Multi, Triggers and Gates... Oh My!

Broadwave

Hi,

All of my ADSR's require a single gate to operate (no trigger required), but this means that I can't play Legato and re-trigger the envelopes.

Many Midi > CV converters allow you to re-trigger the gate with every new note played, but the converter I've just built (4 Ch ACX MIDI2CV) does not provide a trigger out.

Now, please bear with me on this - I've got a circuit that detects a change in the CV voltage and generates a new gate for every new note played, and from that gate voltage, I can create a trigger pulse... with me so far?

What I now need to do is combine the Gate and Trigger to give me a Gate that is initially high, but goes low when a new trigger is detected and switches back to high when the trigger pulse is over. This, hopefully, will give me a "multi-trigger" to fire the ADSRs with every new note played (legato or not).

But... how do I go about doing this? Would something as simple as an XOR do (ie. XOR out is high when a gate voltage is present on IP1, goes low when a trigger is high on IP2 - therefore as soon as the trigger is low (but with the gate still high, the XOR out goes high again).

Am I on the right path, or is there an easier way to do this?

Dave Kendall · Posted: Tue Jul 17, 2012 2:59 am Post subject:

Hi Andy.

Check this out. Some simple and invaluable schematics in there....

It shows numerous ways to get trigs from gates etc. It's definitely fast enough for playing use. It's used in my hardware midi2clock converter too - it's that fast. Only at the uSec level was it too slow.....
(it's all over the Klee sequencer too, IIRC)

Another nice little IC to check out for this sort of thing is the 4538 (the +5V logic HC version is called the 74HC123)

hope it helps Wink

cheers,
Dave

drapdap · Posted: Tue Jul 17, 2012 3:55 am Post subject:

hi!

good topic, i just have the exact same problem.

Broadwave · Posted: Tue Jul 17, 2012 5:38 am Post subject:

Thanks for the info Dave, very useful... I must invest in a Breadboard.

BTW - I don't think Ray's noticed that he's put the working voltage down as 5 to 15v... Pretty sure that'll make a 74HC14 smoke just a little ; )

Dave Kendall · Posted: Tue Jul 17, 2012 6:09 am Post subject:

If you're ever down north of London way, you can have my spare breadboard. I prefer perfboard, so it's never been used.
Would be quite a trek just for a freebie BB though.....

Jaba · Joined: Feb 27, 2009 Posts: 48 Location: Genova, Italy

Hi Andy,

if you built the ACX MIDI2CV/GATE
http://www.acxsynth.com/midi2cv/midi2cvfr.htm
then I think it does have a trig output that you can use;
it is misnamed "MIDI SYNC" on the layout, but it actually is a trig out as can be confirmed by the panel picture and by the text on the web page (in French)

I am building that same ACX MIDI2CV/GATE board, that is why I investigated and since it comes from pin 17 of the PIC it should be your trig out AFAIK

cheers
Jaba

Broadwave · Posted: Wed Aug 08, 2012 8:58 am Post subject:

Hi Jaba,

I built the ACX MIDI2CV, and unfortunately it is a MIDI Sync output - It looks like the previous version (slightly different PCB & Firmware) did have the separate trigger out for every note played in either Poly or Mono Mode, but crashed when you changed the Mode switch Rolling Eyes

The new version (2.3) works ok, but the tracking is slightly off by a few cents in the mid range of 5 octaves. It's useable, but I've put it to one side for the time being, as I have the Paia MIDI2CV8 board.

I'm sure I have a copy of the old website which has the older CV converter, but it'll take some time to wade through my web files.

Jaba · Joined: Feb 27, 2009 Posts: 48 Location: Genova, Italy

Hi Andy,

sorry for sending you wrong information; you seem to know the ACX MIDI2CV board better than I do.

I have one on my bench, probably to be completed next month.
I may try to modify the software in the PIC; if I achieve any useful result, I'll be happy to share it with you and with this forum

Are you sure that the tuning is worse than the PAiA MIDI2CV8 ?

cheers
Jaba

Broadwave · Posted: Sat Aug 18, 2012 10:58 am Post subject:

The Paia is rock solid... but the poly cv outputs are rotational, so you HAVE to have 4 voices, otherwise notes drop out.

The ACX seems to route voice 1 to out 1, voice 2 to out 2 etc, which is better for my setup.

Don't get me wrong about the ACX - the tracking isn't bad, just slightly out, but noticeable in a poly set up.

If you can modify the firmware to regain that separate voice trigger out, I'd be very interested Smile