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 Forum index » DIY Hardware and Software
ARP Odyssey Oscillators
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funkyfarm



Joined: Jan 21, 2007
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PostPosted: Tue Dec 30, 2008 10:27 am    Post subject: Reply with quote  Mark this post and the followings unread

Oh thank you so much !
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LetterBeacon



Joined: Mar 18, 2008
Posts: 454
Location: London, UK

PostPosted: Wed Dec 31, 2008 4:17 am    Post subject: Reply with quote  Mark this post and the followings unread

AndyR1960 wrote:
I've not had a problem using the same PDF - Please remember not to select the Shrink (or Fit) to Page scaling option if you're using Acrobat - make sure you select page scaling as "None", as this will definitely reduce the image... maybe that's the problem?

Cheers,

Andy.


Just to confirm that the PDF is fine if you un-select Shrink To Fit. I attempted to etch this yesterday and the IC sockets matched up perfectly with the holes.

Unfortunately, as this was my first time with Press N Peel, I managed to mess it up, and not all of the design melted onto the copper - damn! Back to the drawing board... Rolling Eyes
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ericcoleridge



Joined: Jan 16, 2007
Posts: 885
Location: NYC

PostPosted: Thu Jan 01, 2009 7:26 pm    Post subject: Reply with quote  Mark this post and the followings unread

I count 6 100k trimpots on this PCB. Could I substitute 50k for any(or all) of these trims without sacrificing tracking?

On the parts placement document, it looks like these are multi-turn trims. But I'm guessing on the odyssey these wre horizontal single turn trims, right?

I have multi-turn trims from Futurlec, but I don't think they work very well. Maybe it's just me, and because they have so many turns, but I can't ever hear much change when I adjust them in past projects.
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ericcoleridge



Joined: Jan 16, 2007
Posts: 885
Location: NYC

PostPosted: Fri Jan 02, 2009 7:11 pm    Post subject: Reply with quote  Mark this post and the followings unread

Yay!!! I tested my Dual Oddy VCO just now and it sounds fantastic and tracks great (I used a 2k tempco from MFOS).

I remember reading hear that the outputs of this circuit are 5v p to p, right?

When I put it through my Buchla 291, the signal was very low. I'm guessing the 291 wants 10v p to p.

How do we increase the signal of the Oddy VCO? Is there a resistor that can be replaced or something?



PS--Andy, thanks so much for this project. This is by far my favorite VCO!!!
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LetterBeacon



Joined: Mar 18, 2008
Posts: 454
Location: London, UK

PostPosted: Sat Jan 03, 2009 3:15 pm    Post subject: Reply with quote  Mark this post and the followings unread

Congratulations! Have you got any photos of the front panel? I'd be interested to see how you've laid it out.

ericcoleridge wrote:
How do we increase the signal of the Oddy VCO? Is there a resistor that can be replaced or something?

I've been trying to figure out how to do this, as well as centering the output around 0, but unfortunately I'm a bit out of my depth when it comes to these things! I've been reading up about DC offsets and amplification but I'm a bit lost when it comes to implementing. If anyone has any ideas then I'd be really grateful too!

Oh yes, don't forget that the square is 0-5v with the saw being 0-6v.
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AndyR1960



Joined: Feb 16, 2007
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PostPosted: Thu Jan 08, 2009 8:13 am    Post subject: Reply with quote  Mark this post and the followings unread

ericcoleridge wrote:


How do we increase the signal of the Oddy VCO? Is there a resistor that can be replaced or something?


Hi Eric,

I think this is what you want. I've lifted this from Thomas Henry's Build a Better Music Synthesizer - it's from his CEM VCO design. He used it on the Triangle output (which is also 0-5v PP) to convert it to 10v PP centered around zero.

I haven't tested it, but in theory it should be fine.

BTW, I've just taken a look at the 4023 VCF PCB foil I posted... definitely the same version as I've used to build my own VCF's. I wish I could be more help - could you PM some high rez images of your board to me, I'll see what I can do.

Andy.


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LetterBeacon



Joined: Mar 18, 2008
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PostPosted: Thu Jan 08, 2009 8:36 am    Post subject: Reply with quote  Mark this post and the followings unread

Andy, thanks so much for that! Being a bit of a beginner, I've had a hard time figuring out how to do that!

If I wanted to use that on the saw output (which is 0-6v), would it just be a case of changing the value of the 100K feedback resistor?
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AndyR1960



Joined: Feb 16, 2007
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PostPosted: Thu Jan 08, 2009 8:51 am    Post subject: Reply with quote  Mark this post and the followings unread

LetterBeacon wrote:
would it just be a case of changing the value of the 100K feedback resistor?


Yes, I'd change the 100k resistor for a 51k and then follow it with a 50k trimmer to allow the voltage to be adjusted back down to 10v PP.

