An Easy AD Envelope Generator

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

Sorry, can't really help you except to suggest you check it all again, and make sure all the components and ics are functioning.

To be honest I don't think I've ever had something work first time...

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

yes it's gonna take some extra troubleshooting apparently.
One more question about GATE signal.
I know what that is on paper,but i'm still having hard time to get it on real world. You said that it can be even a square LFO output,right?

Could i use a ne555 in astable mode, set at very low frequency, to produce a GATE output? is there any other simple circuit to make a GATE signal out there?
that's all i need to start my ADSR and test them wether they work or not.
A plain bloody GATE Cool

Thanks

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

Normally the a gate would be a +5 v rectangle wave. I found that some old mfos circuits are +12v but that's not standard. Hopefully the circuits you are following tell you. Im pretty sure the Thomas Henry ad/atr in this thread will work fine from a +5v.

Yes, you could set up a 555 to give you a train of gates.

If you've got a +5 v supply handy you could even just test it out with a push button momentary switch. I'll admit that I've been know to just probe the gate input point with a +5v jumper wire. Those give you a pretty messy gate signal but it often is enough to test, butyou definitely run the risk of frying chips with this cavalier attitude.

A less brutal option would be to use the switch to trip a transistor which takes the 5v to the gate input point. If you look at some of the mfos designs which have a 'gate button' you can see what I mean. Try one of the lofi noise boxes like the noise toaster schematic.

Yes, I just checked, and page 2 of the noise toaster schematic has a 'manual gate' push button.

Cheers

Lance

wackelpeter · Posted: Wed Sep 14, 2016 6:37 am Post subject:

The TH555 AD/AR work fine with a 5V Gate... Have 5 of them so far...

Your Question regadring the NE555 timer is answered by Thomas Henry himself on the first page i asked the same question...

Even if it works, i would suggest to use sockets and change it later to an 7555 or so... your other circuits will thank you therefore when you keep your power rails clean and with little as possible current consumption... Wink

And yes you can ran also a bipolar square LFO into it...

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

hey wackelpeter,thanks for the suggestions !

I cant wait to eliminate the lousy ne555 from my project. Trouble is, i have a brand new dozen of them in my toolbox ,so they are there to study and poking around with my modules Cool

No doubt they'll be replaced with the better CMOS 7555 after this initial trial phase Very Happy

.

now it's time to get breadbarding.I'll keep you chaps updated ! Smile

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

hi chaps,
i've breadboarded Thomas Henry AR generator, and despite it doing the volume envelope when routed to the VCA, it also heavily affects the pitch of my VCO.
In short, as soon as the AR enters the release phase,along with the volume, as expected, the pitch also goes down.
I've experimented the same issue with other ADSR's , and i can't understand what the culprit is.
Might it be the ne555 used in place of the 7555 ? i used the ne555 in all the ADSR'S i've built and i am starting to think that this is where the problem lies. otherwise, any suggestions? thanks ! Very Happy

wackelpeter · Posted: Sat Sep 17, 2016 11:35 am Post subject:

As said before, the NE555 draws to much current so the 7555 is the better solution... Much current affects the voltage and if your PSU (possibly also a small one) is under much load the voltage will drop and your VCO drifts...

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

hey wackelpeter,
that makes sense.i never thought it would affect so heavily my VCO pitch.
Steep learning curve here Very Happy

i cant wait to drop in a 7555 and see what's what.

thanks again !

daemonik · Joined: Feb 02, 2007 Posts: 13 Location: Zürich Highlands

Hi,
I was hit by this cool 555 AD design while I'm extensively modding my NAVA TR-909 clone. Specifically I'm looking for an AD-ENV for the EPROM sample based Cymbals (Crash/Ride) here.

Main problem I meet is, that I need to reset the AD with every new Trig to 0V before starting attack phase (else the cymbals would sound different on every step depending state of the ENV between 2 steps - actually an interesting option)

Could I go with just a diode+resistor between charging cap and Q1 collector? (CAP > DIODE > RESISTOR > Q1 collector). Would the cap discharge quickly enough? should I prefferably go with a dedicated transistor?

Any other suggestions?

danfan · Joined: May 26, 2008 Posts: 7 Location: chicago, il

Necroposting in case anyone has the same trouble when adding the comparator looper - I found that pulling the envelope out of the threshold pin (which is the same as the final buffer output) decreased the envelope amplitude when looping. Instead, pulling the envelope from the input of the buffer (right after the 4.7uF cap), and sending it through a simple emitter follower before hitting the comparator resulted in no appreciable loss on the output.

mercury8 · Joined: Nov 25, 2018 Posts: 14 Location: grand rapids ohio

can this run on 12v instead of 15 v?? and why does the schematic call for 100pf cap for c2 and the layout has a 10nf for c2??

Grumble · Posted: Thu Dec 13, 2018 3:32 am Post subject:

Is this module retriggerable?

Grumble · Posted: Thu Dec 13, 2018 3:41 am Post subject: Re: ad generator

gabbagabi · Posted: Thu Dec 13, 2018 8:30 am Post subject:

correct me if iam wrong
but retrigger is usfull in "full" adsr, not so in AD / ASR

blue hell · Posted: Thu Dec 13, 2018 10:28 am Post subject:

Nothing wrong .. but I find it very useful to have retrigger on my AR or AD envelopes .. otherwise it needs to finish its cycle (which could be 12 s for my implementation) before a next blip gets trough ... made a non-retriggerable version too but ended up never using it.

