The answer is very simple! We used a VCA Mixer. Specifically the Vestax PMC-07 Pro. Because you know… we’re pro like that.
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.
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.
The Arduino sketch we used can be found here.
In summation here is a list of items you must procure to do this:
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!
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:
Spec + commentary:
ScratchML r6 beta spec:
SML (Scratch Markup Language) is a new file format for recording and replaying turntablism. We’ve developed open-source tools for accurately capturing the record and crossfader movements of a scratch DJ, allowing us to analyze, transcribe, and recreate scratch performances.
At Art Hack Day we collaborated with other artists and programmers to develop the first prototypes of ScratchML. We used timecode vinyl to capture record movements ($10) and a hacked VCA fader + Arduino to record the crossfader ($30).
Scratch data was saved to disk as .sml and broadcast as OSC, which allowed other Art Hack Day participants to build visualizations based on what the DJ was scratching during the exhibition. The apps ranged from spinning-vinyl animations and TTM transcriptions to insane exploding 3D pizzas and a side-scrolling videogame shooter controlled by scratches.
Our goal is to make capturing, replaying, and sharing a scratch performance accurate and easy. SML files can be freely uploaded and downloaded from the ScratchML.com database. We’re particularly looking forward to improving the experience of learning how to scratch — e.g. by building apps that show you just how accurate your autobahn scratches actually are.
Throughout the week here on FAT we’ll be publishing ScratchML projects created during Art Hack Day, data specs, source code, hardware modification details and more.
The expressions published in this site are all in the public domain. You may enjoy, use, modify, snipe about and republish all F.A.T. media and technologies as you see fit.