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Another ARP2600 Clone on it's way...
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diablojoy



Joined: Sep 07, 2008
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PostPosted: Tue Jul 16, 2013 6:26 pm    Post subject: Reply with quote  Mark this post and the followings unread

Andy love the look of the white boards , these are self etch ? wow
the whole thing looks absolutely great .
Quote:
I may put a PDF together with complete details and PCB foils for all the "carrier" boards and 40 series modules (along with corrections to the ARP service manual - quite a few mistakes there!)

that really would be fantastic and very generous of you looking forward to it.

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AndyR1960



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PostPosted: Wed Jul 17, 2013 1:13 am    Post subject: Re: Arp Boards Reply with quote  Mark this post and the followings unread

Smile
adnauseam wrote:


Do you think I'll have any problem building one as my first project? Smile

I soldered lots way back in high school and I'm pretty sure I'll get any logic down pat, but it's the electronics formulas and testing I imagine will give me trouble.

Any plans for another fantastic retro build?


Truthfully? I think it may be ambitious for a first project... but Zthee's TTSH comes on a complete single board (except for the 3 VCO modules), so it's certainly easier to do than messing around with separate boards (23 PCB's in mine!).

I'm taking a break form building for a while, but I'm currently drawing up an Odyssey clone, which, I'm glad to say is a whole lot simpler Smile


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Top row almost complete (Gate push switch needed)... Noise, Processors, S&H and Switch still to do. Not yet routed internally, but all working
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isak



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PostPosted: Wed Jul 17, 2013 1:30 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi Andy,

Looking foreword for the ody and the 2600 files.
Cause of you I become a big Arp fan!
Thank you for revealing the Arp world to me!

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xpmtl



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PostPosted: Wed Jul 17, 2013 3:06 am    Post subject: Re: Arp Boards Reply with quote  Mark this post and the followings unread

AndyR1960 wrote:


I'm taking a break form building for a while, but I'm currently drawing up an Odyssey clone, which, I'm glad to say is a whole lot simpler Smile


bounce banana banana banana bounce

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forbin



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PostPosted: Wed Jul 17, 2013 9:39 pm    Post subject: Reply with quote  Mark this post and the followings unread

Looks fantastic! The screwdriver sitting on the keyboard is a nice touch...
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AndyR1960



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PostPosted: Thu Jul 18, 2013 2:03 am    Post subject: Reply with quote  Mark this post and the followings unread

Still have a problem with the VCF mixer - distorting! Crying or Very sad

I've increased the input resistors from the standard 100k to 330k (to compensate for the fact that I've swapped the 4012 for a 4075)... just wondering if I should take them up to 680k or more as on the Odyssey (0-5v waveforms, but 0-10 or +/-5 for the 2600) or ditch the passive mixing and put an op-amp in there... no cigar yet.

GRRRRRR!!!!!
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isak



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PostPosted: Thu Jul 18, 2013 2:14 am    Post subject: Reply with quote  Mark this post and the followings unread

AndyR1960 wrote:
Still have a problem with the VCF mixer - distorting! Crying or Very sad

I've increased the input resistors from the standard 100k to 330k (to compensate for the fact that I've swapped the 4012 for a 4075)... just wondering if I should take them up to 680k or more as on the Odyssey (0-5v waveforms, but 0-10 or +/-5 for the 2600) or ditch the passive mixing and put an op-amp in there... no cigar yet.

GRRRRRR!!!!!

if i understand correctly you dont want to raise the input resistor cause of the low V, is it right?
if so why dont you boost the signal with this...(from your ody VCO post and working great!!!)

AndyR1960 wrote:
ericcoleridge wrote:


How do we increase the signal of the Oddy VCO? Is there a resistor that can be replaced or something?


Hi Eric,

I think this is what you want. I've lifted this from Thomas Henry's Build a Better Music Synthesizer - it's from his CEM VCO design. He used it on the Triangle output (which is also 0-5v PP) to convert it to 10v PP centered around zero.

I haven't tested it, but in theory it should be fine.

BTW, I've just taken a look at the 4023 VCF PCB foil I posted... definitely the same version as I've used to build my own VCF's. I wish I could be more help - could you PM some high rez images of your board to me, I'll see what I can do.

Andy.


and another thing...

AndyR1960 wrote:
LetterBeacon wrote:
would it just be a case of changing the value of the 100K feedback resistor?


Yes, I'd change the 100k resistor for a 51k and then follow it with a 50k trimmer to allow the voltage to be adjusted back down to 10v PP.

