Kaoss Pad Guitar Mod

Electronics Testing

2012-03-24T12:21:00.003+00:00

On Thursday I was able to get in to the electronics labs and test the connections of the Kaoss Pad. I used an oscilloscope to test the voltages of each of the six connections under a variety of conditions.

These conditions were:

Hold button OFF without using the touch pad
Hold button ON, X and Y on pad set to 1,1
Hold button ON, X and Y on pad set to 9,1
Hold button ON, X and Y on pad set to 1,9
Hold button ON, X and Y on pad set to 9,9
Hold button ON, X and Y on pad set to 5,5
Hold button held down
When touching the touch pad with hold button ON and OFF

Through this I learned that, as expected, a constant signal runs on every connection at all times. This is 6V peak-to-peak on all but one of the channels with a time period of 20ms. When the hold button is pressed down, the voltage is raised to 8V which causes the hold function to switch between the on and off states.

Standard waveform when XY pad is not touched.

All of the recorded values shown below were taken at the guitar end of the connection, though these were checked and found to be the same as at the Kaoss pad end and so only one set was written down. This suggests that the serial cable has no noticeable effect on the signal.

Results page 1

Results page 2

It was also shown that when the touch pad is used, regularly spaced spikes appear in the waveform. They are approximately 0.2ms wide in total and about 2V high. Their shape is changed depending on the position of the finger on the pad. This variation controls the stored parameters of the KP unit.

Additional notes

User Testing

2012-03-15T13:24:00.002+00:00

I have just completed a user testing session with 7 participants. Each was given five to ten minutes to play the guitar and then asked to complete a short questionnaire about their usual playing habits and their thoughts about different aspects of the guitar.

I will be using this information as well as that of any additional participants in the evaluation of the finished guitar.

The questionnaire that was completed can be found here.

User Testing - Studio Booked

2012-03-11T11:26:00.001+00:00

The studio has been booked for an hour on Thursday the 15th of March for User Testing. If further feedback is required then I will book a second session as soon as possible.

I also hope to access the electronics labs over the coming week to test the connections to the kaoss pad.

The Next Step

2012-02-24T13:03:00.000+00:00

After a brief meeting with my project supervisor yesterday, I am now ready to move on to the testing phase of the work.

Although there are still some corrections, changes and adjustments to be made to the guitar, I plan to leave them until after the project is complete since it is currently in a usable state and I don't want to risk breaking anything before it has been tested!

Over the coming weeks I will use the university electronics labs to thoroughly test what has been built. I will also book one of the studios and revisit my planned questions for user testing.

Youtube Demo

2012-02-18T21:38:00.001+00:00

Busy Weekend - Day #2

2012-02-12T16:12:00.000+00:00

Today I finished the build section of the project! I began by cutting a part of the same plastic box used for the front kaoss pad mount to fill the gap in the kaoss pad body where the touch screen was. I then attached the serial connector to it. This is not ideal as a permanent solution as it renders the LEDs inside the unit useless and so I may replace this with clear perspex or something similar at a later date.

I then used more of the same plastic to make a scratch-plate to replace the yellow one provided with the guitar and cover for the back of the guitar. It's not the most elegant solution but will do for now!

Finally I glued the nut to the headstock of the guitar and screwed on the truss rod cover.

I was then able to put strings on the guitar and plug it in to an amp!

Completed guitar & kaoss pad

The guitar circuit works, though the tone pots do not work properly so this will need re-soldering, however for the time being the guitar and kaoss pad are both functioning.

So, the only remaining problems to deal with are:

Setting the intonation of the guitar
Fixing the tone pots so that they work correctly
Finding the source of a slight hum that is only really present when the kaoss pad is turned on (possibly an issue with the lack of shielding between the guitar and touch pad wiring inside the guitar)

Then the purely aesthetic changes I would like to make include:

Replacing the black plastic with something more durable, particularly the replacement screen on the kaoss pad body.
Replacing the yellow hardware
Add the originally planned LED circuit behind the touch pad

I plan to upload a demonstration video of the completed guitar once the intonation is properly set up to make the guitar playable.

