Floating Ground

In an electric circuit, a floating ground is a ground, that is a reference node serving as a common return path for current from other components, which is not electrically connected to the Earth.

This can occur in 3 possible ways

    as the result of intentional design, and entirely harmless
    as the result of failure to ground equipment that was designed to require grounding
    as the result of exposing a live ground that was intended to remain unexposed (live chassis TVs were common until the 1990s (at least in the UK and the Irish Republic), where the set's ground is derived by rectifying live mains)

When an electrical device is accidentally or intentionally grounded to its surrounding structural component (chassis), this is called a "live chassis." Circuit failures resulting in live chassis contrary to design plans can mean that anything (e.g. a person) that touches the device and is grounded on something with a different charge (e.g. terra firma) will now experience a voltage potential across its body. This can lead to death or harm by electrocution.

Intentional floating grounds formed by design are widespread in domestic electronic appliances. Providing the design is satisfactory they aren't a safety issue.

Ungrounded equipment designed to be grounded is a safety issue. It leaves users unprotected against the risk of shock due to a potential further fault.

Exposed live grounds are dangerous. They are live, and can electrocute end users if touched. Headphone sockets fitted by end users to live chassis TVs are especially dangerous, as not only are they often live, but the danger is carried directly to the user's head.

    Sets that have both headphone socket and a live chassis use an audio isolation transformer to make the arrangement safe.

Floating grounds can cause problems with audio equipment using RCA/phono connectors. With these common and somewhat antiquated connectors, the signal pin connects before the ground, and 2 pieces of equipment can have more voltage difference between their grounds than it takes to saturate the audio input. As a result, plugging or unplugging while powered up can result in very loud noises in speakers. If the ground voltage difference is small, it tends to only cause hum & clicks.