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 Forum index » DIY Hardware and Software
ARP Odyssey Oscillators
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Sebo



Joined: Apr 27, 2007
Posts: 538
Location: Argentina

PostPosted: Fri Oct 26, 2012 1:15 pm    Post subject: Reply with quote  Mark this post and the followings unread

I build the dual version and it works perfect, why you don't compare the single and the dual in search of any differences?
I think that would be easier than changing around components...

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steffensen



Joined: Jul 11, 2012
Posts: 95
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PostPosted: Fri Oct 26, 2012 1:59 pm    Post subject: Reply with quote  Mark this post and the followings unread

Sebo wrote:
I build the dual version and it works perfect, why you don't compare the single and the dual in search of any differences?
I think that would be easier than changing around components...


I did that 1 month ago, as well as colortraced the Layout to the Foil to see if it matched up. Also been comparing it all to the original schematics, and i cant find any problems really.

The issue here is probably with the 12V vs 15V which seems to be the voltage everyone with working versions are using.

Ive done everything i possibly could do at this point, so replacing components is the last thing on the list i guess.
Ive had some help with finding the proper resistors to make it more in the lines of 12V, but i havent done them all yet.
Done the major ones tho, with no real change yet.
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Sebo



Joined: Apr 27, 2007
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PostPosted: Fri Oct 26, 2012 2:15 pm    Post subject: Reply with quote  Mark this post and the followings unread

Ahh, OK.
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steffensen



Joined: Jul 11, 2012
Posts: 95
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PostPosted: Fri Oct 26, 2012 2:20 pm    Post subject: Reply with quote  Mark this post and the followings unread

Sebo wrote:
Ahh, OK.


Sorry if sounding on the fence, im a bit tired and frustrated to be so close and still not reaching all the way thru. Smile
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Sebo



Joined: Apr 27, 2007
Posts: 538
Location: Argentina

PostPosted: Fri Oct 26, 2012 5:50 pm    Post subject: Reply with quote  Mark this post and the followings unread

steffensen wrote:
Sebo wrote:
Ahh, OK.


Sorry if sounding on the fence, im a bit tired and frustrated to be so close and still not reaching all the way thru. Smile


Nothing at all.
English is not my native language, so sometimes I use few words because I don't know how to elaborate better.

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isak



Joined: Dec 13, 2009
Posts: 696
Location: Israel
Audio files: 18

PostPosted: Sat Oct 27, 2012 12:14 am    Post subject: Reply with quote  Mark this post and the followings unread

BTW did you try using 15V instead 12V?
Maybe this causing the freq not to go all the scale?
Try using 15V like the original says, with all the original components, you know... just to make sure the vco is ok and scaling correctly, this is what I would do.
After making sure every thing is ok then I would try modding it.
Hope it make sense.

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steffensen



Joined: Jul 11, 2012
Posts: 95
Location: Sweden

PostPosted: Sat Oct 27, 2012 2:01 am    Post subject: Reply with quote  Mark this post and the followings unread

Wish i had a 15v psu to try with yes. Im gonna build one some day.. Something small, cheap and easy to build would be great. Just for testing purposes anyway.
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isak



Joined: Dec 13, 2009
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PostPosted: Sat Oct 27, 2012 2:50 am    Post subject: Reply with quote  Mark this post and the followings unread

I've sent you an MFOS stripboard layout of 15V, it's very easy to do and working!
Just buy a 15VAC 1A wall wart and that's it Smile

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steffensen



Joined: Jul 11, 2012
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PostPosted: Sat Oct 27, 2012 2:52 am    Post subject: Reply with quote  Mark this post and the followings unread

Im looking in to it atm. Smile
As i dont etch (yet), theres always the PCB issue..but stripboard might work.

Back to the Oddy.
My Saw looks like a bowed arrow, instead of a straight line, gonna investigate on this now..

Edit:
The bowed Saw - below. Any idea what i can do about it?
Ive wired all the connections i can think would affect anything to potentiometers (about 10 of them), but all i seem to be able to change, is the "threshold" for the Saw, as well as the oscillation. With that i mean to make it oscillate higher or lower, and als to stabilize it. The bow is there no matter what i do.

Ideas?

Posted Image, might have been reduced in size. Click Image to view fullscreen.
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pdman1



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

PostPosted: Mon Oct 29, 2012 6:40 pm    Post subject: PCBs available? Reply with quote  Mark this post and the followings unread

Been off these boards for a long time. Was wondering if any PCBs are available to build the Arp Oscillator?
Thanks
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home_listening



Joined: Aug 09, 2012
Posts: 5
Location: Melbourne, Australia.