Busy Weekend - Day #1

2012-02-11T23:45:00.000+00:00

Today I have begun my final push to finish the build portion of the project and, after a very long day, am nearing completion.

I began by spraying a few extra coats of paint on to the body. While waiting for these to dry I soldered the wires on to the four touch pad connections to allow these to be connected to the serial connector in the guitar.

Touch pad connections soldered to wires ready to be put in to the guitar

I also cut a front mount to hold the touch pad in place on the guitar body. This was cut from a plastic box but may be replaced at a later date if a stronger and/or more attractive material is found.

The front mount cut for the touch pad

Once the paint was dry, a chisel was used to carefully level off the top ridge of the support for the touch pad and two additional pieces of wood were screwed in to either side of the kaoss pad cavity to brace the touch pad against the front mount.

Touch pad cavity with supports on three sides and a small section filed out at the bottom to allow space for the ribbon cable to fold own in to the hole.

Some parts of the outside edge of the guitar body would not allow the paint to stick and so have been left for now so that the electronic side of the project can be completed. I will most likely come back to these after the project is finished.

Part of the body where the paint would not stick.

Next the various parts of the guitar electronics were added to the body. The bridge and tailpiece bushings were hammered in to place as the holes drilled were a very tight fit. Then the pickups, selector switch and volume and tone potentiometers were put in to place with wires fed through to the various cavities.

Pick-ups and 3-way selector in position with wires fed through the cavities to be connected

The Pickups were then soldered to the pots. The main problem at this stage was that the wiring provided had already had some of the soldering completed but what had already been done did not match any wiring diagrams that I could find, however I managed to combine information from several to complete the circuit.

Volume & Tone Pots in position and wired up

Then the three-way selector was wired up. This was difficult due to the fairly low quality of the wires that came with the guitar body.

3-Way Selector Switch connected up

While the volume and tone pots were being connected up, the hold button was also put in to place and the wires connected to it fed through the additional hole drilled for the kaoss pad wiring.

Hold Button in position between the volume & tone pots

The pickups and pots were then all connected up the the input jack which was screwed in to place.

Input Jack Connections: 1 = Hot, 2 = Ground, 3 = Input Jack Tip

The two wires for the hold switch were then connected to the serial port. Once all of this was complete the touch pad was put in to the guitar and wired through to this same serial port.

Hold Button connected to serial connector

To ensure that the various kaoss pad connections matched to their original locations, the serial port on the guitar was wired identically to the one on the kaoss pad using the arrangement shown here:

1-4 = Four Touch Pad Connections, 5-6 = Hold Button, X = Unused

Finally, the tuning pegs were attached to the headstock of the guitar and the kaoss pad connection was tested.

Tuning Pegs attached to head

The remaining steps should be completed tomorrow. These are as follows:

Cover the back of the kaoss pad cavity
Glue nut to the headstock
Add scratch plate to the guitar
Put strings on the guitar and test the pickups/pots/selector switch
Attach strap buttons
Cover the hole in the kaoss pad & attach the serial connector to the cover.

Mindmap Of Testing/Evaluation Key Areas

2012-02-07T11:57:00.000+00:00

(click to enlarge)

Update: Delays, Plans & Progress Report

2012-02-01T04:59:00.000+00:00

Unfortunately, due to the slight delay in beginning the build portion of the project before Christmas and the time-consuming process of painting the guitar body I was unable to complete the build before returning to university in January. However, rather than bringing the whole kit and any tools back to Derby with me I am returning home for the weekend of 10/2/12 to (hopefully) finish off the rest of the build.

The remaining steps include:

Finishing off paintwork on the sides and back of the guitar and touching up the rest of the paint work
Fitting the guitar electronics
Fitting the Kaoss Pad electronics
Cutting a mounting plate to hold the touch pad in place

I believe that this should be completed since everything is ready to be assembled as soon as the paint work is fully complete.

In the meantime, I have begun the write-up and have been planning the testing and evaluation sections of the project that will follow.

