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

input

• Audio input 1
• Audio input 2
• Audio input 3
• Audio input 4
• noise source is pre-wired to input 4 with nothing present at input jack (noise source can thus be mixed to sum)

control

• Attenuator input 1
• Attenuator input 2
• Attenuator input 3
• Attenuator input 4

output

• noise
• mix

http://birdkids.org

• ? mA +12V
• ? mA -12V
• ? mA 5V

No info about availability.