PostPosted: Sat Nov 03, 2012 12:03 am    Post subject: Reply with quote  Mark this post and the followings unread

You can buy them at:

frequencycentral.co.uk
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frequencycentral



Joined: May 25, 2008
Posts: 186
Location: UK

PostPosted: Sat Nov 03, 2012 4:32 am    Post subject: Reply with quote  Mark this post and the followings unread

Finally got around to finishing this. Well almost, the wife came home just as I was about to fit the RM. doh

Loving it, especially the sync. Compares so well with my own Odyssey.

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

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

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home_listening



Joined: Aug 09, 2012
Posts: 5
Location: Melbourne, Australia.

PostPosted: Sat Nov 03, 2012 4:45 am    Post subject: Reply with quote  Mark this post and the followings unread

Looks great!

Makes me even more excited for the 2 I've got coming from you!
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AndyR1960



Joined: Feb 16, 2007
Posts: 281
Location: Manchester UK
Audio files: 5

PostPosted: Sun Nov 18, 2012 11:44 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi Guys & Gals, Sorry I've been off the radar for a while... Back now : )

@Steffensen - Any chance of a hi-rez (and in focus) pic of both sides of your board... Sometimes two pairs of eyes are better than one. I'm also going to set my PSU up for 12V and see what happens.

@Rick (Frequency Central) - Great looking module, glad it's all OK and pleased to have helped.

I'm currently preparing the artwork for the ARP 2600 VCO & Waveshapers (built 5, all working well), and I'll post this when I'm done... it's a tight squeeze onto the same size board (75x100mm). The only difference from the original VCO core, is that I used discrete transistors because I ran out of 3046's (doesn't impact on the performance at all).

Andy.
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home_listening



Joined: Aug 09, 2012
Posts: 5
Location: Melbourne, Australia.

PostPosted: Mon Nov 19, 2012 12:07 am    Post subject: Reply with quote  Mark this post and the followings unread

I can confirm the osc works at 12V, though I've only gotten 1 of 2 going so far.
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isak



Joined: Dec 13, 2009
Posts: 696
Location: Israel
Audio files: 18

PostPosted: Mon Nov 19, 2012 12:34 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi Andy,

Good to have you back Smile
Looking forward to the sound samples of the arp 2600 vco!

BTW the ody vco sounds amazing, thank you very much for this!
I run it with 12V and sounds great.
The only problem I got into is when I turn the freq pot ccw the shap of the saw become very bowy.
It starts to become bowy from about 35Hz
The pic is at 20Hz
Posted Image, might have been reduced in size. Click Image to view fullscreen.
I think it influence the square as well, cause the square top and bottom lines are not straight as when on low freq, they are very slope lines.

Any idea why is that?

Thanks in advance,
Isak E.

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steffensen



Joined: Jul 11, 2012
Posts: 95
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PostPosted: Mon Nov 19, 2012 2:45 am    Post subject: Reply with quote  Mark this post and the followings unread

AndyR1960 wrote:
Hi Guys & Gals, Sorry I've been off the radar for a while... Back now : )

@Steffensen - Any chance of a hi-rez (and in focus) pic of both sides of your board... Sometimes two pairs of eyes are better than one. I'm also going to set my PSU up for 12V and see what happens.

I'm currently preparing the artwork for the ARP 2600 VCO & Waveshapers (built 5, all working well), and I'll post this when I'm done... it's a tight squeeze onto the same size board (75x100mm). The only difference from the original VCO core, is that I used discrete transistors because I ran out of 3046's (doesn't impact on the performance at all).

Andy.


Welcome back!
This seems odd perhaps, but i actually want to thank you for not getting back to me sooner. This forced me to learn the circuit to really get down to the problem.
By comparing voltages from the service manual, i tracked down my issue to the core of the VCO, and learned that part by detail. Breadboarded it and with the help of my oscilloscope i discovered that my 3904 in the differential pair wasnt doing its job. Seems the RLRA version i used was letting too much current thru so i replaced it with a Fairchild (with much higher hfe) and it all came to life. So, its all working now. All under 12 +/-. Smile

The Sync behaves a bit funny tho. Seems the 2 VCO's almost phases out when turning the frequency relationships. Like on every 5th note or so.. Perhaps this is how the Oddy works tho? Its very noticeable when using a LFO for the slave VCO in Sync.

Awesome news about the 2600 VCO! That was the one i was after in the first place, and have been for so many many years!
Cant wait to get my hands on that. Very Happy

Will it be possible to use a 3046 instead of the discrete trannies tho?