You may find that it's not *exactly* centered around zero, though it'll probably be fine for general use - otherwise I *think* you would need to change the value of the 300k resistor slightly.
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ericcoleridge



Joined: Jan 16, 2007
Posts: 885
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PostPosted: Thu Jan 08, 2009 12:01 pm    Post subject: Reply with quote  Mark this post and the followings unread

AndyR1960 wrote:

I think this is what you want. I've lifted this from Thomas Henry's Build a Better Music Synthesizer - it's from his CEM VCO design. He used it on the Triangle output (which is also 0-5v PP) to convert it to 10v PP centered around zero.


Andy, you're the best!! I'll give this a shot tonight-- I'll post my findings.

AndyR1960 wrote:

BTW, I've just taken a look at the 4023 VCF PCB foil I posted... definitely the same version as I've used to build my own VCF's. I wish I could be more help - could you PM some high rez images of your board to me, I'll see what I can do.


I actually don't own a digtal camera, but as soon as I can borrow one, I'll take some pics and post them. Thanks for your help.
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ericcoleridge



Joined: Jan 16, 2007
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Location: NYC

PostPosted: Thu Jan 08, 2009 1:03 pm    Post subject: Reply with quote  Mark this post and the followings unread

LetterBeacon wrote:
Congratulations! Have you got any photos of the front panel? I'd be interested to see how you've laid it out.


I've got two of these boards etched, ones finished, the other still needs some assembly...

One is gonna get put together with an Arp Axxe MKI PCB (minus the VCF daughterboard) that I picked up on e-bay for $50. I'm gonna add a S+H section, a Yu-Synth Arp 4072 VCF, a mixer, maybe some other odds and ends, and essentially made an Arp 2600 reproduction. I've got some of the panel layed out in FPD with 30mm sliders. I have an Arp Solus, and I'm thinking of this project as a portable modular companion piece to my portable Solus. Both should be around the same size, and fit into the same size cases.

My second Dual Oddy VCO is gonna be the core of a Buchla 259 Programmable Complex Waveform Generator reproduction. I have a panel in FPD ready. The oddy VCOs will get coupled with a Serge style 3900 Norton Amp VC Saw to Tri/Sine waveshaper, a VC X-fader for low harmonic (Sine) to high harmonic (square) cross fading, and an Ian Fritz wavefolder for extreme VC Timbre modulation. there's also a Modulation Index, and all the other 259 sections. I have most everything done already.

i'll definitely try to get pictures up of all these projects as they materialize.

I really like this VCO.
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numbertalk



Joined: May 05, 2008
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PostPosted: Thu Jan 08, 2009 3:05 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi Andy,

If I wanted to use ferrite beads for power supply filtering would I just replace the 2 jumpers for the main + & - voltages or would I also use one on the tap off of the + voltage that goes to the trace that hits the VCO 2 Freq multi-turn trimmer?

Thanks!
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e-grad



Joined: Sep 12, 2008
Posts: 142
Location: Berlin

PostPosted: Tue Jan 13, 2009 4:25 pm    Post subject: Reply with quote  Mark this post and the followings unread

Etaoin wrote:
I used a 2k tempco with a parallel metal film 28.7k in my 4035. This gives you 1.87k with a tempco that should be close to that of the 2k tempco.

Is *28K7* a typo? I think it should be rather 2K87 (or even 1K955)??

I'm new to this is and I could be totally wrong thus will appreciate any hint.
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Etaoin



Joined: Jun 30, 2005
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Location: Utrecht, NL

PostPosted: Wed Jan 14, 2009 1:34 am    Post subject: Reply with quote  Mark this post and the followings unread

No, it's not a typo.

I meant what I said: 28k7 MF parallel with 2k PTC. That gives you a resistance of 1 / ( 1/28.7 + 1/2 ) = 1.87k with a tempco close to that of the PTC (as the MF is stable).

Anything close to 2k (as you're suggesting) would almost halve the resistance.

_________________
http://www.casia.org/modular/
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AndyR1960



Joined: Feb 16, 2007
Posts: 281
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PostPosted: Wed Jan 14, 2009 2:06 am    Post subject: Reply with quote  Mark this post and the followings unread

numbertalk wrote:
Hi Andy,

If I wanted to use ferrite beads for power supply filtering would I just replace the 2 jumpers for the main + & - voltages or would I also use one on the tap off of the + voltage that goes to the trace that hits the VCO 2 Freq multi-turn trimmer?


That would be fine... You could increase the value of the two smoothing caps which would also help, but I've had no problems leaving everything as it is.

Still working on remainder of the modules - LFO, Noise, S&H coming up soon.
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e-grad



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PostPosted: Wed Jan 14, 2009 2:19 am    Post subject: Reply with quote  Mark this post and the followings unread

Etaoin wrote:
No, it's not a typo.

