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 Forum index » DIY Hardware and Software » Developers' Corner
Any tips or schematics for building an advanced LFO?
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Hedefar



Joined: Feb 07, 2013
Posts: 15
Location: Denmark

PostPosted: Thu Feb 07, 2013 4:01 am    Post subject: Any tips or schematics for building an advanced LFO? Reply with quote  Mark this post and the followings unread

Hello out there!

Yesterday, I took my little DIY Mutable Instruments Anushri and went to play with the modular boys in town. It was very inspiring.
One person had a big Doepfer setup and the other had a smaller setup with hand picked modules of different brands.
One module in particular got my attention:

The Bubblesound uLFO.

That thing is amazing. It's range for one cycle goes from approx an hour and way up into the audible range, at 3,6kHz, making it a nice oscillator and all in all, it is just a quite versatile module with many parameters and CV possibilities.

See it here: http://www.bubblesound-instruments.com/ulfo.html
And in action: http://www.youtube.com/watch?v=Zr2iVvYz6YE&feature=channel

The owner had two of them and especially when getting them to modulate each other, they produced some very impressive sounds that the big Doepfer rig with all its modules couldn't mimic.
I liked the sound of the uLFO as an oscillator much better than the Doepfer A110 even though being a VCO is not it's main goal.

I crave that Bubblesound uLFO... but being a student, price is an issue, so I am looking for a way to build one.

I am no engineer and cannot design one myself. Not yet, anyway. But maybe some of you know of advanced DIY projects for something similar to this?

Thanks for taking your time! Smile

//Hedefar
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Uncle Krunkus
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PostPosted: Thu Feb 07, 2013 5:23 am    Post subject: Reply with quote  Mark this post and the followings unread

I've had two ideas about this,
1. An old idea about a module based LFO/EG. You stack the modules next to each other to create different slope speeds between stages. To make a complex LFO, you loop the output back to the start. The timing for each stage could be chargetime related, or it could be forced by a digital timing signal, (works kinda like a sync on a VCO but at low frequencies)
Gate, and/or trigger signals can force or hold up any stage, (for Envelope generator applications)
and,.........
You can add as many stages as you like.

2. A lot simpler, (and newer) idea is a 4017 cycling/resetting/changing steps, with a 100K pot from each output to ground, (Event Horizon style) wipers summed into a TL072 buffer with a glide cap on the feedback, adjustable. Other op-amp gives an inverted output.
Actually, with a TL074 you could get all four:-
Normal
Inverted
Glide
Glide inverted

Three chips and it's done.
If you use a 40106 for the main clock/trigger in processing, that still leaves 4 inverters to send the opposite to the summer, or not, I think.

Which kinda makes it a bit Klee Sequencer, but on a much simpler level. The Klee is, by the way, a really cool complex LFO if you hook it up that way. Cool

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Hedefar



Joined: Feb 07, 2013
Posts: 15
Location: Denmark

PostPosted: Thu Feb 07, 2013 6:30 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks for the reply Uncle Krunkus Smile

I'm afraid you are quite a bit above my level though. I'm new to DIY and so far I just assembled a Shruti-1 and an Anushri by following the written instructions closely.

But I will take my time to read up on the different components you mentioned. It will probably learn a lot from it Smile

And I will check out the Klee as well.
Thanks for helping out!

//Hedefar
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L´Andratté



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PostPosted: Mon Feb 11, 2013 4:48 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi! If you´re a beginner you should try building a cmos lfo with the 40106 chip uncle krunkus is mentioning (they are easy to get).

