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keyboard controller for analog mono synthesizer
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alanwilder81



Joined: Sep 03, 2016
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PostPosted: Wed Aug 02, 2017 8:35 am    Post subject: keyboard controller for analog mono synthesizer
Subject description: midi keyboard to CV gate, or arduino?
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hello chaps,
im bringing a topic that may have been discussed here already, so please excuse me in case.
In short i'm weighing two different options for controlling my small monophonic analog synth i just put together.
-ether the classic MIDI keyboard + MIDI to CV-GATE converter combo.
-or a 70's organ single buss (resistors string) + arduino generating steady CV GATE.

I've seen the latter idea implemented by a friend of mine and absolutely came together.Solid rock voltages outta ARDUINO.

Now, i 'd like to ask you more knowledgeable folks, how would you go about it,considering that all i need is an extremely basic CV and GATE signal.
No bells and whistles, no pitch bend no crazy other modulation possiblity i might find on a pro MIDI keyboard.
Just a plain mean of controlling my humble setup.

thanks for any ideas
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alanwilder81



Joined: Sep 03, 2016
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PostPosted: Wed Aug 02, 2017 8:49 am    Post subject: Reply with quote  Mark this post and the followings unread

in other words, in case i went for a MIDI keyboard, i wanted to be reassured about ther reliablity.
I've seen even 25 keys MIDI keyboards go for as little as 49 dollars.
of different brands.
Just as basic as i need them to be, but are they reliable?
After poking around for long with analog CV GATE controllers ( unstable, and unusable to say the least Sad ), i am looking for a solid and consistent keyb to get me going .
thanks again all folks
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Grumble



Joined: Nov 23, 2015
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PostPosted: Thu Aug 03, 2017 5:23 am    Post subject: Reply with quote  Mark this post and the followings unread

http://electro-music.com/forum/post-428516.html#428516

Maybe this is an idea?

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alanwilder81



Joined: Sep 03, 2016
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PostPosted: Thu Aug 03, 2017 6:29 am    Post subject: Reply with quote  Mark this post and the followings unread

thanks Ed,

watched the video you linked to, great sounding synth !

so, as far as i understand you customized a MIDI to CV-GATE converter in order to interface your old Target midi keyb to your modular.

I am set on buying a basic off-the-shelf MIDI keyboard and a MIDI to CV-GATE converter to drive my VCO s and modules.

Question is: is any given midi keyb just compatible with any given midi to CV converter?
in other words, would i be able to get a good 1 V-OCT response out of that ?
Any specification or requirement are to be checked and considered on coupling the MIDI keyb and the MIDI converter?

excuse the dumb questions !

thanks Wink
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Grumble



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PostPosted: Thu Aug 03, 2017 6:46 am    Post subject: Reply with quote  Mark this post and the followings unread

Ok you are buying ready made stuff? Well than, the only advice I can give you is try b4 buy...
One mistake I made was thinking that a keyboard would give a note-on message when a key is pressed and a note-off message when released, but as it turns out, there is also a kind of 'shorthand' in midi world.
My target keyboard gives, when played relatively fast, one note-on message with a note number and velocity. When I press a key shortly after that it just gives the note number and the velocity, on release it just sends the note number and velocity=0, so my code had to deal with that and it took some time before I figured that out...
To make things worse, the target keyboard also sends an active sensing signal every about 300mSec.

https://www.midi.org/specifications/item/table-1-summary-of-midi-message

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alanwilder81



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PostPosted: Thu Aug 03, 2017 7:15 am    Post subject: Reply with quote  Mark this post and the followings unread

thanks Ed,
yes, i want to purchase a midi keyboard and midi to analog converter already made up. it may cost a bit more but it saves me the hassle of building a converter from scratch.
a well over my head duty and the result wont be guaranteed.

