Stevecham 3-6-2019
Amp off first. AOF!
Millercarbon 3-6-2019
Uh, why? When its so much easier to simply change input?
The OPs issue occurred when he disconnected the RCA cables connecting his preamp to his amp. If the amp is powered up when that is done, as it was in this case, that could easily result in a brief transient being applied to the speakers corresponding to the amp’s maximum power capability, at an arbitrary combination of frequencies. With most of that power very possibly being in the treble region, where the power handling capability of the speaker is probably lowest.
The reason that happens is that when an RCA plug is inserted or removed there is a brief instant during which the center pin is connected but the ground shell is not connected. The amp or other component receiving the signal that is on the center pin responds to the voltage difference between that signal and its own circuit ground. Normally its own circuit ground is at essentially the same potential (i.e., voltage) as the circuit ground of the component supplying the signal, since the return conductor of the interconnect provides a direct connection between the circuit grounds of the two components. But if the signal connection is present while the ground connection between the two components is not present that voltage difference is uncontrolled, and will depend on the happenstance of the impedances between each component’s circuit ground and its chassis/AC safety ground connection, and on how the AC safety grounds of the two components are interconnected in the AC wiring and/or any power conditioners that may be in use, and on AC leakage currents that will be induced into that path to some unpredictable degree by the power transformers of the components.
Interconnections using XLR connectors are much better in that respect, because they are designed such that upon removal the ground connection is only removed after the signal connections are removed, and upon insertion the ground connection is applied before the signal connections are applied.
Regards,
-- Al
P.S: I suspect that Millercarbon's response was a joke, but I thought I'd answer anyway for the benefit of others who may read this thread.