Thanks!
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AndyR1960



Joined: Feb 16, 2007
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PostPosted: Mon Nov 19, 2012 3:54 am    Post subject: Reply with quote  Mark this post and the followings unread

@isak,

At such a low frequency, I wouldn't worry about it - The Oddy only used VCO1 as a low frequency modulation source into the S&H mixer. It could be caused by the charging cap not being fast enough? I don't have a scope anymore, but I'll try and rig something up to see what my MkIII Oddy outputs.

@steffensen,

Glad you finally got it working, I was getting worried : )

The sync behaviour you describe is correct for the Odyssey, it's almost like octave doubling as you slowly change the freq (if you modulate it with the ADSR, you can set the Sustain level so that you get a perfect doubling effect - much like guitar feedback... I use it all the time).

I would have to give the board a major overhaul to use the 3046, but discrete 2N3904's do the job very well.
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steffensen



Joined: Jul 11, 2012
Posts: 95
Location: Sweden

PostPosted: Mon Nov 19, 2012 4:06 am    Post subject: Reply with quote  Mark this post and the followings unread

AndyR1960 wrote:

@steffensen,

Glad you finally got it working, I was getting worried : )

The sync behaviour you describe is correct for the Odyssey, it's almost like octave doubling as you slowly change the freq (if you modulate it with the ADSR, you can set the Sustain level so that you get a perfect doubling effect - much like guitar feedback... I use it all the time).

I would have to give the board a major overhaul to use the 3046, but discrete 2N3904's do the job very well.


Thanks. Smile
Allright, glad to have that confirmed and explained! Then it all seems to working pretty good here now. What an awesome sound it is.. Still getting to know the VCO's, and the possibilities just increases by the minute.

Using 3904's instead of a 3046 would make this one a even easier build actually. They are a lot easier to source. Ill save my 3046's for some other builds instead then.
I figured the 3046 was there for a reason tho? Matching etc. If its not needed and the sound is kinda the same - bring it on! Smile
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isak



Joined: Dec 13, 2009
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PostPosted: Mon Nov 19, 2012 4:32 am    Post subject: Reply with quote  Mark this post and the followings unread

Thank you for your reply Andy.

Ive built the single board version, not the dual.
charging cap...will be...? The 680pF?
thank you for trying helping on this matter Smile

One more thing...the scale, I'm trying to understand something.
If the freq pot is centered I'm getting a scale from C2 to C6 and few notes from lower then C2 but not getting to C1, same for the C6, few notes above C6 and not getting to C7.
So my question is...
If I want to get to C1 or above C6 must I move the freq pot left or right for that?
As I understand there is a limit for how much the octave will go unless I move the freq pot, right?
Sorry for the newbi question, it's my first ever built modul Smile

Cheers,
Isak E.

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steffensen



Joined: Jul 11, 2012
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PostPosted: Wed Nov 21, 2012 3:13 am    Post subject: Reply with quote  Mark this post and the followings unread

@AndyR1960
You have PM sir.
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Uncle Krunkus
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PostPosted: Wed Nov 21, 2012 4:29 am    Post subject: Reply with quote  Mark this post and the followings unread

The only tip I would give you, if you're about to do the resistors, make sure they aren't carbon types. They all need to be metal film around here.
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xpmtl



Joined: Aug 10, 2007
Posts: 158
Location: Brussels, Belgium

PostPosted: Fri Nov 23, 2012 3:59 am    Post subject: Reply with quote  Mark this post and the followings unread

Hey guys,

On the picture attached there is a dashed line surrounding R61 & R61. It is connected to the junction of Q9 and R64 as well.

What is it ??
Can it be left out of the circuit?

x.


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steffensen



Joined: Jul 11, 2012
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PostPosted: Fri Nov 23, 2012 4:04 am    Post subject: Reply with quote  Mark this post and the followings unread

xpmtl wrote:
Hey guys,

On the picture attached there is a dashed line surrounding R61 & R61. It is connected to the junction of Q9 and R64 as well.

What is it ??
Can it be left out of the circuit?

x.


Its a shielding ring, and yes - you can leave it out.
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AndyR1960



Joined: Feb 16, 2007
Posts: 281
Location: Manchester UK
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PostPosted: Thu Mar 21, 2013 10:33 am    Post subject: Reply with quote  Mark this post and the followings unread

Oh dear, not this old thread again Smile

Last week, I finally got off my a$$ and did some work before zooming off for a few weeks.

I'm glad to report that this VCO works fine with +/-12v with no modifications. No problems at all with 1v/Oct scaling or tuning. Unfortunately my scope is down at the moment, so I can't properly check the waveforms, but they sound fine to me, just a slight adjustment on the pulse width to bring it to 50% - I'll check when I'm back home.

I've been meaning to test this for ages - got a new PSU, so I was able to try it before re-calibrating to +/-15.

Hope this helps.
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