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



Joined: Mar 15, 2015
Posts: 57
Location: hobart

PostPosted: Wed Sep 14, 2016 1:48 am    Post subject: Reply with quote  Mark this post and the followings unread

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...
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alanwilder81



Joined: Sep 03, 2016
Posts: 327
Location: italy

PostPosted: Wed Sep 14, 2016 4:24 am    Post subject: Reply with quote  Mark this post and the followings unread

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 Cool

Thanks Very Happy
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EL BO



Joined: Mar 15, 2015
Posts: 57
Location: hobart

PostPosted: Wed Sep 14, 2016 6:06 am    Post subject: Reply with quote  Mark this post and the followings unread

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
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wackelpeter



Joined: May 05, 2013
Posts: 430
Location: germany
Audio files: 10

PostPosted: Wed Sep 14, 2016 6:37 am    Post subject: Reply with quote  Mark this post and the followings unread

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...

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alanwilder81



Joined: Sep 03, 2016
Posts: 327
Location: italy

PostPosted: Wed Sep 14, 2016 7:13 am    Post subject: Reply with quote  Mark this post and the followings unread

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
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alanwilder81



Joined: Sep 03, 2016
Posts: 327
Location: italy

PostPosted: Sat Sep 17, 2016 11:17 am    Post subject: Reply with quote  Mark this post and the followings unread

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
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wackelpeter



Joined: May 05, 2013
Posts: 430
Location: germany
Audio files: 10

PostPosted: Sat Sep 17, 2016 11:35 am    Post subject: Reply with quote  Mark this post and the followings unread

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...
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alanwilder81



Joined: Sep 03, 2016
Posts: 327
Location: italy

PostPosted: Sat Sep 17, 2016 12:12 pm    Post subject: Reply with quote  Mark this post and the followings unread

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 !
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daemonik



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

PostPosted: Sat Apr 29, 2017 11:29 am    Post subject: Reply with quote  Mark this post and the followings unread

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?
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danfan



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

PostPosted: Thu Sep 07, 2017 9:11 am    Post subject: Reply with quote  Mark this post and the followings unread

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.
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