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 Forum index » DIY Hardware and Software
ARP Odyssey Oscillators
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elmegil



Joined: Mar 20, 2012
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PostPosted: Wed May 29, 2013 7:48 pm    Post subject: Reply with quote  Mark this post and the followings unread

The attenuation switch will switch it from 1X to 10X, usually. I believe it makes them higher impedance which should minimize their effect on the circuit.
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prgdeltablues



Joined: Sep 25, 2006
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PostPosted: Thu May 30, 2013 8:42 am    Post subject: Reply with quote  Mark this post and the followings unread

I'm seen that sort of distortion of square waves on my scope, using the probe on x1. Switching to x10 often sorts it out. It's caused by a mismatch between the RC constant of the probe and that of the scope input -using probes with trimmers (which is a pF variable capacitor), you adjust the trimmer until a square wave looks right. Not the only possibility of course, but worth checking out.

Peter
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LetterBeacon



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

PostPosted: Fri May 31, 2013 3:37 am    Post subject: Reply with quote  Mark this post and the followings unread

Turns out this was the problem after all! When I select 10x attenuation the wave shapes are as expected.

Thanks for your help!
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isak



Joined: Dec 13, 2009
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PostPosted: Mon Jun 03, 2013 9:30 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi guys.

I used this scheme to increase the output Vpp of the ody vco and it works great.

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

Can I use the same scheme for LFO or ADSR etc to increase the Vpp as well?

Cheers.

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LetterBeacon



Joined: Mar 18, 2008
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PostPosted: Sat Jun 29, 2013 4:16 pm    Post subject: Reply with quote  Mark this post and the followings unread

Sorry to drag this up again, but I still don't think my saw and square waves are correct!

On the previous page I thought my waveshapes were a little 'wonky' looking. They used to be perfect square and saw waves, but after getting my synth out of storage where it had been languishing for a couple of years, I noticed that they were wonky.

I thought it might have been my oscilloscope that was playing up, and using the attenuator on the probe it looked like the problem had gone away. But I've just recorded my synth straight out into my computer and took a look at the waves in my DAW. They're still wonky! In both oscillators!

I guess I'll have to start poking around the 4011 seeing as that's the component that both oscs share.
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isak



Joined: Dec 13, 2009
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PostPosted: Sat Jun 29, 2013 9:12 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi Smile

How does they look in the scope?
Are they look ok in your scope and in your computer they look wonky?
If yes that's normal.
I have the same thing with mine.
On the scope looks as they should, when connect to the soundcatd (RME FF400) look wonky, it's very obvious when at low freqs.

Cheers.

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LetterBeacon



Joined: Mar 18, 2008
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PostPosted: Sun Jun 30, 2013 2:03 am    Post subject: Reply with quote  Mark this post and the followings unread

Well they look wonky on my scope, until I use the attentuator switch on my probe, when they then appear as expected. On the previous page of this thread it was said that this was an impedance issue.

My problem is though is that if my square and saw wave look wonky in Cubase, after going through my FF400, then surely I'm not able to compose/ record with perfect square and saw waves?

I've attached some screenshots of the audio clips so you can see what I mean by wonky.


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isak



Joined: Dec 13, 2009
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PostPosted: Sun Jun 30, 2013 2:10 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
My problem is though is that if my square and saw wave look wonky in Cubase, after going through my FF400, then surely I'm not able to compose/ record with perfect square and saw waves?

believe me, you will Wink

same shapes i have in my comp, nothing to worry about.

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LetterBeacon



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PostPosted: Mon Jul 01, 2013 1:32 am    Post subject: Reply with quote  Mark this post and the followings unread

Ok, if you're sure...!
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isak



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PostPosted: Mon Jul 01, 2013 2:18 am    Post subject: Reply with quote  Mark this post and the followings unread

It's an AC DC thing.
Not sure why it's happening but it does.
I was in the same situation, with the scope it was perfect shapes.
With the comp scope like yours.
Besides that...the sound is the same sound, nothing to worry about.

Q..
What input of the FF400 you use?
Did you tried to connect to the back of the FF400 inputs or only to front inputs?

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numbertalk



Joined: May 05, 2008
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PostPosted: Mon Jul 01, 2013 8:30 am    Post subject: Reply with quote  Mark this post and the followings unread

I know I forget this as well but just as important is how does it sound? If it sounds ok then it's very likely ok.
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LetterBeacon



Joined: Mar 18, 2008
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PostPosted: Mon Jul 01, 2013 1:58 pm    Post subject: Reply with quote  Mark this post and the followings unread

numbertalk wrote:
I know I forget this as well but just as important is how does it sound? If it sounds ok then it's very likely ok.


Well the reason I'm being so anal with the waveforms is that they sound... well not off, but not quite how I remember them sounding. That's why I'm being paranoid! The only problem is that I haven't played with the synth for a couple of years, so it might just be my memory playing tricks on me!

If this could be an impedance issue, would it be solved by putting 1K resistor in series with the outputs?
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LetterBeacon



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PostPosted: Mon Oct 14, 2013 12:16 pm    Post subject: Reply with quote  Mark this post and the followings unread

Apologies if this has been asked before, but is anyone running this on +/-12v at all?

