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ARP Odyssey Oscillators
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AndyR1960



Joined: Feb 16, 2007
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PostPosted: Fri Jun 06, 2014 11:36 am    Post subject: Reply with quote  Mark this post and the followings unread

patroche wrote:
The next is the seq ARP 1601


Now THAT'S something I'm definitely interested in Smile

If anyone can do it, you can - I gave up after 3 months (couldn't find the PCB foils)
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patroche



Joined: Feb 26, 2012
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Location: montelimar

PostPosted: Sun Jun 08, 2014 11:10 am    Post subject: Reply with quote  Mark this post and the followings unread

ok andy , give me your mail and i give you all my work !
Just a picture of my project
It don't run yet , because i have many vérification , before, on the sequencer.





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

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Sebo



Joined: Apr 27, 2007
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Location: Argentina

PostPosted: Sun Jun 08, 2014 4:32 pm    Post subject: Reply with quote  Mark this post and the followings unread

WOW, the sequencer looks awesome!!!
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isak



Joined: Dec 13, 2009
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PostPosted: Mon Jun 09, 2014 11:30 pm    Post subject: Reply with quote  Mark this post and the followings unread

thats really looks good man!
amazing work!

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isak



Joined: Dec 13, 2009
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PostPosted: Thu Jun 19, 2014 4:00 am    Post subject: Reply with quote  Mark this post and the followings unread

hi guys.

i did the Vpp boost suggested by Andy on page 8.

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

well, works great, i replaced the 100k to 51k and 50k trimmer so i can get it back to 10Vpp, that went out great.

as you see the signal is inverted, i want to invert it back to the original phase, i did a small scheme, someone here can please tell me if i did ok?

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

cheers,
Isak E.

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elmegil



Joined: Mar 20, 2012
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PostPosted: Thu Jun 19, 2014 6:16 am    Post subject: Reply with quote  Mark this post and the followings unread

I've more commonly see 10k or 20k used for the re-inverting op amp, but the layout is correct.
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isak



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PostPosted: Thu Jun 19, 2014 6:53 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks Smile

So 10k to 20k instead 100k?
Ok, I'll take that in mind.

Another thing..
When looking at the scope after the Vpp boost I've noticed that the waveform is no longer from 0 to 5V, it became, (+)(-), i guess it should be like that?
I'm wandering if I wasnt connecting the -15V would it still be (+)(-)?

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elmegil



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PostPosted: Thu Jun 19, 2014 7:04 am    Post subject: Reply with quote  Mark this post and the followings unread

2 x 10ks, or 2 x 20ks. both resistors have to be the same to have unity gain.\

It seems strange that an audio signal would be 0 - 5V; 5Vpp would normally be -2.5 to +2.5. I haven't gone back to look at the prior schematics, is there a DC blocking cap at the end of the prior stage?

In any case, don't try to run your op amp without the -15V rail. And a TL07X is not going to like simply trying to substitute ground there. You'd need a different op amp capable of doing single-sided supply. There are some LM amps (e.g. LM358) that can do that if you really feel you need to.
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isak



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PostPosted: Thu Jun 19, 2014 12:16 pm    Post subject: Reply with quote  Mark this post and the followings unread

hi elmegil

Quote:
It seems strange that an audio signal would be 0 - 5V; 5Vpp would normally be -2.5 to +2.5. I haven't gone back to look at the prior schematics

the saw and the square are 0 to 5, in the ody vco, and 0 to 10 in the 2600 vco, this is the last time i checked.
in the 2600 vco only the Tri and Sine are (+)(-).

Quote:
In any case, don't try to run your op amp without the -15V rail. And a TL07X is not going to like simply trying to substitute ground there. You'd need a different op amp capable of doing single-sided supply. There are some LM amps (e.g. LM358) that can do that if you really feel you need to.

i think you miss understand me, sorry about that.
i meant to disconnect the -15V that connected to the 300k and pin 2 of the opamp.

