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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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Adam-V



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PostPosted: Wed Jul 28, 2010 3:56 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi Jürgen,

I see you're planning for this to run on +/-12V supplies, would there be much required to get it to run on +/-15V supplies for those of us that run them?

Cheers,
Adam-V

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jhaible



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PostPosted: Wed Jul 28, 2010 4:14 am    Post subject: Reply with quote  Mark this post and the followings unread

It will run on 15V AC wallwart, +/-15V DC or +/-12V DC.
There will be footprints for MOTM, Synthesizers.com and Doepfer 10-pin connectors.

JH.

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jhaible



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PostPosted: Wed Jul 28, 2010 6:20 am    Post subject: Reply with quote  Mark this post and the followings unread

TekniK wrote:
ok,and does this vca design add some smoothness or something to the sound.

Your YT demo sounds nice,but its just because of the AR effect or?


I'd say *if* the signal level is high enough for that FET VCA to colour the sound, it will colour it very differently than an OTA, or other classic VCAs.

The closest device I can think of, to that EMS VCA, is the UREI 1178 compressor. - Yes, I think that nails it. A poor man's 1178 modified as VCA. Smile

JH.

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TekniK



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PostPosted: Wed Jul 28, 2010 6:39 am    Post subject: Reply with quote  Mark this post and the followings unread

ok thanks Juergen for the info,interesting
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Adam-V



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PostPosted: Wed Jul 28, 2010 7:24 pm    Post subject: Reply with quote  Mark this post and the followings unread

jhaible wrote:
It will run on 15V AC wallwart, +/-15V DC or +/-12V DC.
There will be footprints for MOTM, Synthesizers.com and Doepfer 10-pin connectors.

JH.


Great news, thanks Jürgen

Very Happy

Cheers,
Adam-V

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machine.cuisine



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PostPosted: Fri Jul 30, 2010 11:07 am    Post subject: Reply with quote  Mark this post and the followings unread

I would like at least 2 of these PCBs.

The demos sound great. Thanks, JH.

Chris

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tomcat



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PostPosted: Mon Aug 02, 2010 7:46 am    Post subject: Reply with quote  Mark this post and the followings unread

Im in for 2!

Regarding the doepfer connector: Allow enough space to use the "Pfosten-Wannenstecker", there superior to the Doepfer Pfostenstecker where you can put the cable in however you like (your modules dont like this). Have no clue why Dieter isnt doing this...
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Adam-V



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PostPosted: Tue Aug 03, 2010 9:44 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hey, the page is up!

http://www.jhaible.de/trapezoid/trapezoid.html

Looking good Jürgen.

Just out of interest, what are the board dimensions?

Cheers,
Adam-V

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jhaible



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PostPosted: Tue Aug 03, 2010 11:53 pm    Post subject: Reply with quote  Mark this post and the followings unread

Adam-V wrote:
what are the board dimensions?


160mm * 100mm

JH.

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jhaible



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PostPosted: Wed Aug 04, 2010 12:01 am    Post subject: Reply with quote  Mark this post and the followings unread

For those who already think about sourcing components:
There is a footprint marked "LM394". This is the easiest solution, and makes sense if you still have one of the unexpensive ones that have been sold in large numbers some time ago.
But the npn pair's parameters are not critical: it's just used for the voltage controlled Decay time. You might as well use a pair of BC550C's (footprint is also on the PCB). You may not even need to match them. If they are _fairly_ matched, everything will work as intended. If you have a severly unmatched pair, and notice an unpleasant range of your Decay potentiometer, you can change one single resistor value to fix it. - (I hope the options are not too confusing. If that last paragraph doesn't make much sense to you, just buy an LM394.)

JH.

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Adam-V



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PostPosted: Wed Aug 04, 2010 2:47 am    Post subject: Reply with quote  Mark this post and the followings unread

jhaible wrote:
160mm * 100mm

JH.


Thank you.

Cheers,
Adam-V

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BananaPlug



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PostPosted: Wed Aug 04, 2010 7:50 am    Post subject: Reply with quote  Mark this post and the followings unread

PCB looks great. Two please!

I'm not qualified to talk about the EMS gear or JH's design but from other things I've read this is most of what makes the EMS trapezoid special:

A/On/D always completes.
Long gates will sustain.
The On time extends the post-attack sustain regardless of gate. It begins after attack is complete and gate has dropped.
Decay follows the On period.
If cycling, Attack begins again after Off time. Turning Off all the way up stops it from cycling
Minimum off period is around 10ms so it becomes an AM effect at that end of the range.
Range of the envelope signal is +/-5v (well, bipolar anyway) with further adjustment available at output.

