electro-music.com   Dedicated to experimental electro-acoustic
and electronic music
 
    Front Page  |  Articles  |  Radio
 |  Media  |  Forum  |  Wiki  |  Links  |  Store
Forum with support of Syndicator RSS
 FAQFAQ   CalendarCalendar   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   LinksLinks
 RegisterRegister   ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in  Chat RoomChat Room 
 Forum index » How-tos
Video Series: DIY Analog VCO
Post new topic   Reply to topic
Page 1 of 1 [12 Posts]
View unread posts
View new posts in the last week
Mark the topic unread :: View previous topic :: View next topic
Author Message
fosimoor



Joined: Nov 22, 2019
Posts: 9
Location: Berlin

PostPosted: Sun Jun 21, 2020 8:05 am    Post subject:  Video Series: DIY Analog VCO
Subject description: How to build a v/oct analog oscillator from scratch
Reply with quote  Mark this post and the followings unread

hi all,

I've started a new video series on how to build a v/oct analog VCO. here's the first part, where I go over the oscillator core and explain what all the components do in detail:



part two's on the way, thanks for watching!
Back to top
View user's profile Send private message
PHOBoS



Joined: Jan 14, 2010
Posts: 5083
Location: Moon Base
Audio files: 673

PostPosted: Mon Jun 22, 2020 4:13 am    Post subject: Reply with quote  Mark this post and the followings unread

great video! I like the balloon analogy party!

And now I need to do an experiment myself because I was expecting the waveform to be much more curved.
So I wonder if that is caused by the resistor to GND (I would have connected it between in and output) or a result
of the schmitt trigger (doubtful).

_________________
"My perf, it's full of holes!"
http://phobos.000space.com/
SoundCloud BandCamp MixCloud Stickney Synthyards Captain Collider Twitch YouTube
Back to top
View user's profile Send private message Visit poster's website AIM Address Yahoo Messenger MSN Messenger
Blue Hell
Site Admin


Joined: Apr 03, 2004
Posts: 23500
Location: The Netherlands, Enschede
Audio files: 262
G2 patch files: 320

PostPosted: Mon Jun 22, 2020 4:51 am    Post subject: Reply with quote  Mark this post and the followings unread

Yeah nice movie, at first I was very sceptical about the anologies used .. and then was surprised by the balloon too Cool

PHOBoS wrote:
So I wonder if that is caused by the resistor to GND (I would have connected it between in and output) or a result
of the schmitt trigger (doubtful).


Maybe the latter yeah .. the signal does not travel full range .. but it should still be part of an expo curve .. unless the schmitt trigger is implemented by feeding back directly to the input .. erm .. well ... a bit of the output is seen at the physical input ... could test that driving the gate with a resistor with a saw or tri wave.

Anyway .. also thought it to look remarkably flat.

Edit: there is some theory about such anologies .. it was something with Tensor and Flow iirc .. but I see Google to seem to have hijacked the terms for something deep learning ...

edit2: ah .. was wrong .. bond graphs it was .. with Flow and Effort ... https://en.wikipedia.org/wiki/Bond_graph

_________________
Jan
also .. could someone please turn down the thermostat a bit.
Posted Image, might have been reduced in size. Click Image to view fullscreen.
Back to top
View user's profile Send private message Visit poster's website
PHOBoS



Joined: Jan 14, 2010
Posts: 5083
Location: Moon Base
Audio files: 673

PostPosted: Mon Jun 22, 2020 7:28 am    Post subject: Reply with quote  Mark this post and the followings unread

Blue Hell wrote:
the signal does not travel full range .. but it should still be part of an expo curve

yeah, now that I am a bit more awake it does make sense. I was thinking it doesn't matter what voltage you use to charge
the capacitor, ie 5V or 10V the cap doesn't care and the curve would look the same. But of course in this case the voltage it
gets charged with is higher than the treshold voltage at which the schmitt trigger stops the charging. And of course this goes
for discharging aswell so you cut of the top and bottom of the expo curve and then it looks a lot more linear. It's still less curved
than I was expecting though.

Doing some tests at the moment after recreating the result which does indeed look rather linear (but it isn't).

_________________
"My perf, it's full of holes!"
http://phobos.000space.com/
SoundCloud BandCamp MixCloud Stickney Synthyards Captain Collider Twitch YouTube
Back to top
View user's profile Send private message Visit poster's website AIM Address Yahoo Messenger MSN Messenger
PHOBoS



Joined: Jan 14, 2010
Posts: 5083
Location: Moon Base
Audio files: 673

PostPosted: Mon Jun 22, 2020 1:36 pm    Post subject: Reply with quote  Mark this post and the followings unread

I did some tests driving an RC filter with the output of the oscillator to see if that would give somewhat different results,
spoiler: it doesn't. Of course I couldn't use a sawtooth oscillator as that would result in a squarewave output with a dutycycle
close to 0% or 100% depending on the direction of the diode. I tested with some different capacitor and resistor values and
the results aren't really surprising, as a matter of fact they are as expected.

