I might be opening up Pandora's box here, but here goes:
this relates to high res music files. If you rip a CD to your computer, that music signal is a 16 bit, 44.1kHz signal. Modern music recording is usually done in a higher resolution these days. You can buy high-res music from websites on the internet like HDtracks. The bit depth is how much music information the DAC "eats" at a time, 24 bits is more info than 16. The kHz rating is how many times per second the analog signal is sampled to convert it to a digital signal. 44.1kHz, or 44,100 times per second, came about because of a scientific reason that escapes me currently, but it is twice the highest limit of human hearing, which is supposedly around 22,000kHz. I sure as hell cannot hear sounds that high, but OK, whatever the scientists say.
It is the sampling frequency that is getting buzz right now, almost all high-res music files are 24 bit, but you will see multiples of both 44.1 and 48 in the sampling specifications on high res music files, which read like this: 24/48, 24/96, 24/192, and the less common 24/44.1, 24/88.2, and 24/176.4. Most modern DACs re-hash incoming digital signals to 24/96 or 24/192, which means every digital audio signal fed to the DAC gets "upsampled," a controversial process that is supposed to push high-frequency artifacts beyond the spectrum of human hearing. But not all DACs that can accept a 24/192 signal coming in. To send this signal, you would have to play the 24/192 music file from your computer.
How does all this relate to the Denon/Onkyo debate? The Onkyo will upconvert to 24/192, the Denon will only upconvert to 24/96. The Onkyo *should* accept 24/192 high res music signals thru its digital inputs, the Denon will not.
Can you hear a difference between 24/96 and 24/192 upsampling? Some people can. Some can't. Some people use DACs that don't upconvert at all. Some people don't care, and just love music!!!
