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 Forum index » DIY Hardware and Software » The layout factory
ARP Odyssey MKII/III VCO - Eurorack Format
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AndyR1960



Joined: Feb 16, 2007
Posts: 279
Location: Manchester UK
Audio files: 5

PostPosted: Tue Jul 24, 2012 12:04 am    Post subject: ARP Odyssey MKII/III VCO - Eurorack Format Reply with quote  Mark this post and the followings unread

Sorry it's taken so long, but here's the single Eurorack version of the Odyssey MkII/III VCO.

I've just posted this in a previous ARP VCO thread, but to save time wading through 13 pages, I thought it would be easier to post it here.

I've built several (5!) and have had no problems with them except that, when I mount them in my grounded rack, the pitch drops about half a semitone!!! Still not sure what's causing this, but once it's in the rack and tuned up, it's perfectly fine.

Again, like the dual version, the FM inputs are "floating" (the Odyssey always has a voltage at the FM input) so please make sure that the input pot is always counter clockwise when not in use, otherwise you will encounter scaling problems.


OK, I'll admit it's a bit of a hack, but it works.

I'm not releasing the 2600 VCO/Waveshaper yet as:
a) It's already been posted here
b) Too many kludges in the pulse width pot wiring (ie. messy!)

The schematic can be found via Google (ARP Service Manual), and please remember that I'm just an enthusiast, with no formal electronics training... so if there's a problem, I may not be able to help... but I'll try

Hope you find it useful.

Oh... and before I forget. The Ring Mod is NOT included on this board, but a 0-10v Square Wave output is provided to feed the ARP's XOR Ring Mod (I'm working on it, and I'll post ASAP), but it's a simple circuit that can be built on strip board fairly easily.


ARP Odyssey VCO Foil.pdf
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ARP Odyssey VCO Layout.pdf
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LFLab



Joined: Dec 17, 2009
Posts: 187
Location: Rosmalen, Netherlands

PostPosted: Tue Jul 24, 2012 12:21 am    Post subject:   Reply with quote  Mark this post and the followings unread

Nice work!
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steffensen



Joined: Jul 11, 2012
Posts: 93
Location: Sweden

PostPosted: Sun Jul 29, 2012 2:56 am    Post subject: Reply with quote  Mark this post and the followings unread

Good initiative to make a new thread for this. Really nice job!

What difference would there be by using a 680pf Polystyrene/Silvered Mica, compared to a high quality Wima Polypropelene?
Would it mean the waveforms being a bit sloppier/imperfect (as the original) using the first option, and more modern/perfect using the Wima option?

Thanks for doing this!
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furio



Joined: Dec 25, 2009
Posts: 103
Location: Austria

PostPosted: Sun Jan 20, 2013 2:22 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi AndyR1960,

Thank you... the PCB looks very nice!

Would it make a difference at all when I install a 3300 or a 3500 PPM Tempco?
Would it also work with a 2K Tempco?

Could a better/extended tracking be expected if I would install a BC847BPN instead of the 2N3904/2N3906 (Exp Conv)?
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AndyR1960



Joined: Feb 16, 2007
Posts: 279
Location: Manchester UK
Audio files: 5

PostPosted: Sun Jan 20, 2013 2:43 am    Post subject: Reply with quote  Mark this post and the followings unread

furio wrote:

Would it make a difference at all when I install a 3300 or a 3500 PPM Tempco?
Would it also work with a 2K Tempco?

Could a better/extended tracking be expected if I would install a BC847BPN instead of the 2N3904/2N3906 (Exp Conv)?


I use SMD 2k 3300 Tempcos, they work fine, the 2N3904/06 is perfectly good for around 7 octaves, I don't think you need to change them.

My modular is built into a fairly air tight case, and the heat from the PSU keeps the internal temperature stable - I have 9 ARP VCOs in my system with no tuning/drift problems.

@Steffensen - Sorry I've not been on the forums fro a while - I've used both Polystyrene and Green WIMA caps, the resulting waveforms are very good and true (sharp flat squares, and great linear sawtooths).
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steffensen



Joined: Jul 11, 2012
Posts: 93
Location: Sweden

PostPosted: Sun Jan 20, 2013 2:52 am    Post subject: Reply with quote  Mark this post and the followings unread

AndyR1960 wrote:

@Steffensen - Sorry I've not been on the forums fro a while - I've used both Polystyrene and Green WIMA caps, the resulting waveforms are very good and true (sharp flat squares, and great linear sawtooths).


