Square to sawtooth waveform conversion?

Peake

Hi, Google hath failed me Smile

I want to add a suboctave module to my system, and want more than a square or pulse waveform. Was it Fritz who posted a sine suboctave generator? Does anyone have a circuit for square to saw conversion?

Thanks..

françois · Posted: Wed Apr 09, 2008 11:49 am Post subject:

Hello,

Generating a sawtooth from a square is not possible since the square has lost almost all time information. OTOH, making a sine is possible by filtering out all the harmonics.

I posted here some weeks (or was it months ?) ago a topic on how to generate sub-octave and super-octave sawtooths (and also ×3, ×5, ÷3 and ÷5 frequencies). I'll try to find it.

EDIT: here it is :
http://electro-music.com/forum/topic-22679.html

Yours,

-- françois

bubblechamber · Posted: Wed Apr 09, 2008 12:19 pm Post subject:

well, if you convert your Square to a Triangle, you can use them both to create a Saw using the EN#129 waveshaper...

françois · Posted: Wed Apr 09, 2008 12:53 pm Post subject:

ian-s · Posted: Wed Apr 09, 2008 1:19 pm Post subject:

You can get a 75% pulse by ORing divide by 2 and divide by 4. This is close to a saw harmonically. Roland do it on some of their synths.

bubblechamber · Posted: Wed Apr 09, 2008 1:33 pm Post subject:

Peake · Posted: Wed Apr 09, 2008 8:07 pm Post subject:

Thank you for all of the replies. Yes, please scan it and post away. I appreciate it and it might create a bit of interest.

françois · Posted: Thu Apr 10, 2008 3:00 am Post subject:

richardc64 · Posted: Thu Apr 10, 2008 3:29 am Post subject:

http://home.comcast.net/~sbernardi/elec/og2/og3_sine_suboctave.html

sneakthief · Joined: Jul 24, 2006 Posts: 569 Location: Berlin

for your edification, i suggest that you read this thread if you haven't already:

http://electro-music.com/forum/topic-23058.html

françois · Posted: Thu Apr 10, 2008 5:25 am Post subject:

Funky40

bubblechamber · Posted: Thu Apr 10, 2008 12:19 pm Post subject:

this is from Jung's Op Amp Cookbook. it doesn't look prefect, but it does look easy...

SQR2SAW.jpg

Description:

Filesize:

214.39 KB

Viewed:

285 Time(s)

This image has been reduced to fit the page. Click on it to enlarge.

françois · Posted: Fri Apr 11, 2008 2:30 am Post subject:

Thank you !

I must have a deeper look on this circuit, but at first view I doubt it will convert a square into a saw at the same frequency. It seems to be just a synchronized sawtooth generator. But I'm not really sure, I'll have a really torough analysis before I can say more.

BTW, which book did you get this from ? I've not seen it in any of mine, so I must have missed one of the (very many) refverence book around there...

-- françois

yusynth · Joined: Nov 24, 2005 Posts: 1314 Location: France

Clack · Posted: Fri Apr 11, 2008 7:15 am Post subject:

yusynth · Joined: Nov 24, 2005 Posts: 1314 Location: France

bubblechamber · Posted: Fri Apr 11, 2008 10:39 am Post subject:

françois · Posted: Sat Apr 12, 2008 1:59 am Post subject:

Danno Gee Ray · Joined: Sep 25, 2005 Posts: 1351 Location: Telford, PA USA

I have the third edition of that book and in mine, the figure is now "Fig. 10-24" and is found on page 492.

JovianPyx · Posted: Mon Apr 14, 2008 6:52 am Post subject:

Some years ago, someone sent me a schematic for a square to saw (or perhaps square to tri) circuit. It was based on successive approximation, but the wave would quickly evolve when the input changed frequency.

Unfortunately, I am not at liberty to reveal the schematic, I promised not to do that.

jhaible · Posted: Mon Apr 14, 2008 8:35 am Post subject:

Has anybody mentioned the old Korg trick to create Saw suboctaves?

You start with a saw in the highest octave, then divide down the frequency with flipflops to get the lower octaves, all in square wave form.
Then you build starcase waveforms from weighted squares of the required octave, and all higher octaves.
And finally, you fill the gaps of this staircase with the saw wave from the highest octave.

Voila, saw wave in every sub octave.

Many old Korg synths did this:

Minikorg, Maxikorg, PS-3100 (and if memory serves, the Polysix as well).

This was mainly used for creating the "normal" oscillator signal in different transpositions rather than for dedicated suboctave generators.

I've used this method in the JH-720, whose VCO was inspired by the Minikorg 700:
http://home.debitel.net/user/jhaible/jh_720_vco_core.gif

JH.

(wondering if it makes sense to ffer some old style Korg synth PCBs at one time - there's a lot of interesing stuff burried in old Korg's - "singing" envelope, anybody? Smile

)

Peake · Posted: Mon Apr 14, 2008 10:49 am Post subject:

That rings a bell- wasn't the SH7 something similar to that Korg design? It would be interesting to have that with mixing versus switching.

jhaible · Posted: Mon Apr 14, 2008 1:25 pm Post subject:

gavgomad · Joined: Jan 29, 2006 Posts: 69 Location: Canada

Ah, the ol' Korg "singing" envelope.... Memories of my ol' maxi-korg that I sold many years ago. Unique instrument, although there were elements of the design that were SO foreign to me that I could never really tell if the synth was actually working to spec, or just "freaking out" - the "Repeat" circuit, for example.... Never understood those modes! ;-P

Gavin.