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 Forum index » DIY Hardware and Software
The LFX experimental LFO (8K LFO and Weird Waveshapers)
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Tim Servo



Joined: Jul 16, 2006
Posts: 924
Location: Silicon Valley
Audio files: 11

PostPosted: Wed Aug 10, 2011 5:03 pm    Post subject: The LFX experimental LFO (8K LFO and Weird Waveshapers) Reply with quote  Mark this post and the followings unread

Here's a LFO design I've been having a lot of fun with lately. The LFO core is my "8K" design that some of you have seen before. It's a variation on the standard Integrator / Comparator triangle core LFO, and I tweaked it a bit to give it a wider range (about 8,000 : 1, hence the name). The waveshapers are a combination of a tri-to-saw waveshaper ("Wave A" which is basically a sign changer) and my own TSQ tri-to-square waveshaper ("Wave B"). Here's a link to a YouTube vid where I put in a different cap to see (and hear) what the various wave combinations looked like:
http://youtu.be/FA88F1nxHDU

I call it the LFX. It's a pretty easy circuit to build, and will definitely provide you some very different LFO waveforms. Enjoy!!

NOTE: THIS IS AN UPDATED REV 02 VERSION WITH A NEW VALUE FOR R5.


MagSmoke_LFX_R02.jpg
 Description:
My Experimental LFO, or the "LFX." New version with different value for R5 (was 470R, is now 220R).
 Filesize:  78.48 KB
 Viewed:  510 Time(s)
This image has been reduced to fit the page. Click on it to enlarge.

MagSmoke_LFX_R02.jpg



Last edited by Tim Servo on Sun Aug 28, 2011 12:19 pm; edited 1 time in total
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tony void



Joined: Apr 26, 2011
Posts: 38
Location: Parma, Ohio

PostPosted: Thu Aug 11, 2011 6:34 am    Post subject: Reply with quote  Mark this post and the followings unread

This looks like a fun build. 1 quad chip for all. Could this produce sub-audidle freqs. to use as a vc source? Those shapes just look like they could weird-out a vco,vcf, or vclfo. Etc.etc.etc. drunken
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emdot_ambient



Joined: Nov 22, 2009
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Location: Frederick, MD

PostPosted: Thu Aug 11, 2011 10:16 am    Post subject: Reply with quote  Mark this post and the followings unread

Interesting...yeah, it would be nice to hear it used to modulate an oscillator and/or filter.
_________________
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bubzy



Joined: Oct 27, 2010
Posts: 554
Location: United Kingdom
Audio files: 62

PostPosted: Thu Aug 11, 2011 3:18 pm    Post subject: Reply with quote  Mark this post and the followings unread

hey thats nice looking. will draw up a toner etch pcb for it and post soonish. currently have dual 8k lfo and waveshapers in my modular (the old version)
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Tim Servo



Joined: Jul 16, 2006
Posts: 924
Location: Silicon Valley
Audio files: 11

PostPosted: Thu Aug 11, 2011 5:04 pm    Post subject: The LFX experimental LFO (8K LFO and Weird Waveshapers) Reply with quote  Mark this post and the followings unread

tony void wrote:
This looks like a fun build. 1 quad chip for all. Could this produce sub-audidle freqs. to use as a vc source? Those shapes just look like they could weird-out a vco,vcf, or vclfo. Etc.etc.etc. drunken


Hi Tony,

Actually, the capacitor value shown will produce low frequency waves for use as a VC source. I used a different cap in the YouTube video so that it would be easier to see the various waveforms (hard to display sub audio waveforms without a lot of flickering), and also because I was curious as to what the waves would sound like. Still, this is meant primarily as an LFO (hence the subject of the thread). The cap shown in the schematic will give you a range of roughly 0.0125Hz (about 80 seconds) to 100Hz. I'll do a sound sample of the LFX modulating a VCO so you can hear how it works as a mod source. Another thing I like about this design is that it still has the triangle and square outputs if you want a more 'normal' LFO. Wink

Tim (less 'normal') Servo
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Tim Servo



Joined: Jul 16, 2006
Posts: 924
Location: Silicon Valley
Audio files: 11

PostPosted: Sun Aug 14, 2011 5:43 pm    Post subject: The LFX experimental LFO (8K LFO and Weird Waveshapers) Reply with quote  Mark this post and the followings unread

Hi All,

Here are links to some YouTube vids showing the LFX being used as a modulator. The first is a simple demo with the LFX driving one VCO:
http://www.youtube.com/watch?v=AdM1-C288Lw&feature=mfu_in_order&list=UL

Then we have the LFX driving two VCOs (probably the best example):
http://www.youtube.com/watch?v=o0xXC9wUAgM&feature=mfu_in_order&list=UL

And then a more complex demo with two VCOs and a VCF:
http://www.youtube.com/watch?v=hifNoMYi5JM&feature=mfu_in_order&list=UL

Enjoy!!