Oh thats allright man. This was long ago now, and this was all covered in the build thread. Smile

I am curious on your 2600 VCO design tho! Any info to share yet?
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AndyR1960



Joined: Feb 16, 2007
Posts: 279
Location: Manchester UK
Audio files: 5

PostPosted: Sun Jan 20, 2013 3:50 am    Post subject: Reply with quote  Mark this post and the followings unread

The 2600 VCO works great... unfortunately the PCB layout is still a mess (too many hardwired links have to be made, and the power is only 3 pin - struggling to find space for the full "Doepfer" style power connector, and I forgot the +15v supply to the frequency pots Rolling Eyes

So a re-draw is required, maybe on a slightly larger board - desperately trying not to use a double sided PCB. But it is getting there Wink

The main problem is, when you build for yourself you tend to think "Oh, that'll do" (even if it is a bit messy). But I'd prefer it to be right if I'm "going public" with something... or... maybe I'm just too fussy Very Happy

And for the life of me, I can't recall what that trimmer is for on the solder side! Don't you just love getting old!

Andy.


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Gaetano_AU



Joined: Oct 08, 2011
Posts: 49
Location: Australia

PostPosted: Sun Jan 20, 2013 4:34 am    Post subject: Reply with quote  Mark this post and the followings unread

Nice job on the board. Just a suggestion for the floating FM input (you may have tried this already), but how about using a switched 6.6mm jack, so the input is grounded when not in use.
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furio



Joined: Dec 25, 2009
Posts: 103
Location: Austria

PostPosted: Sun Jan 20, 2013 1:53 pm    Post subject: Reply with quote  Mark this post and the followings unread

AndyR1960 wrote:
I use SMD 2k 3300 Tempcos, they work fine, the 2N3904/06 is perfectly good for around 7 octaves, I don't think you need to change them.


Thanks Andy, I prefer to use the BC847BPN because I've already got it at home... seems that it may be compatible... I will still be buying the 2N3906/2N3904 seeing that I then have two different brands!

I still have some Magic Smoke Tempco's left.. but they too will soon be finished!
Where have you found the SMD 2K 3300ppm Tempco?
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steffensen



Joined: Jul 11, 2012
Posts: 93
Location: Sweden

PostPosted: Tue Jan 22, 2013 3:10 am    Post subject: Reply with quote  Mark this post and the followings unread

Good work on the 2600's Andy! Glad to hear theyre working. thumb up
Just let us know when you have something together for the mobster to chew on!
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PickNick



Joined: Oct 16, 2009
Posts: 82
Location: BP

PostPosted: Tue Jan 22, 2013 4:38 am    Post subject: Reply with quote  Mark this post and the followings unread

hi furio!

i found cheap SMD tempcos at Farnell:
http://uk.farnell.com/te-connectivity/lt7330002k0jtg/resistor-temperature-sensing-2k/dp/1174312

Peter

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furio



Joined: Dec 25, 2009
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PostPosted: Tue Jan 22, 2013 5:12 am    Post subject: Reply with quote  Mark this post and the followings unread

PickNick wrote:
hi furio!

i found cheap SMD tempcos at Farnell:
http://uk.farnell.com/te-connectivity/lt7330002k0jtg/resistor-temperature-sensing-2k/dp/1174312

Peter

Hi PickNick,
I have also seen this one, but I was insecure whether the 3000ppm were enough to reach 7-8 octaves of tracking.
Though, since I did not find anything else, I will take these ones.
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AndyR1960



Joined: Feb 16, 2007
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PostPosted: Tue Jan 22, 2013 5:41 am    Post subject: Reply with quote  Mark this post and the followings unread

PickNick wrote:
hi furio!

i found cheap SMD tempcos at Farnell:
http://uk.farnell.com/te-connectivity/lt7330002k0jtg/resistor-temperature-sensing-2k/dp/1174312

Peter


Yup, that's the ones - I solder them across a pair of tracks on "strip board", then just attach two pieces of wire to mount them - Don't try and solder wire directly to them, you'll just end up frustrated with burnt fingers and the resistor stuck to your iron Wink

EDIT - Hmmm, Interesting... Those SMD's are rated at 3000ppm. I bought mine a few years ago and I'm sure they were 3300ppm. I'm running short of them, so I'll get some in and see what happens.
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PickNick



Joined: Oct 16, 2009
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PostPosted: Tue Jan 22, 2013 6:08 am    Post subject: Reply with quote  Mark this post and the followings unread

without SMD pastes it's quite hard to work with this kind of components.

i'm not sure these are 3000ppm because the Part No. is LT773300...