Thanks!
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LetterBeacon



Joined: Mar 18, 2008
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PostPosted: Wed Jan 14, 2009 3:03 am    Post subject: Reply with quote  Mark this post and the followings unread

AndyR1960 wrote:
Still working on remainder of the modules - LFO, Noise, S&H coming up soon.


Looking forward to them - an ARP modular will be mine, oh yes, it will be mine!!
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pdman1



Joined: Mar 28, 2007
Posts: 50
Location: North Shore Massachusetts

PostPosted: Thu Jan 15, 2009 11:31 am    Post subject: Reply with quote  Mark this post and the followings unread

is there any chance that ready made PCBs for the Oscillator will become available?
kep up the good work!
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LetterBeacon



Joined: Mar 18, 2008
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PostPosted: Thu Jan 15, 2009 11:49 am    Post subject: Reply with quote  Mark this post and the followings unread

Looks like Magic Smoke are working on a design as we speak...
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funkyfarm



Joined: Jan 21, 2007
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PostPosted: Fri Jan 16, 2009 4:41 am    Post subject: Reply with quote  Mark this post and the followings unread

MODULARIZED ODYSSEY :

These mods include SYNC INPUT and SYNC OUTPUT on frontpanel.

Posted Image, might have been reduced in size. Click Image to view fullscreen.

Hi,

I guess it can be cool to have both vco "syncable".
Just adding another R79/C20 (and a switch).

But I wonder what waveform is present at switch S2.

Sawtooth, roughly 6 volts, centrered around 3 volts.

You can sync it with a standard vco sawtooth ? Smile


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numbertalk



Joined: May 05, 2008
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PostPosted: Sun Jan 18, 2009 11:01 pm    Post subject: Reply with quote  Mark this post and the followings unread

Here's a MOTM style panel I've made. It's huge.

EDIT - I'm not so great with photo software and can't export from FPD, so I'm just attaching the FPD file.

Also, Andy, which VCO is synced to which - which is the master and which is the slave oscillator? I'm guessing what I'll call oscillator 2 is the "slave" osc, , the circuit beneath the power supply pads - that it's the one that resets to the other osc circuit to the left of the PCB image you posted.

Thanks!


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funkyfarm



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PostPosted: Sun Jan 18, 2009 11:08 pm    Post subject: Reply with quote  Mark this post and the followings unread

The schematic above shows us vco1 (master) syncs vco2 (slave).

Very Happy
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numbertalk



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PostPosted: Sun Jan 18, 2009 11:15 pm    Post subject: Reply with quote  Mark this post and the followings unread

funkyfarm wrote:
The schematic above shows us vco1 (master) syncs vco2 (slave).

Very Happy


Thanks - that's what I thought - just not sure which is which on the PCB.
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funkyfarm



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PostPosted: Sun Jan 18, 2009 11:27 pm    Post subject: Reply with quote  Mark this post and the followings unread

According to PCB layout vco1 is on left side.

http://electro-music.com/forum/phpbb-files/arp_odyssey_dual_vco_126.pdf
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numbertalk



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PostPosted: Sun Jan 18, 2009 11:37 pm    Post subject: Reply with quote  Mark this post and the followings unread

funkyfarm wrote:
According to PCB layout vco1 is on left side.

http://electro-music.com/forum/phpbb-files/arp_odyssey_dual_vco_126.pdf


Thank you!

One more question I can't quite figure out from the schematic and Andy's layout - which throw is the switch flipped to for sync to be active? As it is on Andy's diagram - http://electro-music.com/forum/phpbb-files/arp_odyssey_dual_vco_126.pdf - as he has that switch illustrated here, the switch right now is connected to the lower throw (which connects the pole of the switch to a jumper leading to a 100K resistor and then a 2N3904 transistor etc..., while the other "upper" throw is connected to the negative voltage rail through a 100K resistor). Which throw activates the sync connection? In the schematic the sync switch simply has an "off" throw which connects to the positive voltage, so this seems different than what I'm seeing on Andy's layout.

Thanks again.
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AndyR1960



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PostPosted: Mon Jan 19, 2009 2:04 am    Post subject: Reply with quote  Mark this post and the followings unread

numbertalk wrote:
In the schematic the sync switch simply has an "off" throw which connects to the positive voltage, so this seems different than what I'm seeing on Andy's layout.

Thanks again.


The schematic above is for the Mk 1 VCO (although there's not much difference soundwise) my layout is from the Mk 2/3.

VCO 2 provides the sync signal, and as shown on my layout, sync occurs when the switch toggle is down. In the "up" position the sync input to VCO 1 is tied to -15v via a 100k resistor, which prevents any spurious re-triggering.
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