4-to-1 Audio Mixer with an Analog Transistor-based Noise source

input

4 Audio inputs
Noise source is pre-wired to jack 4 with nothing at input jack (noise can be mixed to sum)

control

4 input signal attenuators

output

• noise
• mix

http://birdkids.org

• ? mA +12V
• ? mA -12V
• ? mA 5V

No info about availability.