Hum coming through speakers via Bat 300X

volume descrepancy is normal simply because your phonostage/cart combo gives larger input voltage vs. your CDp.
one way you maybe having a ground loop and need to isolate ground by using cheater plug. another way if that won't help, i'd try to get in touch with VK and possibly with seller that might've been aware of the existing problem...

Unplug your sources. Does the hum go away?

Then reconnect one source at a time and see when the hum starts up again. When it does, put a cheater plug on the PC coming from the offending source component and see if it goes away. Be sure to turn off the BAT each time you disconnect/reconnect any RCAs.

Thanks for the info, I will try this tonight when I get home. One question, why do i need to turn off the Bat every time I disconnect/reconnect??

"Thanks for the info, I will try this tonight when I get home. One question, why do i need to turn off the Bat every time I disconnect/reconnect??"

Do it every time and with your other components, as well. Its good practice. Most of the time you can get away without powering down, but why take a chance.

If you disconnect (or connect) a component to your amp while the amp is on you can cause a 'pop' which could blow out a driver, usually a tweeter, in your speakers. This is especially true with an amp to pre-amp connection with separates (which you do not have).

Now if you want to risk this happening connecting/disconnecting source components you can, just turn the input selector to an unused input, not the one you are going to connect, then turn the component on. Minimal risk I think, but do not connect it if the source component is turned on and connected to the imput you plan to use for it.

FWIW making changes and not turning off the power amp once cost me the woofers and crossovers in an expensive set of speakers about 25 years ago. It hasn't happened since! :-)

Thanks again everyone for sharing, point well taken! POWER DOWN!!!!!!!!!

Problem solved! It was the CDP, installed cheater plug----dead quiet. All is right with the world again, almost. Thanks again everyone.

Your amp has a Volume Offset feature that lets you adjust the levels of each input individually so they have the same subjective playback volume at a given volume setting. Check your manual, it's a great feature and a great amp. I love mine.