Great questions and thoughts - thank you very much.

The house is 63 years old.  Yes, the "Open Ground" duplex outlet was identified with a three prong plug-in outlet tester, before I opened it up.  Inside there are only two sets of two wires for the two outlets; the wires are cloth and rubber covered.  There is no ground wire   The outlets are three prong so presumably were added after the original wiring. 

Other room outlets test as "Grounded," hence my idea to first use one of these outlets and move my audio equipment, furniture, carpets, under lay et al around(!)

Longer term I'm considering having an electrician install a dedicated 20A branch circuit and/or a GFCI duplex outlet...thank you all again for all your kind help.  It is much appreciated.  Enjoy your music! 

The house is 63 years old.  Yes, the "Open Ground" duplex outlet was identified with a three prong plug-in outlet tester, before I opened it up.  Inside there are only two sets of two wires for the two outlets; the wires are cloth and rubber covered.  There is no ground wire 

63 years old, 1962... I imagine the branch circuit wiring is cloth covered NM, Romex. Though going from memory, the two conductor where insulated with TW thermal plastic, PVC insulation. 

It is possible, because of local Fire Codes, Electrical Codes, AHJ (Authority Having Jurisdiction) in your city required houses back then to be wired using BX, steel armored cable. (In 1962 the steel armor was not used as an equipment grounding conductor,) In 1962 it may have still had cloth covered rubber insulation covering the bare conductors.

Yes, the "Open Ground" duplex outlet was identified with a three prong plug-in outlet tester, before I opened it up.  Inside there are only two sets of two wires for the two outlets;

That indicates a convenience outlet branch circuit. More than likely a 15A circuit. The outlet terminals were used for feed through in and out circuit through the box. Good chance there are several wall outlets, and possibly ceiling lights on the circuit.

Shut off the breaker at the panel and check what is dead. Identify with a piece of tape or a post-it at each dead wall outlet.

Turn back on the breaker and check the wall outlets for a ground with your plug-in tester. Upstream, (toward the electrical panel), from the one for your audio equipment may show there is a ground. Down stream will show an Open Ground.

If it is BX don’t assume the integrity of the safety equipment ground. Good chance it will fail in the event of a Hot to ground fault event.  Back in 1962 there were not any 120V 15A or 20A 3 wire grounding type outlets. They were only 2 wire.

My home was built in 1956 and has two wire open ground outlets in much of the house. This is true in my listening space. 

I am a fairly avid follower of posts on AG and realize amps, in general, should be plugged directly into the mains outlet. When I do this, I can actually feel low levels of current on the metal faceplate. Pretty scary.

I have plugged my amp into my Panamax surge protector/power conditioner. The grounding issue was resolved. Hopefully this hasn't impacted the overall sound of the amp. It seems like a decent compromise to not have the scary feeling grounding problem.

@motown-l  said:

and realize amps, in general, should be plugged directly into the mains outlet. When I do this, I can actually feel low levels of current on the metal face plate. Pretty scary.

On the metal face plate? As in wall metal outlet face plate? A metal face plate should never be used on a 2 wire branch that uses a steel outlet box... Replace all metal wall plates with plastic or non breakable nylon plates.

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I have plugged my amp into my Panamax surge protector/power conditioner. The grounding issue was resolved.

Model? 

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So this would work for protection on a two wire outlet? Thoughts...Thanks 

Panamax MD2 2 Outlet Direct Plug In Surge - White