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 Forum index » DIY Hardware and Software » Jürgen Haible designs
Trapezoid VCA anybody?
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Would you buy a Jh Trapezoid VCA PCB?
no - only interested in the original EMS circuit (this is not goint to happen - sorry)
2%
 2%  [ 1 ]
yes - if it emulates the behaviour of the EMS circuit, and doesn't need component selecting
97%
 97%  [ 40 ]
Total Votes : 41

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jhaible



Joined: May 25, 2007
Posts: 2014
Location: Germany
Audio files: 24

PostPosted: Fri Nov 26, 2010 12:43 pm    Post subject: Reply with quote  Mark this post and the followings unread

zarko wrote:
Hi Jurgen, i made a new front panel with the attenuator pot,would you tell
me what do you think about Wink


Looks great.

And you could still improove it by making it a reversible attenuator, i. e. zero at 12 o'clock position, and increasing Decay time on cw end (with a positive CV), decreasing decay time on ccw end.

Also, the DC shift potentiometers have no effect in 12 o'clock position. Turning them cw will add a positive DC shift, and turning them ccw will add a nagative DC shift. This refers to both pots: The "+" and "-" means the normal and the inverted output. You can DC-shift them both in both directions.

JH.

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zarko



Joined: Mar 25, 2010
Posts: 22
Location: France

PostPosted: Fri Nov 26, 2010 2:56 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks Jurgen i think now that we have the right final panel.
Let me know if i have to modify other ting Wink


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jhaible



Joined: May 25, 2007
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PostPosted: Fri Nov 26, 2010 3:51 pm    Post subject: Reply with quote  Mark this post and the followings unread

Looks great! Smile

JH.

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"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)
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numbertalk



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PostPosted: Fri Dec 03, 2010 5:52 pm    Post subject: Reply with quote  Mark this post and the followings unread

Not sure if anyone's keeping track or adding fixes to the BOM that got created here anymore, but found 2 more errors - there's a 91K resistor missing and a 3K resistor listed that's supposed to be 2K4.
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zarko



Joined: Mar 25, 2010
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PostPosted: Mon Dec 06, 2010 10:06 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi
I think that the right value is 3K on the PCB


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numbertalk



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PostPosted: Mon Dec 06, 2010 10:20 am    Post subject: Reply with quote  Mark this post and the followings unread

zarko wrote:
Hi
I think that the right value is 3K on the PCB


Yeah, I saw that on the web site image too, but my board has 2K4 there, as well as the schematic. JH?
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jhaible



Joined: May 25, 2007
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PostPosted: Mon Dec 06, 2010 1:18 pm    Post subject: Reply with quote  Mark this post and the followings unread

numbertalk wrote:
zarko wrote:
Hi
I think that the right value is 3K on the PCB


Yeah, I saw that on the web site image too, but my board has 2K4 there, as well as the schematic. JH?


2k4 is right.

It was a last minute change. 3k will also work, sort of; but 2k4 will work better in combination with extreme Decay CV settings.

JH.

_________________
"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)
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MR-808



Joined: Sep 30, 2010
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Location: Portland, OR

PostPosted: Tue Dec 07, 2010 2:28 am    Post subject: Reply with quote  Mark this post and the followings unread

MR-808 wrote:
janvanvolt wrote:
Anybody got an idea for the frontpanel (5U?)


My partner in synth-building is working on one. I hope to have something worth showing soon!


Too many irons in the fire! We finally put together something we both like. It doesn't conform to the usual MOTM conventions, which will probably tick some people off. Wink My collaborator convinced me that it would be better to put the inputs on the left and the outputs on the right.

I still have a little bit of tweaking to do on the horizontal spacing, but it's very close to what we'll screenprint.


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decaying.sine



Joined: Aug 31, 2009
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Location: New Haven, CT, USA

PostPosted: Tue Dec 07, 2010 5:39 pm    Post subject: Reply with quote  Mark this post and the followings unread

MR-808 wrote:
MR-808 wrote:
janvanvolt wrote:
Anybody got an idea for the frontpanel (5U?)


My partner in synth-building is working on one. I hope to have something worth showing soon!


Too many irons in the fire! We finally put together something we both like. It doesn't conform to the usual MOTM conventions, which will probably tick some people off. Wink My collaborator convinced me that it would be better to put the inputs on the left and the outputs on the right.

