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 Forum index » DIY Hardware and Software » Thomas Henry designs
VC Delay pcb redesign - SAD1024
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The Peasant



Joined: Nov 13, 2009
Posts: 99
Location: Sunny Alberta
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PostPosted: Thu Nov 19, 2009 12:16 pm    Post subject: VC Delay pcb redesign - SAD1024 Reply with quote  Mark this post and the followings unread

I am building a couple of T.H. VC Analog Delays in my current synth project, from 3 original parts kits that I purchased some time ago. I wanted to keep at least one of my SAD4096 ICs as a spare, and so I decided to redesign the pcb board layout to use the SAD1024 IC for one of the delays. As the 4096 is basically unobtainium these days, I thought that others who had access to a SAD1024 and wanted to build this delay could use this.

Take care,
Doug


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The Electronic Peasant

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philpeery



Joined: Nov 08, 2006
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Location: new jersey, usa

PostPosted: Fri Nov 20, 2009 6:11 pm    Post subject: Reply with quote  Mark this post and the followings unread

Really nice job Doug! This is one that I've been meaning to tackle myself for a while, glad you got to it! I have a couple of quick questions - did you generate a parts layout, or is it essentially the same as TH's? Also, did you replace the unobtainium 4739 opamp chips with a modern part? I think there are 3 in this project. As I recall, that chip has an unusual pinout that few other opamps share.

Great work! I'm going to go over the layout and try to get at least one built over the holidays!

Regards,
Phil
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The Peasant



Joined: Nov 13, 2009
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PostPosted: Fri Nov 20, 2009 7:09 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi Phil,

Glad that you can make use of this. To answer your questions - other than the delay chip and a couple of parts immediately around it the layout is identical. I can do a quick layout diagram for the differences in the next while if you like. I did add room for ferrite beads on the power inputs and moved the electolytics there over a bit. I also beefed up the traces a lot.

It does use the 4739 op amps, but it should be fairly easy to modify the board for something more standard. If I was to do it again I would change the trimpot pads to something smaller as well.

Please note that I have not yet actually tested this design. I have an etched and populated board ready to go into my latest project, so this will happen in the next couple of months. Also note that there are two different ways to utilise the dual delay lines in a SAD1024, this design uses the parallel method for a higher quality, shorter delay.

I am also planning on adding VC regeneration to this module using a MFOS VCA pcb.

Take care,
Doug

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philpeery



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PostPosted: Fri Nov 20, 2009 8:14 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
there are two different ways to utilise the dual delay lines in a SAD1024, this design uses the parallel method for a higher quality, shorter delay

Wasn't aware that the SAD1024 could be used like that. So I am assuming that in parallel you are getting 512 stages, yes? Is this enough for chorus type effects, or are we still in the flanging range with this number of buckets? If you could share your design surrounding the SAD for this one, and have something that shows a serial, 1024 stage design, I might be inclined to expand on your nice layout.

Also, I would think that TL072's would be a decent replacement for the 4739's.

Let us know how your experiment with the MFOS VCA for controlling regen goes, this sounds very interesting to me as well! I do have a few of those pcb's laying around. If it's a viable way to go, one might make it into this project.

Thanks!
Phil
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richardc64



Joined: Jun 01, 2006
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PostPosted: Sat Nov 21, 2009 5:00 am    Post subject: Reply with quote  Mark this post and the followings unread

Welcome, "Peasant."

I consider myself one of your disciples, and emailed you once to tell you so and exchange ideas on synthsized drums. Is your monster project still on hold?

Glad to see you here.

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StephenGiles



Joined: Apr 17, 2006
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PostPosted: Sat Nov 21, 2009 5:38 am    Post subject: Reply with quote  Mark this post and the followings unread

I built this wonderful flanger (aren't they all!!) back when "Device" was still being published - back in the days when we had postal deliveries by 8am in the UK!! The original articles are still up at Mark Hammer's site.

I used the Eventide bounce with Deluxe Electric Mistress clock/LFO which worked well together. I must fire it up again, I remember that the regeneration sounds were superb.

No - I'm talking rubbish, I'm referring to Craig Anterton's VC Flanger - una pava distinta de pescados Rolling Eyes
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The Peasant



Joined: Nov 13, 2009
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Location: Sunny Alberta
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PostPosted: Wed Nov 25, 2009 10:59 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
Wasn't aware that the SAD1024 could be used like that. So I am assuming that in parallel you are getting 512 stages, yes? Is this enough for chorus type effects, or are we still in the flanging range with this number of buckets? If you could share your design surrounding the SAD for this one, and have something that shows a serial, 1024 stage design, I might be inclined to expand on your nice layout.


512 stages is correct. As I am building one of these with an actual SAD4096 chip, I already have one long delay, and so decided to go for the shorter route with this one. I believe that this will be sufficient for chorus effects, but time will tell for sure.

The design that I used for the SAD1024 is straight out of the data sheet, which is available various places online. So if you download this you can see what modifications are required to make it 1024 steps.

Quote:
Also, I would think that TL072's would be a decent replacement for the 4739's.


I would agree with this.

Quote:
Let us know how your experiment with the MFOS VCA for controlling regen goes, this sounds very interesting to me as well! I do have a few of those pcb's laying around. If it's a viable way to go, one might make it into this project.


I will post here when it is working. It could be a month or two before I complete these modules.

Take care,
Doug

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The Peasant



Joined: Nov 13, 2009
Posts: 99
Location: Sunny Alberta
Audio files: 1

PostPosted: Wed Nov 25, 2009 11:04 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
Welcome, "Peasant."

I consider myself one of your disciples, and emailed you once to tell you so and exchange ideas on synthsized drums. Is your monster project still on hold?

Glad to see you here.


Thank you Richard!

I spent some time last year developing circuits for my Monster Drum Synth, but unfortunately I was not making good progress and decided to focus on my modular projects for a while instead. That way I can design using the modular itself instead of breadboarding everything that I wanted to try. I will get back to it eventually, but the new projects keep piling up...

Take care,
Doug

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The Peasant



Joined: Nov 13, 2009
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PostPosted: Sun Dec 06, 2009 11:23 pm    Post subject: Reply with quote  Mark this post and the followings unread

OK, I can now confirm that this pcb layout works with the SAD1024, and that the MFOS Dual VCA can be easily used for VC Regeneration. Just connect the VCA in place of the potentiometer and use the VCA panel offset control to set the regeneration amount.

I have also made some modifications to the MFOS VCA, see here for the details: http://electro-music.com/forum/topic-38568.html

Below is a picture of the pcbs all wired up and working. I added some voltage regulators to the board as well.

Take care,
Doug


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aerogramma



Joined: Feb 27, 2008
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Location: Roma, Italy - London, UK
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PostPosted: Tue Dec 08, 2009 1:48 am    Post subject: Reply with quote  Mark this post and the followings unread

all the ebst from here Peasant

your designs are very inspiring... I have just completed salvaging enough material for a VDF Ring mod so it will be next!

Wink

aero
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