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 Forum index » DIY Hardware and Software
Help/Info Required - ARP2600 ADSR
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AndyR1960



Joined: Feb 16, 2007
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PostPosted: Fri Apr 19, 2013 2:08 am    Post subject: Help/Info Required - ARP2600 ADSR Reply with quote  Mark this post and the followings unread

I've got an ARP2600 in for service, but I would like some info on the ADSR envelope generator...

If anybody has a 2600 handy, could you please let me know what sort of attack time you're getting. I'm getting the following times from the ADSR out (all sliders at max):

Attack time - 1.5 seconds
Decay time - 11/12 seconds
Sustain voltage - 9.8
Release time - 11/12 seconds

As you can see, I'm a little concerned about the maximum attack time... 1.5 seconds! I have replaced the two parallel 1uf 25v timing caps on the 4020 module, but it's made no difference.

I suspect that everything is right, and that the 2600 attack time really is this short, but I would like confirmation if possible.

Many thanks.
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isak



Joined: Dec 13, 2009
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PostPosted: Sat Apr 20, 2013 1:53 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi Andy.

after giving us so much i went for a quest for you searching in youtube what your looking for.
i think the answer to your question is YES, the Attack is very short.
from 4:25 he is talking about the ENV of the arp2600, look at the position of the Attack from the right top of the vid.
i hope it helps you Smile

http://www.youtube.com/watch?v=NqQV5mLVNWs

cheers,
Isak E.

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AndyR1960



Joined: Feb 16, 2007
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PostPosted: Sat Apr 20, 2013 6:20 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks Isak,

I think that just about confirms it... very short!

Strangely enough, doubling up the caps to 4.7uf doesn't make much difference to the attack time, although it lengthens the decay/release - Weird!

Andy
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isak



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PostPosted: Sat Apr 20, 2013 6:30 am    Post subject: Reply with quote  Mark this post and the followings unread

Happy I was able to help you Andy.
Hope youll "fix" what your trying to fix.

Cheers Smile

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steffensen



Joined: Jul 11, 2012
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PostPosted: Tue Apr 23, 2013 2:31 am    Post subject: Reply with quote  Mark this post and the followings unread

And here i was hoping for the 2600 ADSR layout! Very Happy
Isak already confirmed this question, but yes - it is that short. I guess this is one of the reasons many seems to use the 2600 for drums. Smile

What caps did you double? C1 & C2? If so, im not surprised they changed the Decay & Release. They should have changed the Attack too however.. weird.

How about decreasing/increasing R12?
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AndyR1960



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PostPosted: Tue Apr 23, 2013 9:15 am    Post subject: Reply with quote  Mark this post and the followings unread

steffensen wrote:


How about decreasing/increasing R12?


I'll give it a try Smile

Quite handy getting a late 2600 in for servicing... none of the modules are potted Wink
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isak



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PostPosted: Tue Apr 23, 2013 9:22 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi Andy,

Are we gonna get the arp2600 env layout? Rolling Eyes

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AndyR1960



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PostPosted: Tue Apr 23, 2013 11:40 pm    Post subject: Reply with quote  Mark this post and the followings unread

isak wrote:
Hi Andy,

Are we gonna get the arp2600 env layout? Rolling Eyes


Yes, I'll give one a try this weekend Very Happy

I'm copying the module layouts as fast as I can - the 2600 goes back to it's owner tomorrow Crying or Very sad

I may not have time to get the 2600 VCF. It's a slightly different design to the 4075 found in my Odyssey (the module adds an op-amp, which look like I/O level adjusters - maybe compensation for the higher VCO outputs?).

Some of the module layouts look like a bizarre mess... but as long as they work, I'm not complaining Smile
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steffensen



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PostPosted: Wed Apr 24, 2013 12:49 am    Post subject: Reply with quote  Mark this post and the followings unread

AndyR1960 wrote:
isak wrote:
Hi Andy,

Are we gonna get the arp2600 env layout? Rolling Eyes


Yes, I'll give one a try this weekend Very Happy

I'm copying the module layouts as fast as I can - the 2600 goes back to it's owner tomorrow Crying or Very sad

I may not have time to get the 2600 VCF. It's a slightly different design to the 4075 found in my Odyssey (the module adds an op-amp, which look like I/O level adjusters - maybe compensation for the higher VCO outputs?).

Some of the module layouts look like a bizarre mess... but as long as they work, I'm not complaining Smile


Sweet! I can trash my try on the 4020 then. Razz
I read there were some (intentional?) errors in the 4020 schematic, so its good to have the original around!
Id love to help if possible in any way. Also, Rob at AM Synths have some good notes on this matter on his site, if needed.
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AndyR1960



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PostPosted: Wed Apr 24, 2013 1:54 am    Post subject: Reply with quote  Mark this post and the followings unread

I noticed errors straight away! No wonder my attempt a few years ago didn't work Rolling Eyes

The 2600 service manual addendum for the ADSR is also wrong!
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steffensen



Joined: Jul 11, 2012
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PostPosted: Wed Apr 24, 2013 2:02 am    Post subject: Reply with quote  Mark this post and the followings unread

AndyR1960 wrote:
I noticed errors straight away! No wonder my attempt a few years ago didn't work Rolling Eyes

The 2600 service manual addendum for the ADSR is also wrong!