Now , what you described and warned me about are the things i will want to avoid !
that's why i hope there is a plug and play combo ( MIDI keyb +MIDI-analog converter) that works straight away.And hopefully without having to face problems and issues i couldnt' even start to get my head around.
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comrade_zero



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PostPosted: Sat Aug 05, 2017 3:41 am    Post subject: Reply with quote  Mark this post and the followings unread

Have you looked into the Arturia keystep? Mini keyboard, MIDI in/out, onboard sequencer/arpeggiator and cv/gate/mod outputs... Also very reasonably priced. I use my microBrute for MIDI-to-cv duties so I can sequence in software on the DAW and play it out on the modular...
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alanwilder81



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PostPosted: Sat Aug 05, 2017 3:55 am    Post subject: Reply with quote  Mark this post and the followings unread

hello comrade_zero,

that would be a great solution, perhaps.
saving the hassle of building MIDI to analog converters kits, and interfacing MIDI keyboards to MIDI converters.

i believe i've seen the Arturia keyboard before ! it would kill two birds with one stone !

is it then ready to drive my VCO's without any additional mods?

Steady CV-GATE output? at the end of the day its all i need.

have you used it ?
thanks ! Smile
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comrade_zero



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PostPosted: Sat Aug 05, 2017 4:20 am    Post subject: Reply with quote  Mark this post and the followings unread

I use the microBrute (also from Arturia) and it handles MIDI to CV just fine. If you look at the product page, the Keystep has outputs for Pitch CV (which you would connect to the input of your oscillator) and Gate output (which you would trigger an envelope generator to control a VCA) IF the keystep is similar to the 'brute, then a MIDI in message should output the correct pitch control voltage and corresponding gate.
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alanwilder81



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PostPosted: Sat Aug 05, 2017 4:44 am    Post subject: Reply with quote  Mark this post and the followings unread

thanks comrade_zero, Smile Smile Smile

and yes, i took a look at the specs and it absolutely meets my needs. Also arpeggiator and sequencer are there. Not much more is needed to control my analog modules. The price is fairly reasonable too.

are you aware of similar specs-wise products, of other brands too, whithin that price range? say around 100 dollars or there abouts...

cheers Wink
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Boerge



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PostPosted: Thu Aug 10, 2017 10:39 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thinking about the same problem I would go for an Arduino. Circuit and code could be reused from here:

https://janostman.wordpress.com/2016/01/15/how-to-build-your-very-own-string-synth/

A contact matrix for the input and PCM for generating CV. MIDI In should be possible if needed. A µC has nice advantages: transposing. arpeggiator or sequencer functions are possible.

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alanwilder81



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PostPosted: Fri Aug 11, 2017 12:42 am    Post subject: Reply with quote  Mark this post and the followings unread

thanks Boerge
if only i could program it! have you built it ?
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Boerge



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PostPosted: Fri Aug 11, 2017 1:26 am    Post subject: Reply with quote  Mark this post and the followings unread

alanwilder81 wrote:
have you built it ?


Yes and no Wink I built the stringsynth, and of course it worked. But I didn't like the paraphonic style of playing Wink And because I was looking for a keyboard controller for my JH Living VCOs I came up with the idea to use this thing. Ok, I have a little knowledge of C language, not much, but hopefully enough to steal some code here and there and glue it together Wink The PWM-CV part I found here:

https://sites.google.com/site/diyanalogsynth/plug-in/midi2cv

(schematic and code for CV out and MIDI In)

Now I'm looking for arpeggiator/sequencer code Wink

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alanwilder81



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PostPosted: Fri Aug 11, 2017 1:48 am    Post subject: Reply with quote  Mark this post and the followings unread

thanks Boerge Wink

bear with me i know nothing about digital and even less about Arduino !
i got this idea from a friend of mine , who got together a 70's organ keyboard with a resistors chain, and programmed Arduino to produce CV and GATE.

question is...does Arduino need a different setting and programming to control the string synth and say, an analog monosynth?
id like to learn more about the string machine.How is it controlled?
Definitely not by CV and GATE Cool Cool which are the only signals i need out of it
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Boerge



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PostPosted: Fri Aug 11, 2017 3:01 am    Post subject: Reply with quote  Mark this post and the followings unread

No, not CV. But the gate signal is indeed already available via pin D10 of the Arduino. The sound is generated via PWM output of the Arduino. My idea is to use the PWM out for CV with codeparts of the other link, leaving out the LFO/phaser/oscillator code and maybe implementing MIDI In as described at Jan Ostmans stringsynth page.
A diskrete single bus keyboard scanner may be easier to built, when you are not into software. But the µC gives you more features.

