SUT Hum


I bought a Hashimoto HM3 SUT.
It has a ground connection, but when the ground cable from the turntable is connected to the SUT, there is an audible hum. However, when the ground cable is connected to the ground connection of the preamp, there is no hum.

Is it a common problem? I'm OK as long as the SUT does not generate hums. But I wonder whether it is due to faults in the SUT.
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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.
Have you tried connecting the ground cable from the table to the SUT, and then from the SUT to the preamp?
The point is to have a hum free SUT. Whether that is accomplished with or without a ground wire, or where that ground wire gets placed, doesn't matter.
What happens when you tie the ground of the SUT to the preamp While the phono ground is also at the same point? Still get the hum?
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.
Don't get this thread. Ground connected to preamp, NO hum. No problem.
I'm just say'n ✌️
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?

Yes- that is normal.
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.
Good to know that there is nothing wrong with the SUT.
Thanks.