Yes, sneaky bastards. Razz
What errors did you find btw? Curious if its the same i have discovered myself.
I hope you do HQ pics of the modules in the 2600 before you return it, those might be handy!
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AndyR1960



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PostPosted: Wed Apr 24, 2013 2:37 am    Post subject: Reply with quote  Mark this post and the followings unread

steffensen wrote:
Also, Rob at AM Synths have some good notes on this matter on his site, if needed.


Just found it : )

Yup, same errors - I'm copying the module directly... no point in redrawing everything as it may introduce further mistakes!

I'm not sure what to use as the NPN/PNP's, although I'm pretty sure standard 2N3904/6's will work (I've got no 2N3702's).

I'll see how I get on, it'll probably take a day or two.
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steffensen



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PostPosted: Wed Apr 24, 2013 2:47 am    Post subject: Reply with quote  Mark this post and the followings unread

AndyR1960 wrote:
steffensen wrote:
Also, Rob at AM Synths have some good notes on this matter on his site, if needed.


Just found it : )

Yup, same errors - I'm copying the module directly... no point in redrawing everything as it may introduce further mistakes!

I'm not sure what to use as the NPN/PNP's, although I'm pretty sure standard 2N3904/6's will work (I've got no 2N3702's).

I'll see how I get on, it'll probably take a day or two.


Great! Its even cooler with a direct copy. Very Happy
Im sure 3904/06's will work fine. If they worked in the Oddy etc..
Really looking forward to this! (im such a ARP junkie)
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The Real MC



Joined: Jun 20, 2008
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Location: Painted Post NY

PostPosted: Wed Apr 24, 2013 7:57 am    Post subject: Reply with quote  Mark this post and the followings unread

Back then, it wasn't uncommon to put intentional errors in schematics to deter copycats. ARP wasn't the only one, Buchla did it too.
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AndyR1960



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PostPosted: Thu Apr 25, 2013 12:08 am    Post subject: Reply with quote  Mark this post and the followings unread

ADSR board built and working... sort of Rolling Eyes But it is useable.

The only problem is that there's some kind of voltage overshoot. With all pots at minimum, I'm getting an offset voltage from the decay control - it's not noticeable when you use the ADSR to modulate either the VCF or VCA, but definitely shows up when you modulate a VCO... Hmmm, strange - I need to look into it further.

Maybe it's the fact that ARP delay their keyboard trigger pulses, or my gate to trigger converter isn't as good as I thought or a bad transistor substitution or maybe the Moon is in the wrong phase Wink


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steffensen



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PostPosted: Thu Apr 25, 2013 1:36 am    Post subject: Reply with quote  Mark this post and the followings unread

Thats a fun looking build! Should be room for 2 EG's on the same board there perhaps?

About the voltage overshot, i cant say much, but the 2600 do have something going on regarding this. Its definitely noticeable on all the drum patches ive heard/made on it. Makes it very special, and also one of the big reasons i dearly want it!

Good work Andy! Smile
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alcide



Joined: Apr 20, 2012
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PostPosted: Sat Apr 27, 2013 10:18 am    Post subject: Reply with quote  Mark this post and the followings unread

Regarding the length of the complete ADSR cycle of an unmodified 2600, and the unwanted behaviour you're talking about, the section about the 'Contour generators & vca', in this article, may be of some interest (it's an exhaustive comparison between the original synth and its virtual counterpart):

http://www.soundonsound.com/sos/jun05/articles/arturia2600.htm

Hope it helps !
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AndyR1960



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PostPosted: Sat Apr 27, 2013 10:32 am    Post subject: Reply with quote  Mark this post and the followings unread

alcide wrote:


Hope it helps !


Yes it did help. Thank you.

So as far as I can tell, the ADSR I've built seems ok although I'm going to tinker with it for a while to see if I can improve anything... or maybe just leave well alone as it has a certain character Smile
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steffensen



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PostPosted: Sat Apr 27, 2013 10:48 am    Post subject: Reply with quote  Mark this post and the followings unread

AndyR1960 wrote:
alcide wrote:


Hope it helps !


Yes it did help. Thank you.

So as far as I can tell, the ADSR I've built seems ok although I'm going to tinker with it for a while to see if I can improve anything... or maybe just leave well alone as it has a certain character Smile


I really would like to play with it as is. Very Happy
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patroche



Joined: Feb 26, 2012
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PostPosted: Tue Dec 09, 2014 11:49 pm    Post subject: Reply with quote  Mark this post and the followings unread

Here the schematic of Module ADSR 4020 corrected
Posted Image, might have been reduced in size. Click Image to view fullscreen.

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