Adding manual gate to ADSR: Fixed...

Coriolis · Joined: Apr 11, 2005 Posts: 616 Location: Stilling, Denmark

I've just built one of these:

http://www.charlielamm.com/synth/adsr.php3

Supposedly an old Thomas Henry design. I want to add a manual gate switch, like on the Soundlab, and I've experimented with closing a switch from ground to gate in, but it doesn't work, and now that I think of it, a gate signal is +5V, right?
What would be a good way of doing this? I'm thinking I would need to debounce the switch, yes? How would I do this best?

C

Coriolis · Joined: Apr 11, 2005 Posts: 616 Location: Stilling, Denmark

Nobody?

C

fluxmonkey · Joined: Jun 24, 2005 Posts: 708 Location: cleve

yup, you'll need a momentary switch connnected to a voltage source, not to ground. depending on the circuit, you can often get away with a pretty basic "debounce" using a capacitor.... see the schematic for the wiard joystick at http://www.musicsynthesizer.com/Joystick/1209.htm

b

Coriolis · Joined: Apr 11, 2005 Posts: 616 Location: Stilling, Denmark

Thanks a bunch! Looks like it's what I need. I guess the gate voltage I need isn't 5V but 10V? If it is to be 2/3 of the supply voltage?

Just checked the documentation for the Paia midi2cv8 I'm going to be using (when it's finished), but there's no info on what gate voltage it outputs.

I guess I could start with 5V, and if that doesn't work, ramp up to 10.

Thanks again,

C

Coriolis · Joined: Apr 11, 2005 Posts: 616 Location: Stilling, Denmark

Well, I tried a voltage divider giving 10V to a momentary switch, and now it works, so thanks bbob!

One weird thing though: The Attack pot doesn't seem to do anything - but the Decay pot lets me vary the attack time of the envelope... Confused

Must have miswired something...

C

Edit: I didn't put in a cap to debounce the switch (forgot to), but it still works.
If I don't get false triggers, does it matter if it's debounced?

Coriolis · Joined: Apr 11, 2005 Posts: 616 Location: Stilling, Denmark

Ok: So I checked Charlie Lamm's site again, and he mentions a mod to fire the adsr with a trigger signal (not gate like mine) from a switch. This apparently changes the circuit into an ASR envelope, with the Decay pot working as Attack - exactly what mine is doing! Shocked

But why, is beyond me. All I'm doing, is applying 10V to the gate input.
He also mentions that the circuit expects a trigger signal and a gate signal at the same time, to work as an ADSR, which makes no sense to me.

Anybody got any clues?

C