use TRS/Trigger inputs instead?

Chris posted Aug 18 '16, 21:31:

Has anybody successfully modified this design to accept TRS trigger inputs (ie; drum pads)?

I am trying to set something up that would allow a friend to select samples (kick drum, tambourine, claps, whatever) and I love the idea behind the samplerbox but he's got pads already with no midi outs.

Any suggestions/thoughts would be helpful!!

HansEhv posted Aug 18 '16, 22:40:

Hi Chris,
This a very different technique which will require some soldering.... Ready to use solutions I can think of are devices like "Alesis trigger IO" or "ddrum DDTi Drum Trigger Interface". New about 150 euros or so, but a second hand one can do the job as well :-)
Other creative solutions are possible.
I've reused my old Roland SPD-8 that I set aside years ago because the sound module is too limited... but the midi processing is still OK.

Opus.quatre posted Aug 19 '16, 02:48:

Thé problem might be in the nature of the midi note on sent by the drum pads.. Are they à short pulse, i mean a note on immediately followed by a note off ?? In that case, your sample will never be played in full length, you'll have just a few milliseconds of playback..
Or are they just note on, and no note off ?? In that case, the samplerbox's behaviour might be weird when you hit several times the same pad.. Probably it will retrigger a new voice of polyphony at each hit, if you hit twice or more, the cymbal, for example, you might have 2 or more cymbals ringing at the same time.. Until all voices of polyphony are used ?? And then, without note off message to free the voices, will they initialize and be ready for the next hits ?? Not sure..
Unless you use Erik's files to limit notes in sustain mode..
This way it might work.. Not sure though..

Opus.quatre posted Aug 19 '16, 02:57:

Or, in case of short note-on/ note-off messages.maybe the answer is in Hans Webpage about mode..
I suppose the definition text will specify that the sample must be played regardless of the "trigger"duration..
" once - "Playback": play sample from start to end ignoring standard note-off."

HansEhv posted Aug 19 '16, 16:14:

Drum controllers must send note-off to adhere to MIDI standard. They usually have a programmable time between note-on and note-off, because the actual trigger time is indeed very short :-).
You are right, leaving no note-off causes the the playing-notes queue to grow to polyphony limit, which is not ok. In the alternative playing modes I therefor use a technique similar to Erik's sustain limiting for cleaning this up (the sustain queue is an extra one next to the main play queue). In fact when the note is played again, the missing note-off is processed first.

But the actual question here is that the drum triggers mentioned don't produce midi signals and obviously the sound unit they are connected to has no midi output. So we need something to catch these analog signals and convert them to a correct midi message with a note number assigned per pad. As mentioned above there are ready made solutions - at a price :-(
In the DIY area I've only found arduino projects (quite a lot actually) addressing this, interesting ones are and, both needing adaptation for this purpose.
Like I said, there are a lot more. If anyone finds/makes something fit for this purpose, please share :-)

Chris posted Aug 22 '16, 16:44:

thank you for the feedback so far! Yeah, I saw the alesis solutions and they're kinda pricey plus I wanted to homebrew something as a way to gain experience. :)

i'll take a look at the links and hopefully come up with something!

I will have to take a look at what the output of the kick trigger is. Can anybody think of something that may be a foot pedal solution that could take abuse from a touring musician? hmm.

I mean I could always embed a light sensor in his shoe and go that route ;)

Chris posted Aug 22 '16, 16:48:

oh and lastly, I wanted this box to basically be able to have the kick drum input, a sample library stored on a flash card, and then output directly to a speaker - no other interface required (VST/computer).

Kick pedal -> box -> PA system.

HansEhv posted Aug 22 '16, 23:17:

Hi Chris,
Both commercial (Alesis/ddrum) and DYI (microdrum) support both switches and "TRS triggers" as input (I didn't check other examples). So it may suit your needs.
Samplerbox in fact functions as VST (with its library on usb memory).
So there seem to be possibilities here.

Erich posted Sep 12 '16, 21:27:

Hi all, I believe, the easiest would be to use an Arduino to convert Piezo-Triggers into Midi-Signals. There is no need to really transfer them like MIDI, ... I would suggest to use the Midi-Out 5v from arduino to the Raspberry IO-Ports via simple Resistors rather than optocopler.


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