DIY (14bit) MIDI fader?

[Rodrigo]

So I've been looking around and I've not seen anything like this, so I figured I'd ask to see if anyone has done something like this before, or seen it.

 

The idea is to build an Arduino Teensy and a fader (more on this below) to create a high resolution class compliant MIDI fader, which I can then use in custom software I would write.

 

 

The reason I'd want to build this is to use a dj-style (fast) fader in the context of other instruments/music, without needing a gigantic dj mixer, or running my whole audio chain through a tiny passive fader.

 

I'm mainly thinking that having a fader in the signal path for this stuff I'm doing with feedback based around a snare drum and condenser mic. Feedback is very sensitive to changes in gain, so having a high resolution fader is ideal, as a regular MIDI fader would give 'steppy' changes in gain (in a feedback context). Kind of hard to explain, but this is the kind of thing I'm doing, to give you an idea:

 

 

So pretty left-of-center, but having a fader in the mix would allow for really interesting rhythmic work, especially on the more white-noise-y scrapes and stuff.

 

I would likely use a Teensy as I've built some projects using them before, they handle USB-MIDI very easily, and are cheap/compact, and using high resolution (14bit) MIDI would give a lot more detail in terms of fader position. The nice thing about 14-bit MIDI is that if you use the most significant/least significant bits approach, you still get 'regular' 7-bit (0-127) MIDI as the first CC value, but if you combine both, you then get the full 14-bit (0-16,383) range.

 

So the Arduino/ADC side of things is pretty straight forward. Where things get a bit murkier is with the actual fader.

 

So looking at using something like a Raiden or JDD fader as a starting point, the fact that they are passive works well as I could just send the 3.3v through them and read the analog pin and get my value that way.

 

The downside is that both of those have pretty extreme curves built in, and cut out at one (or both) ends. That means that I'd be married to that curve/profile pretty much, as trying to compensate for a log curve in the digital world would mean a loss of resolution at one end.

 

 

So being passive is useful, but being non-linear is not.

I suppose there are some good/fast (passive) faders with a linear response, so I welcome suggestions there.

 

BUT

 

Then there are things like the Innofader and magnetic faders. Since I plan on using an Arduino anyways, there will be 5v power coming in from a USB connection, so I could easily tap into that for a non-passive fader. The issue here is that I'm not sure what kind of signal these are putting out. I imagine that both use some kind of hall sensor and an internal adc/mcu in the case of the Innofader, but would it be possible to just tap into the output of that directly with the Arduino?

 

I've also seen the Nanofader, which I could try using, but it seems like it would overkill to go from Innofader to Nanofader, only to use both as variable resistor for the Arduino's adc.

 

My concern with the Innofader is that the comparison webpage lists the resolution as 256 (or 1024 for the pro2, which is physically too big for what I have in mind), which is not great resolution when it comes to gain stages (i.e. using one in a feedback loop).

 

There's also a quick-and-dirty approach that would involve using a passive fader in conjunction with the laptop to create the same kind of output. It would basically mean sending a high pitched, loud sinewave out from the computer to the fader, then getting the audio back into the system and reading the volume with an envelope follower, to determine the position of the fader. This approach is what DJ Sniff does in his setup, where his mixer crossfader isn't actually in the signal path, but rather being used as a controller for the software.

 

 

This solves some problems as it requires no specialized equipment, but still has the problems of being married to the fader's curve, using up I/O on my soundcard, and requiring a bunch of extra cables in the mix.

 

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So, has anyone tried something like this, come across anything like this, or have any thoughts on things to look at?

[Guest rasteri]

You're after a decent linear-curve fader with resolution that'll translate well to 14bit midi? Pretty much any slide potentiometer will do.

 

These are good for example - http://www.digikey.com/product-detail/en/tt-electronics-bi/PS45G-C1LBR10KN/987-1402-ND/2620671

[Rodrigo]

Ah that's easy enough!

I'll just build up a list of other crap to buy off the uk page, to not get murdered on shipping.

