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

OP should have listened to the Pass Labs engineers.

Yes my amp is a stereo Pass 250.8 and the manufacturer said don’t bother. I originally had a $500 going into the Pass and replaced it with the expensive cord

@immatthewj 

Thanks for noticing.

I stand corrected.

Nope!!!!  Never happened to me.  Over the years, every single time I've changed or upgraded a power cable, whether it be for an amp or any other component, I always heard some kind of change in their sound.  Sometime the change in sound was subtle, and sometime it was more pronounced.   

davetheoilguy  and    jpwarren58 :   Completely avoiding the issue of value and the ability to discern any differences between a stock cord and an upscale one  - I applaud your efforts to focus on what can make a difference vs. whether that difference is worth the cost and can be heard by the system owner on their system. EVERY cord and component will be affected by its interaction with the surrounding environment and every element in the signal chain - including relative positioning. 

Both Cables and tube grids are excellent antennae, and grids, like styli and tone arms, are wonderful emitters/receptors of microphonics as well.  Although every system will vary, the length, shielding and relative positioning of each system element will have an impact on the final sound quality to a greater or lesser degree.  In a crowded server room, ethernet cables are almost always as short as possible and well shielded for a good reason. The same should apply to any situation where there is a signal quality concern.  How much induced noise is tolerable depends on the system components and what is necessary to achieve the desired result - be it good sound or good data.  

My only suggestion is to optimize what each user has first, then look at what might make the most obvious improvement.  E.G. - when swapping out a cable, is it the same length?  An extra foot or so of wire will make minimal difference on ANY given cable, but what you do with that extra foot may make a lot of difference.  Is it now closer to another cable, cross one at a different angle, get routed on a different path, get coiled up at all, or sit nearer or further away from a component?  This will significantly affect coupling between various elements, and for folks who feel that putting their cables on a riser to minimize coupling to the materials in the floor, being closer or further from a massive transformer in some devices' power supply may be what makes a significant difference, and whether the change in location or the change in cable shielding made the most difference can be tough to quantify.  

Bottom line - experiment freely with what you have now and optimize that.  THEN go out and search for whatever tweaks you wish to indulge yourself with, thus giving those new goodies the best possible baseline to start from.  

Most folks on this forum know it may be sub-optimal to sit your turntable on top of one of your speakers, but how many will search for room and component resonances with a test tone sweep, a good mic and their headphones (or a persistent-trace 'scope) to find the several places that are the worst, but perhaps not obviously bad locations for that turntable?  Is this a tweak?  Certainly. But the results may be just as obvious and avoidable as having a power cord that would best be routed around the other side of the equipment rack.  No two systems / listening rooms will ever be the same, and the same applies to sets of ears.  The optimal result is what pleases you most within the time and cost budget you have at the moment.                   Then, as always, take time to enjoy the music! 

You're one of the few who are not dealing with expectation bias and realize there is no objective difference between power cables and I applaud you.

@roadcykler  , if you read the OP, he states that he did hear a difference when he replaced the power cord on his preamp.

What I am interested in is whether he heard a difference when he replaced his OEM power cord with the $500 power cord.