Originally Posted by anoutsos
So, does this imply that I can make an cheap DAC/amp combination sound better than a state-of-the-art one just by turning up the volume on the cheap one by a fraction of a dB? If this is true, it could save a lot of people a lot of money. However, I thought that high-quality DACs/amps should sound better than cheap ones regardless of volume.
It depends. With a properly made DAC, it should sound as good as it is possible for it to sound. Or, in other words, no human will hear any improvement with a "better" one, when the two are properly level matched and one listens "blind" (there is also the aspect of human bias, which affects all sorts of things besides audio; for example, studies have shown that when someone believes that a wine is expensive, it tastes better to them than when they believe it is cheap, even when they are given the exact same wine).
In the case of well-made modern amplifiers, with them sounding the same when operated within their design parameters, that still does not mean that there is no reason to pick one over the other. For one thing, the design parameters are often different, with one being more suitable for a wider range of speaker impedances, one may be capable of putting out vastly more power, etc. Plus there are unexciting things, like reliability, as some brands have gotten too sloppy in their manufacturing and sometimes make a receiver that is unreliable (which should never happen these days, given the state of knowledge of how to make such things, and how reliable these things can be). But, of course, companies want to maximize profits, so they like to make the things as cheaply as possible.
In my case, I have some nominally 3 ohm Apogee ribbon speakers, and so (when I first got them) I decided to buy an amplifier rated for such a low impedance, instead of just using what I had that was rated for 4 ohms minimum. I might have been able to get away with using what I had (I think I probably could have), but I do sometimes listen at fairly high volumes for extended periods of time, and I did not want my amplifier to go up in a puff of smoke (possibly also destroying the speakers in the process). It may have been okay, but I did not want to take the chance, and so I purchased a more capable amplifier. At least at low volume, I noticed no difference in sound whatsoever. Of course, I did not buy the amplifier to improve the sound; I bought it to prevent damage from using an amplifier in a manner not consistent with the warnings on the back. Since I could afford buying a better amplifier (though I saved a lot of money by buying it used), I figure it is better to be safe than sorry, as the trite old saying goes.
So when one pays attention to the science of what is going on, one still often has reason to not buy the cheapest piece of equipment one can find. (In fact, the science will tell you not to, when one finds things that are very cheap that measure very badly.)
You might be interested in the discussion in this thread:
It is long, but it should help with your questions.