If CD players do sound different, I want to know why.
So should we all. Manufacturers will manufacture their own reasons like this kind of oversampling, that kind of filter, an improved power supply, isolation, premium parts, lower jitter, the DAC game...you name it. Some of it are nothing more than technical improvements, some are things that sound like improvements but are cost-cutting, a lot is just hot air.
Chu Gai says (I think) when they are level-matched with precision, they sound the same (with the exceptions he noted).
I'm saying unless
you do that, you're confounding your evaluation with a variable that needn't be there. Small broad band discrepencies in volume amounting to a quarter dB or so are not readily recognizeable
as something that is louder or softer. Instead, people will say that player is more forward or recessed...clearer...soundstage...focussed. Think of a term.
This is an attractive theory, so the question I have is does it hold up when tested.
Try an experiment in your own home with some friends that don't know you're going to pull a fast one on them. Take your existing player and figure out using a VOM, what's 1/4 or 1/2 dB louder. Bring in the new CD player and fake hooking it up except for the power cord. Let your friends listen to the first player, then tell them you're going to have them listen to the second player but instead, adjust the settings so that the first player is playing 1/4 to 1/2 dB louder. Enlist their opinions.
If the argument is correct, that's all the explanation needed for why it's advocated.
It's advocated for the reasons given in my second comment above. I'm not saying there won't be a difference or that there can't be on. I'm saying unless you eliminate that one important variable that exists, you'll never know if the difference you heard was due to a minute, or not so minute, overall level difference. That's all. If there is no difference when level matched, you can use whatever criteria that's important to you to select the player. It doesn't mean you have to buy the cheapest one. OTOH, if you're on a severely constrained budget, you can evaluate your budget selection to something way out of your price range. If there's no difference, you've saved money that can go to something more important. Like speakers.
I wonder what price point you'd want to hit if sound quality was your only consideration. Does anyone in the "reality-based community" have an idea?
Sound quality can and is a matter of personal preference with no general consensus. It can sometimes mean a piece having a euphonic character that's pleasing to you. Consider there are players and DAC's without reconstruction filters that to some sound spectacular. I'm of the opinion, that if a vendor plays by the rules (adherence to the Nyquist criteria) that you might find the differences are pretty damned small. So small that simply being scrupulously precise with level matching that it becomes very tough to tell one from another. Throw in blind testing and you might find you've got better odds at playing craps in Vegas.