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ARP Odyssey Filters
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AndyR1960



Joined: Feb 16, 2007
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PostPosted: Sat Sep 06, 2008 1:56 am    Post subject: ARP Odyssey Filters Reply with quote  Mark this post and the followings unread

Just a teaser Smile

The 4023 12db is on the right, the 4035 24db "Moog" is on the left.

I'll try and get the layouts up today for both filters. Again, like the Oddy VCO's I'm surprised that these two have been ignored for so long.

Yusynth has the 4072 LM3900 based filter on his site... go on collect the whole set - you know you want to Twisted Evil

Andy.


ARP VCF's.JPG
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4023 & 4035 VCF's
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ARP VCF's.JPG


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rjd2



Joined: Sep 02, 2007
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PostPosted: Sat Sep 06, 2008 5:48 am    Post subject: Reply with quote  Mark this post and the followings unread

sweet-these, im definitely building-i'll probably wait til tim's pcb's are done for vco's. hate to ask this, but do you have any docs/bom for the parts?

andy, how easy would it be to toss off the vca and eg circuits? Very Happy then we can all recreate a full on arp modular! thanks a ton for doing these, looking forward to this stuff.
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AndyR1960



Joined: Feb 16, 2007
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PostPosted: Sat Sep 06, 2008 6:36 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi all,

Ok, here's the PCB and component layout for the 4023 VCF, one or two things though...

The original TZ81/581 expo pair have been replaced with 2N3904/06 (perfectly acceptable subs), and the original 2N5172's are now 2N3904's (again, perfectly acceptable sub).

You will need to watch out when you insert the trannies, as I haven't changed the PCB foil from the original, so you'll have to twist the transistors a bit, as the originals had different pin-outs.

There are two fly leads (marked as blue on the pdf, ugly solution I know) and a wire link which is obscured somewhat by one of the 61.9k resistors - please don't forget these.

The only other change I made was for the CV summer, the original was an LM301 with compensation cap, I had none left so that's been replaced with a TL071 (you can also replace the other two 301's with the TL071, but remember to remove the 33pf caps... In fact, the VCF will probably sound better using TL0's).

I seriously like this filter, I know everyone goes on about 24db Moog VCF's and how fabulously powerful they are, but this cuts through anything, it's a real sizzler - but be carefull when you crank up the resonance, as there's no gain compensation... I don't want you to blow your speakers Smile

I'll get a BOM and samples up for everything when I've slept... been awake now for 36 hours... need... sleep... peaceful... sleep... ZZZZzzzz...

Andy


ARP 4023.pdf
 Description:
ARP 4023 12db VCF

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 Filename:  ARP 4023.pdf
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Last edited by AndyR1960 on Sat Sep 06, 2008 8:14 am; edited 1 time in total
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AndyR1960



Joined: Feb 16, 2007
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PostPosted: Sat Sep 06, 2008 8:13 am    Post subject: Reply with quote  Mark this post and the followings unread

rjd2 wrote:
sweet-these, im definitely building-i'll probably wait til tim's pcb's are done for vco's. hate to ask this, but do you have any docs/bom for the parts?

andy, how easy would it be to toss off the vca and eg circuits? Very Happy then we can all recreate a full on arp modular! thanks a ton for doing these, looking forward to this stuff.


Hi rjd2,

Unfortunately I have no other info on these VCF's (just a couple of very good friends who let me poke around inside their Oddy's - I just copied the PCB directly from the modules). It's seems that anyone who *does* have detailed info on these, tends to keep it to themselves Sad

You may get some useful info here:

http://www.till.com/arptech/40235/index.html

I tried to build it last year, unsuccessfully though, as I'm not too hot on double sided boards... but getting better! Smile

The Oddy VCA is dead simple, the AR/ADSR are both made from discrete trannies (there's a joke there... but I'm not biting!), and they, along with the Noise/S&H/LFO will be my next quest.

