Originally Posted by Mikesculpt
Though I've been researching for a while I really don't have a background for this. Playing an audio CD through my Sony Bluray into an Integra 40.3 and Goldenear Triton II's sounds fantastic.
Hooking up my iPod via aux cable to the Integra sounds notably worse.
Your Bluray probably puts out a signal that is about twice or more that coming out of the iPod. A stand-alone home audio optical disc player usually puts out 2-2.5 volts peak. An ipod is usually limited to about 1 volt.
Peak signal voltage differences are usually thought to be different than inherent sound quality differences. If you want to to a fair comparison, you'd first make them the same.
Also, the production that goes into downloads from wherever varies. It is possible for iTunes downloads to have excellent sound quality, but when you start comparing specific files, they are what they are.
But if I use a Toslink from my mac, iTunes downloads sound as clear as the CD in A/B testing by my ears.
That may go a long way to equalizing signal levels. Or not. Apparently it does.
My understanding is that when you use the digital out from the mac you bypass the cheap internal DAC and use the one (Burr Brown) from the receiver.
The converters in Macs are supposed to be pretty good. The ones in iPods are supposed to be pretty good. I wouldn't expect any of them to be significantly better sounding than any of the rest in a good, fair test.
However using the "garbage in, garbage out" methodology, how can a 256k (at best) download sound like 16 bit audio?
The answer is that 256k does not represent enough lossy compression to cause night-and-day signal quality losses, if you actually do a fair comparison. This is especially true if we are talking AAC, but a well-made 256k or 320k MP3 can work a treat.
Can the DAC really be that good?
Even fairly inexpensive but good DACs can be undetectable in comparisons with a straight piece of wire. Most of what you read from audiophiles and journalists saying otherwise is based on poorly-done listening tests.
Most people are pretty mind blown about what they hear sounding like other things they dispise in well-run listening tests. A lot of current public wisdom about DAC SQ traces back to the bad old days in the early 1980s.