I've seen schematics on the Bryston web site of their big amps and they definitely implement a DC off set circuit ... it's two electrolytic caps in series by passed by a diode bridge ... the caps center the wave and the diodes prevent damage from reverse biasing ..
Bryston also uses a ground blocking circuit on the safety/ground wire with a diode bridge that allows a fault to be conducted to the ground rod but blocks any voltage being conducted on the ground wire in the opposite direction towards the amp
Not sure who else or if any employ these circuits
Stringreen ... I'm going to go out on a limb here but I think your amp's protection is against DC (direct current ) riding on the the line and most likely the analog ICs ... the amp shuts down when it senses the DC current so it is not pass onto the speakers were it can damage the drivers ... DC offs set does not harm the speakers only reduces components efficiency
gdhal if you could develop a perfect world scenario with no switching power supplies and half wave bridge rectifiers there would be no DC off set to defeat and no use for a blocker
But the blocker can serve another important role if and when not defeating the off set
I think the worst offenders are the commercial and industrial users that use 3 phase power ... they create a lot of harmonics that get back on the line and pollute the grid that you draw your power from
The power your components draw from the grid is loaded with these line harmonics that do the same thing in reducing transformer efficiency and you have the same issues ... reduced dynamics and head room
So even if you can evade the DC off set scenario some how ... you still have a big issue with the 3 phase users distorting the line and here is where a blocker like the Humbuster can be beneficial Enter your text ...