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 
Live streaming at radio.electro-music.com

  host / artist show at your time
  Jez Adventures in Sound
Please visit the chat
 Forum index » DIY Hardware and Software
Simple triangle to saw shaper?
Post new topic   Reply to topic Moderators: jksuperstar, Scott Stites, Uncle Krunkus
Page 1 of 2 [34 Posts]
View unread posts
View new posts in the last week
Mark the topic unread :: View previous topic :: View next topic
Goto page: 1, 2 Next
Author Message
crashlander42



Joined: Oct 21, 2006
Posts: 292
Location: Orlando, FL (US)

PostPosted: Sat Jul 26, 2008 5:20 pm    Post subject: Simple triangle to saw shaper? Reply with quote  Mark this post and the followings unread

Can anyone point me toward a simple triangle to saw/ramp shaper? I'd like to add a saw output to my VCO-1, but I'm feeling stupid because my searches are turning up nothing.
_________________
When they plug me in the lights go down in Hong Kong.

http://www.myspace.com/isaciongun
http://www.youtube.com/user/Crashlander42
My DIY stuff Flickr
Back to top
View user's profile Send private message
yusynth



Joined: Nov 24, 2005
Posts: 1214
Location: France

PostPosted: Sun Jul 27, 2008 12:33 am    Post subject: Reply with quote  Mark this post and the followings unread

Check Jurgen Bergfors Complex VCO Wavshaper at

http://hem.bredband.net/bersyn/VCO/vco_complex.htm

http://hem.bredband.net/bersyn/VCO/VCO%20complex%20waveshapers.gif

_________________
Yves
Back to top
View user's profile Send private message Visit poster's website
richardc64



Joined: Jun 01, 2006
Posts: 609
Location: NYC
Audio files: 25

PostPosted: Sun Jul 27, 2008 5:06 am    Post subject: Reply with quote  Mark this post and the followings unread

From Scott Bernardi's Obesifier. http://home.comcast.net/~sbernardi/elec/og2/og3_obesifier.html

[Edit: Oops. Misread the subject as saw2triangle. Well, maybe it'll be of use to someone.]


saw2tri.gif
 Description:
 Filesize:  7.16 KB
 Viewed:  278 Time(s)
This image has been reduced to fit the page. Click on it to enlarge.

saw2tri.gif



_________________
"I am endeavoring, ma'am, to create a mnemonic memory circuit... using stone
knives and bearskins." -- Spock to Edith Keeler

Last edited by richardc64 on Sun Jul 27, 2008 5:22 pm; edited 1 time in total
Back to top
View user's profile Send private message Visit poster's website
ryktnk



Joined: Apr 24, 2008
Posts: 191
Location: london
Audio files: 1

PostPosted: Sun Jul 27, 2008 6:31 am    Post subject: Reply with quote  Mark this post and the followings unread

Hello

I had the same problem with an LM13700 VCO
so I tried adapting the Roland 100m SAW to TRI
which in reverse seems to work.

It is designed for levels from the LM13700 VCO in the app notes
so for the TH VCO you might have to adjust the input/output values a bit.

NB +-15v


RYK_TRI_to_SAW.jpg
 Description:
 Filesize:  83.17 KB
 Viewed:  326 Time(s)
This image has been reduced to fit the page. Click on it to enlarge.

RYK_TRI_to_SAW.jpg


Back to top
View user's profile Send private message Visit poster's website
bubblechamber



Joined: Nov 04, 2006
Posts: 276
Location: NYC
Audio files: 1

PostPosted: Sun Jul 27, 2008 11:12 am    Post subject: Reply with quote  Mark this post and the followings unread

thanks ryktnk..... that roland circuit looks a lot like a simplified version of the electro notes tri2saw shaper...

http://electronotes.netfirms.com/free.html
very last link... #129. this one works really well, but the roland looks much easier.

_________________
You can check your anatomy all you want, and even though there may be normal variation, when it comes right down to it, this far inside the head it all looks the same.
Back to top
View user's profile Send private message Visit poster's website
ryktnk



Joined: Apr 24, 2008
Posts: 191
Location: london
Audio files: 1

PostPosted: Sun Jul 27, 2008 1:19 pm    Post subject: Reply with quote  Mark this post and the followings unread

ah, yes
sorry it is from the Electronotes TZO, I was getting
confused.

