Another cheater plug thread

Al (Rodman), what he's saying is that he is using a cheater plug to defeat the connection of the safety ground pin on the preamp's power plug to the safety ground pin of the PS Audio unit's outlet. Therefore the preamp's chassis has no connection to safety ground, other than perhaps (depending on the internal grounding configuration of other components in the system) via the return conductors of interconnect cables going to other components, and from there via the safety ground connections of those other components.

If a fault were to develop in the preamp that shorted the AC line voltage to the preamp's chassis, there are various scenarios in which that could result in both a shock hazard and a fire hazard. How great are those risks? Very, very small. But it cannot be said that they are zero. Grimace, as I said in your thread on the original problem, it's your call.

BTW, a suitably chosen Jensen audio isolation transformer (one of those shown towards the bottom of the page), as suggested in the Jensen paper I linked to in my post of 3-30-12 in the other thread, would most likely make the whole issue moot.

Regards,
-- Al

09-11-12: Newbee
Don't the rca's connecting the CDP to the pre-amp effectively ground the CDP chassis?

Not necessarily.

A good design will often have circuit ground and chassis connected together through a low value resistor (to minimize ground loop susceptibility, compared to having them connected directly together). That creates an excellent chance that the resistance will reduce the amount of fault current (that would flow from the CDP's "hot" chassis through the return conductor of the interconnect through the resistor to the preamp's AC safety ground) to a level that is too low to cause the breaker to trip. The result would be that the resistor and/or the interconnect and/or anything close to them might go up in flames. The resistor would most likely burn out, in any event. Then when the user comes over to investigate, the hot chassis would still be hot.

Sometimes high current diodes are paralleled with the resistor (as is a capacitor, for RF filtering purposes), to prevent those possibilities. But I wouldn’t count on the diodes being present.

Also, if the user is connecting the CDP or other component having a hot chassis into the system while it is plugged into the AC, and with one hand he touches either the hot chassis or the ground sleeve of an RCA connector on an interconnect that is connected to the CDP and is about to be connected to the preamp, while touching the chassis of the preamp (or anything else that is grounded) with the other hand, 120 volts would be placed across his chest and arms.

Unlikely? Yes. Inconceivable? No.

Best regards,
-- Al