Kaoss Pad Modification

2012-01-17T01:42:00.000+00:00

Now that the painting is under way, I have also further modified the Kaoss pad wiring:

Four wires replacing the four connections to the touch pad

Soldering on the reverse side

Two additional cables soldered to the hold button

Hold button connections

All six connections wired to a DB9 Female Socket

Painting

2012-01-15T23:53:00.000+00:00

Having drilled all of the necessary holes for the hold button (positioned between the four volume and tone pots to make use of the pre-existing control cavity) and for the additional output port, I have been able to begin painting the guitar body.

I have also test-fitted the neck to the body and drilled pilot holes to allow me to attach it after the painting is complete.

Woodwork

2012-01-04T03:43:00.000+00:00

Today I have been making all necessary changes to the guitar body. I initially drilled holes in the corners of the marked space for the cavity and used a hack saw to cut along the edges.

However it quickly became clear that I did not have a saw that would reach far enough in to the body to use this technique all the way around the shape and this approach was very slow. Instead I carefully chiselled the shape out by shaving off layer by layer. This was much more effective, though did not give a very tidy finish on the fourth side, which will need to be smoothed off before putting any electronics in to the hole.

I also drilled holes down for the bridge and tail piece bushings, though I need to find a very slightly wider drill bit to widen these holes enough to fit.

Marking Up The Guitar Body

2011-12-23T04:38:00.000+00:00

Before the guitar could be painted and assembled, the holes for the tail-piece and bridge bushings needed to be drilled and additional a cavity for the touch screen cut out of the body. In order to accurately measure the touch pad cavity, it must first be removed from the main body of the unit.


The four connections between the PCB and touch screen from the KP-1 Service	Manual

I began by removing the back of the kaoss pad, followed by the two large PCB's, the third small board containing the headphone volume control, and finally the touch screen itself.These four connections are wired via a ribbon cable which must be disconnected from the PCB.

The connection can be seen at the top of the unit in this picture.

All PCB's and touch screen removed from the unit casing

The ribbon cable was connected to the PCB through a small plastic jacket which I opened to disconnect the touch panel. I then had to de-solder the four connections of the remaining half of the jacket from the the PCB

The removed panel and half of the plastic jacket

Remaining half of the plastic jacket

De-soldered connections on the PCB

The jacket was then put back together to give something to solder connections to later in the build.

Having removed the touch panel, I was able to position and draw around it on the guitar body and work out the best positions for the bridge and tail piece.

Final Design Summary

2011-12-09T21:08:00.000+00:00

I now have a design which I believe will work most effectively for this project.

I decided on the Les Paul shape because it should have enough space at the tail of the guitar for the Kaoss Pad screen.

Guitar Body Layout Ideas

As well as the touch screen from the Kaoss Pad, I have included a momentary switch to control the hold function of the unit from the body of the guitar as this function is useful for the use of the effect and should be cable of being wired via the same cable as the touch screen.

Kaoss Pad Modification Plan

The Kaoss Pad is definitely too big to mount on the performer or guitar, however this may be an area for further study in a future project. I also believe that the use of wireless will force me well outside the budget for this project. However, I do not think that the use of an additional cable will be too restrictive and will aim to make the connections between the Kaoss Pad unit and the screen on the guitar as aesthetically and ergonomically pleasing as possible.

Planned circuit for LEDs

As an entirely aesthetic feature, I have bought some RGB colour-changing LED bulbs which I would like to put behind the touch pad to make the modification look more professional and visually interesting for use in performance. I am unsure whether the LEDs could be powered by the same feed from the Kaoss Pad as the touch pad, though I will be investigating this. In the meantime I will assume that this will operate on a separate circuit powered by a 9v battery stored securely inside the body of the guitar.

Regarding the actual building of the guitar, I am currently about 2 weeks behind my planned schedule, however I will use the next few weeks to catch up and get back on track. If possible I hope to build a test version of the LED circuit before Christmas break. I will build the entire guitar during the christmas break and aim to be ready to test it in detail after teaching resumes.

