An Easy AD Envelope Generator

Thomas_Henry

Hi Gang,

I saw a circuit for an AD envelope generator elsewhere on this forum and instantly thought it was way too complicated:

So, just as a diversion, I decided to come up with one that does the same thing, but with far fewer parts.

Here's the scoop. Most people think of the 555 as a timer, either astable or monostable, which tends to lock one into a rigid way of thinking. I prefer to think of the chip as a collection of parts. In particular, the circuit mentioned above requires an RS flip-flop, a comparator and some steering logic (diodes). In fact the 555 contains these. (Well, I did have provide one steering diode, the other imitated by the internal open collector transistor).

In one fell swoop (the only kind of swoop worth having), the circuit shrinks by leaps and bounds.

My good buddy Scott Stites gave it a shakedown with the test instruments and measured:

Minimum attack: 692 us
Minimum decay: 248 us

Maximum attack: 4.6 s
Maximum decay: 25.8 s

Max voltage: 5.04V

These are pretty specs, if I may be so immodest. It would also make a fine drum envelope generator, methinks.

Thomas Henry

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mrmrshoes · Posted: Thu Mar 06, 2014 6:59 pm Post subject:

Man great work as always. thanks for sharing.

you sure have gotten your moneys worth from the 555 like Wink

I'll breadboard this up as soon as.

mcop · Joined: Apr 27, 2012 Posts: 46 Location: Brighton UK

Oooh! Thanks, going to try this one as well. Another elegantly simple design.

mcop · Joined: Apr 27, 2012 Posts: 46 Location: Brighton UK

Tried this out this morning as I have a day off work and this envelope works beautifully.
Have replaced the input with a comparator which gives it the ability to work with a gate signal or extract a trigger signal from a gate.

Excuse my drawing!

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Thomas_Henry · Posted: Fri Mar 07, 2014 9:45 am Post subject:

Thanks for the comments.

The comparator add-on is unneeded; the original circuit will work directly with a gate input. The cap and transistor already differentiate whatever is applied, gate or trigger.

Thomas Henry

mcop · Joined: Apr 27, 2012 Posts: 46 Location: Brighton UK

StephenGiles · Joined: Apr 17, 2006 Posts: 507 Location: England

Hi Tom, great circuit as usual! From a guitarist's viewpoint, could the peak voltage level of the attack phase be controlled by a voltage extracted from a "pluck follower"? (Craig Anderton's AMS 100?) The point being that if the AD output drives a VCF, the smooth decay phase should be completely ripple free.

Thomas_Henry · Posted: Fri Mar 07, 2014 12:16 pm Post subject:

Hey Mcop,

Try this. Just wire a SPST switch across the input cap. When closed, the unit becomes an AR envelope generator, when open it is an AD type. I find I can fire it either way with a gate or trigger whose amplitude is at least 1.8V.

I'll add the switch in the next draft. Thanks for suggesting it.

Thomas Henry

Thomas_Henry · Posted: Fri Mar 07, 2014 11:06 pm Post subject:

Hi all,

Okay, here is the updated schem. You can plug in a Gate to get an AR response, or a Trigger to get an AD response. If both are plugged in at once, the Gate takes precedence.

The Gate will respond to +1.8V signals, while the Trigger will respond to +4V signals.

The input impedance is 100k, while the output impedance is 1k, per the usual Electronotes standards.

Thomas Henry

AD-AR Envelope Generator.jpg

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AD-AR Envelope Generator
Please do not reproduce, but instead send others to this Electro-Music Forum.

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mcop · Joined: Apr 27, 2012 Posts: 46 Location: Brighton UK

Thanks, will try this when I get a chance to get back to my breadboard.

seanpark · Joined: Mar 15, 2013 Posts: 4 Location: nashville

This is quite an efficient circuit!

Patched up a bass drum sound, breadboarded this thing and bam.

First time I've used an AD. Thanks, Thomas! Cool circuit.

Been reading the Drum Cookbook a few times through, maybe its time to start building some things.

