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 Forum index » DIY Hardware and Software » Thomas Henry designs
An Easy AD Envelope Generator
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wackelpeter



Joined: May 05, 2013
Posts: 130
Location: germany
Audio files: 6

PostPosted: Thu Mar 13, 2014 11:10 am    Post subject: Reply with quote  Mark this post and the followings unread

ahhh thanks for that info... already finished some modules from fonik's site and fit them into my briefcase... as i wrote in another topic i fear of getting too much addicted to modulars so i choose not to invest in an rack full of modules and choose that method filling big aluminium briefcases with new analogic life... Smile
for me the nice thing is that i can keep them with me and do not have much work when taking them anywhere...

the first one is nearly full now... luckily i could get hold of 3 other ones... so there's some space for expansion...

i should maybe ask fonik/Matthias himself if he has some spare PCB's from various projects left...
by now i have mostly spent time on building circuitry to process signals... time to build an oscillator i guess as it seems to be a bit odd to feed only signals from my normal synths into it...
what caught my interest is the 555VCO and the 4046vco...
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khakifridge



Joined: Jul 15, 2014
Posts: 11
Location: UK

PostPosted: Fri Aug 15, 2014 5:06 am    Post subject: Reply with quote  Mark this post and the followings unread

Slight necro-bump here... I came across this great little circuit the other day. Are the pots linear or log taper? Does it matter? TIA.
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vansweej



Joined: Sep 22, 2014
Posts: 2
Location: Belgium

PostPosted: Mon Sep 22, 2014 11:57 am    Post subject: Reply with quote  Mark this post and the followings unread

I found this little gem here last week and builded it over the weekend, together with the VCA of Thomas Henry (I managed to get hold of 5 3080's, blew up one).

I made a small movie of it and posted it on youtube:

https://www.youtube.com/watch?v=2tnjnhQjG3Y&feature=youtu.be

My signal is a sine wave, so the vca is still giving a lot of distortion, I need a better scoop to check this, however after this movie I fidled a bit more with it and the tone now is a better sine wave.
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lancej



Joined: Mar 15, 2015
Posts: 8
Location: hobart

PostPosted: Tue Mar 17, 2015 9:34 pm    Post subject: Reply with quote  Mark this post and the followings unread

This is my first electromusic post after 9 months or more of lurking!

Anyway,

I built up one of these on a nasty little bit of left over stripboard for my learn-as-i-go portable modular.

Out of curiosity I did two breadboard trials in parallel.

For one I used TL072 and TLC555 as per Thomas' original,
For the other I used M5218L SIP opamp pulled out of an old stereo unit, and an NE555 that was lying around.
The M5218L is more or less the same as a 741 according to the datasheet, so is basically an old no frills item as far as I can tell. I've got a dozen or more so I have been looking for uses...

Anyway, for my low tech purposes there was no discernible difference between the two breadboard builds, so I went with the salvaged goods for, well, recycling reasons!

I saw pretty damn similar results in both attack and decay/release times between the two. I don't have the facilities to do really good measurements.

Since there is an unused opamp sitting around, I made the most of it and hooked the other up as an attenuverted secondary output as per Ian Fritz's suggestions on his analog XOR build. (somewhere on electromusic!)

This is great! I quite like main -> VCA and attenuverted -> Cutoff CV and was well worth the 100k pot and panel space I had, especially since I don't have any single op amps lying around...

So, all in all, yes, its worth testing an NE555,or any old opamp you've got lying around if you want to trial.

cheers

Lance
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lancej



Joined: Mar 15, 2015
Posts: 8
Location: hobart

PostPosted: Tue Mar 17, 2015 9:37 pm    Post subject: Reply with quote  Mark this post and the followings unread

Oops,

Also forgot to say that I used 1M linear and 500k linear pots as they were all I had, but that they are very sensitive in the early phase, so I assume this means that a log pot would be better.
I've got a dozen or so on the slow boat from china so will probably replace them once they arrive...
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J3RK



Joined: Jun 05, 2006
Posts: 113
Location: Seattle

PostPosted: Wed Apr 08, 2015 8:09 am    Post subject: Reply with quote  Mark this post and the followings unread

You might be able to skew the taper or the pot a bit with a resistor.
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okelk



Joined: May 08, 2014
Posts: 58
Location: Vienna

PostPosted: Mon May 04, 2015 2:03 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks!

I just put together a dual unit with a 556 and a tl72.
Works nicely.

Is there any easy way to make this loopable?
That would be awesome.
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elmegil



Joined: Mar 20, 2012
Posts: 1680
Location: Chicago
Audio files: 14

PostPosted: Mon May 04, 2015 2:27 pm    Post subject: Reply with quote  Mark this post and the followings unread

I would expect that to be doable with a comparator on the timing capacitor set to fire when it hits zero.
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okelk



Joined: May 08, 2014
Posts: 58
Location: Vienna

PostPosted: Mon May 04, 2015 2:58 pm    Post subject: Reply with quote  Mark this post and the followings unread

elmegil wrote:
I would expect that to be doable with a comparator on the timing capacitor set to fire when it hits zero.


thanks, yes, pretty sure that this would work, and one 555 plus a dual opamp would still be pretty small. scratch
but I'm not sure what voltage to set the threshold to...
Ground would work of course, but due to the exponential response it would take a really long time until the envelope restarts...So I guess something like 0.2 volts or so would be more usefull....

Is there an easy way to set the threshold of a comparator to 'half a diode-drop over ground' or something like that? ...that way it would be independent from the rail voltages (unlike a voltage divider)...
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elmegil



Joined: Mar 20, 2012
Posts: 1680
Location: Chicago
Audio files: 14

PostPosted: Mon May 04, 2015 3:14 pm    Post subject: Reply with quote  Mark this post and the followings unread

Interesting question. A full diode drop would be easy, Vcc > current limiting resistor > diode > ground, but then half that? Maybe just use a diode with a small forward voltage like a schottky?
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okelk



Joined: May 08, 2014
Posts: 58
Location: Vienna

PostPosted: Mon May 04, 2015 3:47 pm    Post subject: Reply with quote  Mark this post and the followings unread

elmegil wrote:
Interesting question. A full diode drop would be easy, Vcc > current limiting resistor > diode > ground, but then half that? Maybe just use a diode with a small forward voltage like a schottky?


hm..yeah...If the 0.25 - 0.30mV from a schottky turn out to be a good value that may be a good option.
I guess combining the "Vcc > current limiting resistor > diode > ground" thing with a voltage divider would work too.
...but on the other hand, maybe I should just keep it simple and make sure the rail voltages are stable enough...
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okelk



Joined: May 08, 2014
Posts: 58
Location: Vienna

PostPosted: Wed May 13, 2015 10:41 am    Post subject: Reply with quote  Mark this post and the followings unread

in case anybody's interested this is the looping mod I came up with:

It probably works for other envelope generators too.
I ended up using a regular voltage divider for the threshold voltage (ca 0.54v) of the comparator, but added a additional cap for stability.
you might want to play with those resistor values and maybe raise the threshold voltage a bit...


I think I'll make a euro compatible board for a dual version with my mod (556 + TL074 ) ...and if it's ok with thomas henry share it here of course.

EDIT:
I think I put the diode in there to protect the transistor from a negative base-emiter voltage...but since there is a diode between the base and ground anyway, I think it can be omitted.


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