GKC Research & Development MODEL 600 Monitor Amplifier

GKC Research & Development MODEL 600 Monitor Amplifier 1/8" & 1/4" outputs

GKC Audio Implements Model 201 Cell Phone Amplifier Box

Vintage NEW - GKC Research & Development Model 650 Monitor Amplifier w/ Dialer

GKC Audio Implements Model 650

GKC Research & Development Model 650 Monitor Amplifier w/ Dialer

GKC Audio Implements Model 305

GKC Research & Development MODEL 600 Monitor Amplifier 1/8" & 1/4" Untested