StephenGiles · Joined: Apr 17, 2006 Posts: 507 Location: England

wackelpeter · Posted: Tue Mar 11, 2014 10:09 am Post subject:

would this work with an ne555 too or must that be an cmos 555 ic? just asking as i have some spare NE555 already here but no CMOS timers at hand right now...
Please forgive me taht stupid question but my basic electronical lessons are now roughly 20 years ago so only a few things of that small knowledge left in those few of my braincells that continue working until today Wink

Looking at the datasheet i would say it could work that way too or i am wrong?

bubzy · Posted: Tue Mar 11, 2014 11:26 am Post subject:

****NOT TESTED****

single sided pcb artwork I haven't got the facility to etch at the moment, laser printer died Sad

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mcop · Joined: Apr 27, 2012 Posts: 46 Location: Brighton UK

Knocked up a dual version on stripboard as I only had TLC556's. Works great, thanks.

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Thomas_Henry · Posted: Tue Mar 11, 2014 11:42 pm Post subject:

Hello all,

I'm delighted to see a few folks are having fun with this.

This might be a good time to remind E-M people, that I do have special arrangements with Scott Stites, Tim Servo and Fonik for applications and dispersal of my designs. In fairness to them, be sure to secure permission from both me and them before posting any sort of derivative work that could cut into the hours they have spent or are spending spreading this stuff around. All it takes is a request, and I've rarely turned anyone down if I know what is coming.

Otherwise, feel free to make your own versions for private use and let us know your results. For example, Mcop's rendition looks just great!

Thanks,

Thomas Henry

bubzy · Posted: Wed Mar 12, 2014 12:39 am Post subject:

sorry Thomas, would you like me to remove the pcb artwork?

StephenGiles · Joined: Apr 17, 2006 Posts: 507 Location: England

Thomas_Henry · Posted: Wed Mar 12, 2014 12:03 pm Post subject:

Hi Stephen,

Sorry, I kept overlooking your question somehow.

If I understand it properly, I do believe the answer is no, at least for this circuit. The envelope peak is set by those three series resistors inside the 555. This is the divider that sets the comparator thresholds. Look at a block diagram for the 555 and you'll see how 10 volts is the magic number for the peak.

I will be incorporating this circuit within a complete synth voice, and providing artwork myself for a PCB, possibly for an article. But, Bubzy, you can leave what you have done up for others to play with.

And Wackelpeter, this is such a small circuit, that the easiest way to answer your question is just to breadboard it and see if a bipolar 555 will work. There will probably be some difference in how the internal transistor on pin 7 behaves which might affect the decay, but logically the circuit should work the same.

Thomas Henry

wackelpeter · Posted: Wed Mar 12, 2014 1:13 pm Post subject:

Hi Thomas,

thanks for your reply... still had built this circuit on stripboard, but only got the same signal on output which i fed to the input... that was the reason why i wasn't sure... and now checking my stripboard again with an magnifiying glass i found a strip not drilled correctly which shorted the input after the condensator with the output... well that's stupidity at work so please don't laugh at me.. it's the usual thing that i oversee the simple mistakes i made... don't wanted to show that i'm an idiot what i now have to admit Smile

With that strip fully parted no wonder it works... Wink

But now i have to re-work my power supply as my self-built one after Ken Stone's design doesn't work properly... voltage drops down the more modules i'm connecting to it... it's as i assume not the current as i have 60mA fuses on each rail it's the transformer 2x24AC that feeds a bit too much to the15V DC Regulators i think.... will go for an traco power supply unit so far... Guess that also is the issue for some of my other problems... LFO clicking in my Steiner Parker filter as each cycle of the lfo the voltage goes down on the positive rail... i'll see what of These issues left when i run everything on a stable psu...

Thank you again Thomas and sorry for entering this thread with my other issues...

Keep your nice work going.

StephenGiles · Joined: Apr 17, 2006 Posts: 507 Location: England

Nardu · Joined: Feb 28, 2011 Posts: 62 Location: Braila, Romania

With Thomas Henry's permission, a stripboard layout.

AD-AR Env Gen.jpg

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Easy AD Envelope Generator - Stripboard layout in Lochmaster

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elmegil · Posted: Wed Mar 12, 2014 7:22 pm Post subject:

wackelpeter · Posted: Thu Mar 13, 2014 9:28 am Post subject:

mcop · Joined: Apr 27, 2012 Posts: 46 Location: Brighton UK

If there are runs of boards happening people normally start threads to see what interest there is both here and at muffwigler.com. Fonik in particular has done some excellent boards for some of Thomas' other designs.