Noise coming through speaker changes when plugged into the wall

[Holmz]

thanks can there be a ground issue with the power cord that interacts with the tube amp? There are three brand new power cords I am testing so I doubt all three have a problem but they are all causing the same noise. Very strange indeed. jh

Well - it could be the amp.

But at this point the high-$ cord is the worst performer.

 

[EERecordist]

In radio a tuner is a downconverter. The simplest radio receiver was a crystal radio. So inside any electronic device that is not properly designed, a transistor can downconvert RF to audible. It is possible for poor/corroded physical connections to act as a downconverter.

Interference heard in the tweeter if likely due to switching power supplies or RF downconversion. Heard in the woofer, it is more likely to be improper power supply filters or bypass capacitors, a design problem; or ground loops.

 

[Extreme_Boky]

Hi I did a search and could not find what I was looking for. I don't understand how this happens so any help appreciated.
System is tube power amplifier and Grimm MU2 player and Devore O/96 10ohm speakers.

Amp and Grimm plugged directly into wall generic power cord = least noise heard from tweeter of speaker
amp and Grimm plugged directly into wall with Audioquest power cord = audible hum
amp and Grimm plugged into panamax power strip/protector = less audible hum but more than directly into the wall.

confused as to how the audioquest power cord would cause a significant hum and why the panamax power strip would cause a hum?

Any thoughts greatly appreciated
jh

Variable-speed drives... do a bit of research on those and you'll arrive at the answer.