No. I don't think so. I think you just create a ground loop. My tables and preamps work the same way: some on, some off.
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Thanks for all response.
I connected the ground cable from the turntable to SUT and a wire from the SUT to the phono preamp.
Then, most of the hums were gone. The level of hum was further reduced compared to the ground cable connected to the phono preamp or the preamp.
Is it normal?
Previously I had a cinemag SUT and I only connected the ground cable from the turntable to the SUT, and the hum level was very low.
Yes - this suggests that in your SUT the chassis is not grounded unless you connect a wire to the preamp from the earth post of the SUT. If the SUT chassis is not grounded then all the soldered connections inside are unshielded and prone to RF and this is why the noise reduces further when you connect the SUT ground to the preamp.