 

Feel wise, would I be better off going with a dual rail type fader (ala Rane magnetic ones):

And/or am I misunderstanding how the Innofader works (is it really 256 steps of resolution?)

 

Either way I'll likely be getting an Innofader to build into my PT-01 (hopefully nabbing one of the next batch of Nanofaders), but I'd like to have a really crisp one to use as a controller.

[Guest rasteri]

That digikey fader has dual rails inside it. They're basically mini innofaders without the electronics.

 

Dismantle them, clean all the grease off with isopropyl alcohol then re-lube them with something like F100. They're certainly scratch-capable.

[Mutis Mayfield]

About the high pitched tracking position this has implemented it (and maybe djSniff take from here the idea as I ask him for the pinout for tascam ttm-1)

 

http://www.digitalvertigo.co.uk/forum/index.php?showtopic=33437

 

Details:

http://www.skrasoft.com/ (Turntable surgeon tab and dev blog tab)

 

Video:

https://youtu.be/S8izg3jHIfI

 

Also at scratchML ggroup it was discussed the possibility of implementing it via raspberry pi (as blackbox) including high pitch and dvs position vector but the project seems dead, sadly. So if I can help in some way just told me.

 

Nice project for sure Rodrigo.

 

Edit:

http://www.rodrigoconstanzo.com/gibgab/

 

This could be useful for some "blocked/near to bury" projects which are hurting my soul and make me feel old and old... some of them maybe in your radar...

[Rodrigo]

That digikey fader has dual rails inside it. They're basically mini innofaders without the electronics.

 

Dismantle them, clean all the grease off with isopropyl alcohol then re-lube them with something like F100. They're certainly scratch-capable.

 

That's super great to know, thank you so much!

 

 

 

Details:

http://www.skrasoft.com/ (Turntable surgeon tab and dev blog tab)

 

Video:

 

Edit:

http://www.rodrigoconstanzo.com/gibgab/

 

This could be useful for some "blocked/near to bury" projects which are hurting my soul and make me feel old and old... some of them maybe in your radar...

 

Ah that's quite cool!

 

So you were part of the dev team on that?

From what I can see on the page/vids it's been abandoned in general?

 

Looks like an amazing training/pedagogical tool.

 

And having an embedded system for tracking DVS would be really slick too. I think for my purposes I would still use Max as all of my sampling/playback would happen there anyways, so doesn't really save much work to have external vector calculation going on, but for general usage DVS stuff would be really slick.

 

 

Yeah if you're up for having a skype about some of your projects, I'm happy to help. Send me an email and we can talk about it further (rodrigo (dot) constanzo (at) gmail (dot) com).

[Guest Symatic]

that drumming vid was so sick

[Mutis Mayfield]

 

That digikey fader has dual rails inside it. They're basically mini innofaders without the electronics.

Dismantle them, clean all the grease off with isopropyl alcohol then re-lube them with something like F100. They're certainly scratch-capable.

 

That's super great to know, thank you so much!

 

 

 

 

Details:http://www.skrasoft.com/ (Turntable surgeon tab and dev blog tab)

Video:https://youtu.be/S8izg3jHIfI

Edit:http://www.rodrigoconstanzo.com/gibgab/

This could be useful for some "blocked/near to bury" projects which are hurting my soul and make me feel old and old... some of them maybe in your radar...

 

 

Ah that's quite cool!

 

So you were part of the dev team on that?

From what I can see on the page/vids it's been abandoned in general?

 

Looks like an amazing training/pedagogical tool.

 

And having an embedded system for tracking DVS would be really slick too. I think for my purposes I would still use Max as all of my sampling/playback would happen there anyways, so doesn't really save much work to have external vector calculation going on, but for general usage DVS stuff would be really slick.

 

 

Yeah if you're up for having a skype about some of your projects, I'm happy to help. Send me an email and we can talk about it further (rodrigo (dot) constanzo (at) gmail (dot) com).

It will be great for sure.