ARP Axxe VCO

furio

I have just cloned the power isulation by Yusynth VCO http://yusynth.net/Modular/EN/VCO/index.html on the ARP Axxe VCO 3046 clone by EFM http://www.modular.fonik.de/files/EFMforum/orgEFMfiles/3046_VCO.pdf ...I have implemented it to increase the stability and for the use with +/- 15V power supply. I would like to share my little PCB, which is very nice and a much cheaper VCO to simplify the build for all or to help me to find eventually bugs.

VCO3046-mod-15V.pdf

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PCB Layout

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VCO3046-mod-15V.pdf

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vladosh · Posted: Thu Apr 28, 2011 3:36 am Post subject:

hi
Did you get that EFM vco working as it is in the schematic or you had to modify it .. i was thinking on building it on stripboard
thanks
vlad

furio

vladosh · Posted: Thu Apr 28, 2011 4:25 am Post subject:

..sorry i'm still noob for modifying circuits .. maybe someone from the forum will give you a suggestion .. nice that it's working the vco .. i spotted it and have a few 3046 so i just hope it'll work .. was thinking on adding PWM ..
greetings

furio · Posted: Thu Apr 28, 2011 5:06 am Post subject:

I just thought that, before installing a Tempco... I think it's best to do well the power.

CJ Miller · Joined: Jan 07, 2007 Posts: 368 Location: 127.0.0.1

I am the guy who dug up the 3046-based EFM Axxe VCO for Fonik. If there is any chance you cats have the schematics for the EFM VCO 8a or 8b *please* let me know. It was the original 3096-based version of Tom's Axxe clone. He had it up on EFM from about 1/2000-2/2000 but took it down when he became paranoid that a certain German synth company was stealing his ideas, it never appeared again. The 8a was basic like the 3046 version, while the 8b had an extensive all-transistor waveshaper. I copied the 8b schematic out on paper years ago but it was destroyed, and my original internet archive on floppy corrupted. I do not know if anybody has this one anymore.

I might just go ahead and combine bits of the 3046 version and the real Axxe schem, but I would really like the EFM version to play with, and for the archive.

furio · Posted: Sun Jun 05, 2011 2:32 am Post subject:

Hello,
I have tested this PCB, it is very stable, but I can't calibrate the scale.
Maybe for inexperience or some value is wrong...
Hopefully someone would help me to solve this little problem Smile

Link for a quick sound test...
http://dimenticato.org/files/3046VCO-modFMcgsLFO_Yusynth4072_cgsTubeVCA.ogg

3046VCO.jpg

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furio · Posted: Sun Jun 05, 2011 3:36 am Post subject:

CJ Miller · Joined: Jan 07, 2007 Posts: 368 Location: 127.0.0.1

Sebo · Joined: Apr 27, 2007 Posts: 564 Location: Argentina

Nice project, Thank You!!!

furio · Posted: Mon Jun 06, 2011 12:15 pm Post subject:

Hi Sebo,
Thanks for the interest Smile

I can track now this VCO for 3-4 octaves, but with only with very squeezed waveforms:

http://demosynth.dyndns.orgfiles/ARPaxxeVCOrect.ogg
http://demosynth.dyndns.org/files/ARPaxxeVCOsaw.ogg
http://demosynth.dyndns.org/files/TB-303VCOrichsquare.ogg

This comparison test is a bit stupid, because the VCO is very nice with the FM modulation.

citric acid · Joined: Jun 11, 2011 Posts: 45 Location: germany

sorry for my stupid question...i know from other diy project´s that you can runt this modules also with +12 -12 V . is this also with this module, take it sense ? like to have it in my doepfer case Smile

furio · Posted: Sat Aug 20, 2011 11:30 am Post subject:

isak · Posted: Thu Oct 25, 2012 9:51 am Post subject:

Hi furio,

Did you manage do get a scaling above 3-4 octaves?
By saying very squeezed...what exactly do you mean?
I can't open the sound clips, I really want to hear this VCO.
I hope you be able to answer fast cause I'll be making the boards to tonight Smile

Cheers,
Isak E.

furio · Posted: Thu Oct 25, 2012 10:14 am Post subject:

isak · Posted: Thu Oct 25, 2012 10:45 am Post subject:

Hi Furio,

It seems that I cant open it with my iPhone Mad

I'm sure I can tune it, my question is if you mange to tune it above 3-4 octaves like you stated few posts above.
If yes what was the max octave you manage to get?
More questions if I may..
What is the output Vpp?
Can I replace j112 to j111 or another fet? What you recomand?
I'm thinking to add fine tune and another V/ocv cv in for octave switch, do you think it would be easy to do?