I still have a little bit of tweaking to do on the horizontal spacing, but it's very close to what we'll screenprint.


I really like the panel design for your dual trapezoid. Great work!
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numbertalk



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PostPosted: Tue Dec 07, 2010 5:50 pm    Post subject: Reply with quote  Mark this post and the followings unread

2 more corrections for the BOM:

There should be 2 470n caps
There should be 2 BC560Cs and 4 BC550Cs (not counting the matched pair that can be replaced by an IC)
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wjhall



Joined: Dec 09, 2010
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PostPosted: Thu Dec 09, 2010 7:47 pm    Post subject: 5U JH Trapeziod VCA panel designs
Subject description: a few design ideas from Bill and Will
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Hi guys -

Will found this thread and thought perhaps we might offer his panel ideas. He did this graphic design, as we usually do, to illustrate the feature set before the panel actually get laid out in FPD or by Scott Deyo or whoever... I think he's got a good handle on the feature set.

This first of his 3 designs includes all of the features represented on Jurgen's schematic diagram. It needs a 3U wide panel. He did another two - one with attenuators for the 3 audio inputs (also 3U wide), and another with just the Trapezoid Generator portion of the features (2U wide).

Please let us know what you think.

Thanks,

Bill and Will


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bennethos



Joined: Apr 18, 2009
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PostPosted: Tue Feb 08, 2011 6:09 am    Post subject:  Sharing is power Reply with quote  Mark this post and the followings unread

I just ordered a PCB as well.
Can't wait to start it !

Thanks again JH for sharing you're brilliant designs to us synth lovers.

Here's an updated and corrected version of the Trapezoid VCA BOM. (I applied the corrections that I've found reading throug this thread).

All the best,
Benjamin


vca_trapezoid_JHaible_BOM.xls
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Trapezoid VCA BOM 08/02/2011

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jhaible



Joined: May 25, 2007
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PostPosted: Tue Feb 08, 2011 6:14 am    Post subject: Reply with quote  Mark this post and the followings unread

My Prototype PCB of the trapezoid will be on ebay tonight, starting at 20:00 MEZ.

JH.

_________________
"I tell you the truth, if anyone says to this mountain, 'Go, throw yourself into the sea,' and does not doubt in his heart but believes that what he says will happen, it will be done for him. Therefore I tell you, whatever you ask for in prayer, believe that you have received it, and it will be yours." (Mk 11,23f)
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MR-808



Joined: Sep 30, 2010
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PostPosted: Tue Jun 28, 2011 1:07 pm    Post subject: Reply with quote  Mark this post and the followings unread

I'm finally getting around to building my JH Trapezoid VCAs, and now that the pcbs are stuffed and missing some parts, I have a few corrections to Bill & Will's BOM (dated 12/9/10). To wit:

Resistors - (3, not 1) 220 Ohm, (5) 470 ohm, (1) 620 Ohm, (1, not 6) 470kOhm.

Capacitors - (9, not 8) 100nF.

Diodes - (11, not 10) 1N4148.

Transistors - (1) 2N5461.

That's it AFAIK. Can't wait to get them wired up and hear how they work!
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emdot_ambient



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PostPosted: Wed Jun 29, 2011 7:47 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks for the update...I've got 2 of them almost built...not sure where I left off, though. My backlog pile is rapidly becoming my "almost completed PCB" pile. After a while I kind of lost track what's missing from what. Sad
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MR-808



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PostPosted: Wed Jun 29, 2011 10:32 pm    Post subject: Reply with quote  Mark this post and the followings unread

LOLZ. My "almost completed PCB" pile is growing, too. Wink I've got a "pick-up sheet" where I track what's missing, because I always seem to miss something.
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Davedatt



Joined: Jan 12, 2012
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PostPosted: Thu Jan 12, 2012 10:42 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hey there,

I am debugging the 2nd JH board for our Dual Panel TG. I have reached a point where I am looking for the final bug that is so slight that despite the fact I have it's twin working perfectly now I am at my wits end.

The problem is simple. At maximum off time I still get the unit self cycling about every 7 seconds.

All controls work as its twin.
Maximum cycle times are identical.
No DC offsets on the outputs.

