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Design of a Sawtooth wave generator
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Grumble



Joined: Nov 23, 2015
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PostPosted: Thu Oct 13, 2016 1:57 am    Post subject: Design of a Sawtooth wave generator
Subject description: And a question about the Moog sawtooth
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I start to feel the need for a Sawtooth waveform generator because it has a distinct sound, very different from sine, triangle and square waveforms.
I could make one with my sequencer in audio mode, but this will only give about 8 levels of voltage maximal.
So, in the line of my other builds it will be a module with an Arduino, an AD9833 DDS in square mode to provide the clockpulses for 3x 4 bit up/down counters (74LS193) and a 10 bit DAC AD9760 from Analog Devices.
It wil have a midi(ish) input, a CV (and pot) for frequency shift and a sawtooth and squarewave out.

Question: I have noticed looking at the signals from the sawtooth wave of a Moog that at the steep edge of the waveform there is a very short negative goint glitch.
Is that important soundwise? Will it be audible? Because if it is I will add this glitch to the near perfect sawtooth constructed by the counters and DAC

When the design evolves I will put diagrams here.

edit= corrected the link to AD9760

Last edited by Grumble on Sat Nov 05, 2016 11:17 pm; edited 1 time in total
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Grumble



Joined: Nov 23, 2015
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PostPosted: Sat Nov 05, 2016 7:46 am    Post subject: Reply with quote  Mark this post and the followings unread

The SAW module is finished.
Sorry, have to go, later more...


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Grumble



Joined: Nov 23, 2015
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PostPosted: Sat Nov 05, 2016 10:13 am    Post subject: Reply with quote  Mark this post and the followings unread

This saw-tooth module basically consists of a counter that is clocked with a DDS. Lowest frequency is about 0.4Hz and max. frequency is about 10kHz.

The top knob holds a rotary encoder, and with every step the frequency is up or down one full note.
The second knob from the top holds a potmeter for fine tuning and will shift the frequency one octave up and one octave down, the same as the CV.
Than the two switches: the left switch will turn Midi-in on and off, the right switch is to choose between a positive or a negative saw-tooth signal.
Below the switches are 4 3.5mm jacks, from top to bottom:
- Saw-tooth output, 0 - 5 volt.
- Square output, 0 - 5 volt, this square wave voltage has the same frequency as the saw-tooth wave and is 50% duty cycle.
- CV input, may be used as CV or as an FM input , input frequency 0 - 500Hz.
-(hard) SYNC input, a negative transition will reset the counter to zero to 766.


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Grumble



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PostPosted: Sat Nov 05, 2016 10:27 am    Post subject: Reply with quote  Mark this post and the followings unread

The soundfile: first just the sawtooth, and than with some filtering and last but no least, with the reverb module.

You analog guys might think that this is somewhat overkill, but mind you: This module has perfect Midi tracking well over 7 octave Rolling Eyes


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PHOBoS



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PostPosted: Sat Nov 05, 2016 8:56 pm    Post subject: Reply with quote  Mark this post and the followings unread

you're building some nice stuff with this modern approach to a modular synth, keep up the good work. Razz

(the link to the DAC is incorrect btw)

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Grumble



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PostPosted: Sat Nov 05, 2016 11:18 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thank you, and I corrected the link.
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Cfish



Joined: Feb 24, 2016
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PostPosted: Sun Nov 13, 2016 5:26 pm    Post subject: Reply with quote  Mark this post and the followings unread

Sounds great grumble
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Grumble



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PostPosted: Sun Nov 13, 2016 10:26 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks Chris Very Happy
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L´Andratté



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PostPosted: Sat Nov 19, 2016 3:03 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hey grumble, I´m total analog guy, and I personally have no use for any midi tracking, still it´s inspiring to see some good stuff as yours. Wink
Btw I plan for my actual synth project using a digital oscillator by electric druid (VCDO).Because it sounds soo good. Nice wavetables and good for drones. With a good vcf and vc delay you enter sitar territory /ramble off
Could you add such a thing (wavetable) easily to your digital oscillator? (as mentioned I´m happily lost with programming)
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Grumble



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PostPosted: Sat Nov 19, 2016 3:29 pm    Post subject: Reply with quote  Mark this post and the followings unread

Yes, it is possible, one way is to use the counter outputs as an address for an eeprom which data is fed to the dac.
In the eeprom you could store the wave table.
But its not a very user friendly type of generator that way.

The DVCO you are mentioning does sounds real good, considering its only 8 bits....
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L´Andratté



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PostPosted: Sat Nov 19, 2016 3:49 pm    Post subject: Reply with quote  Mark this post and the followings unread

Grumble wrote:
Yes, it is possible, one way is to use the counter outputs as an address for an eeprom which data is fed to the dac.
In the eeprom you could store the wave table.
But its not a very user friendly type of generator that way.