Email from Korg

2011-12-06T07:43:00.000+00:00

I emailed Korg's technical support team asking for any relevant information to my project, in particular the voltages and current fed to the touch screen. Unfortunately I didn't receive any direct answers to my specific questions, however they sent me a pdf copy of the service manual for the unit which I will use to try to calculate the answers to my own questions!

I have uploaded the manual to my Google Documents here: Korg KP-1 Kaoss Pad Service Manual

Portability Considerations

2011-11-28T12:22:00.000+00:00

As the purpose of the finished artefact is to operate effectively in live performance, the portability of the device is very important. It should not unreasonably restrict the performer's movement on stage. However, as this model of Kaoss Pad is too large to fit entirely inside the guitar, the guitar must be connected in some way to the rest of the unit to allow the touch pad to control it.

For this reason I have looked in to the following alternative options to improve the units portability when in use:

Attaching the unit to the performers guitar strap
Implementing a wireless connection between the touch pad and the rest of the effects unit.

However, while it would be possible to attach the unit to the performer, it is quite a large unit that would not be very appealing aesthetically to the user (or the audience!)

The wireless option, on the other hand, could be easily concealed and would also allow much more movement away from the unit. However, there are two negative points associated with this. Firtsly that the touch pad currently draws its power from the effects unit and I believe acts as a sort of variable resistor, so an alternative power supply would be required for the touch pad and there may be issues with the main body of the Kaoss Pad if this section that it is powering is removed. I have contacted Korg to ask for any technical diagrams or information that they could provide me with to help in calculating this, but am waiting for a response regarding this. Secondly the additional expense of a wireless transmitter and receiver makes this infeasible for this project. Both the transmitter and receiver would presumably also require some power source which further complicated the design.

I have decided to continue with my original plan to use a serial cable connection between the touch pad and the rest of the unit, though this may slightly limit the performers movement. If Korg are able to supply me with more detailed information - for example about current and voltages required by different parts of the unit - I will hopefully be able to decide on the longest usable cable for the connection.

Parts Collected So Far

2011-11-20T07:18:00.000+00:00

Whilst working on the final design, I have been collecting the parts that I know will be required.

Guitar Build Kit

I believe that I have almost all of the parts required to begin to build the guitar. Once I have the final parts I will begin by doing all necessary routing and adjustments of the guitar body before finishing the wood and putting the guitar together. The hardware will then be fitted, along with the Kaoss Pad modification.

Korg KP-1 Kaoss Pad, DB9 Serial Connectors & Cable

For the time being, I plan to connect the Kaoss pad screen back to the body of the unit using serial connections which should not require any additional power to be supplied to the touch screen. However, this connection will be tested and alternatives will be researched before this is affixed to the guitar.

The use of a Les Paul style design allows enough space for the touch screen to be attached at the base of the guitar, beneath the bridge. From a few sketched ideas, this seems to be the most appropriate placement for the screen as it should be reasonably comfortable for the performer to use without looking out of place in the design.

Rough Outline of Planned Touch Screen Placement

The remaining barriers to be overcome before beginning the build are to find a button which will be used to operate the 'hold' function of the Kaoss Pad, to decide on a placement for this on the guitar body, and to decide on a way to firmly hold the touch pad in place.

2nd Meeting With Project Supervisor

2011-11-11T04:10:00.000+00:00

After my second meeting with Duncan Werner, I intend to investigate ways of improving the portability of the design I am working on in order to ensure that it is well suited to live performance.

Two potential options that will be investigated are to mount the full effects unit about the guitarists person, or to make use of wireless technology between the guitar and the rest of the effects unit.

Project Proposal Amendments

2011-10-31T21:22:00.000+00:00

Aims Of The Project

The identification of potential benefits and problems of incorporating effects in to the guitar.
The designing of a system to incorporate an effects unit or effects controller in to a guitar.
Realisation of the final design.
Evaluation of the finished artefact.

