philipf22

I've waited a while to finally test this. I have a set of RCA cables that were put in with the stereo and run into the cabin. I use an adapter from RCA to standard headphone size to my Zen Micro MP3 player.

the good news is it works. The bad news is that the quality isn't as good as I'd thought it would be, specifically the volume. When I have a CD in I can barely put the volume past 18. With the MP3 player attached through Aux, I can go well into the mid 20's before the volume comes up to what on a cd would be a 10 on the volume control.

I tried varying volume settings on the mp3 player going all the way up. The volume on the MP3 does adjust but even at max, is nowhere near the volume of when a CD is in.

Is this normal? It seems like I might need an Aux gain control (which I couldn't find)

Neutered Sputniks

It has to do with the output of the mp3 player.

Because it's only designed to interface with headphones (which don't really need much volume), the volume doesn't get as loud and the quality is going to be severely lacking.

Headphones are right next to the ears, and they force a wide soundstage because of the physics involved with their placement in relation to the ears. This allows mp3 players to use lower quality replay in order to save battery/space. Unfortunately, nothing you can do will bring that 32-64kbps output back up even relatively close to CD quality (close to 1mbps)...

That's the main reason I went back to using CDs in my vehicles... Even mp3s burned to CD don't match the sound quality. The very function of the mp3 file format is to remove sounds that are mathematically calculated to not be 'noticed' in order to make a smaller file. However, with a high quality system, it is indeed noticeable. A full 8-9/10 of the sound data is lost when a .wav is converted to a .mp3

SheDrivesIt

Or maybe just turn the volume control higher on the Alpine. What difference does it make unless you get in to a lot of hiss from the Zune's output stage?

Neutered Sputniks

Problem isn't just a lack of volume. It's a very narrow sound stage...think...tunnel sound without an echo

SheDrivesIt

That should just be a matter of crappy MP3's. Most people are worried more about small size than sound quality.

philipf22

it is more than just the mp3. the same mp3 plays great from cd, not so great from the mp3 player. I really didn't push tuner too high. I'm not pushing my components with it anyhow. But I fear this may be as good as it gets.

SheDrivesIt

Well, then if the same MP3 sounds ok from CD, it is either a gain problem or a crappy output stage on the Zune. Remember, the volume knob has nothing to do with how much power is delivered to your speakers, think of it as a valve that controls how much of the signal that you have is delivered to the fixed amplification stage.

Neutered Sputniks

Perhaps I didn't explain clearly enough:

Your mp3 player is processing the music through a 16bit processor. Your CD player will process the same mp3 through a 32/64bit processor. You lose a lot of sound quality due to the lack of processing (check out my first post where I already mentioned this). Additionally, the mp3 player doesn't have to worry about soundstage processing - the headphone on each side of your head forces the soundstage to be wide. However, when that same output is plugged into a set of speakers not directly attached to your head (so the sound from both speakers reaches both ears), the soundstage appears more narrow (and volume becomes affected as well because not as much volume is needed to make the headphones loud)...

If you think CD quality = mp3 quality, then why is the wav format so much larger? The mp3 is a compressed file - it becomes compressed by tossing out musical info that a computer determines is non-essential...that does affect sound quality.


But, hey, what would I, a guy on an internet forum, know about electronics and signal processing...

oth

if your major complaint is volume, the answer is that your average
headphone jack produces significantly less voltage than your average
aux in is expecting, my guess would be less than half.
an additional factor in sound quality is that most MP3 players have some
equalization built in, designed for the headphones, which may or may not
sound good through your speakers, in your car.

SheDrivesIt

Especially now days since they started limiting output level to protect against hearing loss lawsuits. The answer may be here or in a similar device:
http://www.logjamelectronics.com/soundavm2.html