In very good physical condition and perfect working condition, we obtained this unit when purchasing a monster system using an AR SP 15 Flagship Preamp and two AR Classic 150's. The previous owner raved about the unit.
From MIT
The Z-1 contains patent-pending circuitry to control Audio Frequency Distortion (AFD) and works in parallel with your audio system. Therefore it cannot limit current or add its own distortions, as most series transformer-based "power line conditioners" do. With the Z-1, your audio system will reproduce more, and more accurate, low-level musical details and a clearer, extended soundstage. The greater the power-line problems, the greater the improvement you will notice in your system.
The Z-1 was designed to work with your power amplifiers. If your amps are on a single circuit breaker/line, you need only a single Z-1. You may place the Z-1 on a shelf or on the floor. It is better not to stack it on or under other components. Do not use an extension cord on the Z-1. Keep is as close to your audio/video equipment as possible.
The instant you plug in the Z-1, it is on and working. There is no on/off switch. There is no break-in period.
The A/B switch controls how much of the Z circuitry you use. We Recommend that you begin with the A position, because most listening reports indicate that this gives the optimum results. However, we urge you to try the B position also, which is intended to handle extreme problems on the power line.