Entreq is not very public about how their boxes are designed except that they contain various types of metals and minerals. The article in hifiplus describes very well what I mean, and I respect the CAD company as a very serious player in the hifi business. CAD and Entreq are doing very similar products, and both have upgraded their lines in recent years. CAD certainly looks better, but I cant say which is the superior.
Connecting the ground pin in a wall outlet to a gounding box is probably similar to gounding the chassis of an amplifier. They are both part of the safety ground. But I dont mix safety ground and signal ground (e.g. the negative poles of the power amplifier) in one gounding box. I dont think that is advisable. I use both signal grounding and safety ground grounding (if you can put it that way) in my system. Signal grounding gives the best result, no question.
CAD and Entreq have different philosophies when it comes to signal grounding. CAD does not recommend gounding the loudspeaker negative poles of the amplifier. Entreq do recommend this. CAD prefers signal gounding at the sources (XLR, USB etc). Entreq also recommend gounding the sources along with the amplifiers negative speaker poles.
I have tried both and I think signal grounding the amplier gives a better result than signal grounding at the sources. Groundíng both amplifier and sources is probably the best. I havent done that -- I dont have enough boxes.
But I understand the CAD position -- gounding the amplifiers speaker connectors can be hazardous. In my opinion you need two separate gounding boxes -- one for each negative pole. Some amplifier can possibly be connected to the same box on both negative poles, but its hard to know what applies to a specific amplifier. Using two boxes should be safe.
This begs the question where it noise is coming from and which component is the most sensitive to high frequency noise. Noise on the live and neutral lines of the power cables is definitely detrimental. In my experience it reduces the speakers bandwidth --both bass and high frequency of the music. This can be dealt with if you have a power filter like Gigawatt.
Signal grounding has a similar effect -- it expands the bass -- but above all I get a lot more dynamics -- especialy microdynamics with signal grounding. This translates into a lot more space and natural sounding voices in the music.
Grounding the safety ground seems to lower the noise level -- I dont hear much changes in the nature of the sound.
So which component is the most sensitive? Im not sure, but I think the loudspeaker is a good candidate. As to the worse source of noise I think the power line is the worse offender. Regular power lines are perfect antennas in a completely toxic high frequency environment. Measurements in Stockholm have disclosed dangerous levels of 5G microwaves in the city center and with the new WiFi7 opening up new 6GHz bands it will only get worse.