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furio



Joined: Dec 25, 2009
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PostPosted: Tue Jan 22, 2013 8:05 am    Post subject: Reply with quote  Mark this post and the followings unread

Unfortunately, since I am operating privately and not as a company, Farnell refuses to sell me anything! Therefor I pay much more by doing business with this Austrian Company... as they are much more expensive.
At least now I'm sure you can buy without fear 25 pieces.... http://www.mercateo.at/p/1331-1174312/WIDERSTAND_TEMPERATURSENSOR_2K_Typ_LT7330002K0JTG.html

I posting here the untested changes I made to your PCB. With this Mod, the SMD Tempco and the BC847BPN are soldered together on a DIP8 adapter.


ARP_Odyssey_VCO_single_untestedMOD.pdf
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AndyR1960



Joined: Feb 16, 2007
Posts: 279
Location: Manchester UK
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PostPosted: Tue Jan 22, 2013 11:34 am    Post subject: Reply with quote  Mark this post and the followings unread

furio wrote:
Unfortunately, since I am operating privately and not as a company, Farnell refuses to sell me anything!


I've always been able to purchase privately from them, but it's a bit strange that Mercateo's web site is almost identical to Farnell's!!

Great mod Smile
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alcide



Joined: Apr 20, 2012
Posts: 5
Location: Lille, France

PostPosted: Wed Feb 27, 2013 10:25 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi there !

I'm trying to build some kind of eurorack-lite-odyssey system, and have already succeeded in making two of these great VCOs, plus the 4023 vcf. (thanks, AndyR1960 !). As i've never drawn any pcb, but would like to, I've decided to begin with the Odyssey's Ring mod.
Here's what i've done, so far...I've etched this pcb, and powered it, plugged in two square waves, but did not get any sound from the output. I've certainly forgotten something or made a typical newbie error. Could someone help me, please ?


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elmegil



Joined: Mar 20, 2012
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PostPosted: Wed Feb 27, 2013 11:24 am    Post subject: Reply with quote  Mark this post and the followings unread

On its face, the schematic seems to match the circuit, so I don't see a problem there.
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alcide



Joined: Apr 20, 2012
Posts: 5
Location: Lille, France

PostPosted: Wed Feb 27, 2013 11:19 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks for your attention, elmegil!
The strange thing is : I don't get any signal from the output when this board is powered. But I do get something when it's not. And that's what puzzles me: on the schematics, CD4011 is clearly connected to v+ on pin 14, and grounded on pin 7...

(Note : I've already tried several IC's. All of them are TI CD4011BE, not AE...)
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AndyR1960



Joined: Feb 16, 2007
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PostPosted: Thu Feb 28, 2013 1:00 am    Post subject: Reply with quote  Mark this post and the followings unread

Don't forget that both square wave inputs need to be 0-10v... the Oddy VCO's have a separate 10v output for the Ring mod. The the 0-5v "audio" output is not enough to drive the ring mod.
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elmegil



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PostPosted: Thu Feb 28, 2013 6:21 am    Post subject: Reply with quote  Mark this post and the followings unread

Since the NANDs are effectively hooked up as inverters (second leg tied to Vcc), could you use an inverting schmitt trigger (e.g. 40106) in place of the 4011 and get more sensitivity to incoming signals?
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AndyR1960



Joined: Feb 16, 2007
Posts: 279
Location: Manchester UK
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PostPosted: Thu Feb 28, 2013 6:33 am    Post subject: Reply with quote  Mark this post and the followings unread

I've also noticed you have the spare NAND inputs floating i.e. not connected to anything (pins 1, 2, 12 & 13), CMOS doesn't like floating inputs, so it's best to solder those 4 pins to +V. It's perfectly ok to leave the outputs unconnected Wink
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furio



Joined: Dec 25, 2009
Posts: 103
Location: Austria

PostPosted: Sat Mar 23, 2013 12:48 pm    Post subject: Reply with quote  Mark this post and the followings unread

I've inserted my front panel into the grid!
http://www.modulargrid.net/e/other-unknown-arp-odyssey-vco


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steffensen



Joined: Jul 11, 2012
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PostPosted: Sat Mar 23, 2013 12:56 pm    Post subject: Reply with quote  Mark this post and the followings unread

Cool stuff furio! Smile
Love that graphic. Any chance you could share those knob graphics?

I also have my Oddy VCO in the grid, but in private. Need a better photo before i dare to share it around. Razz
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furio



Joined: Dec 25, 2009
Posts: 103
Location: Austria

PostPosted: Sat Mar 23, 2013 1:18 pm    Post subject: Reply with quote  Mark this post and the followings unread

steffensen wrote:
Cool stuff furio! Smile
Love that graphic. Any chance you could share those knob graphics?

The jacks, knobs and light are by Hannes Pasqualini... It would be a job done in courtesy of the HexInverter's graphic designer. http://www.papernoise.net/
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