Single supply ADSR

[StephenGiles]

Found this just now - could be useful

http://electro-music.com/forum/phpbb-files/basic_850.png

I'm actually with my wife in hospital - she has a very nasty leg infection called Pseudomonas. I'm using an 11 year old laptop running Vista into my home PC via Teamviewer - as they say on twitter #techtechtech !!!

[Kipper4]

Excellent. Thanks Stephen. I hope wifey gets well soon.

[Mark Hammer]

Couldn't Anne just share some of this with you?  It seems you're the one who is always in fabulous shape and she's the one with the health issues.  Tell her not to be so greedy.  But seriously, best wishes for a speedy recovery.

If it helps boost your spirits, there's a 1972 Albion Country Band show on the new files list at Sugarmegs (http://tela.sugarmegs.org/_asxtela/asxcards/AlbionCountryBand1972-08-23KudosBoathouseLondonUK.html)

Thanks for the ADSR circuit.

[GibsonGM]

Is the opamp critical? Would "any old" one do?  (TL07x)?

Good luck with her leg!! Nasty, good to tend it properly right off...

[ElectricDruid]

That ADSR will suffer from the same problem I had when I designed one. As the voltage decays towards the sustain level, it reaches the point at which there is no longer enough forward voltage for the diode to conduct, so the diode turns off. It seems like you've then reached the sustain level, but in fact the voltage continues to drop slowly the remaining 0.6V over the next twenty or thirty seconds. The same thing happens on the release stage. I've seen some designs that use an offset to push the last part of the release below 0V so you don't get stuck close to off, but not quite there.

Often it doesn't matter (filter envelope, for example - you probably don't care) but if you're doing a pitch envelope that comes up from flat, goes sharp and then sustains at the correct pitch (like a vocal sound, for instance) then it's a disaster, since your note pitch droops horribly.

There are two ways I know to deal with this. You can either deal with it like Ian Fritz does:

http://electro-music.com/wiki/pmwiki.php?n=Schematics.AD-ARByIanFritz

The other way is to avoid the use of diodes for separating the stages. Designs that use analog switches don't have this issue. In the end, this is the route I took. It seemed silly to be spending circuitry fixing a problem which didn't need to be there.

HTH,
Tom

[Kipper4]

Care to share that Tom?
Thanks
Rich

[ElectricDruid]

Care to share that Tom?
Thanks
Rich

Yeah, one day. It isn't anything like finished, and I've moved onto other things. For a while, I was interested in solving the problem, and I spent some time doing sims with Ian F's solution, but in the end, I decided it was looney to try and fix something that didn't need to be broken, so I redesigned it with an analog switch. The logic is just a uP, which controls the switches. The uP also contains a comparator, so that deals with the Attack/Decay switching too.

It's fairly neat, but I was aiming for a "one chip" analog envelope, and now it's two. The 555 (ok, 7555) based designs I've seen are still probably neater.

Tom

[Kipper4]

Thanks mate.