Maybe the Journey is Over?........Well......

I used 4 of them at critical locations...Cheap chinese battery one and a USB one ...

As said above by baclagg they made a difference in the blooming of the sound making it more natural ...A better impression of depth is true impression indeed ...For the effect on digital glare i dont know but i believe it...I never had digital glare in my system before trying the S.G.but it makes the sound "aura" more natural for sure ...

I never read any real explanation why they work so well ...

My own explanation but i am no scientist, is that they introduce some dithering effect making clearer the noise/ signal/ratio... I put them near my gear ...

I experimented with cheap 10 bucks one, then i discovered that they dont need to be precisely spot on on the Schumann frequency...The cheap one are not precise and work well ... I deduced that they work more as a dithering effect tool than the precise magical 7.83 effect ... Any low hertz range frequency near 10 hertz will do and his harmonics as some dithering effect ...

But beware : dont experiment with that BEFORE your system is already  relatively  satisfying ... S.G. is not A SOLUTION ... The effect could even not be perceived on bad audio system ...It need some minimal quality synergy already in the system ... S. G. are cherries on a cake not the cake ...But if your system is already good they will make it shine ...

The same is true with ionization of the room ...very subtle but real ...it is cherries on a cake not acoustic or gear solutions ...

@baclagg

RE: replacing H390 with 590.

You don’t mention a DAC so I assume you’re using the 390’s on-board DAC, which is somewhat on the lean side.

I’m not familiar with your speakers. I also own an H390 and Jay’s CDT2MKII. Both my Silverline monitors and Aqua La Voce DAC are on the warm side and I had to swap out ICs and footers in order to tame what was, for me, too forward of a sound, in conjunction with the 390 and Jay’s.

Be aware that the H590 is both more resolving and more neutral than the 390. You might consider purchasing a 590 from a seller that offers a return policy, such as Listen Up! as moving up the Hegel line might prove "too much of a good thing", depending upon your taste.

Just my 2 cents...

BTW, I'd be very curious to know what you think of the QStab.   

@stuartk thank you for the advice on the 590. I will definitely get one to try out before I buy it. My 390 is giving me what I need for now.

The Qstab was a good addition. More bass response and the thing I notice more than anything is that piano notes have a more realistic tone to them. I love it!

@baclagg 

You're welcome.

Thanks for the feedback on the QStab. 

I have heard the same thing from others. 

Not sure it would be worth the expense, in my case. 

Your wife does know that you will never be done, right?