Grail? Far from it. Mine are Synergistic Master Coupler, Designer's Ref .5, and Shunyata Cobra. All are early 90's and easily the furthest behind of anything in my system. I do have one DIY someone sent me to evaluate and it is in the same league, in some ways at least, as the Cobra. This confirms there's easily lots of ones out there that would be a huge improvement. Which if you heard my system, to think there could be huge improvement let alone from a power cord....
No doubt there are many fine ones out there to choose from. The mere fact a DIY is even close, well what is professional anyway but DIY done right? The difference is nuance and detail where the best ones get the most balanced sound. The vast majority get sold because they caught someone's interest. This is just like speakers or anything else where the magic formula is to wow you just enough to pull the trigger and hopefully not get sick of the hyped up wow factor for at least a few months. Because by then you forget it was the hype that you loved that you now hate, enough time has gone by to convince yourself its just time for something newer/better. The very definition of the upgrade hamster wheel, but it pays the bills.
That's why I recommend Synergistic. Not because I'm a shill. This is the insult of a lazy mind. Not because it is the best. I have no freaking idea what is the best. Maybe if someone would send them all to me and pay me full time I might be able to figure it out in a year or three.
Instead I guess what I am saying, there are bigger fish to fry. You can spend untold hours and dollars chasing to find what everyone else somehow missed (not bloody likely!) or you can go with what is known to work, and work well. Not as exciting, but it is the safe play. The smart money's on Ted.