Tim (my wife loves my synth music - as long as I'm in the other room with the door closed) Servo
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marvkaye



Joined: Mar 14, 2011
Posts: 225
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PostPosted: Mon Aug 15, 2011 1:34 pm    Post subject: Reply with quote  Mark this post and the followings unread

Just curious, Tim... which opamp did you use for this guy?

<marv>
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Tim Servo



Joined: Jul 16, 2006
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PostPosted: Mon Aug 15, 2011 1:46 pm    Post subject: The LFX experimental LFO (8K LFO and Weird Waveshapers) Reply with quote  Mark this post and the followings unread

Hi Marv,

Just a pair of plain old TL072s, although a TL074 would work just fine. I like the dual package because it makes routing things a little easier, and you can separate circuit blocks that might otherwise interfere with each other if they were all on the same chip (although this is a pretty rare problem, especially in an LFO).

Cheers,

Tim (plain old) Servo
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marvkaye



Joined: Mar 14, 2011
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PostPosted: Tue Aug 16, 2011 9:17 am    Post subject: Reply with quote  Mark this post and the followings unread

Hey Tim,

Thanks for the heads up on the opamps.... I laid out a stripboard for this last night, haven't gotten through the verification so don't want to post it just yet. I used the 2- TL072's as per your suggestion, came out pretty tiny, about 1.3x3 including room for mounting. I'm anxious to see how it works... thanks again for sharing.

<marv>
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bubzy



Joined: Oct 27, 2010
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PostPosted: Tue Aug 16, 2011 12:25 pm    Post subject: Reply with quote  Mark this post and the followings unread

Here's a PCB for the lfo, i havent built it, but have checked against the schematic and its correct.
its in EXPRESSPCB format
best to have the schematic to hand while you build it as i havent drawn up build docs (too lazy)

Edit : R2 to GND problem fixed and layers sorted out, thanks marvkaye


LFX PCB.zip
 Description:

Download
 Filename:  LFX PCB.zip
 Filesize:  14.14 KB
 Downloaded:  228 Time(s)


Last edited by bubzy on Mon Aug 22, 2011 11:23 pm; edited 2 times in total
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marvkaye



Joined: Mar 14, 2011
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PostPosted: Tue Aug 16, 2011 4:15 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi bubzy... thanks for posting that PCB layout... very cool indeed. (I need to learn how to do that... Confused ) I have one simple question, though.... are the trace layers reversed?? The ExpressPCB specs say that red traces are the top layer and green ones are the bottom. I'm sure that swapping them is no big deal, I just want to make sure I'm not missing something that should be obvious. I also found that with a little judicious tweaking I can fit two of your layouts on one of their Mini-board blanks, makes them very reasonably priced....

Your thoughts??

<marv>
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bubzy



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PostPosted: Tue Aug 16, 2011 4:37 pm    Post subject: Reply with quote  Mark this post and the followings unread

i have actually put the green traces in as jumpers. but yeah you're probably right about the layers being the wrong way around. id wait until someone (or me) has actually built one of these before spending money though.. there can always be problems that aren't obvious until you build something Very Happy ill probably get on it this week.
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marvkaye



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PostPosted: Tue Aug 16, 2011 5:45 pm    Post subject: Reply with quote  Mark this post and the followings unread

Good idea... I'll await a progress report before going further. BTW, swapping the traces was a snap. Nice piece of software.

<M>
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marvkaye



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PostPosted: Mon Aug 22, 2011 4:45 am    Post subject: Reply with quote  Mark this post and the followings unread

Hey bubzy, just curious if you had a chance to do anything with this PCB?? I started work on my stripboard for it but got distracted with other chores... I'd really prefer the PCB version, though, so my motivation to complete the stripboard was probably reduced considerably. I'm really looking forward to your update.

<marv>
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tokyomatik



Joined: Jan 20, 2011
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PostPosted: Mon Aug 22, 2011 5:38 am    Post subject: Reply with quote  Mark this post and the followings unread

the videos are really interesting, and i woud like to give it a try, unluckily i can't open the pcb file with Eagle, any chances to have a version in pdf?
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marvkaye



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PostPosted: Mon Aug 22, 2011 7:03 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
unluckily i can't open the pcb file with Eagle


Do yourself a favor and go to ExpressPCB http://www.expresspcb.com/ and download their free software. It's pretty popular for PCB layouts and lets you access their files directly and be able to modify them yourself as well... much more convenient than fooling with a PDF. Just a suggestion...
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tokyomatik



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PostPosted: Mon Aug 22, 2011 4:15 pm    Post subject: Reply with quote  Mark this post and the followings unread

i already went to that web site but i use a mac, i didn't found a version for osx Sad
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bubzy



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PostPosted: Mon Aug 22, 2011 4:45 pm    Post subject: Reply with quote  Mark this post and the followings unread

I havent yet tried the pcb, but here it is in pdf format.

top copper layer will be jumpers unless you have a method of printing dual sided boards.

edit : that was the PCB file Razz now posted pdf's sorry for the confusion (note to self dont put things on forum at 1am)


LFX PDF.zip
 Description:

Download
 Filename:  LFX PDF.zip
 Filesize:  37.72 KB
 Downloaded:  208 Time(s)


Last edited by bubzy on Mon Aug 22, 2011 11:41 pm; edited 1 time in total
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marvkaye



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PostPosted: Mon Aug 22, 2011 6:12 pm    Post subject: Reply with quote  Mark this post and the followings unread

I'm sorry to hear that, I didn't know they didn't have a Mac version. All things considered, though, since bubzy apparently didn't have time to do his PCB over the weekend I thought I'd give it a once-over to see if I could find any errors. I was surprised to catch one right out of the gate... see the attached picture.

