There are already several way to use push buttons in your projects (e.g. hacking mouse and keyboard, or Arduino, gainer, MCK). This probides alternative way to use faders with audio input and output.
As side effects, it provides you with precious sampling resolution and frequency than the previous ways (i.e. 16bit to 8-10bit, 44.1KHz to 1KHz).
We present an application of this instructable from a work The SINE WAVE ORCHESTRA stay amplified.
All you need is just a fader, some soldering, and some software.
Note: This is for variable resistor type faders only. This will not work on optical type.
Note2: This is a series of "How to coonect with Audio". Please see others: Button, and Sensor.
Step 1: The Parts
The fader should be a variable resistor type. It has three (or even more) connectors and change its resistance with the position of the fader. Some mixing console use optical fader (mostly for DJ cross fader) and it doesn't work with this instructable. In this time, we use 'PROFADER SVA-1100' from TOKYO KO-ON DENPA. It has a very smooth movement.
2 3.5mm Mono Plug
One for audio input and another for audio output.
1 Twin Cable
You could use loudspeaker cable for this purpose. The length depends on how long you want.
1 Heat Shrink Tube
To cover the connector of the fader.
Step 2: The Tools
Step 3: Cutting the Cable
Step 4: Check the Fader
Step 5: Soldering the Fader (1: Resistor Side)
Step 6: Soldering the Fader (2: Ground Side)
Step 7: Soldering the Plugs
Step 8: Quality Control
Step 9: Connect to the Audio Input and Output
Step 10: Some Software
In this time, we use MaxMSP.
Assign an audio signal (e.g. 10000Hz sine wave) for audio output.
Set volume calculator for audio input. In this time, we use 'peakamp~' object.
Add a receiver for the calculator. In this time, we use 'multislider' object.
Here is a basic example of MaxMSP patche.
Step 11: Moment of the Connection
If it does not work, you just need to adjust the volume for audio output.
Step 12: Uses? Sine Wave Oscilator
Here is the setup. You will need split you audio output with stereo to dual mono cable. On one channel you connect the fader, and on another, you connect a speaker. Then you add a sine wave oscillator and a scale changer to fit the value frome fader to the frequency of the sine wave oscillator in your software. Now, you can finely control the sine wave oscilator in 16-bit resolution.
Here is a MaxMSP patch.
Step 13: Application: the SINE WAVE ORCHESTRA Stay Amplified
We detect the resistance of a fader controller as the amplitude of audio signal.
Step 14: Possible Improvements and Modifications
As the fader is one of a variable resistor, you can use other types of resistors instead (e.g. shaft, CDS)
You can use two faders with 3.5mm stereo plugs and triple cable.
If you need more faders, you can extend with external audio interfaces. In this time, you need to use proper plugs for the port of the audio interface.