PPI difference in potential between grounds

[jkrokenberger]

I've got a number of PPI M/AM/ProMOS amplifiers and have noticed that they all have a slight(0.6V-1.2V) voltage between the power supply ground and the audio side grounds. I read this voltage with the black meter lead on the power supply ground and the red meter lead on the audio ground. Is this intentional or a fault? Would there be any advantage in having them closer(lower V) to each other?

 

[Perry Babin]

With nothing connected to the amp, what's the resistance from the RCA shields to the primary ground?

 

[jkrokenberger]

270 ohms.

 

[Perry Babin]

Does it change (polarity, voltage) when the amp LED changes from red to green?

 

[jkrokenberger]

The amplifiers only have a single red power LED and the polarity and voltage does not change at any time.

 

[Perry Babin]

All of those have a single LED?

The design may be older than the information I have is.

If they all have the voltage and don't have engine noise, I'd suspect that it's normal.