Plan Of Work

June-Sept.	Background research and preparation of project proposal carried out.
October	Background research begun during summer continued and design of the system and ordering of parts begins. Proposal refined ready for finalisation at the start of November.
November	Final design created and any remaining parts required will be ordered/purchased. Building of the artefact will start in Mid-November.
December	Building of the artefact should be completed by the end of the month.
January	Before returning from the Christmas break, the build section of the report will be written and preparation for the testing and evaluation of the completed guitar will begin. Test recordings (both audio and video) will be made to demonstrate the functionality of the working artefact. These recordings will be submitted with the final report.
February	Listening tests and interviews will be carried out in order to gain impartial evaluation of the product. Writing of the evaluation section of the report will begin at this time.
March	The report will be reviewed, revisions and alterations made and a conclusion written.
April	The final two weeks before submission on April 17^th will consist of proof reading and finalisation of the report.
May-June	Preparation for the Viva-Voce in June will begin after submission of the final report.

Meeting With Project Supervisor

2011-10-28T03:00:00.000+01:00

After a meeting to discuss the submitted proposal, I have been directed to make some alterations to the project aims and plan of work section.

I will submit these changes in the next few days.

Parts List

2011-10-16T23:10:00.000+01:00

The following are the parts that I believe will be required for the project:

Guitar Build

Body
Neck
Output Jack
Tone & Volume Pots
3-way pickup switch
Back Plate
Neck Position Pickup
Bridge Position Pickup
Stop plate
Bridge
Tuning pegs
Neck Plate
Strap Buttons
Pick Guard

Kaoss Pad Modification

Kaoss Pad (KP-1 or KP-2 model)
DB9 connectors (2x Female)
Straight serial cable, (Male-to-Male)
Solder
Frame
Back cover
LED circuit

Whilst I work on the design of the modification I have now begun to buy any parts that will definitely be needed for the build. I will buy/order any additional parts as and when I find that they are needed.

Risk Assessment

2011-10-12T06:50:00.000+01:00

The risk assessment document can be found here.

Project Proposal

2011-10-12T06:44:00.000+01:00

Project Title:

Practical Project: Designing & Building An Affordable Modified Electric Guitar With Built-In Effects Controller

I - Overview

The electric guitar has long been associated with various forms of effects processing. When used in live performance, many guitar effects are applied through the use of foot-operated pedals; however, this arguably offers little flexibility during live performance, as it can be difficult to change parameters whilst playing and using tools such as MIDI data to “generate effects that mimic those created by digital signal processing” is “increasingly common” (Roads, 1989). This project will look at an alternative to this method of control in order to allow a new form of musical expression in performance.

As with many traditional instruments, the electric guitar is played “by performing gestures shaped by the physical representation of the instrument”, (Kayali, Pichlmair & Kotik, 2008) which will have had “a material influence on the processes of composition and performance” (Manning, 2004). However the boundary between acoustic and digital sounds produced is arguably blurred by the use of effects. Therefore, challenging “this practical link with traditional performance” (Manning, 2004) by introducing a new form of gestural input may allow composition and performance to move in a new direction.

The use of a touch pad provides an interface similar to Max Mathews’ “Sequential Drum”, which consisted of “a grid of horizontal and vertical wires and an associated handheld beater” that generates “coordinates that are analysed by the Conductor program.” (Manning, 2004)

A unit such as the Korg Kaoss Pad, which is “built around a two dimensional touch controller” which “outputs MIDI data” (Steiner, 2005) allows the touchpad to control a wide range of effects built in to the unit. It also offers a MIDI Out connection. Given that “less obvious uses of MIDI data include the control of lighting by assigning specific notes, patches or songs to specific lighting configurations” (Roads, 1989), this could allow a wide range of aspects of live performance to be controlled. By building this touch controller in to a guitar, a performer may use the effects using their hand when not playing the instrument itself.

In addition to this, due to the real-time control element of the control surface and the range of possible settings and effects, the output would be difficult to reproduce identically and therefore could be thought of as unique to each performance and arguably a “move toward conceiving of types of musical sound not amenable to conventional notation” (Kahn, 1999), adding a new semi-random element of impermanence to performance with the instrument.

II - Aims Of The Project

Investigate the incorporation of effects controllers in to a guitar body.
Produce a fully functional guitar with built in effects controller using materials that cost no more than £150.
Evaluate through detailed analysis and testing the effectiveness of the finished artefact.

