from the public before putting it into production.

This is what it looks like:

DVINA (laboratory prototype)

“We want to show it to the world to get an idea if there is a market for an instrument like this,” said
Vlad Kreimer, the designer of DVINA. “If the reaction is positive, we can start mass production.”

DVINA is the first electro-acoustic experiment created by Soma. This unique string instrument was
inspired by classical Hindustani music, but lends itself to Western music just as well. References
include the bowed instruments - the Sarangi and the Dilruba which have more in common in spirit, than in design.

The DVINA produces a similarly full, warm and organic sound using modern technical innovations.



This DEMO video shows DVINA's construction and possibilities. 

A key feature of DVINA and its sound is that there is no pick-up inside. Instead, the electric signal
is taken directly from the strings that vibrate in the strong magnetic field of a neodymium magnet,
hidden in the neck. Sound is generated by strumming, plucking the strings (pizzicato) and by
playing with a bow (not included). DVINA has a minimalist design – no one part can be removed
without losing the functionality of the instrument. 
The length of the neck is 88cm, and the scale length is 52cm. The instrument weighs 1.2kg. The DVINA in the demo video is tuned C#, G#, but other tunings are of course possible. You can also use strings with a different gauge. Aside from the wooden body, an integral part of DVINA is the special step-up transformer that boosts the weak signal from the strings, enough for further processing.

After the transformer, the signal is ready to be put into stompboxes, mixer or a guitar cube.
The final part of DVINA is a custom built high quality pre-amp with one-tap delay and a soft distortion in the delay’s feedback. This is the pre-amp used in the demo.

You can of course use your own processing chain instead, but the Soma pre-amp does play a role in shaping the unique sound of DVINA.

Like with Soma's other instruments, there are some underlying concepts to DVINA.
There is the minimalism in design, and the link to the Hindustani tradition's meditative roots that can help the contemporary person focus on his/her inner state. 

 
“Two sticks, two strings, no frets, it's as simple as possible, everything unnecessary has been removed,” said Vlad. “It's only you and your spirit, mastery and imagination. This is a very simple but powerful instrument, with a strong connection to your body.”

DVINA is lightweight, small and very portable. It's actually the only bowed instrument that can be assembled from pieces that can be folded into a compact container.

“This instrument is perfect for the 21st century cultural ninja-spy, who travels alone with little luggage, is hopeful, flexible and completely independent, trying hard to still be a human in a complex time of impetuous changes.”

PRICE: The main part (wooden DVINA + step-up transformer) will cost in the range of 200-500 euros, while the pre-amp/delay/distortion unit will be around 200-300 euros. The exact price will be known once SOMA has a better idea of the market interest and the volume of production.

If you're interested in this kind of instrument, please let SOMA Laboratory know at omhohom@gmail.com

PS:
DVINA is also the name of a major river in Russia.
" (The) Northern Dvina River is the major river of the North zone of  European Russia and the White Sea basin. The river irrigates the Vologda and Arkhangelsk region and drains into Dvina Bay in the White Sea. Along with the Pechora River to the east, it drains most of Northwest Russia into the Arctic Ocean.

PSS:
Spotted at a Prodigy concert on their instagram account

The Lyra-8

CMP-DIV Video Effecter - Vidiffektor

I came across an old post on Electro-Music for a video effects box.
 http://electro-music.com/forum/viewtopic.php?t=54113

It looks very cool
Credit for this goes to James Schidowsky.
His website is here:
http://www.jamesschidlowsky.ca/electronics.html

The info in the post is very clear with lots of schematics and even a breadboard.
The parts count is very low.
Just two ICs ... a LM339 quad voltage comparator and a CMOS 4040
Should be a fun DIY build.

Links:
youtube 1
youtube 2
Workshop
Facebook workshop Aug 2018

I've ordered some parts and will document the build on this page.
To be continued................... 

Friday, 25 January 2019

Happy Australia Day 2019

Happy Australia Day everyone.



Here is a list of some Australian Synth manufacturers:
Amalgamod
Analog-ordance
Beast-Tek
Cat full of Ghosts
CGS - Cat Girl Synths
Elby Designs
NLC
Oscillosaurus
Worng
Innerclock Systems
Metro-modular
GOLT !
Mungo Enterprises

I'f I've missed anyone please let me know.