Embarassed

-ryk
Back to top
View user's profile Send private message Visit poster's website
crashlander42



Joined: Oct 21, 2006
Posts: 292
Location: Orlando, FL (US)

PostPosted: Sun Jul 27, 2008 2:05 pm    Post subject: Reply with quote  Mark this post and the followings unread

Sweet! thanks! I'll be giving these a try later on today!
_________________
When they plug me in the lights go down in Hong Kong.

http://www.myspace.com/isaciongun
http://www.youtube.com/user/Crashlander42
My DIY stuff Flickr
Back to top
View user's profile Send private message
bubblechamber



Joined: Nov 04, 2006
Posts: 276
Location: NYC
Audio files: 1

PostPosted: Sun Jul 27, 2008 3:28 pm    Post subject: Reply with quote  Mark this post and the followings unread

it worked pretty well. i couldn't get the 2 triangle halves to line up, but it sounds great. if i spent an hour on it i'm sure i could have gotten closer, but the slight jagginess of the wave seems to thicken the sound up a bit. i had slightly better luck using the pn4301 as the FET. this is the first simple saw converter that I've played with that actually worked. thanks for posting this...
d

_________________
You can check your anatomy all you want, and even though there may be normal variation, when it comes right down to it, this far inside the head it all looks the same.
Back to top
View user's profile Send private message Visit poster's website
sneakthief



Joined: Jul 24, 2006
Posts: 525
Location: Berlin

PostPosted: Sun Jul 27, 2008 4:40 pm    Post subject: Reply with quote  Mark this post and the followings unread

whoa - deja vu: http://electro-music.com/forum/topic-23058.html&highlight=
_________________
Sneak-Thief - raw electrofunk
Back to top
View user's profile Send private message Visit poster's website
crashlander42



Joined: Oct 21, 2006
Posts: 292
Location: Orlando, FL (US)

PostPosted: Sat Sep 20, 2008 8:23 pm    Post subject: Reply with quote  Mark this post and the followings unread

This worked really well for me. I used it on the triangle out from my VCO-1. I replaced the R33/R37 with a 100k trim, so I had no problem getting the two sides to line up. I also changed R28 to 15K because the saw seemed to be clipping. The final result is perfect!
_________________
When they plug me in the lights go down in Hong Kong.

http://www.myspace.com/isaciongun
http://www.youtube.com/user/Crashlander42
My DIY stuff Flickr
Back to top
View user's profile Send private message
bubblechamber



Joined: Nov 04, 2006
Posts: 276
Location: NYC
Audio files: 1

PostPosted: Sun Sep 21, 2008 4:05 pm    Post subject: Reply with quote  Mark this post and the followings unread

thanks for sorting this out for us crash.
we ought to make a sticky out of this, it seems to come up a lot and you guys seem to have finally found a simple solution to this.
david

_________________
You can check your anatomy all you want, and even though there may be normal variation, when it comes right down to it, this far inside the head it all looks the same.
Back to top
View user's profile Send private message Visit poster's website
nicolas3141



Joined: May 25, 2007
Posts: 136
Location: Christchurch, New Zealand

PostPosted: Mon Sep 22, 2008 4:24 am    Post subject: Reply with quote  Mark this post and the followings unread

I am using a slightly simpler circuit with an LM324 and a bjt instead of a fet. Works fine with +/- 9v supply, should be okay with higher voltages, but not tested. My tri input is around 1.2 V p-p (should be okay with somewhat higher voltages, but not tested) and sqr input around 14V p-p. At normal audio frequencies.


tri2saw.JPG
 Description:
 Filesize:  12.1 KB
 Viewed:  9487 Time(s)

tri2saw.JPG


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



Joined: Nov 04, 2006
Posts: 276
Location: NYC
Audio files: 1

PostPosted: Mon Sep 22, 2008 1:59 pm    Post subject: Reply with quote  Mark this post and the followings unread

that is slightly simpler.. thanks for posting this, i'm looking forward to trying it out. is this an original design or did you come across it somewhere else?
david

_________________
You can check your anatomy all you want, and even though there may be normal variation, when it comes right down to it, this far inside the head it all looks the same.
Back to top
View user's profile Send private message Visit poster's website
nicolas3141



Joined: May 25, 2007
Posts: 136
Location: Christchurch, New Zealand

PostPosted: Mon Sep 22, 2008 5:15 pm    Post subject: Reply with quote  Mark this post and the followings unread

My design, but nothing startlingly original about it. I am currently teaching a night class where we are making a simple synth. Because I am using it to teach basic electronics I am simplifying the circuits as far as possible while still being musically useful. On my to-do list is to collect all the material together and put it up on the web. Will require a bit of work because I do quite a bit of it on the board, so the hand-outs are only half the story. Anyone in Christchurch, New Zealand who would like to be involved, let me know.
Back to top
View user's profile Send private message
sneakthief



Joined: Jul 24, 2006
Posts: 525
Location: Berlin

PostPosted: Fri May 15, 2009 7:54 am    Post subject: Reply with quote  Mark this post and the followings unread

OK, long delay here but I finally integrated nicolas3141's saw shaper into my standalone SN-Voice. Thanks again for providing this handy little circuit Smile

I couldn't get a saw per se, but it sounds nice enough. I tried varying the triangle volume and this had very little effect on the timbre.