Thanks, I actually understood that Idea Confused Just asking for curiosity
Grumble wrote:
The DVCO you are mentioning does sounds real good, considering its only 8 bits....

Yeah and reducing those sounds even better Rolling Eyes
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Grumble



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PostPosted: Sun Nov 20, 2016 5:40 am    Post subject: Reply with quote  Mark this post and the followings unread

L´Andratté wrote:
Grumble wrote:
Yes, it is possible, one way is to use the counter outputs as an address for an eeprom which data is fed to the dac.
In the eeprom you could store the wave table.
But its not a very user friendly type of generator that way.

Thanks, I actually understood that Idea Confused Just asking for

In fact, it's just the way the DDS from Analog Devices work!
Check out the datasheet of the AD983, I use a lot in my synth.
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mmagin



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PostPosted: Sun Nov 20, 2016 1:20 pm    Post subject: Reply with quote  Mark this post and the followings unread

Nifty design, and very clean output. (I have no idea whether the Moog imperfection is discernable to the ear.)

Is the 10 bit ADC in the arduino pro mini (atmega328) really sufficient resolution for pitch CV? I guess maybe so once the fine adjustment is set so it is in-tune on both high and low notes?
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Grumble



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PostPosted: Sun Nov 20, 2016 2:04 pm    Post subject: Reply with quote  Mark this post and the followings unread

I do not use that ADC for resolution of the pitch, for that I'm running a serial data thru my synth that represents the midi note and calculate the frequency when needed.
That way I have a very accurate and stable note, but am able to add some pitch with a potentiometer and/or a CV input.
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mmagin



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PostPosted: Sun Nov 20, 2016 2:27 pm    Post subject: Reply with quote  Mark this post and the followings unread

Oh, got it, I missed the midi input!
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cslammy



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PostPosted: Thu Nov 01, 2018 7:59 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:

Check out the datasheet of the AD983, I use a lot in my synth.


Very cool use of the AD9833. Great work on this!

You have inspired me to buy some and mess w them, Banggood has them very cheap with free shipping to US.

Thanks, I hadn't heard of this very cool chip before.

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Grumble



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PostPosted: Thu Nov 01, 2018 8:58 am    Post subject: Reply with quote  Mark this post and the followings unread

Yes, the AD9833 is a great little chip, usable for clock generation well in the MHz frequencies as well as sound generator using the sine wave ir triangle wave output.
I even was able to hard sync it!

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Grumble



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PostPosted: Thu Nov 01, 2018 9:01 am    Post subject: Reply with quote  Mark this post and the followings unread

L´Andratté wrote:
Hey grumble, I´m total analog guy, and I personally have no use for any midi tracking, still it´s inspiring to see some good stuff as yours. Wink
Btw I plan for my actual synth project using a digital oscillator by electric druid (VCDO).Because it sounds soo good. Nice wavetables and good for drones. With a good vcf and vc delay you enter sitar territory /ramble off
Could you add such a thing (wavetable) easily to your digital oscillator? (as mentioned I´m happily lost with programming)

In the mean time I built a generator incorporated the wavetables from Electric Druid (with permisdion and converted to 9 bit)
https://youtu.be/qyvAb40cOTY

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gabbagabi



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PostPosted: Thu Nov 01, 2018 10:18 am    Post subject: Reply with quote  Mark this post and the followings unread

wow, nice!
one would need superman to stop this grumble-train Smile
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cslammy



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PostPosted: Thu Nov 01, 2018 10:22 am    Post subject: Reply with quote  Mark this post and the followings unread

g.gabba wrote:
wow, nice!
one would need superman to stop this grumble-train Smile


Indded!

Grumble for President!

I got a sample of the MAX260 coming, another Grumblechip I hadn't heard of.

Grumble on, Wayne!

Grumble on, Garth!

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Grumble



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PostPosted: Thu Nov 01, 2018 11:51 am    Post subject: Reply with quote  Mark this post and the followings unread

If you would like to I can help you a bit with programming the max260.
Just pm me if you would like that.

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cslammy



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PostPosted: Thu Nov 01, 2018 12:16 pm    Post subject: Reply with quote  Mark this post and the followings unread

Grumble wrote:
If you would like to I can help you a bit with programming the max260.
Just pm me if you would like that.


Will do. I could learn a lot from you!

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ixtern



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PostPosted: Fri Nov 02, 2018 5:40 am    Post subject: Reply with quote  Mark this post and the followings unread

Grumble wrote:
The SAW module is finished.

It's amazing how fast are you going from a concept to the finished product. You are an excellent source of great electro-music ideas Smile Thanks!
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