Actually such an LFO recently posted in the delay circuit by papaver yesterday
in his stylo-stereo-delay http://electro-music.com/forum/phpbb-files/jellyfish_schematic_143.jpg

the part that´s in the left lower corner repeated twice, it´s not exactly an advanced LFO but a very nice beginner circuit, with different timing capacitors can do wide freq range and in fact the ken stone psycho lfo is just this thing six times and intermodulating and THAT is a very cool module! albino

now time togo to sleep for me!
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Hedefar



Joined: Feb 07, 2013
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PostPosted: Tue Feb 12, 2013 2:54 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hey L´Andratté,

Thanks for the info. Sounds interesting!
I will definitely look into that! Smile

Cheers!
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bubzy



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PostPosted: Wed Feb 13, 2013 6:19 am    Post subject: Reply with quote  Mark this post and the followings unread

arduino + dac
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Uncle Krunkus
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PostPosted: Wed Feb 13, 2013 8:03 am    Post subject: Reply with quote  Mark this post and the followings unread

bubzy wrote:
arduino + dac


I'd like to try an Arduino one day, but at the moment it's just not in my budget to set it all up.
Crying or Very sad

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Hedefar



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PostPosted: Wed Feb 13, 2013 8:51 am    Post subject: Reply with quote  Mark this post and the followings unread

Yes, Arduino has been in my mind for quite some time now. I will probably dig into it at some point. A lot of possibilities seem to come with those little things!
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bubzy



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PostPosted: Wed Feb 13, 2013 10:56 am    Post subject: Reply with quote  Mark this post and the followings unread

Uncle Krunkus wrote:

I'd like to try an Arduino one day, but at the moment it's just not in my budget to set it all up.
Crying or Very sad


well, you can buy an atmega328 with the arduino bootloader, a usb>serial doodad, a crystal and 2 caps pretty cheap, and whammo! a diy arduino for about 1/6th of the price of a "proper" one.
Smile

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elmegil



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PostPosted: Wed Feb 13, 2013 1:55 pm    Post subject: Reply with quote  Mark this post and the followings unread

My first arduino was a "Mintduino" which is the ATMega chip, all the support necessary, a small breadboard, all in a mint tin.

I think it was $20. In my case I did spend another $25 on the FTDI chip to do the USB programming, but today you can buy a Leonardo for $20 that has the USB built in.

US prices, of course.

MCP4922 DAC gives you serial access to a 2 channel DAC for $5 or so.
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Hedefar



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PostPosted: Fri Feb 15, 2013 12:36 pm    Post subject: Reply with quote  Mark this post and the followings unread

Great!
Thanks for the tips, guys! Smile
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cloudscapes



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PostPosted: Sun Feb 17, 2013 3:09 pm    Post subject: Reply with quote  Mark this post and the followings unread

elmegil wrote:

MCP4922 DAC gives you serial access to a 2 channel DAC for $5 or so.


I prefer the PT8211 DAC

It's 2 channels, about $0.50 on ebay, 16-bit, lower pin count and faster. I use it for anything between full audio to CV/LFOs.

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bubzy



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PostPosted: Mon Feb 18, 2013 2:02 am    Post subject: Reply with quote  Mark this post and the followings unread

that is a nice chip!
no spi though :/
*buys some*

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Uncle Krunkus
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PostPosted: Mon Feb 18, 2013 4:25 am    Post subject: Reply with quote  Mark this post and the followings unread

Hedefar wrote:
Yes, Arduino has been in my mind for quite some time now. I will probably dig into it at some point. A lot of possibilities seem to come with those little things!


How about an LFO whose waveshape is analogus to an iteration graph across the mandelbrot set where the origin is set by two incoming CVs and the angle of the slice is set by a third CV, driven by another LFO!! Shocked Cool Laughing

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cloudscapes



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PostPosted: Tue Feb 19, 2013 7:00 pm    Post subject: Reply with quote  Mark this post and the followings unread

bubzy wrote:
that is a nice chip!
no spi though :/
*buys some*


which one, the 8211? I could interface to it easily enough via SPI and a couple manual pin toggles

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johncronan



Joined: Feb 24, 2013
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PostPosted: Sun Feb 24, 2013 6:25 pm    Post subject: Reply with quote  Mark this post and the followings unread

The MOTM-320 is what I would call an "advanced LFO." CVable (freq and shape), temperature compensated, very wide range. Synth Tech has a nice manual that you can download here. You would certainly be able to save a fair bit of money over the Bubblesound if you bought the PCB from Bridechamber for 40 bucks and sourced the other parts yourself.
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