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Jiffer Harriman 220c page

CCRMA Spring Concert 2012

I finished the instrument in time to be able to play in the spring concert with a loosely improvised set. It was also part of Cecelia Wu's piece at the same event. Stay tuned for more pictures I took along the way and more details.

Spring Concert 2012

Week 6 - 5/14/2012


I took measurements of the puck and my prototype bridge and thanks to Ale Palandjoglou in the D-school, got a laser cut acrylic bridge. Here is what it looks like:

[CAD screen shot]

[bridge mounted to transducer]

Here is the CAD file used.

Final Construction

The peghead has been cut and holes drilled for tuning pegs. I also built a custom nut out of some chunks of metal found at ACE: [guitar nut]

I think I finally have all the parts needed to complete construction and hope to do that this week and then start making sound

Week 5 - 5/7/2012

Working with someone from the D-school to build a custom bridge which will fit snug on the transducer. Began testing with my wood bridge prototype and results are promising

I also began playing with other patches to simulate a bank of sympathetic strings to be used as accompaniment.

Week 4 - 4/30/2012

Began building a prototype instrument out of a 2x4, then spent most of the rest of my week on SlorK.

Week 3 - 4/23/2012

Prototype Testing

I installed a "Puck" into my Craigslist guitar and began feeding the signal back into the guitar. The first mounting hole had too much overlap with the pickup and created EM feedback from the voice-coil directly back into the pickup which was cool, but not what I wanted. I made a new hole offset so it is still under the bridge but not overlapping with the pickup.

It is easily able to drive the body enough to get the low E string vibrating, however the higher strings were difficult to get moving. I think this may be partly to do with the transducer's frequency response as well as coupled with the guitar. I experimented a bit with a smaller driver I took out of an old speaker and it seemed to be better suited at driving the higher strings.

Guitar Issues

The guitar jack was wired wrong which was causing some serious hum. I rewired that but the signal needs to be boosted to be able to easily pipe it into an amp or even the computer. I found a simple non-inverting op-amp circuit and started to build it: pre-amp circuit Still need a couple components to finish this.

Other references

Chris pointed me to this: Charles Besnainou. Transforming the voice of musical instruments by active control of the sound radiation. In Proceedings of the International Symposium on Active Noise and Vibration Control, 1999. Which lead me to more of Edgar Berdahl and Julius work from a couple years ago with electromagnetic actuators:

Ed sent me a whole bunch of other stuff: (pp. 136-137) (sound examples on

Week 2 - 4/16/2012

Gathering Parts

I've been collecting components and some tools to begin construction. - Tactile Transducer - T-amp Lap steel components: - 2x6 hardwood (Red Wood "heart") - tuning pegs

Still need a guitar pickup - there's lots of cheap single coils on ebay which I'll probably go for.

Prototype Construction

I found a cheap electric guitar (plus a bonus amp) on Craigslist for $50. The plan is to begin hacking it up and attach a voice coil to it as close to the bridge as possible.

Once I have the ability to put acoustic energy into the guitar I will start trying various patches. Some ideas I know I want to try:

- direct feedback of the signal coming out of the guitar

- harmonics of what is coming from the guitar

- driving with noise

Other Inpiration

Electromagnetically Prepared Piano

Feedback Guitar

Steven Backer, Edgar Berdahl, and Per Bloland

Les Paul's "log" guitar

Week 1 - 4/9/2012 - Initial Project Plan

Ideas and goals

My initial plan was to expand the performance system I developed for 220b which became Pickin' On Chuck. For this the dialog between performer and computer was the area I felt most lacking and hoped to improve upon.

I also am interested in exploring the use of tactile transducers to reproduce sound. I used these some in my 255 intermedia final project with a piece of plywood and sheet-metal mounted in a picture frame. What I really want to do is put these in a musical instrument and explore the possibilities. This concept has been inspired by a couple of instruments created by Dan Overholt:

Overtone Violin

Overtone Fiddle

To complicate matters further, I have been meeting with Bill Verplank to talk about his work with "The Plank", as a small scale, affordable haptic device for musical instruments.

To focus this a little bit I am going to begin by starting with explore possibilities of an actuated instrument using tactile transducers. I have acquired a couple different flavors of these from Parts Express. The puck and the sound exciter. These are basically the same thing except for the weight, and probably coil construction, which give them different frequency responses. These can be driven with a fairly inexpensive digital T-Amp.

Current Plan

My current plan is to build a lap steel guitar based on the plans available from Near the bridge will be mounted a tactile transducer, most likely the "Puck" since it seems to have more weight and I believe will be mounted more sturdily. I would like to be able to use the voice coil to put energy into the strings of the guitar to provide a means for mechanical feedback as well as explore other possibilities such as exciting harmonics. Depending how long the construction takes, I would love to mount a Plank on this instrument for control.

Next Step

Next step is to make a shopping list and start getting all the parts I need for construction of the instrument.

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