Radial Twin City Active ABY Amp SwitcherThe Twin City lets you connect any two guitar amps and switch between them or drive them both simultaneously without noise, loss of gain, or any degradation to your natural guitar tone. The Tonebone Twin City uses a class A input buffer to drive the amp outputs, which reduces susceptibility to noise and allows for completely silent switching on stage. To eliminate hum and buzz from ground loops, the Twin City is equipped with an isolation transformer