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elmegil



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PostPosted: Thu Jun 19, 2014 12:54 pm    Post subject: Reply with quote  Mark this post and the followings unread

Sorry for the misunderstanding. Seems like a good chance of it working as you say....
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isak



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PostPosted: Thu Jun 19, 2014 11:32 pm    Post subject: Reply with quote  Mark this post and the followings unread

elmegil,

I don't think there is a DC block.
I guess the the -15V and the 300k is for center it around zero.

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furio



Joined: Dec 25, 2009
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PostPosted: Tue Jul 08, 2014 5:19 am    Post subject: Reply with quote  Mark this post and the followings unread

isak wrote:
I don't think there is a DC block.
I guess the the -15V and the 300k is for center it around zero.

With +/-12V power supply, should the 300K be reduced by 10%, 20% or nothing?
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isak



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PostPosted: Tue Jul 08, 2014 5:55 am    Post subject: Reply with quote  Mark this post and the followings unread

furio wrote:
isak wrote:
I don't think there is a DC block.
I guess the the -15V and the 300k is for center it around zero.

With +/-12V power supply, should the 300K be reduced by 10%, 20% or nothing?

i was right when i said..
Quote:
I guess the the -15V and the 300k is for center it around zero.

i didnt connect the -15V so there is no need for the 300k.
so it works perfect Smile

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furio



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PostPosted: Tue Jul 08, 2014 9:08 am    Post subject: Reply with quote  Mark this post and the followings unread

isak wrote:
i didnt connect the -15V so there is no need for the 300k.
so it works perfect Smile

So you do not just connect the 300K or even the -15V power of the TL072?
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isak



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PostPosted: Tue Jul 08, 2014 9:17 am    Post subject: Reply with quote  Mark this post and the followings unread

furio wrote:
isak wrote:
i didnt connect the -15V so there is no need for the 300k.
so it works perfect Smile

So you do not just connect the 300K or even the -15V power of the TL072?


yep

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furio



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PostPosted: Thu Jul 10, 2014 12:19 am    Post subject: Reply with quote  Mark this post and the followings unread

isak wrote:
yep

No, I tried!
The 300K resistor seems indispensable.
It also works well with 12V.
Not installing it, simply amplify the wave without centering.
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isak



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PostPosted: Thu Jul 10, 2014 2:47 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
Not installing it, simply amplify the wave without centering.

this is what i wanted, this is what were talking about here.

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kanji



Joined: Aug 17, 2012
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PostPosted: Sun Aug 17, 2014 4:33 am    Post subject: Reply with quote  Mark this post and the followings unread

Hello all. I've build several DIY synths and decided to build Odyssey using Dual Oscillator PCB.

First of all I want to thank Andy for his amazing work and dedication in this thread. Even with issues my oscs have, they sound really powerful and your work has helped a LOT to get where my project is now Smile

I've build VCOs, Yusynths Arp filter and Yusynths VCA. ADSR/AR circuits I build from original ARP schematics, same with Mixer section, LFO and S/H.

I was happy with the raw nature the instrument has, but always thought that square waves arent as clean as they seem in odyssey videos in youtube.

I don't have scope, but I checked both oscillators using visualanalyzer and it seems that squarewaves aren't right. Saw sounds nice and looks "ok" in analyzers screen. Squares seem to droop right after their edge has risen to peak voltage. Peak voltage doesn't stay up, instead droops before cycle starts its second half.

I'm running this on 12V and powersupply is checked and tested three times. Same goes with the PCB itself. I also tested changing 274k resistor that affects PWM but that didn't do the trick. My board sets squares dutycycle to 50/50 with original components, but squares shape is the issue.

I've used CA3146 instead of CA3086 and 2N5459's I replaced with 2N3823. All other components are like in original BOM.

If some one has any idea where to start looking solution, help would be awesome.

Thanks in advance Smile


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furio



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PostPosted: Sun Aug 17, 2014 7:01 am    Post subject: Reply with quote  Mark this post and the followings unread

kanji wrote:

I don't have scope, but I checked both oscillators using visualanalyzer and it seems that squarewaves aren't right.

Hello kanji, nice work !!! Smile

Respecting the descriptions of the resistors shown in the schematic... you'll get a perfect clone... respect the original scheme, it definitely will have better waves & Sound. Though it could also become very unstable, difficult to calibrate and plunder often over time the tuning.

