950 Keyboard circuit

[analogmonster]

Hi,

a question concerning the maximum trigger pulse length of the 950 circuit: How long does it last? Does anybody know that (Perhaps Kevin )? The internal trigger pulse length of my Prodigy (measured at the 556 dual timer) has a duration of about 2 seconds (maximum of course).

Thanks

[Kevin Lightner]

Although I understand pulsewidths, I have no idea what you're talking about.
The pulsewidth of a 950 keyboard is how long one holds down a key.

[thealien666]

In looking at the schematics of the 950, I'm not sure what you are asking about

The trigger will last for as long as a key is held down.

EDIT Ooops, Kevin and I replied at the exact same time, with the same answer...

[thealien666]

When looking at the Prodigy schematics I've noticed that, on that synth, the envelopes are made up of a timer (556) and a CD4007 for the different portions of the cycle. And that the cycle is started with a 200 microseconds drop to 0 volt as a trigger signal to the timer, when a key is depressed.

Completely different implementation than the 950 keyboard and 911 envelope generator of the Moog modular system, which uses a continuous trigger signal from the keyboard for sustain and a discrete flip-flop for the different envelope stages. No timer there.

[Kevin Lightner]

Regardless of trigger style, the Prodigy still uses a signal that remains as long as one holds down a key.
Call it a gate or trigger as you like.
There would be no control over sustain otherwise.

[thealien666]

Ooookay. You're right. It's logical.

I don't quite get the use of a timer, then... ? As a flip flop ?

[analogmonster]

Ok, it was a silly question. I was mislead by the expression"trigger", as for me this is a rather short pulse. On the other hand a signal which lasts as long as a key is pressed I know as "gate". But of course a keyboard provides the information how long a key is pressed, also a 950.
Thanks