Wednesday, 23 January 2019

The Integrator Circuit - analog computers, Buchla, Serge & eurorack modules

The Op-amp integrator is a very important electronic circuit which I come across again and again.
The West Coast style of synthesis uses it a lot in modules like function generators, and slope generators.
In the synth world, what is possibly the most popular of all modules, the Make Noise Maths I think uses this circuit. (let me know if I'm mistaken).



The Fritz chaos circuits are also made of integrators.

The op-amp integrator is, as the name implies, based on the operational amplifier (op-amp). It performs the mathematical operation of integration (with respect to time). The magnitude of the output voltage is proportional to amplitude as well as the length of time a voltage is present at its input.

This probably sounds like lots of gobbledy gook to most people. Sorry.
To simplify all this nerd stuff.....
Usually operational amplifiers are used as part of a feedback loop circuit involving a resistor.
 Something like this:


 But what if we swap the resistor with a capacitor?
We now have a RC network This new circuit is commonly called a Op-Amp Integrator


Electronic integrator circuits can be found  in old analogue computers:

The COMDYNA GP-6

Integrators, mutipliers, dividers, counters, function generators, operational amplifiers, differential amplifiers, voltmeters... etc etc... These old analog computers had many of the modules you will commonly find in a modular synthesizer. They are arguably the inspiration for many of today's synths.


 Digital systems Lab

Anyway, probably my favorite module, the Buchla 281 QUAD FUNCTION GENERATOR uses it, as does the Buchla 257..... this is a voltage processor. Don experimented with integrators well before the 257. He created the Buchla 155 Dual Integrator module for  the system 100. These are extremely rare and I have never even seen a vintage one.
---------------------------------
"Model 155 Dual Integrator
Produces continuous control voltage functions when used in
conjunction with sources of discrete control voltages (e.g. keyboards, sequencers).
Positive and negative  slopes  may  be  individually  and  continuously varied from
15 volts in .0025 seconds to 15volts in 10 seconds; either or both slopes may be
voltage controlled. Particularly useful for generating complex voltage controlled envelopes,
frequency glides, and repetitive control functions." 


(from a catelog for the 1992 Ars Electronica exhibit Eigenwelt der Apparatewelt.
Pioneers of Electronic Art, edited by David Dunn)



--------------------------------------------------------------------


Buchla Dual voltage processor . Buchla 257.

It's looks a bit confusing. M is a control voltage. "It provides the capability of transferring control from one applied voltage (Vb) to another (Vc). The algebraic manipulations include addition,  subtraction, scaling, inversion, multiplication". You can crossfade & use this module as a VCA.


There is also a intergrator section in the lower right corner of the Buchla 266

 In the Serge world the DUSG (Dual Universal Slope Generator)... often referred to as the "Swiss army knife" is all about the integrator. The Slope generator is an amazing module. 


These Positive & Negative Slews preceded the DUSG


Depending on how one patches it, the DUSG can be a VCLFO,  a envelope generator; a oscillator; a  slew generator; a voltage and audio mixer; an attenuator and inverter; an envelope follower; a comparator; a VC pulse delay, a audio processor,.... whew !!! ........... it's pure genius !!!!

Bananalogue put out the  VCS almost a decade ago I think. This is based on a Serge slope generator

MATHS = DUSG/Buchla 281 and Buchla 257.???

The Befaco Rampage is another variation of the DUSG.


Just released during NAMM 2019 is the Verbos Control Voltage Processor:
It's a bit of DUSG and Buchla 257. Can't wait to get one.

So to sum up....in most op amp circuits, the feedback that is used is usually a resistor. However for the integrator this is not the case - the component providing the feedback between the output and input of the op amp is a capacitor.
It works a bit like this:
When a voltage is initially applied to Vin, the capacitor has almost zero resistance.... it acts like there is a short circuit.... so no current will flow through the op-amp. A virtual earth exists at the op-amp’s inverting input.

As the capacitor starts to charge, negative feedback forces the op-amp to produce an output voltage to maintain that virtual earth at the op-amp’s inverting input. The rate at which the output voltage increases (the rate of change) is determined by the value of the resistor and the capacitor, “RC time constant“.

Once the capacitor fully charges, it acts like a open circuit.
The flow of current then stops.

If we apply a rapidly changing signal to the input then the capacitor will charge and discharge quickly. At higher frequencies, the capacitor has less time to fully charge. This type of circuit is also known as a Ramp Generator. 
A ramp generator is a way of converting a square wave to a sawtooth.... but that's another story.