You may find that it's not *exactly* centered around zero, though it'll probably be fine for general use - otherwise I *think* you would need to change the value of the 300k resistor slightly.


i know its not like the original and i'm definitely not a pro but hey ...just trying to help Smile


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AndyR1960



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PostPosted: Thu Jul 18, 2013 2:29 am    Post subject: Reply with quote  Mark this post and the followings unread

@Isak, thanks for that... but I've solved the problem Very Happy

Just found out that it wasn't the VCF mixer that was the problem... I was using a 15v gate from my modular for the AR envelope, which in turn was pushing the VCA too hard... DUH!

Dropped the gate voltage down to 10v, now sounds great... I LOVE the ADSR exp control of the VCA, it really give the amp a kick.
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isak



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PostPosted: Thu Jul 18, 2013 2:33 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
... no cigar yet.

how about now? happy smoker

happy to hear you fixed it Smile

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AndyR1960



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PostPosted: Sun Aug 25, 2013 1:48 am    Post subject: Reply with quote  Mark this post and the followings unread

I've finally completed it Very Happy

The only real problem I had was with the VCF - I didn't like the 4012 (Sorry to say this, but I'm a bit fed up with the Moog VCF hype, it's everywhere now) and replaced it with an Odyssey 4075 (which I had to botch to get to work)... I still wasn't 100% happy with the result, So I ended up searching for details on the 2600's 4072 VCF - not a lot of info available!

I ended up copying the tracks from a pretty bad photo of the back of a genuine 4072 module, then painstakingly sorting out where the components should go from the schematic that's available.

I was disappointed when it didn't work, but eventually (after 3 days) found that a 2N5459 had found it's way into my bag of 2N3906's causing the exponential pair to be duff.

I changed the offending transistor, and it worked beautifully Very Happy

I've also put a few pics of various projects up on Flickr:

http://www.flickr.com/photos/arp2600clone/


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isak



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PostPosted: Sun Aug 25, 2013 1:57 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
I ended up copying the tracks from a pretty bad photo of the back of a genuine 4072 module, then painstakingly sorting out where the components should go from the schematic that's available.

wow man, crazy job!
Looks a beauty, for sure sounds a beauty!
YouTube Vids!!!!!
I want to see Smile

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steffensen



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PostPosted: Sun Aug 25, 2013 2:21 am    Post subject: Reply with quote  Mark this post and the followings unread

What a beauty! Good job!
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diablojoy



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PostPosted: Sun Aug 25, 2013 2:41 am    Post subject: Reply with quote  Mark this post and the followings unread

wave
salut
orsm work we should all be in awe.

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emmaker



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PostPosted: Mon Aug 26, 2013 12:59 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
Truthfully? I think it may be ambitious for a first project... but Zthee's TTSH comes on a complete single board (except for the 3 VCO modules), so it's certainly easier to do than messing around with separate boards (23 PCB's in mine!).


I actually think your way of doing individual boards is better. With one board it could get screwed up bad enough to have to scrap the whole thing. With individual boards only the module that is hosed can be replaced. There are going to be a few hobbyists whose skills won't be up to what's required for this project and will probably trash their board.
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THeff



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PostPosted: Mon Aug 26, 2013 7:41 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi Andy,

I just checked out your pictures on Flickr and you do fantastic work! My DIY ARP-2600 works very well but but can't touch the panels and cases you have made...excellent!

I just made four 4035 filters for a current project from your layout and they work great.

Thanks for posting your DIY projects!

Regards,

Theff
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AndyR1960



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PostPosted: Tue Sep 03, 2013 11:13 pm    Post subject: Reply with quote  Mark this post and the followings unread

THeff wrote:
Hi Andy,

I just checked out your pictures on Flickr and you do fantastic work! My DIY ARP-2600 works very well but but can't touch the panels and cases you have made...excellent!

I just made four 4035 filters for a current project from your layout and they work great.

Thanks for posting your DIY projects!

Regards,

Theff


Thanks for your kind words Theff, much appreciated.

I set out 5 years ago with the though of building one, but didn't have any clue where to start - That's when I started dabbling with Odyssey VCO's etc and realised that it was a possibility.

