Thanks for the nice words, gentlemen.
As is usually the case, I agree with everything Jim has said. Including the fact that the ground lift switch can be presumed to not interrupt the connection between chassis and AC safety ground. In contrast to using a 3-prong to 2-prong cheater plug to defeat the AC safety ground connection, which is sometimes done to resolve ground loop problems despite the safety risk.
There are many conceivable effects that can depend on the position of that switch, and most of those effects tend to be system dependent and to generally have little predictability. But keep in mind that if setting that switch to the "lift" position resolved the hum problem, it may also have resolved other adverse sonic effects related to the ground loop that was present. Even effects occurring at frequencies that are themselves too high to be audible, but that may have had audible consequences by intermodulating with audible frequencies in the audio signal.
Also, an experiment that may provide added confidence would be to disconnect the input cable from each of the amps (leaving the speakers connected!), and using a multimeter to measure the AC voltage, if any, between the ground sleeve of the RCA input connector and chassis, on each amp. That would provide an indication of how far the circuit ground of the amp "floats" from chassis, when the switch is in the "lift" position. If the reading is small, say just a volt or two, it would provide added confidence in using that switch position. Have the amp turned off, of course, when you disconnect the input cable, and then turn it back on for the measurement.
And BTW, in the absence of specific information to the contrary I would not change the position of that switch while the amp is powered up, or within the first few seconds after turning it off.
Best regards,
-- Al
As is usually the case, I agree with everything Jim has said. Including the fact that the ground lift switch can be presumed to not interrupt the connection between chassis and AC safety ground. In contrast to using a 3-prong to 2-prong cheater plug to defeat the AC safety ground connection, which is sometimes done to resolve ground loop problems despite the safety risk.
07-19-15: TmmvinylAs Jim suggested, it would probably be worthwhile asking Mr. Blume. (I assume, btw, that you are referring to your Coincident Dragon amps, as I don't think the Franks have a ground lift switch, based on their description at the Coincident website).
Does lifting the ground on my power amplifiers do anything to degrade the amp's sonic capabilities?
There are many conceivable effects that can depend on the position of that switch, and most of those effects tend to be system dependent and to generally have little predictability. But keep in mind that if setting that switch to the "lift" position resolved the hum problem, it may also have resolved other adverse sonic effects related to the ground loop that was present. Even effects occurring at frequencies that are themselves too high to be audible, but that may have had audible consequences by intermodulating with audible frequencies in the audio signal.
Also, an experiment that may provide added confidence would be to disconnect the input cable from each of the amps (leaving the speakers connected!), and using a multimeter to measure the AC voltage, if any, between the ground sleeve of the RCA input connector and chassis, on each amp. That would provide an indication of how far the circuit ground of the amp "floats" from chassis, when the switch is in the "lift" position. If the reading is small, say just a volt or two, it would provide added confidence in using that switch position. Have the amp turned off, of course, when you disconnect the input cable, and then turn it back on for the measurement.
And BTW, in the absence of specific information to the contrary I would not change the position of that switch while the amp is powered up, or within the first few seconds after turning it off.
Best regards,
-- Al