Andy.
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widdly



Joined: Jun 25, 2007
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PostPosted: Sun Sep 07, 2008 7:06 pm    Post subject:   Reply with quote  Mark this post and the followings unread

Just checked out your broadwave modular page....that things is AWESOME!
Last edited by widdly on Thu Aug 05, 2010 10:06 pm; edited 1 time in total
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Peake



Joined: Jun 29, 2007
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PostPosted: Sun Sep 07, 2008 7:16 pm    Post subject: Reply with quote  Mark this post and the followings unread

You might wish (or might not wish) to check out the circuit with the 301 in place, for input overload characteristics, etc. That IC, IIRC, soft clips rather nicely, even though it's slow as hell.

There really isn't much to the Odyssey partswise, is there? Just a lot of pots and sliders..thanks for making these available.

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AndyR1960



Joined: Feb 16, 2007
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PostPosted: Mon Sep 08, 2008 1:30 am    Post subject: Reply with quote  Mark this post and the followings unread

Peake wrote:
You might wish (or might not wish) to check out the circuit with the 301 in place, for input overload characteristics, etc. That IC, IIRC, soft clips rather nicely, even though it's slow as hell.

There really isn't much to the Odyssey partswise, is there? Just a lot of pots and sliders..thanks for making these available.


Hi Peake,

Just received a bunch of 301's - Yes, you're right it does clip rather nicely, and if you really push it, it sounds positively evil Smile

No, there's not much to the Oddy at all, apart from the occasional difficult to get part (a couple of dual FET's for the 24db VCF and S&H - 2 x 2N5459 work well - and the elusive 2N5910 in the VCO's).

Apart from that, it's all hardware - I'd love to rebuild everything with sliders, but I've not found a decent and tidy way to cut slots into Aluminum.

Andy.
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rjd2



Joined: Sep 02, 2007
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PostPosted: Mon Sep 08, 2008 5:59 am    Post subject: Reply with quote  Mark this post and the followings unread

sorry to ask for even more info when you have already provided so much, but do you have a similar pdf for the 4035 filter? no rush, im not ready to move on this stuff right away; ive just been looking for months and months for arp cloned module info, so this is all great news to me!
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AndyR1960



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PostPosted: Mon Sep 08, 2008 8:18 am    Post subject: Reply with quote  Mark this post and the followings unread

rjd2 wrote:
sorry to ask for even more info when you have already provided so much, but do you have a similar pdf for the 4035 filter


Hi rj,

4035 details up soon, I noticed a bit of a boo-boo on the original board I made, just need a bit of time to correct it Smile

Andy.
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rjd2



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PostPosted: Tue Sep 09, 2008 10:05 am    Post subject: Reply with quote  Mark this post and the followings unread

just wanted to make a comment on this whole arp thing, and why its really awesome to me....

i had wondered for the longest why noone had done a clone of the 4035 filter, which is in some monumental arp designs that i love the sound of. the answer i always got was " its the moog lawsuit filter, and peeople make moog filters, so just do one of those".

and yet, arps with this filter sound NOTHING LIKE MOOG INSTRUMENTS! (to me, at least). glad that im not the only yahoo who sees it this way....
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brother303



Joined: Nov 02, 2010
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PostPosted: Sat Jan 01, 2011 12:59 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hello,

an old thread is coming up again... Smile

I got my board etched from a local pcb-service and now there is one question on the 3 trimmers on this pcb.

PDF is here... http://electro-music.com/forum/phpbb-files/arp_4023_163.pdf

What does the "CV-reject"trimmer do? And how to adjust it?

Is there any kind builder around here who would like to share his knowledge about the secrets of adjusting this? Hail the Master Please

Thanks and best regards
Greg
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LektroiD



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PostPosted: Mon Jan 03, 2011 3:40 pm    Post subject: Reply with quote  Mark this post and the followings unread

This certainly looks like a great project, although I do have a query (and please excuse my ignorance here), but I don't see what the tempco is doing here, it's not thermally coupled to the transistors or anything, so surely it can be substituted with a fixed metal film (or similar)?
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brother303



Joined: Nov 02, 2010
Posts: 139
Location: ruhr-area/germany

PostPosted: Tue Jan 04, 2011 2:39 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi,

LektroiD wrote:
...but I don't see what the tempco is doing here, it's not thermally coupled to the transistors or anything, so surely it can be substituted with a fixed metal film (or similar)?