Here's the closest sounding wave I could get - it doesn't have quite as many harmonics as a real saw but it sounds fine:

Posted Image, might have been reduced in size. Click Image to view fullscreen.

The square wave volume is crucial to this circuit. Luckily my SN-Voice has a volume control so I can dial in the small sweet spot where the approximated saw works.

Here are some mp3's:

1. http://sneak-thief.com/modular/sn-voice-saw-shaper-lfo.mp3

This is the sweet-spot (as seen in the graph above) with an lfo driving the frequency

2. http://sneak-thief.com/modular/sn-voice-saw-shaper-square-volume-change.mp3

Here's what it sounds like when you change the volume of the square wave. The closest thing to a saw is maybe 1/6 of a turn of the volume knob.

3. http://sneak-thief.com/modular/sn-voice-saw-shaper-with-pwm.mp3

And finally, this is what happens when you use PWM instead of a square. Sounds nice, doesn't it? The volume drops and the waveform looks like a PWM plus some kind of weird ramp or triangle.


Note: I used 15v to power the LM324

_________________
Sneak-Thief - raw electrofunk
Back to top
View user's profile Send private message Visit poster's website
nicolas3141



Joined: May 25, 2007
Posts: 136
Location: Christchurch, New Zealand

PostPosted: Sat May 16, 2009 3:35 am    Post subject: Reply with quote  Mark this post and the followings unread

Hello sneakthief

It is doing something interesting all right, but not quite what was originally intended. My circuit is designed to connect to a typical triangle core oscillator where the phase of the square is locked to the phase of the triangle such that the square wave transitions at the same time as the triangle changes from up-ramping to down-ramping.

In the SN oscillator it may not be like that, so perhaps that is one source of strangeness. If the square wave is instead triangle derived (rather than vice-versa) the circuit will give you a triangle wave an octave up, rather than a sawtooth.

The other issue you raise is the voltages. My circuit expects that the triangle input will be fairly low voltage, say +/-1V or similar, while the square input will be higher voltage, say +/-5V or similar. It almost looks as though there is something wrong with the transistor, but it could just be that the square voltage you are feeding it is insufficient to get it to turn on properly.

HTH,
Nicolas
Back to top
View user's profile Send private message
g.gabba



Joined: Nov 29, 2008
Posts: 32
Location: berlin

PostPosted: Sat May 16, 2009 10:02 am    Post subject: Reply with quote  Mark this post and the followings unread

Hello nicolas3141

this works good! in the audio range.

but it looks not perfect when it goes lower.

is that rigth?

Ahoi , g.gabba
Back to top
View user's profile Send private message
g.gabba



Joined: Nov 29, 2008
Posts: 32
Location: berlin

PostPosted: Sat May 16, 2009 11:25 am    Post subject:   Reply with quote  Mark this post and the followings unread

edit: i was wrong
Last edited by g.gabba on Mon Apr 14, 2014 2:43 am; edited 1 time in total
Back to top
View user's profile Send private message
nicolas3141



Joined: May 25, 2007
Posts: 136
Location: Christchurch, New Zealand

PostPosted: Sat May 16, 2009 2:16 pm    Post subject: Reply with quote  Mark this post and the followings unread

That's great. It works at most low to mid frequencies, but at high frequencies (up towards 10kHz) mine gets glitchy and doesn't produce a proper sawtooth. But using better op-amps in both this and the source oscillator would probably fix that. The LM324 does have it limitations.

Cheers,
Nicolas
Back to top
View user's profile Send private message
sneakthief



Joined: Jul 24, 2006
Posts: 525
Location: Berlin

PostPosted: Sun May 24, 2009 1:50 am    Post subject: Reply with quote  Mark this post and the followings unread

sorry for the late reply. thanks for your feedback and suggestions, Nicolas!

1. varying the triangle input volume had no effect on the symmetry or saw-like shape of the waveform, only the overall volume.

2. the square wave output of the sn-voice can reach 10vpp, so that shouldn't be an issue here.

3. here's what the simultaneous square & triangle outputs are from the sn-voice:

Posted Image, might have been reduced in size. Click Image to view fullscreen.


and here is the phase comparison between the two sn-voice outputs and the triangle-to-saw output:

Posted Image, might have been reduced in size. Click Image to view fullscreen.
Posted Image, might have been reduced in size. Click Image to view fullscreen.

