What is the click I hear when I turn on my SUBWAY D-800?
The relay click you hear when turning on a SUBWAY® D-800™ is both normal and essential. The power supply is an over-voltage protected auto-ranging switch-mode power supply. There is a critical sequence of events at start-up that allows all of this to happen. When the power switch is moved to the on position, the power supply looks at the incoming voltage to be sure it is in range (if the voltage is too high or too low it will not allow the next step to proceed). If the voltage is in the low range (100-120V) the voltage doubler enable relay closes. Once the bus voltage is stabilized, the DC bus is connected (via relay) to the rest of the power supply.
The SUBWAY® D-800™ will only power up once within a 20 second window due to a short cycle controller. This is essential to protect its inrush current management circuits. If the amp is powered up, shut down, then immediately powered up again, the protection circuit will prevent power up until a total of 20 seconds lapses. Should you accidentally turn the amp on and then off right away, you can leave the power switch on, and after the 20 seconds have elapsed, the amp should power up. It may be possible, under the rare instance of a high AC voltage disturbance, for the amplifier to require a reset by unplugging and plugging back into the AC power source. This likelihood would be really rare but is possible.