Exactly what I think. I´ll try building this filter without tempco...and maybe add one later if really required.

Btw,any idea on the "cv-reject" trimmer and how to adjust it?

Cheers
Greg
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alcide



Joined: Apr 20, 2012
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Location: Lille, France

PostPosted: Wed Apr 10, 2013 4:24 am    Post subject: Reply with quote  Mark this post and the followings unread

I've spent some time now with the tremendous 4023, and have achieved some tones I was after for a very long time...I have, however, a question: at high frequencies (cutoff) when resonance is high, if I apply a lot of CV's, the filter produces short and uncontrollable screams (the resonance doesn't track anymore, and doesn't follow any enveloppe: just ultra high-pitched clicks). May it have something to do with LM301's weaknesses (i didn't select them, and only used one tl071 for cv-summing) / bad transistor matching ? Or is this a normal behaviour ?

(And thanks again, Andy, for your Ody-projects !)
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isak



Joined: Dec 13, 2009
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PostPosted: Fri Apr 12, 2013 2:24 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi Andy.

The Tempco resistor is for keyboard tracking?
If I'm not interested in keyboard tracking can use regular 1% resistor?
If I use the tl071 instead lm301 you said to remove the 33pF caps, do I need to put jumpers instead?


cheers,
Isak E.

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AndyR1960



Joined: Feb 16, 2007
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PostPosted: Fri Apr 12, 2013 2:40 am    Post subject: Reply with quote  Mark this post and the followings unread

isak wrote:
Hi Andy.

The Tempco resistor is for keyboard tracking?
If I'm not interested in keyboard tracking can use regular 1% resistor?
If I use the tl071 instead lm301 you said to remove the 33pF caps, do I need to put jumpers instead?


The Tempco is mainly for frequency "stability" which is vital in a VCO, but not so much in a VCF, so it's ok to use a regular resistor.

Just remove the 33pf cap, no jumper required Smile
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AndyR1960



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PostPosted: Fri Apr 12, 2013 2:45 am    Post subject: Reply with quote  Mark this post and the followings unread

alcide wrote:
I have, however, a question: at high frequencies (cutoff) when resonance is high, if I apply a lot of CV's, the filter produces short and uncontrollable screams


The 4023 will overload (not in a nice way) if the CV is to high - The ARP Odyssey is designed to keep the CV mixer levels within a certain range to avoid this happening. I think you probably just need to attenuate your CV's a little... or a lot Smile
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isak



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PostPosted: Fri Apr 12, 2013 3:43 am    Post subject: Reply with quote  Mark this post and the followings unread

Thank man Smile
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alcide



Joined: Apr 20, 2012
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PostPosted: Mon Apr 22, 2013 8:49 am    Post subject: Reply with quote  Mark this post and the followings unread

Problem fixed ! I replaced the lm301's with TL071, and everything's fine now (maybe I should have selected, as required, the 301 ? But I don't know how to do it, and I don't care anymore, in fact: it sounds a LOT better, now, i must say (by modern standards, at least...)

Thanks !
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The Real MC



Joined: Jun 20, 2008
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PostPosted: Wed Apr 24, 2013 8:03 am    Post subject: Reply with quote  Mark this post and the followings unread

The 301 is an uncompensated opamp which required the right capacitor to prevent oscillation. That may had been the "squealing" you heard. 301s were also prone to latchups.

The TL071 that you substituted has internal compensation and that may have fixed the problem.

Could had been a bad cap or bad 301 opamp. ARP did have a selection process for the 301 opamps. The 301 offered that design flexibility of tailoring the compensation circuit towards the application circuit, but it was not without its thorns and in the long run the industry favored the internally compensated opamp.
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paulstone



Joined: Apr 14, 2013
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PostPosted: Wed Sep 25, 2013 8:07 am    Post subject: Reply with quote  Mark this post and the followings unread

Hello guys


will the Jfet BF245B work instead of the 2N5459 ?

i have build one of this filter but no work

for build it i have use :
BF245B (soldered SGD with pin reversed) instead of The 2N5459
TL071 (both whitout 33p caps) instead of the LM301
Harris CA3080

Suggestion ?

thx
Paolo
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