A New Ground -- Benefits of introducing the Synergistic Research Active Ground Block SE

I’m fascinated by this subject but have not thrown money at it. I messed around with star grounding in the past, did have one of those cheapy Granite Audio boxes that, to my understanding, was like star grounding everything at one place, but gave you switches to mess with the ground planes or impedances of various "channels’ of connection. I used it temporarily to ameliorate some hum, but the answer turned out to be my Lamm ML2 amps. When I bought them, the previous owner had disconnected the wire of the circuit board to the chassis and no hum, but when I sent the amp to Vlad to go over, some years ago, it came back with the hum. We looked and that little wired had been replaced. I don’t like cheating the grounds, but that seems to be the only solution (unless I get into the unit which I’m reluctant to do).
I have a new isolation transformer that was just installed --a 10kVa and it doesn’t really address ground since, by code, it has to be connected to the main household ground (a Ufer, installed when this house was restored, along with all the electrics). I did install a separate or "clean" grounding point within the room- not isolated-- one of those big copper bars with holes (looks very much like the top of the passive Synergistic ground block) that runs back to the main household ground via a 4 gauge cable. That, obviously, didn’t make much difference either. The electrics for the hi-fi are dedicated, and pull from a subpanel to 20 amp hospital grade receptacles using 10 gauge Romex. The feeders are 4 gauge.
I gather Ralph is talking about inter-component grounding differences that cause the hum or weird ways of grounding a particular circuit within a piece of gear.
I get the concept that external star grounding as a supplement (not as a replacement) for grounding equipment could theoretically quiet a system- my speakers are very sensitive at 104db/meter so you here every gremlin.
I did get into a discussion with an EE who said the isolation transformer does zip unless it has an isolated ground, but I gather there are still benefits to nasties on the hot and neutral.
My plan was originally to build a separate building in the backyard of this house-- we had the feasibility study done, and zoning pre-approvals. In the meantime, the system is installed in a large loft space at the top of the house and it isn’t bad. In fact, even the current out of the wall-- the so-called "dirty power" is way better than what I had in NY metro-(up in the country), quiet, more stable, no brown outs (so far) despite the considerable heat here in central TX. The room is made of shiplap-- old planks (although covered with drywall in this upstairs loft area) and seems to sound very good, though I’m only just beginning to dial in the system. The whole grounding thing is a bit of a puzzlement--I should ask Vlad- since he has always been very responsive to me, and I love the sound of these old amps. Otherwise, I haven’t heard the really fancy external or supplemental grounding boxes but call me intrigued.

@whart If you have a DVM there is a simple measurement that will tell you if the amp/preamp/whatever is properly grounded.

With the unit unplugged and out of the system, the DVM set to the Ohms scale:

The center pin of the IEC connection (or ground pin of the AC cord) should measure a short to the chassis; IOW about 0.5 ohms or less.

If the ground of the audio input connection measures the same then you have a problem. If it seems to measure significantly higher than things are good.

If you have no connection between the chassis and the ground pin of the AC cord then the equipment can be considered dangerous and will not meet UL standards nor EU Directives (CE mark).

Thanks, Ralph. I know it is grounded now, but will hum unless I lift the ground. I do have a decent meter and will poke around without opening up the units. 

@atmasphere , Ralph, I understand when you say that all components must have the safety ground wired to the chassis, which in turn is grounded to the ground pin of the AC cord. When connected to a properly wired circuit box with separate ground and neutral, there should not be any grounding problems.
Two questions; will all components then have the same ground potential?
Star-grounding a component is an improved grounding technique, but does it change the ground potential from a traditional component grounding design as stated above? 

Whart, It seems to me that your problem can be solved by the tweak that Ralph recommended further up the thread.  Where Lamm has re-installed the connection between the PCB audio circuit ground and the chassis, place a 10- to 100-ohm resistor, or I use Ralph's alternative suggestion, "back to back" high current diodes.  To do the latter, you may need to do some additional reading; it's not quite as simple as it sounds. But what is simple is the resistor trick.