An Easy AD Envelope Generator

wackelpeter · Posted: Thu Mar 13, 2014 11:10 am Post subject:

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...

khakifridge · Joined: Jul 15, 2014 Posts: 27 Location: UK

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.

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

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.

cyclic · Joined: Mar 15, 2015 Posts: 95 Location: hobart

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

cyclic · Joined: Mar 15, 2015 Posts: 95 Location: hobart

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...

J3RK · Joined: Jun 05, 2006 Posts: 123 Location: Seattle

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

okelk · Joined: May 08, 2014 Posts: 71 Location: Vienna

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.

elmegil · Posted: Mon May 04, 2015 2:27 pm Post subject:

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

okelk · Joined: May 08, 2014 Posts: 71 Location: Vienna

elmegil · Posted: Mon May 04, 2015 3:14 pm Post subject:

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?

okelk · Joined: May 08, 2014 Posts: 71 Location: Vienna

okelk · Joined: May 08, 2014 Posts: 71 Location: Vienna

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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Snaper · Joined: Feb 28, 2014 Posts: 217 Location: Hungary

Guys, can I omit the 1M Attack pot?
I mean, not totally omit, but replace with a 0OHM resistor?

I would like to create a simple quad decay module.

In the other hands, is there any way to boost the output to swing from 0 to 10V?

okelk · Joined: May 08, 2014 Posts: 71 Location: Vienna

indigoid · Joined: Apr 20, 2016 Posts: 5 Location: Sydney, Australia

This looks pretty good!

I've made a basic PCB layout for my own use, in Euro format. I added an attenuverter (Ian's uncomplicated single-opamp design) on the output and a bipolar LED driver. Will order some boards soon (again, for my own use; I only have the freeware version of Eagle at present), maybe later this week.

The other idea I had was similar to the above but smashing the attack and decay controls together into a single knob (via a dual-ganged pot) and calling it Shape, then adding an attenuverter and an Offset pot. Should still fit in 4hp without being horribly cramped. A single knob obviously isn't as flexible as separate A & D/R controls, but it would work quite well for the way I tend to use these kinds of envelopes.

PS: First post. I am incredibly grateful for the sharing spirit here and elsewhere in the community. Wonderful. Thanks <3

cyclic · Joined: Mar 15, 2015 Posts: 95 Location: hobart

the 'shape' concept you are talking about would probably be achieved more simply with a slew limiter such as Yusynth's one.

I built one slew limiter with two switches and an tl072 : one switch selects log/lin and the other on-off-on selects attack only, attack and decay or decay only (just as per Yusynth's design) but I skipped the gate control.
It gives a good, simple adjustable trapezoid, ramp or saw. I usually it with an LFO, but can also do portamento from my sequencer/keys etc.

Its a very useful unit for a one-knobber. Next time I may even leave off the log/lin option or just make it jumperable instead.

oculus · Joined: Oct 30, 2011 Posts: 35 Location: Iceland, Reykjavik

thanks thomas for making this really nice circuit available to us,
i just breadboarded it and try´d it both with 15v and 12v
i was hoping to make this work for 12v.

i noticed the output is less with 12v which was expected. but i just changed the output resistor to 1k insted of 2k and that brought the level up enough

do you guys know if i should be watching out for anything else when using this circuit on 12v ?
thanks

indigoid · Joined: Apr 20, 2016 Posts: 5 Location: Sydney, Australia

http://smallbear-electronics.mybigcommerce.com/alpha-dual-gang-9mm-pc-mount-dual-concentric/

Posted Image, might have been reduced in size. Click Image to view fullscreen.

Posted Image, might have been reduced in size. Click Image to view fullscreen.

This might be a better option than the limited-functionality "shape" knob, or separate attenuvert/offset knobs. I wish I'd noticed earlier that Alpha sell these!

(I am trying to achieve a balance of compactness and utility/usability... One of my portable Euro cases is only 54hp)

alanwilder81 · Joined: Sep 03, 2016 Posts: 310 Location: italy

hello guys,
could i use a regular ne555 in place of the cmos 555? Very Happy

cyclic · Joined: Mar 15, 2015 Posts: 95 Location: hobart

Yep, that's what I did. See my post from March last year up above.

alanwilder81 · Joined: Sep 03, 2016 Posts: 310 Location: italy

wow thanks el bo for quick response ! Smile

i'll breadboard it this afternoon. How do i go about using it with a VCA ?

i built a VCA as well as a VCO, but, where do i get the GATE signal from?
Do i necessarily need it to come from a keyboard controller?
thanks in advance Very Happy

cyclic · Joined: Mar 15, 2015 Posts: 95 Location: hobart

That's ok.

The gate can come from anything square or sharp edges (ie a trailing saw)

So it could be a keyboard gate out, or just a simple single switch( probably with a transistor buffer) or a square lfo, or a gate sequencer, or ... I think you get the idea.

You patch the gate in to the EG, set the knobs and send the output to the VCA CV-in. You send the audio ( or whatecer you are VCAing) into the other In and get the result Out. That's just your bog standard envelope patch though and there are a million other things you can do with it once your synth takes up a whole Wall!

Cheers

Lance

alanwilder81 · Joined: Sep 03, 2016 Posts: 310 Location: italy

thanks Lance for the accurate response! Smile

so, in a nutshell

GATE >> AR generator input

AR generator out >> VCA CV input

VCO out >> VCA signal in

i've been trying the above architecture with other DIY modules,with crappy resoults,though.
It's probably the cmos 7555 core ADSR circuit i built to blame,as i havent got the 7555, replaced with a regular ne555. All i get is a weird VCA output.

So, i decided to back up a bit and to switch to this extremely simple design. Easier to troubleshoot,looks promising and low components count.
Let's see what i come up with.
I'll keep you posted !

please excuse my rough english, i am italian! Smile

simone

cyclic · Joined: Mar 15, 2015 Posts: 95 Location: hobart

Yes that's right.

Can't tell you about the adsr, but I know the yusynth one he specifically says you need a 7555 so you might as well spend a euro and get two envelope generators if you can...

alanwilder81 · Joined: Sep 03, 2016 Posts: 310 Location: italy

thanks ElBo,

it's time to get the 7555,yes. And ,as for the Thomas Henry AR, i breadboarded yesterday in no time.
Then,i connected my signal generator square output to the AR input,but surprisingly, no output at all visible on the scope.
i wonder what that is about