Most of the stuff I've done is pretty crudely put together, but I went all out for the 2600 project as I wanted it to look as good as I could get it - I was initially put off by the price of having the panel laser cut and the screen printing, but I'm really pleased with the result - I seem to spend more time looking at it than playing with it Wink

I'm currently working on the 3620 duophonic keyboard clone (the controller I've built is "ok", but just not quite right). Unfortunately, I had to pay a fair amount for decent and clear documentation as the available schematic downloads for the 3620 are unreadable... It should be completed by the end of the week, but I'm a bit concerned about what capacitors to use for the keyboard S&H. Standard metalized poly caps work well in the 4015 S&H module, but I'll have to see if they're good enough for the keyboard.
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LFLab



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PostPosted: Wed Sep 04, 2013 10:55 am    Post subject: Reply with quote  Mark this post and the followings unread

Styroflex or Silvermica? Alternatively, wima has a line of caps intended for applications involving short pulses, not sure what parameter is optimised in these.

edit:
Checked and those are the fkp1, not really suitable, big, and aimed at high power electronics.
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roglok



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PostPosted: Fri Sep 06, 2013 9:07 am    Post subject: Reply with quote  Mark this post and the followings unread

great work, andy respect
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DES



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PostPosted: Sat Sep 07, 2013 7:03 am    Post subject: Reply with quote  Mark this post and the followings unread

Wow! That is impressive!
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diablojoy



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PostPosted: Sun Sep 08, 2013 6:04 pm    Post subject: Reply with quote  Mark this post and the followings unread

Andy I would recomend using polystyrene for sample and hold circuits
Rushonline capacitors are a good source for these and close to you.

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AndyR1960



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PostPosted: Sun Sep 08, 2013 11:40 pm    Post subject: Reply with quote  Mark this post and the followings unread

diablojoy wrote:
Andy I would recomend using polystyrene for sample and hold circuits
Rushonline capacitors are a good source for these and close to you.


Thanks for the info, they've got 500n in stock Smile

I'm currently using a good quality metalized poly, which seems to work ok, I've just got to sort out a slight problem I have with the upper voice generation circuit (not scaling to 1v/oct)... I thought I'd just need to change a few resistor values to bring it in line, but it's having a knock-on effect to the main lower voice cv out.

Still scratching my head on this one Rolling Eyes
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diablojoy



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PostPosted: Mon Sep 09, 2013 2:46 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
Thanks for the info, they've got 500n in stock

holly crap Andy 500nf Shocked thats going to be physically quite large in a polystyrene cap. I have some 330nf polystyrenes - they are about the size of a sub c battery so yeah they are going to be big
last ones i used in a sample and hold were 10nf
(the MFOS 1v/oct keyboard circuit and rays sample and hold also)

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AndyR1960



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PostPosted: Mon Sep 09, 2013 6:11 am    Post subject: Reply with quote  Mark this post and the followings unread

Yup, they're big... The original 3620 Keyboard used BIG Polycarbonates, the polyester ones I'm using are fine for testing, but the voltage drop over time is not really acceptable.

But, at least I found the problem I had with the second voice CV scaling... It's the keyboard I used (converted from a matrix scanner - the carbon switch pads introduce too much additional resistance when a second note is played, causing havoc with the resistor chain).

I tested the PCB with the keybed from my Odyssey and it works fine... Looks like I'm going to have to build my own with J-Wires etc or get two MIDI CV converters - one low note and one high note priority... I can't see either being easy. Rolling Eyes
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diablojoy



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PostPosted: Mon Sep 09, 2013 3:00 pm    Post subject: Reply with quote  Mark this post and the followings unread

Ah those damn pesky carbon pads
I have been getting keybeds from old home organs (usually for free)
so they are the bendy wire types. good for low note priority using rays circuit hmm but you want upper and lower note priority . so just a simple resistor chain based system wont work.
not sure if either of these will get you where you want to be but
maybe this ?
http://electro-music.com/forum/topic-29746.html
and / or
http://www.muffwiggler.com/forum/topic-75544.html

However maybe 2 resistor chains running opposite directions to each other could be utilised if you could come up with a way of preventing the second note on each being involved for each one , thinking lots of magnetic micro reed switches so probably painful to implement and to set up.

edit : oh or 2 of these one set to low note priority and one set to high note priority and a standard midi keyboard of course
http://www.kentonuk.com/products/items/m-cv/prosolo.shtml

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AndyR1960



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PostPosted: Mon Sep 09, 2013 10:42 pm    Post subject: Reply with quote  Mark this post and the followings unread

diablojoy wrote:
Ah those damn pesky carbon pads


Just bought some silver conductive paint - apparently less than 0.2r per cm, so I'll give that a try on the PCB pads and bubble contacts.

The ARP 3620 keyboard is duophonic from a single resistor chain - It derives the upper voice by detecting the voltage difference between the two notes played... that voltage difference is passed though a standard S&H and then mixed with the lower CV to produce the second upper voice - quite a simple but elegant design.

Kimber Allen, here in the UK, is going strong and still sell 2 pole "make" contact block assemblies - I'm waiting for them to get back to me, but I suspect they'll be expensive, but probably still cheaper than two Kenton Solo's Wink
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