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

Imagine power supply that works like this. You charge big battery from mains, disconnect it and then use to power your amp with clean DC, disconnected from mains. No noise from electrical lines.

So ideal power supply should work exactly like this, rejecting noise and interference. Amp schematics and parts placement may be more or less sensitive to what comes from the AC mains.

Different amps have different designs and different power supplies. Thus some are more sensitive to power cables and some less. Perhaps yours is in the “less” category.

You said “Yes my amp is a stereo Pass 250.8 and the manufacturer said don’t bother”

So, Nelson Pass then properly designed the amp and its power supply. I am not surprised you don’t hear any differences. Why not listen to one of the best engineers?

I own Pass phono stage, headphone amp. Used to own several power amps, starting from Aleph. I use fairly simple cables, properly shielded, soldered and have sufficient capability to deliver appropriate current without picking up additional RF interference. In $100 price range.

I generally think “what would be used in a fighter plane electric power delivery system”…

@rodman99999 - this is exactly what I mean. There is little critical audio listening in the fighter plane, but i am sure quality cables are selected to deliver power in environment full of RF interference and when performance may literally mean life or death. They would perform well in a less hostile conditions :-)

@rodman99999 My ed is in applied math, signal processing and hobby is DYI audio. I don't specialize in avionics, it is just I tend to look up what is used in real advanced cases. Just to be sure there is no Barnum... I've seen "big box" fancy looking gear, but when opened it was basically empty inside with 3"x3" poorly soldered board and unshielded power supply. But it costed $$$. So I always check the engineering side.

There is a list of MILSPEC cables that list material, shielding, etc. So it is handy to check if that exotic metals cable wrapped in Japanese silk is truly necessary :-) 

@squared80 this is not entirely true. First, often supplied power cables are poor quality. Cost cutting. Pass cables are pretty good actually, properly designed. Hospitals use medical grade connectors - so they care about better power connection, right?

There is indeed a LOT of snake oil. But there are also poorly designed power supplies…

Nelson has an excellent writing on how much Class A amp must weigh. And if weigh less, you are getting scammed. Because amo must have proper power transformers and headsinks and they weigh a lot.