EDIT:
Will want to add also PW pot and PWM, is it possible to add or to complicated?

Sorry for lots of questions.
I wanted to build the arp Odyssy vco but I'm missing a lot of components so this looks farley easy and I have all the components Smile

Cheers,
Isak E.

furio · Posted: Thu Oct 25, 2012 12:00 pm Post subject:

I don't have lab instruments and electronic knowledge... I've built only 3 pieces and forwarded them to my friends. Some friends have build it, and they are all very happy.

My preferrence is the Ody VCO and it sounds two times louder and 10x more beautiful: http://electro-music.com/forum/topic-28604.html

I think this Axxe VCO is a nice experience and tool for the cost, maybe with the CA3086 it sounds fetter... Test and report it!

With the +/- 15V power and 12V regulators the square looks & sound better... Maybe there are errors o buffers needed. Someone reported to me crash problems with the Rene' Sequencer.

I've posted the project to get help and improve it all together!

isak · Posted: Thu Oct 25, 2012 12:48 pm Post subject:

isak · Posted: Tue Oct 30, 2012 11:57 pm Post subject:

Hi Furio

I have build it, as you stated the square not sound like square (using 12V).
The saw is strong as you said but the top of the saw is cut, don't know why tho...
It is unstable, when trying to tune it with a tuner, I see the the guide line of the tuner is moving all the time.
For scaling trimmer I used 100k instead of 50k for wider range.
I use 1k tempco, didnt have j112 so I used 2n5457, and tried also with 2n5459.
With the 2n5457 I have more range in octaves but when playing with other notes with keyboards the notes are not in tune.
Anyway it's nice but not as stable as you said it is.

I Thank you for the layout, I wish it could work better Confused

Any help with troubleshooting is more then welcome.

Cheers,
Isak E.

LFLab · Posted: Thu Dec 20, 2012 10:54 pm Post subject:

Etched this board this week and built it this week. Worked on first startup, but I haven't tried to tune it yet.
Quite a simple build, do think the outputs benefit from a buffer. One of the two outputs is quite a bit softer than the other.
Used a J201 jfet, will need to check the scope to see if how the waveforms look.

Edit:
Had it on the scope tonight, saw output looks great (2.2v p-p), square output is looking more like a ramp wave, very low amplitude (0.3v p-p) and with a big DC component (2v). Needs a bit of tweaking, it seems.

LFLab · Posted: Sun Jan 20, 2013 5:51 am Post subject:

Bought some J112 FETs on eBay, and received them this week. It does seem to make some difference in the shape of the square wave.
Both outputs are now about 2v p-p, but the squarewave output still has a DC component, so I put a capacitor in series with the that output.

Nice VCO, didn't tune it yet, not needed for the noises I am making now.

Snaper · Joined: Feb 28, 2014 Posts: 217 Location: Hungary

It seems I can't find the BOM.
Is it possible to get a componenet placement for this?

Snaper · Joined: Feb 28, 2014 Posts: 217 Location: Hungary

Sorry about bumping out this old thread, etched two of these...
Non of the 2 working Sad

I can get 2-4 V (depending on the the PW trimpot) but thats all.

No sound, no reaction to the Freq pot or to external CV.

Did anyone else experienced this?

acidblue · Joined: Jun 26, 2009 Posts: 226 Location: The Darkside

Are you guys putting thermal paste on your tempco's?

Nisp · Joined: Mar 02, 2019 Posts: 1 Location: Sweden

Hi, all
I have been using this forum for learning more about modular synthesis and i have built a few bits that i will show in another tread but now i have stumbled upon this axxe clone.
I etched a circuit board and placed all of the components but i cant seem to get it to work.
i also did a test on a proto boeard but same issue there.
Any pointers on what could be wrong or atleast where i should start measuring... i looked so nice and it would be awesome to get this one to work.