_________________
Sneak-Thief - raw electrofunk
Back to top
View user's profile Send private message Visit poster's website
nicolas3141



Joined: May 25, 2007
Posts: 136
Location: Christchurch, New Zealand

PostPosted: Sun May 24, 2009 2:46 pm    Post subject: Reply with quote  Mark this post and the followings unread

This is very odd behaviour. Perhaps the transistor is suffering some kind of zener breakdown (it is subject to reverse voltage during half the cycle). It is possible that the higher voltages in your circuit (compared to mine) have damaged the transistor so that even when you turn things down it still doesn't work properly. Have you tried swapping the transistor?

Or perhaps the opamp is doing something weird. What power supply voltages are you giving the opamp? Are you sure the input voltages never exceed the supply voltages? Is it an LM324 or something different? If it is a dual/quad opamp, what are the other opamps in the chip doing?

If you were wanting to achieve this waveform deliberately you could get pretty close by using two diodes in place of the transistor (B to E and B to C). That makes me very suspicious that the transistor is in some kind of trouble.

Has anyone else seen this behaviour with this type of circuit?

Cheers,
Nicolas
Back to top
View user's profile Send private message
sneakthief



Joined: Jul 24, 2006
Posts: 525
Location: Berlin

PostPosted: Sun May 24, 2009 5:07 pm    Post subject: Reply with quote  Mark this post and the followings unread

As I mentioned, I used 15v to power the LM324. the 3 other opamps are tied (-ve and out) and grounded (+ve). It's powered by the same supply that's powering the SN-Voice.

Unless I misunderstood your query, the SN-Voice can only do 10vpp so I'm not sure if that qualifies as exceeding the input voltage.

I just tried another LM324 and it was the same.

The bc549 is brand new but I haven't tried another one yet.

_________________
Sneak-Thief - raw electrofunk
Back to top
View user's profile Send private message Visit poster's website
nicolas3141



Joined: May 25, 2007
Posts: 136
Location: Christchurch, New Zealand

PostPosted: Sun May 24, 2009 5:46 pm    Post subject: Reply with quote  Mark this post and the followings unread

So just to be quite clear, on the LM324 you have pin 4 to +15V and pin 11 to -15V. The emitter of the trannie is to 0V. The triangle and square inputs are more or less symmetrical either side of zero, with the waveforms peaking at around +/- 5V. In that case I am pretty sure that there is something wrong with your transistor. Are you sure you have it connected the right way round? I think with BC549s they are usually base in the middle, collector on the left and emitter on the right if you have the flat face towards you and the legs pointing down. Try any other general purpose NPN transistor you have lying around. I only used the BC549 because it was the first thing to hand. Very perplexing indeed.

Cheers,
Nicolas
Back to top
View user's profile Send private message
toppobrillo



Joined: Dec 10, 2005
Posts: 766
Location: oakland, ca
G2 patch files: 1

PostPosted: Sun May 24, 2009 6:58 pm    Post subject: Reply with quote  Mark this post and the followings unread

@sneakthief: what software is this? thx

josh
Back to top
View user's profile Send private message Visit poster's website
sneakthief



Joined: Jul 24, 2006
Posts: 525
Location: Berlin

PostPosted: Thu May 28, 2009 1:21 am    Post subject: Reply with quote  Mark this post and the followings unread

aha... and oops! I had just configured the LM324 with a single-side voltage supply (as per the typical datasheet configuration with pin 11 to ground).

here's what happened when i used -15v instead of simply grounding the lm324:

Posted Image, might have been reduced in size. Click Image to view fullscreen.


that looks somewhat better - but why the secondary saw? it looks like the triangle is clipping - and this happened regardless of the triangle input voltage.

Re. BC549 - I always verify the B/C/E of my transistors with the Hfe tester on my meter before sticking it in a circuit. do you still think i should still try replacing it?


topp - I'm using Oscillometer: http://shmelyoff.nm.ru/ ...but the 2nd screenshots (like this one here) came from WaveLab

_________________
Sneak-Thief - raw electrofunk
Back to top
View user's profile Send private message Visit poster's website
Display posts from previous:   
Post new topic   Reply to topic Moderators: jksuperstar, Scott Stites, Uncle Krunkus
Page 1 of 2 [34 Posts]
View unread posts
View new posts in the last week
Goto page: 1, 2 Next
Mark the topic unread :: View previous topic :: View next topic
 Forum index » DIY Hardware and Software
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
mps board

Please support our site. If you click through and buy from
our affiliate partners, we earn a small commission.


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