Affordable Grounding

I don’t know what the wooden tube does, but I concur with @bolivarjoy, I had a dedicated line from the panel with true earth ground rod and hospital grade pure copper AC outlets installed. Digital source, 20 wpc 300b/845 SET tube amp and high sensitivity Klipsch Forte speakers.  The dedicated line dropped the noise floor to the floor! Also powers the router, dedicated switch box, and LP supplies.

I could always hear transformer hum through the speakers in between tracks or with quiet passages.  Tried DC filters, USB filters, lower gain signal tubes, and even minus 10dB attenuation, still hum.  Worse some days than others, quietist late at night. Once the dedicated line installed, transformer hum virtually gone, I no longer can hear from seat.
 

Second best upgrade was a DDC between a fanless mini PC streaming source and the DAC, darker background, larger soundstage and way better stereo images. Together with dedicated line, I might actually be done…with this system anyway. Have four others I can tinker with. 

Lots of discussion of these devices, primarily DIY, here:

DIY Ground Box Thread

I haven't tried nor do I advocate these tweaks but if one were to do so, I'm guessing the improvement would be more substantial with one of these. A relative bargain compared to similar offerings from Nordost and Entreq at 10 to 20 times less cost.

Ground Box for Sale

A'gon user @mahgister has written here previously about devices such as this, IIRC.

Yes.  Best results(for me) was installing a ground rod just outside the wall, running CU cable through wall to my dedicated AC outlet(hospital Grade) ground connection,  then ALL AC power to my system plugged in to that receptacle.

Write Synergistic Research on it in crayon, charge $600 for it and whole-heartedly recommend at least 3 for best results, and the cable sniffers will follow you to the ends of the earth.