My tube EQ also has ground loop hum like low frequency noise from the beginning & it’s so obvious. While guitar sound is sustaining, may be no noise or I can’t feel the noise but as soon as guitar sound stop, the noise coming out. It’s from Frequency knob. Noise going to be almost unnoticeable if I turned the knob more than 12 noon. Noise get so obvious as I turn the Frequency knob to before noon (sound gets bassy). No noise at all when it’s bypassed. I use same AC power source for my mixer, amp & this tube EQ.

Live music with noisy venues may be OK but I can’t use this device for professional recording studio or Theater music in the pit situation which often require us to be dead quiet while actors playing without music.

I like this EQ but it’s yet consumer product level, not a professional one.

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P.S.:
I found a following trick & noise problem got much better after a few try, but still silent hum noise exist though.

< The problem is, that the tubes are not shielded against the electromagnetic interference of the tubes.
So I opened the pedal, took a piece of self adhesive aluminium foil, and placed it between the power supply jack and the tubes. Make sure that the foil is not touching the wires so it can’t conduct (use another layer of paper, to be sure). And that’s it, all noise is gone.

As this hiss/hum seems to be a general issue with the Tube EQ, I can’t understand how EHX does not fix this bug in future pedals.

Now I am totally happy with my Tube EQ, no noise/his/hum anymore. It’s an amazing pedal that does sooooo much to your guitar’s tone. I never expected that would make such a big difference.

Hope that helps:)