III - Project Definition

In order to design the most effective possible design, the project will begin with in depth research, covering available options for layout and wiring. Existing products with any similarity to this project will be examined along with any similar modifications and the electronics involved.

After this, the item will be designed thoroughly and any parts required will be purchased.

Building the product will involve assembling the guitar itself, making any modifications required to the body in the process before. The effects controller will be installed during this process.

As it is designed for performance, the finished artefact will be evaluated based on its audio output, ergonomics and its aesthetics. Listening tests and interviews will be devised for impartial listeners. They will answer questions regarding the audio and aesthetic qualities of the device, which can then be evaluated to allow the conclusion as whether the build has succeeded in meeting each of the proposed targets.

IV - Plan Of Work

Background research, which began during the summer, will continue until all details of the proposal are finalised and a final design can be created. To save time after this, preliminary designs will also be created and any components that will definitely be needed for the final build will be gathered together.

Following the finalisation of the proposal, a final design will be created and any additional materials required will be purchased. The report will be started once this stage is reached. Building of the artefact will begin in mid-November with the goal of completing construction by Christmas.

Before returning from the Christmas break, preparation for the testing and evaluation of the completed guitar will begin. Listening tests and interviews will be conducted in January and February. Writing of the evaluation section of the report will begin around this time. Further tests with impartial listeners and guitarists will take place following this. Recordings will also be made to demonstrate the functionality of the finished artefact which will be submitted with the final report.

After the conclusion has been written, the final two weeks before submission on April 17^th will consist of proof reading and finalising the report.

A logbook and/or online blog will be kept throughout the process of designing, building and evaluating the artefact. Preparation for the Viva-voce in June will then begin.

V - Limitations

Due to time and budget restrictions, the guitar itself will not be built from scratch. However, as modifying a completed guitar may prove difficult and result in poor result aesthetically the guitar will be built using pre-purchased components.

In addition, some aspects of the final tests of the guitar may be affected by personal taste in guitar and therefore questions will need to be limited to non-subjective qualities of the design as far as possible.

The parts required for the build may need to be ordered online so any delay in delivery must be factored in to the build time.

VI - Resources

In designing and planning the guitar build, the books ‘Make Your Own Electric Guitar’ (Hiscock, 2006), ‘Building Electric Guitars’ (Kahn, 1999), ‘Electronic Projects for Guitar’ (Penfold, 1992) and ‘Audio Electronics’ (Linsley Hood, 1995) should provide most information required.

The modification of the guitar will require the use of electronics equipment, such as a soldering iron. Therefore access to the university electronics labs may be necessary.

After the building is complete, space will be required for the listening tests and for recording the evidence of functionality. The university recording studio space will be used for both of these tasks.

References

Bacon, T. & Day, P. (1993) The Gibson Les Paul Book. London: Balafon Books.

Hiscock, M. (2006) Make Your Own Electric Guitar. 2^nd Edn. NBS Publications.

Hunter, D. (2006) The Electric Guitar Sourcebook. USA: Backbeat Books

Kahn, D. (1999) Noise Water Meat. USA: MIT Press

Kayali, F., Pichlmair, M. & Kotik, P. (2008) Mobile Tangible Interfaces As Gestural Instruments. [Online] Available at: http://www.uni-ak.ac.at/ (Accessed: 24/09/11)

Koch, M. (2001) Building Electric Guitars. [Online] Available at: http://www.buildyourguitar.com (Accessed: 25/09/11)

Linsley Hood, J. (1995) Audio Electronics. Oxford: Newnes

Manning, P. (2004) Electronic & Computer Music. Revised & Expanded Edn. Oxford: Oxford University Press

Penfold, R.A. (1992) Electronic Projects for Guitar. Kent, PC Publishing

Roads, C. (1989) The Music Machine: Selected Readings from Computer Music Journal. USA: MIT Press

Steiner, H. (2005) Building Your Own Instrument With PD [online] Available at: http://citeseerx.ist.psu.edu/ (Accessed: 24/09/11)