The curve of Rx=10K/Cx=470pF, Rx=10K/Cx=4.7nF is more in line with how I thought it would look. This makes sense as
the window of the schmitt trigger is actually much smaller than I thought. With a 12V supply the amplitude of the voltage
over C seems to be only about 2.75V.


CCT1.png
 Description:
 Filesize:  64.46 KB
 Viewed:  53 Time(s)
This image has been reduced to fit the page. Click on it to enlarge.

CCT1.png



CCT2.png
 Description:
 Filesize:  222.88 KB
 Viewed:  43 Time(s)
This image has been reduced to fit the page. Click on it to enlarge.

CCT2.png



_________________
"My perf, it's full of holes!"
http://phobos.000space.com/
SoundCloud BandCamp MixCloud Stickney Synthyards Captain Collider Twitch YouTube
Back to top
View user's profile Send private message Visit poster's website AIM Address Yahoo Messenger MSN Messenger
fosimoor



Joined: Nov 22, 2019
Posts: 9
Location: Berlin

PostPosted: Tue Jun 23, 2020 12:56 pm    Post subject: Reply with quote  Mark this post and the followings unread

ha, you got me! nice analysis PHOBoS. yeah the wave is definitely not clean. I was surprised myself that I could get the oscillator to stay in tune over 5 octaves. but I think that makes it a very nice, rewarding first build for complete beginners.
Back to top
View user's profile Send private message
PHOBoS



Joined: Jan 14, 2010
Posts: 5083
Location: Moon Base
Audio files: 673

PostPosted: Tue Jun 23, 2020 2:58 pm    Post subject: Reply with quote  Mark this post and the followings unread

fosimoor wrote:
ha, you got me! nice analysis PHOBoS. yeah the wave is definitely not clean. I was surprised myself that I could get the oscillator to stay in tune over 5 octaves. but I think that makes it a very nice, rewarding first build for complete beginners.

I was just curious why it looked so straight. Wondering if somehow the schmitt trigger had some weird linearizing effect.
But it's just due to only using a small section of the expo curve which looks rather straight. Just using the oscillator to drive
an RC network with similar values would have been enough as it shows that the result is pretty much identical but I got curious
about what would happen with different values. If you make the values larger you get an even straighter shape but at a lower
amplitude. Note that for the oscillator itself it shouldn't make a difference what values you choose, the shape remains the same
and it doesn't have any influence on the tracking.

I don't know yet how you added voltage control though so maybe it affects the treshold levels which will also change the
waveshape. Looking forward to the next video Wink

_________________
"My perf, it's full of holes!"
http://phobos.000space.com/
SoundCloud BandCamp MixCloud Stickney Synthyards Captain Collider Twitch YouTube
Back to top
View user's profile Send private message Visit poster's website AIM Address Yahoo Messenger MSN Messenger
fosimoor



Joined: Nov 22, 2019
Posts: 9
Location: Berlin

PostPosted: Thu Jul 09, 2020 11:21 am    Post subject: Reply with quote  Mark this post and the followings unread

good to know that it doesn't negatively affect the tracking! here's the next episode:



i hope my BJT explanation isn't too far off. it's been consistent with my experiments though. when i swap the 2.2 nF cap for a 10 uF one (and the 100k drain resistor for a 2k), the wave becomes really curved and wonky, which is in line with PHOBoS' experiments i think!

next up is getting rid of temperature dependence, fixing the scaling and possibly some waveshaping to get a variable pulse wave!
Back to top
View user's profile Send private message
fosimoor



Joined: Nov 22, 2019
Posts: 9
Location: Berlin

PostPosted: Sat Jul 25, 2020 12:11 am    Post subject: Reply with quote  Mark this post and the followings unread

and here's part three!

Back to top
View user's profile Send private message
fosimoor



Joined: Nov 22, 2019
Posts: 9
Location: Berlin

PostPosted: Wed Aug 19, 2020 5:08 am    Post subject: Reply with quote  Mark this post and the followings unread

#4:

Back to top
View user's profile Send private message
PHOBoS



Joined: Jan 14, 2010
Posts: 5083
Location: Moon Base
Audio files: 673

PostPosted: Wed Aug 19, 2020 4:34 pm    Post subject: Reply with quote  Mark this post and the followings unread

excellent video Very Happy
_________________
"My perf, it's full of holes!"
http://phobos.000space.com/
SoundCloud BandCamp MixCloud Stickney Synthyards Captain Collider Twitch YouTube
Back to top
View user's profile Send private message Visit poster's website AIM Address Yahoo Messenger MSN Messenger
fosimoor



Joined: Nov 22, 2019
Posts: 9
Location: Berlin

PostPosted: Mon Sep 28, 2020 9:05 am    Post subject: Reply with quote  Mark this post and the followings unread

thanks! here's part 5:

Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic
Page 1 of 1 [12 Posts]
View unread posts
View new posts in the last week
Mark the topic unread :: View previous topic :: View next topic
 Forum index » How-tos
Jump to:  

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum


Forum with support of Syndicator RSS
Powered by phpBB © 2001, 2005 phpBB Group
Copyright © 2003 through 2009 by electro-music.com - Conditions Of Use