New expensive power cord for amp and no change in sound?

westcoast, I think I got you confused with another poster. So my somewhat aggressive stanch may have been directed at another person on this thread. Keep this in mind if you respond. 

I have 2 highly regarded power cords right now. They are both around 10ish years old. New equivalent models would be in the 4K range. Cord one causes a loud hum hooked up to tube integrated. Cord 2 everything is dead quiet. Neither made noise on another amp I had them hooked up to. Strange. 

Most likely some sort of grounding issue. A thing you can try is get a 3 prong to 2 prong cheap adaptor which will remove the grounding pin at the wall outlet to see if this changes things. This is just to identify the problem this is not a permanent solution. FWIW.

@roxy1927,I too have a Pass 250.8 and an ARC REF 6 pre.  Switching from the stock ARC power cord to a Shunyata Alpha v2 yielded a definitely noticeable improvement in the sound.  On the other hand, I first replaced my Pass stock power cord with an Audience Power Chord that I had.  There was a definite improvement in the tightness of the bass, audible but not amazing.  Then I replaced the Audience with another Shunyata Alpha v.2 and really didn’t notice any improvement,  So I think that it depends on whether you are replacing a stock cable and where in the system you place it.

I have noticed the most improvement on digital devices using better power cords. Noticed this primarily on friend's systems who have invested more in digital than I have in my systems. In fact one of the cables used in these comparisons was about a $ 3,000.00 Shunyata. Bettered the cord I brought over by a healthy margin. Of course my cord retailed for about $ 750.00 and I got it at dealer cost.