I'm going to continue checking and will post additional corrections as they appear. Hopefully there won't be many more and I can put up a copy that matches Tim's schematic faithfully. Just remember, this is bubzy's PCB layout, I'm just being a second pair of eyes. When it's all proofed and if he doesn't mind, I'll be happy to post a PDF version for you.


LFX_PCB_162_mod-01.jpg
 Description:
Detail of fix for R2 to ground problem... shows move of top-surface trace as well to give more space between it and R1-R5 resistor pads.
 Filesize:  247.59 KB
 Viewed:  134 Time(s)
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LFX_PCB_162_mod-01.jpg


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marvkaye



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PostPosted: Mon Aug 22, 2011 7:20 pm    Post subject: Reply with quote  Mark this post and the followings unread

I didn't find any other errors. Disclaimer... I am complete noob at checking PCBs (although I have done several successful stripboard layouts), so please check closely to insure I haven't missed anything. Bubzy did some fine work and deserves all the credit for this layout.

The picture shown is a screen cap of the actual ExpressPCB layout on one of their mini-boards (2.5" x 3.8"). I'll U/L the actual file later. Green traces are bottom, red traces and yellow silkscreen are top.


LFX_double_PCB.jpg
 Description:
Picture of double LFX PCB.
 Filesize:  313.49 KB
 Viewed:  142 Time(s)
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LFX_double_PCB.jpg


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tokyomatik



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PostPosted: Mon Aug 22, 2011 8:24 pm    Post subject: Reply with quote  Mark this post and the followings unread

i'm trying to open the file but it's not pdf or is damaged Sad
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bubzy



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PostPosted: Mon Aug 22, 2011 11:15 pm    Post subject:   Reply with quote  Mark this post and the followings unread

marvkaye : nice work. how the heck did i miss that (considering that i follow the schematic with a highlighter pen....... :S)? original now changed. please post the expresspcb files up, dual board is a nice idea too.

new pdfs uploaded (instead of the wrong zip file last time. sorry)
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marvkaye



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PostPosted: Tue Aug 23, 2011 4:48 am    Post subject: Reply with quote  Mark this post and the followings unread

Glad you liked it. Here are the ExpressPCB file and PDFs.


LFXx2_PCB_bot.pdf
 Description:

Download
 Filename:  LFXx2_PCB_bot.pdf
 Filesize:  10.35 KB
 Downloaded:  160 Time(s)


LFXx2_PCB_top.pdf
 Description:

Download
 Filename:  LFXx2_PCB_top.pdf
 Filesize:  9.62 KB
 Downloaded:  158 Time(s)


LFXx2_PCB_screen.pdf
 Description:

Download
 Filename:  LFXx2_PCB_screen.pdf
 Filesize:  12.49 KB
 Downloaded:  176 Time(s)

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marvkaye



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PostPosted: Tue Aug 23, 2011 4:55 am    Post subject: Reply with quote  Mark this post and the followings unread

Weird... for some reason the PCB file wouldn't attach to that last post. Let's try again..... interesting.... worked fine as a ZIP. Here ya go.


LFXx2_PCB.zip
 Description:
ExpressPCB file

Download
 Filename:  LFXx2_PCB.zip
 Filesize:  27.7 KB
 Downloaded:  174 Time(s)

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Tim Servo



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PostPosted: Fri Aug 26, 2011 4:01 pm    Post subject: The LFX experimental LFO (8K LFO and Weird Waveshapers) Reply with quote  Mark this post and the followings unread

Wow, looks good. I haven't checked the layout carefully, but at first glance it looks like everything is there. About the only thing I might recommend is adding a name and date. You can even put it in the bottom layer copper. Something as simple as "LFX - 2011-08" might save you some time and head scratching if you etch a board and then don't get to actually putting parts on it for a few months. Wink I like adding the date so that I have a rough idea what schematic I used - in case an update gets posted later.

One more thought: I'd probably add a transistor and a few resistors for an LED rate monitor. I have some designs I was going to post, so you might want to hold off for just a bit if you want to add this to your layout (otherwise, the transistor buffer is so simple, it would be easy to add it with a small piece of perf board).

In any case, hope everyone has fun with the LFX. Smile

Tim (LFX Rated) Servo
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