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OI – series
premiered at  [DAM Berlin] ‘Reply All’ solo show, Jan 27 – March 10,  2012

4 unique pieces
50 x 5 x 160 cm
LED signs, wooden rod, wooden board

Aram Bartholl 2012

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Posted on February 11, 2012

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OR: How I Learned to Stop Worrying and Track my Fader

 

How did we track the crossfader during the Art Hack Day?!? ZOMG!! So many questions!

The answer is very simple! We used a VCA Mixer. Specifically the Vestax PMC-07 Pro. Because you know… we’re pro like that.

I hear you asking now, “But, sir! WTF is a VCA Mixer?!?!”

Well, I’m glad you asked. Allow me to explain: VCA or Voltage Controlled Amplifier means that instead of sending the audio signal to the crossfader the mixer instead sends a voltage which in turn controls the volume level for each channel. This makes determining the position of the fader very easy; simply measure the voltage for each channel.

In the case of the PMC-07 Pro the voltage that is sent to the crossfader is 10V DC. We used an Arduino Uno to monitor the voltage. It maxes out at 5V. Not wanting to explode the Arduino with 10V we used a simple voltage divider on each channel utilizing two (four total) 1 megaohm resistors. We would have been a lot better off using 100 kilohm resistors. Using an opamp would have been even more betterer but… we didn’t have any of those.

Because we’re so damn pro and didn’t have any of the parts to make a proper Y cable we just soldered everything to the crossfader.

Go team awesome!

 

Yes, I hear you. You’re wondering, “That’s all well and good, but how am I supposed to hook it all up?!?”

 

Simple! Follow these amazeball instructions. The PMC-07 Pro uses a 4 pin connector on the crossfader. The outside pins are power and ground the middle pins are for the channels. Use a volt meter to determine which pin is power and which pin is ground. Plug ground into one of the ground pins on the Arduino and the two center pins from the fader through a voltage divider and into two analog pins on the Arduino. We used A0 and A1. You do not need to hook anything up to the 10V power pin on the mixer. Got it?

 

Here I drew you a picture too!

CLICK TO EMBIGGEN

The Arduino sketch we used can be found here.

In summation here is a list of items you must procure to do this:

  • Vestax PMC-07 Pro mixer (Any VCA mixer will do, just drop the voltage to 5V or less.)
  • Four 100 kilohm resistors
  • An Arduino
  • A proper Y cable for the PMC-07 Pro. Instructable for building it is here
  • Arduino sketch found here

Build your Y cable. Make a couple voltage dividers. Hook it up like the picture above and BLAMO!

#Pro-Tip: Elliot Marx informed me that if you use an Innofader (the origional, not the Pro or PNP) it will limit the VCA voltages of the PMC-07 Pro to 5V eliminating the need for the voltage dividers. Wire colors for the Innofader are as follows:

Blue = 5V
Green = VCA1 (varies from 0 to 5 volts)
Yellow = VCA2 (varies from 5 to 0 volts, moves opposite from VCA1)
Grey = ground

Thank you Elliot!

 

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Posted on February 9, 2012

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We know what the white girls say, and what flute players say, and even what black guys say to pregnant girls. But what don’t you know who said what to whom? Has anyone said this shit?

A live search engine for all the shit people say. Over 700 videos at last count.
A collaboration with Lindsey Weber and Tanner Ringerud at BuzzFeed.

Speed Project: 8 hours

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Posted on January 31, 2012

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ScratchML, like GML, is an XML-based format for storing information about the position of the record and crossfader during a scratch performance.

This is a “beta” release of the .SML file format, with sample data for 1 turntable and 1 crossfader. The format is designed to accomodate multiple turntables and crossfaders and a wide variety of data capture techniques, but we’ve only field-tested it against the basic 1 deck + 1 mixer scratch setup, which is what we were working with this weekend.

The two most important fields are:

  • <turntable> — stores data about the playback position on the record as a consistently sampled stream of floats, with <samplerate> samples per second.
  • <fader> — stores data for crossfader movements, ranging from 0 (full-left) to 1 (full-right). This data is stored only when the fader actually moves, and is stored as <p> (position) and <t> (time) tuplets.

Sample data produced by LM4K, mostly baby scratches and flares: XML / JSON

Spec + commentary:
ScratchML r6 beta spec:

The ScratchML.com database can also automatically convert from XML to JSON for use in javascript visualizations. Change the .xml file extension to .json, and optionally pass a JSONp ?callback= parameter, like this.

During Art Hack Day we converted SML to OSC and broadcast it over the wifi for realtime visualizations — more info to come about that.

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Posted on January 31, 2012

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