8038 VCO PCB layout for press'n'peel blue

janvanvolt · Joined: Nov 24, 2005 Posts: 285 Location: Mainz, Germany

The current version does work with an 8038 ? I am a bit puzzled as you speak about various chips for the core ...

(and no, i have not yet received my copy of the vco cookbook)

fonik

fonik · Posted: Thu Oct 11, 2007 4:43 am Post subject:

i'd recommended to STOP this project for a time. according to thomas' valuable comments concerning the cross-talk i will redesign the PCB layout hopefully next week.
see here:
http://electro-music.com/forum/topic-20737.html

fonik · Posted: Mon Oct 29, 2007 5:13 am Post subject:

i just finished a new layout. the two oscillators now only share the THAT IC which is a passive device anyway. the other parts of the oscillators are isolated from each other.

it is reviewed and triple checked (PCB against schematic) but i did not build it yet. so it's on your own risk!

www.modular.fonik.de/pdf/TH_dual8038VCOv2.pdf

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softfin · Posted: Mon Oct 29, 2007 5:23 am Post subject:

fonik · Posted: Mon Oct 29, 2007 5:24 am Post subject:

you're the man, softfin. that's great.

Etaoin · Joined: Jun 30, 2005 Posts: 760 Location: Utrecht, NL

Thanks Fonik!

Where did you get the THAT320? I can't seem to find that anywhere.

fonik · Posted: Wed Oct 31, 2007 1:16 am Post subject:

there was a groupbuy on the german forum, got just two from a member.

take a look here:
http://www.ka-electronics.com/that300/that300.htm
or
http://www.cedos.com/transistor_arrays.htm

softfin · Posted: Mon Nov 12, 2007 1:32 am Post subject:

Almost finished this 8038 project! I didn't have any THAT chips so I had to improvise. Laughing

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fonik · Posted: Mon Nov 12, 2007 1:38 am Post subject:

sweet, looks pretty exceptional! hope it all works out all well... you are the prototyper for the new layout...

softfin · Posted: Wed Nov 14, 2007 6:27 am Post subject:

Finished!
The Coarse Tune controls seem to interact somehow with each other... But not on all settings. Any guesses what could be the reason for this ?

Btw, I really like the character of the sine wave produced by this VCO, it's very soft, perhaps somewhat "wooden" sounding.

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fonik · Posted: Wed Nov 14, 2007 11:52 pm Post subject:

softfin · Posted: Thu Nov 15, 2007 12:01 am Post subject:

OK, ground remains shared between the two circuits, but I cut the connections for +-15 between the two VCOs and provided the +-15V separately to both sides.
Works fine now!

fonik · Posted: Thu Nov 15, 2007 12:12 am Post subject:

yes, i got it. the layout provides just shared filters for the power rails (R1/R2). i will have to change this!

glad you solved it.

Luka · Joined: Jun 29, 2007 Posts: 997 Location: Melb.

im looking for some top notch sine vcos

would this fit the bill?

can you gents post some examples pls

numbernone · Joined: Aug 16, 2006 Posts: 476 Location: new york city

I have been poking at a layout for the 8038 myself, and may have to become the second tester for your design FONIK.

What level of Sine trimming is implemented on this layout?

And for my obvious and or dumb question...The layout currently on your site is the revised version??

Thanks

fonik · Posted: Thu Feb 07, 2008 2:31 pm Post subject:

numbernone · Joined: Aug 16, 2006 Posts: 476 Location: new york city

Wow glad to hear you can get a decent sine without any of the add on circuitry, damn glad!!!

Great work Fonik! I think this will be the foundation of my 10,000 oscillator ANS meets Raymond Scott monstrosity (OK maybe 6).

numbernone · Joined: Aug 16, 2006 Posts: 476 Location: new york city

I did a quick test run on my new 8038VCO this morning, needs a couple lil kludges, but it seems like it will be very healthy!

I fit a pair on a tiny little ExpressPCB mini board, with separate power sections and grounding. it is definitely a crowded party, no room for parts to be lying down.

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softfin · Posted: Mon Feb 25, 2008 12:57 pm Post subject:

I finally put the dual 8038 vco in my modular.
It had been gathering dust for months because of lack of space in the modular, but now that I've got power in my 3rd cabinet, it was time to tune this vco, put it in the cabinet and test it further.

For some reason, I find it quite hard to tune it. After several hours of adjustments, I was able to achieve only about 4 octaves tracking.
In comparison, it took 10 minutes to get clean 6 octaves with a xr2206 osc.
Would appreciate any suggestions how to improve the tracking Smile

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janvanvolt · Joined: Nov 24, 2005 Posts: 285 Location: Mainz, Germany

My module is also working so far. See waveforms on my flickr! page...

Flickr: http://www.flickr.com/photos/jczmok/sets/72157616434119843/

But ... I experience the TL's are getting quite hot, but not the 8038's ..
Wonder if somebody has an idea. Module is powered by +/- 15V

fonik · Posted: Thu Apr 16, 2009 10:16 pm Post subject:

janvanvolt · Joined: Nov 24, 2005 Posts: 285 Location: Mainz, Germany

Sidenote: Make sure you use TL071/TL081 for U8/U9. I mistaken TL072 and all the TL's got very hot then. So if you experience this error, try to check the TL's first.

As fonik outlined: It's working perfect now. I used a .COM VCO and a octave switch to tune both OSCs.

kupfer_m · Joined: Oct 14, 2010 Posts: 47 Location: Belgium

I have some 8038 chips laying around here and I'd like to build this VCO but I can't find the VCO cookbook nor a schematic of this design.

Any help appreciated!!

thanks!

Tim Servo · Posted: Thu Dec 02, 2010 11:34 am Post subject:

Hey Kupfer,

I'm working to get the VCO Chip Cookbook available for sale. It's a big chore, as I'm preparing a PDF from paper originals. Lots of scanning and cleaning.

I hope to have this available soon, but in the meanwhile I think some of the PCB layouts should be available. Right?

Tim (even have my wife helping scan stuff) Servo