Please chime in if I misrepresented anything.
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jhaible



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PostPosted: Wed Aug 04, 2010 9:23 am    Post subject: Reply with quote  Mark this post and the followings unread

BananaPlug wrote:
PCB looks great. Two please!

I'm not qualified to talk about the EMS gear or JH's design but from other things I've read this is most of what makes the EMS trapezoid special:

A/On/D always completes.
Long gates will sustain.
The On time extends the post-attack sustain regardless of gate. It begins after attack is complete and gate has dropped.
Decay follows the On period.
If cycling, Attack begins again after Off time. Turning Off all the way up stops it from cycling
Minimum off period is around 10ms so it becomes an AM effect at that end of the range.
Range of the envelope signal is +/-5v (well, bipolar anyway) with further adjustment available at output.

Please chime in if I misrepresented anything.


This is probably how a theoretical Trapezoid generator would work. Smile
The EMS (and mine also) is more quirky. For instance, the ON-Time begins before the Attack Time is fully completet, so the two always depend on each other. I never made an attempt to describe all these little specialities in words. You "feel" them when you turn the knobs and change the parameters, and the whole thing reacts in a pleasant, yet not entirely expected way.

JH.

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emdot_ambient



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PostPosted: Wed Aug 04, 2010 1:14 pm    Post subject: Reply with quote  Mark this post and the followings unread

Absolutely, I think 2 at least. afro
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v-un-v
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PostPosted: Fri Aug 06, 2010 6:24 am    Post subject: Reply with quote  Mark this post and the followings unread

Jurgen, wouldn't it be wise to set the price for this project so the final cost to build the generator is lower than the price that Analogue Systems are currently selling (the only licensed version) for? The AS version costs £155 (UK Pounds).
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jhaible



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PostPosted: Fri Aug 06, 2010 7:11 am    Post subject: Reply with quote  Mark this post and the followings unread

v-un-v wrote:
Jurgen, wouldn't it be wise to set the price for this project so the final cost to build the generator is lower than the price that Analogue Systems are currently selling (the only licensed version) for? The AS version costs £155 (UK Pounds).


The PCB will be 27 Euros.
There aren't any expensive components.
Ad you can omit half the component on the PCB if you only want to emulate the Trapezoid and VCA, and don't need the extra functions.

JH.

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v-un-v
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PostPosted: Fri Aug 06, 2010 7:34 am    Post subject: Reply with quote  Mark this post and the followings unread

Brilliant! Very Happy

A bargain! Cool

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parasitk



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PostPosted: Mon Aug 09, 2010 8:57 pm    Post subject: Reply with quote  Mark this post and the followings unread

Ooh I'd likely be interested in one, excellent!
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vtl5c3



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PostPosted: Sun Aug 15, 2010 5:46 pm    Post subject: Reply with quote  Mark this post and the followings unread

Just noticed this. I'd be in for one or two.
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zarko



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PostPosted: Tue Aug 17, 2010 12:35 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi Jurgen I'd be in for two.
Regards.
Fred
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e-grad



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PostPosted: Tue Aug 17, 2010 3:07 pm    Post subject: Reply with quote  Mark this post and the followings unread

Given my backlog I shouldn't do it but will take two!
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adambee7



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PostPosted: Tue Aug 17, 2010 3:43 pm    Post subject: Reply with quote  Mark this post and the followings unread

go on then ill take two please. Very Happy Very Happy
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source66



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PostPosted: Tue Aug 17, 2010 8:36 pm    Post subject: Reply with quote  Mark this post and the followings unread

in for two please!
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softfin



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PostPosted: Wed Aug 18, 2010 2:13 am    Post subject: Reply with quote  Mark this post and the followings unread

Interested in a pair of these. well-done
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v-un-v
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PostPosted: Wed Aug 18, 2010 2:19 am    Post subject: Reply with quote  Mark this post and the followings unread

Interesting that the majority want pairs- yet in the highly acclaimed Synthi, there is only one. Why do you want two? (I would also want two! Laughing )

Is it fear, of one not being 'enough'? I think that would be my answer- although I've still got a big box of PCB's here that still need constructing! Shocked

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