Grumble · Posted: Thu Dec 13, 2018 2:31 pm Post subject:

Soo... is it?
Retriggerable? Rolling Eyes

blue hell · Posted: Thu Dec 13, 2018 3:22 pm Post subject:

looking at the 555 datasheet ... once the internal flip-flop is reset by the trigger input the only thing to set it would be the threshold input to go over 2/3 Vcc .. which would happen at the end of the attack phase .. after that it should be possible to re-trigger it.

(edit: it actually ends the attack phase)

Set and reset are a bit confusing here .. but the default flip-flop state is to be set .. and the trigger resets it to be cleared.

mtts · Joined: Dec 16, 2018 Posts: 4 Location: Netherlands

Hello everyone, regular lurker here. First of all, thanks for the great resource! Lots of fun and very educational. I think I *almost* understand what this thing is doing. So thanks for that!

That said, I ran into a little problem building this on stripboard (breadboarding went fine), using the circuit at the top of the thread:

If I bypass everything starting from C2 to the base of Q1, the envelope is triggered (using a square wave LFO). If everything from C2 to the base of Q1 is included, nothing happens. I've also tried leaving out bits of that part of the circuit in various configurations, all to no avail. The transistor base needs the unmodified gate input, otherwise it does nothing.

I'm guessing the problem might very well be elsewhere as it worked fine on breadboard, but the thing is - I'm done troubleshooting this thing and I would really like to just slap it behind a front plate and be done with it.

So my question is: how bad would it be to leave out that bit of the circuit? If I understand it correctly all it does is protect against strange input signals, correct? So if I make sure to never send it anything strange, it should be fine, right?

Thank you very much in advance for your help

JovianPyx · Posted: Sun Dec 16, 2018 9:07 am Post subject:

Check D1 to ensure it's oriented correctly. If reversed, the circuit won't work.

mtts · Joined: Dec 16, 2018 Posts: 4 Location: Netherlands

Thanks for the suggestion. Unfortunately it is oriented correctly.

JovianPyx · Posted: Sun Dec 16, 2018 10:55 am Post subject:

Is it possible the diode is bad, as in shorted? Maybe disconnect one end and check it with DMM? That bit of circuit isn't complex, maybe a bad solder connection in that input circuitry? Shouldn't be too hard to reflow the solder on that input circuit. Look for solder blobs that could short stuff...

mtts · Joined: Dec 16, 2018 Posts: 4 Location: Netherlands

Unfortunately it isn't. All parts are fine, as is all the soldering in this part of the circuit. Just to double check I rebuilt this part of the circuit on breadboard - still no dice. Played around with swapping some components for different values, still nothing.

Basically if there is any sort of decoupling between the input (capacitors or resistors or, as it's supposed to be, both) and the transistor base, nothing happens.

So what I'm wondering is: can I just bypass C1 and R2 completely without it causing a problem (frying another module in my rack)? The modified schematic with separate inputs for triggers and gates suggests bypassing C1 would be no problem. If I replace R2 with 1K would that be OK?

JovianPyx · Posted: Sun Dec 16, 2018 1:17 pm Post subject:

I would not eliminate those parts of the circuit. You indicated that the circuit (with input protection) on breadboard worked and we know that Thomas Henry is an excellent designer - so there must be something amiss in the stripboard version.

C2 is there to provide a narrow positive pulse for triggering the 555 regardless of the input trigger pulse length. R3 provides a path to ground to allow C2 to charge and sets the pulse width of the C2/R3 combination. R2 transfers the pulse to Q1 and D1. D1 looks reverse biased, but it's there to protect Q1from the negative pulse cause by C2/R3 at the falling edge of the input pulse. Make sure that R2 and R3 are both 100K and C2 is 100pF. Sorry about these questions, but it's important. Q1 is used as an amplifier to increase the C2/R3 pulse amplitude because a 555 needs more than a 5 volt pulse when it's powered by 15 volts. This is where an o-scope is very helpful. I'd scope pin 2 of the 555 to see whether any pulse makes it there and if so, how many volts the pulse peaks at. If no pulse is seen, then I'd move the probe down the signal path toward the input (if no pulse or too small of a pulse is seen at pin 2) to see what is happening. At the base of Q1 and before, you'll not see any taller pulse than 5 volts.

Without an o-scope, this isn't easy so another thing to try is if you have the parts, try to build the circuit again on breadboard and see if it works. If it works, then there's definitely something wrong with stripboard version. When you checked for solder blobs etc. did you check the entire circuit or just the input bit?

Again, I apologize if these questions and suggestions seem a little simplistic, but I'm going by my own troubleshooting experience and the crazy things I've seen in my own solder work.

mtts · Joined: Dec 16, 2018 Posts: 4 Location: Netherlands

Conceivably what could have happened is that the breadboard version shorted the input protection circuit somehow.

Everything else has been checked, measured, checked again.

This is not entirely unlikely because I stuck it in a Eurorack box. The output resistors R6 and R7 were swapped with 1K to compensate but maybe C1, R1 and R2 should have different values as well. Dunno ...

C2 is apparently not needed if you don't use triggers (which I don't), as per Thomas Henry's post at Thu Mar 06, 2014 5:44 pm.

But you're probably right - there's something really wrong with the stripboard version. Back to breadboard it is and try again ... sigh.

Thanks for your help, though. Much appreciated.

mercury8 · Joined: Nov 25, 2018 Posts: 14 Location: grand rapids ohio

can this run off 12v?? and I thought most gate signals were +5v and it says that the gate responds to 1.8v? does this mean I need to have a gate that is a minimum of 1.8v? sorry about noob questions. im just trying to use this as a typical ar generater. typical 1voice snyth setup