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alanwilder81



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PostPosted: Fri Aug 11, 2017 3:44 am    Post subject: Reply with quote  Mark this post and the followings unread

i wonder how the early analog synthesizers made do without MIDI and Arduino.
I've been taking a look at some ancient mono synths keyboard schematics from the 70's, and most of them show a rather simple circuitry.
is there any convenience to go analog all the way?
i wonder how nobody dared rebuilding those... Smile
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Grumble



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PostPosted: Fri Aug 11, 2017 6:46 am    Post subject: Reply with quote  Mark this post and the followings unread

Alan, have you seen this thread?
http://electro-music.com/forum/topic-66640.html

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alanwilder81



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PostPosted: Fri Aug 11, 2017 7:41 am    Post subject: Reply with quote  Mark this post and the followings unread

hi Ed,
not only did i see that 3d, but i also actively contributed to it Smile
i brought in the Yusynth analog keyboard controller circuit.
Asked for help, got many suggestions but never quite managed to get it right no matter what i tried.
There is almost ALWAYS a random and unpredictable pitch fall on releasing the key.
i totally screwed up and gave up on it

the reason for that misbehaving is well over my head
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Boerge



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PostPosted: Fri Aug 11, 2017 9:57 am    Post subject: Reply with quote  Mark this post and the followings unread

alanwilder81 wrote:
i wonder how the early analog synthesizers made do without MIDI and Arduino.


Often with a resistor chain, followed by a sample/hold circuit. Needed for keeping the pitch when you release the key. Another way you can find at musicfromouterspace.com: a digital keypoard controller without µC. It can store the key in a register, which makes the job of the S&H. As I said: maybe easier to build, but less features Wink

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Boerge



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PostPosted: Fri Aug 11, 2017 10:02 am    Post subject: Reply with quote  Mark this post and the followings unread

alanwilder81 wrote:

There is almost ALWAYS a random and unpredictable pitch fall on releasing the key.


When you release the key, the behaviour of your keyboard controller depends on the particular circuit. To keep the pitch you may need a sample&hold circuit after the keybcontroller. Another advantage of a µC-circuit tongue

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alanwilder81



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PostPosted: Fri Aug 11, 2017 1:34 pm    Post subject: Reply with quote  Mark this post and the followings unread

the sample and hold did the job -ish- , but more often than not the pitch would drop on key release. Someone suggested that it may be a poor grounding problem.who knows
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Boerge



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PostPosted: Mon Aug 14, 2017 1:32 am    Post subject: Reply with quote  Mark this post and the followings unread

Just a first quick draft Wink


KeybController.pdf
 Description:

Download
 Filename:  KeybController.pdf
 Filesize:  50 KB
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alanwilder81



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PostPosted: Mon Aug 14, 2017 1:50 am    Post subject: Reply with quote  Mark this post and the followings unread

thanks boerge ! Smile Smile
looks simple. May you explain roughly how it works?
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Boerge



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PostPosted: Mon Aug 14, 2017 3:01 am    Post subject: Reply with quote  Mark this post and the followings unread

The 74154 has (controlled by the Arduino) always one output LOW, the µC reads the 4bit input and identifies the pressed key. Via an internal table the µC determines the corresponding voltage, which is generated via pulse width modulation. Velocity can be calculated by measuring the time between the contact closings (needs two contacts per key, one closing after the other).
The PWM output goes through a LPF, the rest of the analog part is common.
The only problem is the software, but as mentioned: there are many Aruino solutions out there with code that can reused or adapted. But, lazy as I am, it will take time... Wink
It ist only a first quick draft, have still to check for details (orientation of the diodes, correct handling of the SELECT-Inputs of the 74154 etc)

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alanwilder81



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PostPosted: Mon Aug 14, 2017 4:35 am    Post subject: Reply with quote  Mark this post and the followings unread

thanks Smile
it's all well over my head. But i am trying to get grasp with it Very Happy
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