Hi! cascadesphil...
The shungite tile, I created and named "golden plate", must be used properly, with the copper tape on the external side, to polarize the effect, and with some other stones, like Herkimer diamond, and tourmaline, to balance the effect...
If not used optimally even a degradation of sound is possible ( a compressed dynamic or imaging for example)... The most interesting utilization are :
On the exterior electrical meter of the house
On the central breakers panel of the house
On the peripheral breaker panel of the room
Behind the speakers
On unused wall plugs
On some interconnections ( not all of them) determined by listening experiments
On the computer router or modem
On some of the computer connectors (hard drive, optical convertor etc)
On the power conditioner
(Using a golden plate on a dac, like did this friend of cascadesphil is not an ideal utilization and certainly not the first one move I recommend at all and the same for an amplifier, speakers is best to begins with the basic audio gear...)
But one of the most astounding was coupling the Golden plate +tourmaline or H.D. on a schumann generator, that act like an enhancement filter for the room acoustic...
With all this area covered, no upgrade seems interesting for me anymore... Less than this impression is sign that the golden plates were not used optimally...
My best to you cascadesphil and to all...