Just wondering if anyone else has seen this. Yes I am and have gone thru the tedious job of checking resister and cap values. I am wondering if I have a tolerance issue with a component.

Sigh....
Dave
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Davedatt



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PostPosted: Fri Jan 13, 2012 12:47 pm    Post subject: Reply with quote  Mark this post and the followings unread

Has anyone measured the maximum cycle time or frequency of the trapezoid generator? Or measured stability of the device?

Dave
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MR-808



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PostPosted: Wed Jan 18, 2012 5:19 pm    Post subject: Reply with quote  Mark this post and the followings unread

I don't think anybody has actually completed theirs yet. ;)

NOTE: Dave and I have been working on our Trapezoid panels together. I am posting debug comments here in case they help someone else.

In Jürgen's video: http://www.youtube.com/watch?v=KzcAhTQQx3s , he demonstrates the trapezoid being off. So we definitely have a problem.

I also tried to determine the maximum frequency. I couldn't get a good audio signal from the video, so I tuned a synth by ear to match and measured it on the scope. It seems like Jürgen's trapezoid will go up to ~125Hz; ours does about 89Hz. Looking at the images, the attack slope isn't as steep on ours - that could be a clue.

Did using a lower current LED affect the max frequency of yours?

Hmmm...

PS Jürgen, I miss you, and not just because I could use your help debugging this thing. :(
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Davedatt



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PostPosted: Wed Jan 18, 2012 7:29 pm    Post subject:   Reply with quote  Mark this post and the followings unread

No, I don't think anyone else has built them. Smile

Looks like we are on our own.


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emdot_ambient



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PostPosted: Thu Jan 19, 2012 9:08 am    Post subject: Reply with quote  Mark this post and the followings unread

Pugix, aka Richard Brewster, has completed them:
http://pugix.com/synth/jurgen-haible-trapezoid-vca/

You might want to contact him.

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MR-808



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PostPosted: Fri Jan 20, 2012 3:32 am    Post subject: Reply with quote  Mark this post and the followings unread

I'm not sure if I fixed it, or if I just applied a band-aid to cover up a build error, but both of mine appear to be working normally. :)

The first clue was when a 'scope probe applied to what I call the "trigger node" (where R19 & R20 meet) caused the occasional trigger to completely go away. At first I thought it might be the capacitance of the probe & cable. Now I'm pretty sure it was the paralleled resistance of the probe dropping the resistance slightly. I replaced R19 with a 1M trimpot and dialed it down to ~950k, and that did the trick! Now it's possible to turn the triggering off completely by turning the OFF TIME all the way down.

I don't think it had any other effect on the circuit - it seems to be able to retrigger just as fast as before the mod.

I'm curious to hear if anybody else has a retriggering problem. Did we make a mistake? Are there parts out of tolerance (resistors are 1%, caps 5%, pots 5%)? Is it just a quirky circuit?

It is odd that Dave had a 4558 and 741 blow. And we both had several bypass caps blow (might just be a bad batch from Jameco - they no longer stock those, I see). I'm going to burn mine in for several hours before I finish assembly. Unless I encounter some other problem, though, I'm going to call it good for now.

Pictures when I'm done testing!
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v-un-v
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PostPosted: Fri Jan 20, 2012 4:03 am    Post subject: Reply with quote  Mark this post and the followings unread

Does anyone know what will come of the PCB for the Trapezoid? I was saving for one, and then we lost Jurgen Sad
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emdot_ambient



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PostPosted: Fri Jan 20, 2012 2:07 pm    Post subject: Reply with quote  Mark this post and the followings unread

I haven't seen anything lately on what's happening with JH's estate. I suspect it will take a while before they figure out what to do with his electronics stuff.
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Davedatt



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PostPosted: Sun Jan 22, 2012 1:27 am    Post subject:
Subject description: My Build.
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Now works great. Same thing as Mr. 808. 1 meg trim in place of R19, dialed down slightly. I did replace my LED's with 2ma LEDs as well. I suspect our origional or power up failures are related to the original 30ma LED's placing a transiant on the PS busses. Possibly responsible for the bypass cap problems. Little bit concerned about the soft off time, after about 3:00 o'clock I am in a manual time mode. Or at least I got tired of waiting for a re-trigger.

dave
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