Line Conditioning and possible ground issues?

I get the notion that many power conditioners no matter brand or cost cannot correct and do their intended jobs if for faulty-improper wiring and/or lack of proper ground.  Is this correct?

Mostly.  You cannot/should not fix a wiring problem with a conditioner, that’s for sure as you may ignore life safety issues.  You should not put in a 3 prong outlet if you lack a ground unless that outlet is GFCI protected.  That is allowed. 

You also won’t fix things like bad neutrals, reversed hot to neutral, etc. etc. so if in doubt you 100% should have an electrician check it first.  Also consider an inexpensive outlet tester like this one.  Your N-E should be 2 V or less, and watch it under load (when your system is playing) to make sure your main voltage does not sag and the N-E stays low.  

Having said all of that, if you do not have a true ground, a lot of surge protectors won’t work correctly.  So, if you have a really old home and replace an outlet with a GFCI outlet (totally legal only with GFCI) you'll gain shock protection but most surge protectors you plug into that outlet won’t work correctly.  

Now, if your internal house wiring is solid but you suffer voltage sags due to time of day, seasonal AC use or overall a poor power company it is perfectly acceptable to use a conditioner with voltage regulation.

I understand what you say, thank you for your comments. 

I live in a home built in 1956. Much of the existing circuitry is ungrounded, two wire. We did have a new panel installed and an amperage upgrade, but old wiring still predominates.

Against the advice of some on AG, I plugged my amp into a decent line conditioner/surge protector. The effects of the ungrounded circuitry, which was the feeling of small amounts of current on the metal faceplate, disappeared. 

Not being an expert or trained in electrical circuitry, I would say the line conditioner helped with my major grounding issue.

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I've been doing some research across the web about such.  Some older equipment never had provision for 3 prong cabling with ground.  Perhaps in these cases and if one had an issue with some ground loop hum, you used a cheater plug and the world was right again. 

And that most small kitchen appliances for example cannot have 3 prong plugs.

Of course with a Toaster, where not looking to lessen-squelch line noise like with modern day electronics. 

Some older equipment never had provision for 3 prong cabling with ground.  Perhaps in these cases and if one had an issue with some ground loop hum, you used a cheater plug and the world was right again. 

It’s really not the preferred way to deal with a ground loop issue.  IMHO, at best, it is a way to diagnose a ground loop issue.  

Important to know why that ground pin is there.  It’s there to carry voltage from the chasis to ground when there’s an internal short.  This can be 15A to 20A, the full current at the AC input.  

We recently had an a’goner who had a partial short.  The current went from the chassis, through his interconnects to the next piece of equipment and burned it out.  He literally reported feeling a tingling when he touched the chasis.  That was a huge sign something was wrong.   Had he had a full short a fire could have started by having 15A going through the tiny little grounds in the interconnects.  Had he not had the interconnects and been barefoot he could have had an electrocution.  

If you are sure your house wiring is good, and absolutely cannot diagnose your audio any other way, the best solutions are the small hum busters.  They do disconnect the ground, but restore it on a short.  

Other AC issues which can cause hums are DC on the line, as well as a lifted neutral.  The usual way to deal with DC is to find the source.  Turn off every other breaker and device in your house.  Sometimes things like LED power supplies can cause massive amounts of DC.  A neutral which is not actually well bonded to ground at the service entrance can do similar things.  That's why I suggested the inexpensive test plug to start.