High AC Voltage Between Grounds

[ridikas]

I've built a couple of preamps and amps. The way I do the grounding scheme:

I keep the chassis ground and signal ground separate.

All panels in the metal chassis conduct with each other and I connect a metal tab to a bolt near the IEC and run a short wire to the ground pin.

The RCAs, binding posts, etc. are all insulated and only connected to the signal ground. Signal ground is in a star ground configuration.

Power supply is a very simple design where the transformer has two secondary windings and the center tap is grounded to the star ground (signal).

If I take an Ohm meter and measure AC between let's say one of the RCA connectors (ground) and the chassis, I get anywhere from 25VAC (amplifiers) to 50 VAC (preamps). DC between the two grounds is practically zero.

The systems work perfectly.

Should this cause for a concern? Is it improper to keep the two ground separated?

Thanks for all of the help!

 

[DF96]

For safety the two grounds should be connected together. For low hum this should be in one and only one place.

 

[ridikas]

For safety the two grounds should be connected together. For low hum this should be in one and only one place.

But if these two grounds are not connected, is having such high AC voltage pretty normal?

 

[Speedskater]

Well the should be connected together just as DF96 wrote.
But you may just be reading what electricians call phantom voltage.
Try jumpering a high value resistor (10K - 100K) between your two measurement points.

 

[DF96]

Yes, a combination of high impedance voltmeters (typically 10M) and low value capacitors (such as mains filters) can create unnecessary alarm.