Do I need to re-calculate some resistor values for it to work, or should I be fine just plugging it in?

Thanks!
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steffensen



Joined: Jul 11, 2012
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PostPosted: Mon Oct 14, 2013 12:26 pm    Post subject: Reply with quote  Mark this post and the followings unread

LetterBeacon wrote:
Apologies if this has been asked before, but is anyone running this on +/-12v at all?

Do I need to re-calculate some resistor values for it to work, or should I be fine just plugging it in?

Thanks!


Im running mine on +/- 12V with no problem. The only thing that might need a lower value is the 274K controlling the PW.
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LetterBeacon



Joined: Mar 18, 2008
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PostPosted: Mon Oct 14, 2013 12:29 pm    Post subject: Reply with quote  Mark this post and the followings unread

That's good to know, thank you.

What sort of value would you recommend?
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steffensen



Joined: Jul 11, 2012
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PostPosted: Mon Oct 14, 2013 12:31 pm    Post subject: Reply with quote  Mark this post and the followings unread

I havent tried modding mine yet, but the value i will try when doing so will be something around 180K - 220K.
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LetterBeacon



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PostPosted: Mon Oct 14, 2013 12:32 pm    Post subject: Reply with quote  Mark this post and the followings unread

Great, thanks a lot!
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steffensen



Joined: Jul 11, 2012
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PostPosted: Mon Oct 14, 2013 12:35 pm    Post subject: Reply with quote  Mark this post and the followings unread

LetterBeacon wrote:
Great, thanks a lot!


Np, let me know if you find the value before i get around to it. Smile
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isak



Joined: Dec 13, 2009
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PostPosted: Mon Oct 14, 2013 1:03 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi steffensen Smile

Back then I think we talked about the 56k of the PWM, not the 274k..
If I remember correctly one should add 16.5k to the 56k in the 12V version.
So when you turn the PWM all the down you will get the square you want.

Just found it in one of our emails...
Quote:
In the 12V I needed to add more resistance for the square to sound like a square, i found that if I take the PW pot all the to the left I can still hear the PW works, only when I turn the pot CW few millimeters I get the square that should be.
So in the 12V I checked how many resistance I get when turning the PW pot till I hear the perfect square, it turns out to be 16.5k so I added this value to the 56k that in series with the PW pot and it worked like a charm Smile

I wrote PW but meant PWM, sorry for the mixup.

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steffensen



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PostPosted: Mon Oct 14, 2013 1:14 pm    Post subject: Reply with quote  Mark this post and the followings unread

isak wrote:
Hi steffensen Smile

Back then I think we talked about the 56k of the PWM, not the 274k..
If I remember correctly one should add 16.5k to the 56k in the 12V version.
So when you turn the PWM all the down you will get the square you want.

Just found it in one of our emails...
Quote:
In the 12V I needed to add more resistance for the square to sound like a square, i found that if I take the PW pot all the to the left I can still hear the PW works, only when I turn the pot CW few millimeters I get the square that should be.
So in the 12V I checked how many resistance I get when turning the PW pot till I hear the perfect square, it turns out to be 16.5k so I added this value to the 56k that in series with the PW pot and it worked like a charm Smile

I wrote PW but meant PWM, sorry for the mixup.


Hi Isak,
I would rather suggest tweaking the impact of the trimmer controlling the PW rather than modding any of the PW pot-ranges. Thats why changing the 274K will do the trick.
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isak



Joined: Dec 13, 2009
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PostPosted: Mon Oct 14, 2013 8:47 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hhoo...
Got your point Smile

Cheers.

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LetterBeacon



Joined: Mar 18, 2008
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PostPosted: Wed Nov 13, 2013 4:46 am    Post subject: Reply with quote  Mark this post and the followings unread

If I wanted to be able to control the pitch of each oscillator separately, which trace should I cut?

Looking at the PCB layout posted on page 1, it looks like I need to cut the trace that goes from the 1v/Oct to the VCO2 Scale trimmer. Does that sound look right?
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xpmtl



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

PostPosted: Fri Jan 10, 2014 8:34 am    Post subject: Reply with quote  Mark this post and the followings unread

Working on SMD version of this great little module.

So far it sounds great, need to verify tracking and stability and also how it performs on 12V.

I'm tracking 4-5 octaves (the fifth is a bit sharp) with unmatched trannies.

How does yours track? how many octaves?

I'll add pads for Thru-hole transistors for the expo pair in next revision, just want to know if i'm having the same results.

Cheers,

X


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isak



Joined: Dec 13, 2009
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PostPosted: Fri Jan 10, 2014 1:47 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi Smile

that look nice, good job.
I can track mine with no matched transistors up to 9 fully octaves.
It perform great with 12V although the signal is a bit low comparing to 15V.

cheers,
Isak E.

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xpmtl



Joined: Aug 10, 2007
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PostPosted: Sat Jan 11, 2014 2:12 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks Isak

What did you use as trannies for the expo pair?

I'm wondering why I only get 4 good octaves when you get 9, must be something else perturbing the thing.

Back to testing I guess Smile

cheers,

x

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