I preferred to give up a little of musicality and increase stability to the maximum of the exponential converter and sync. Though unfortunately it is metal film, I tried anyway to use the best available Hi End Resistors.

From my tests, I noticed that a square wave acceptable, I obtained according to the schematic and placing Carbon Film Resistors at least for the waveshaper circuit.

P.S. This VCO allows +/- 0.1% tracking accuracy and stability.


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Sebo



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PostPosted: Mon Aug 18, 2014 10:31 am    Post subject: Reply with quote  Mark this post and the followings unread

The squares look like that because you are using a sound card to get the audio into the computer for analizing it. The sound card have a high pass filter to block DC, and that HP filter is deforming the waves.
If you use a real oscilloscope or get hold of a sound card without the high pass filters (there are a few of them, MOTU for example) you would see an almost perfect square.

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furio



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PostPosted: Mon Aug 18, 2014 1:12 pm    Post subject: Reply with quote  Mark this post and the followings unread

Sebo wrote:
The squares look like that because you are using a sound card to get the audio into the computer for analizing it. The sound card have a high pass filter to block DC, and that HP filter is deforming the waves.
If you use a real oscilloscope or get hold of a sound card without the high pass filters (there are a few of them, MOTU for example) you would see an almost perfect square.

The use of the correct types of resistors as schematic, would have always been crucial to mitigate the distortion of the square. As well as exact types with little bandwidth (low noise) deforms the waves.

Whether the worst converters can accentuate the problem, would be another interesting question..

This would be the schematic: 5% & 10% = Carbon Film / = 1% Metal Film.
http://electro-music.com/wiki/pmwiki.php?n=Schematics.ARPOdysseyMKII-IIIVCO
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Sebo



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PostPosted: Mon Aug 18, 2014 3:31 pm    Post subject: Reply with quote  Mark this post and the followings unread

The converters have nothing to do. The problem are the High Pass Filter that blocks the DC at the input of the sound card.
Just look at the waves with a proper oscilloscope and you will see the diference.
It's funny, this subject is popping out again and again. Software oscilloscopes aren't good for some tasks because the DC blocking filters of the sound cards. You can't measure DC offset (to calibrate a VCA for example), you can't properly see an LFO, and waveforms of VCO will be deformated, specially in lower frequencies...

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AndyR1960



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PostPosted: Tue Aug 19, 2014 1:22 am    Post subject: Reply with quote  Mark this post and the followings unread

I agree with Sebo - I had a similar result using software. It wasn't until I bought a cheap Hitachi Scope, that I was able to monitor waveforms directly from the PCB... they were correct Wink

I'm now using a DSO201 updated with BenF's firmware (recommended). It may not be the most accurate scope out there, but it does the job well and I can take it anywhere.


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kanji



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PostPosted: Wed Aug 20, 2014 12:51 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks guys for the help and info. What drow me to take a look more closely to the waveforms was an interference/sidenoise that could be heard on both oscillators. I thought that its a side product of wrong shaped wave. Like square mixed with little bit of saw wave. This side noise reacted to pitch so I thought it must have something to do with the shape of square wave.

Later I noticed that I forgot to solder in 10uf decoupling caps and when those didn't eliminate the issue, I added 100n caps to powerrails aswell.


Funny though, while I googled info about oddys square waves and known issues, I stumbled on this Very Happy

http://www.gearslutz.com/board/electronic-music-instruments-electronic-music-production/778218-arp-odyssey-wonky-square-waves.html


EDIT : Got it working.. problem was most embarrassing.. Oscillators sounded great when I tested those out from the synth, but when I installed PCB back in, side noise came back. I started to hook modules one by one to powersupply until sidenoise appeared. Problem was that my powersupplys caps were bit too small for the load all these modules take. I boosted in total more than 10000uf more to my PSU and now everything works great.

Thanks again Andy for sharing your work Smile

Here is a small clip how my oddy clone sounds. All sounds (apart white noise) made using these oscillators.

https://soundcloud.com/tiergrinder/clockwork-odyssey
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