Andrew Benson over at the Cycling ‘74 site put together a really solid post on connecting a camera to your Max patch:
Making Connections: Camera Data
He covers the hardware requirements (cost, Quicktime drivers for mac users, and manual controls) as well as the handling you may want in your patch. What frame rate do you want to deal with? What are a few ways you could extract useful information from the feed?
The Altmann Creation ADC is a converter that contains ‘No Analog or Digital Filters.’ This is a really interesting claim. Non-ideal brickwall filters will introduce some phase shift, but the consequences of not implementing the filters at all seems much, much worse. Any content above the sample rate will alias down, creating a tones that are not harmonically related to the original signal.
Arduino - Photo by Nicholas Zambetti
Last year I had the opportunity to help out a friend with a project for a class he took at MassArt. We used a microcontroller with buttons for a UI, and fed the data into the serial port of a computer. We used Max/MSP to generate MIDI data and finally used Ableton Live to trigger audio sample playback from the MIDI.
The system was overly complex, but the coding was actually a minimal amount of work. It got me thinking about a few μController-based projects that have been on the back burner for a few years. I figured it would be good to conduct a quick survey of the chips that are being commonly used and have the best online support networks.
The Arduino is actually what we used for the Max-Ableton project I mentioned above. This is a family of creative commons controlled boards, with open source software to build on. My experience working with the Arduino was very enjoyable - the combination of a high-level language and lots of support online made the job easy. You can get a great board for as little $30, and you’re pretty much ready to go out of the gate. The boards are based around ATmega RISC micros.
There’s also a great series of articles on producing sound from an Arduino here.
Phidgets are a system of chips and sensors linked to a computer via USB. These boards are designed to operate in tandem with the computer, instead of as standalone processors. There’s an API for pulling together interfacing applications on the computer side, and there’s a Max/MSP object for interfacing directly with the Phidgets. The sensors available include buttons, encoders, accelerometers, PH sensors, and thermocouples, ranging in price from $28-95.
Handyboard is an MIT design, with a focus primarily on robotics. These boards are setup for reading sensors and driving motors. There are only a few vendors, and the boards run in the $100 range. There’s a fair amount of information on the MIT site, but the online community using the Arduino platform seems to be a lot larger.
The PIC platform has been around for years, and is a simple solution for the serious DIYer. This solution is a little messier than some of the others listed above, because you’re dealing a lot more at the component level and coding in assembly language. You’ll need a PIC programmer, and then you’re pretty much ready to go.
The biggest benefit I can see from PICs are the low cost of the chips. With the Arduinos you’re likely buying $30 boards; you can can PIC chips for anywhere from $1-8. The economy of scale is very nice here, but for building a one-off circuit I’d likely stick to the pricier options above.
I added this to the list because of the audio capabilities, but this is less a microcontroller system than it is a tiny Linux computer. The cost is greater than the systems listed above, and the documentation is still under development. I tried a project on this about a year ago, and ran into a number of issues. I attribute them to my limited experience with Linux, something I’d like to rectify.
This list is far from complete - it’s just a few of the platforms I know people are working from. As I gear up for a new project, I’ll continue to look into suitable μController platforms and post about them here.
For a while, I’ve been meaning to recreate the ‘Time Lag Accumulator’ used by Brian Eno and Robert Fripp on their early ambient music. The setup was simple - two tape decks with a single loop of tape, guitar feeding in one. The output of the second deck was fed back and mixed with more guitar. A very simple delay, 3-5 seconds in length.
This was pretty easy to do using Ableton Live and 10 ‘Simple Delay’ plugins, although this is cumbersome:
Ableton Live - Time Lag Accumulator
I included to inputs to the loop - a microphone feed (from guitar, mic, whatever) and a MIDI instrument channel. The MIDI instrument is fun to play with, but I’d love to connect the Rhodes once I’ve finished cleaning it up…
Links:
TimeLagAccumulatorProject.zip - Ableton Live Time Lag Accumulator
Frippertronics - Wikipedia entry on Eno/Fripp’s Time Lag Accumulator
Removing the transformer from an SM57
Tonight I got around to the destructive part of this mod. I pulled the SM57 apart, which is pretty straightforward. A small screwdriver to loosen the XLR connection, and then you can just unscrew the mic capsule from the body. Cut the wires, and you’re ready to attack the transformer.
I put the body of the mic in a pot with a small amount of water - the water just covered the body while it was on its side. I heated the water, and as it approached a boil, I picked up the mic body with needle nose pliers and an oven mitt. Then I used the needle nose pliers to grab the transformer, and it slid right out of the mic. Check the gallery to the right.
I cleaned up the glue from the transformer, in case I need or want to use it again. If I don’t like the way this mod sounds, I could hot glue the mic back together (for better or worse).
The only comment I have on this step is the effect of the hot water on the exterior of the microphone - it seems to have really affected the finish. It’s much rougher on this section of the microphone now than it is on the capsule end.
The only remaining step is to connect the mic capsule directly to the XLR jack and screw the body back together. Pin 1 will still go to the body of the mic, and the blue and red wires will go to pins 2 and 3. I’ll just have to try one arrangement, look at the polarity, and flip as needed. I’ll post again once I’ve finished!
Back in the March/April 2006 edition of Tape Op, I saw an article about modding an SM57. The premise is that the transformer adds a lot of unpleasantness to the sound. The solution? Remove the transformer!
Of course, the transformer is in there for a reason. The two biggest reasons are to balance the output, and provide better voltage/impedance matching. Removing the transformer will then unbalance the output (which could cause noise issues if you’re dealing with a significant cable run), and knock down the voltage output (by 10-20dB, reportedly).
With a small stack of 57s, it seems worth a try. I’ll report back on my progress.
SM57 - Pre-Mod
Links:
Tape Op - Best recording magazine available.
Gearslutz Forum #1 - Discussion of the mod outcome, plus pics.
Gearslutz Forum #2 - More discussion.