I did a mixing session for a video for Molly Lewis recently, and since we were taping for a video, at the request of the video guy, we recorded all the audio tracks at 48khz because that's what his video editor software expects to receive.

We mixed everything in Logic Pro X for the Mac, which has an option to bounce down the final mix to MP3. So I did so, and slapped that MP3 onto my Empeg Car Mark 2, to preview the mix during my commute. To my horror, it sounded distorted all the way through. It was faint and subtle distortion, but definitely audible, especially around the high notes in the lead vocal.

Oddly, the MP3 sounded fine when I played it back on any other gear such as other computers and such. No distortion. Later I looked more closely, and WinAmp's "file properties" box tells me that the MP3 was encoded at a 48khz sample rate: Logic didn't even offer us an option to convert the sample rate to 44.1khz, so it just did a straight 1:1 encode.

Remembering that the Empeg uses a DAC originally designed for car CD players, I'll bet that the DAC is hard-wired to accept only 44.1khz input, am I correct? I'm convinced that the 48khz sample rate of the MP3 is the culprit, and the reason I heard the distortion. The type of distortion I heard was consistent with what a playback engine would sound like when it did a poor conversion from 48 to 44.1 (i.e., it sounded like a direct "just drop the samples you don't need" conversion, without any noise shaping or dithering algorithm).

I want to convince my friend who is on the Logic Pro X team at Apple, that the lack of samplerate conversion options on their MP3 bouncedown feature is a bug. To do this, I will need to know that the Empeg Car is not the only hardware MP3 player that doesn't play 48khz MP3s well. And it occurs to me that the people who would know this would be the Empeg/Rio hardware guys, folks like Hugo and Patrick.

So my questions to you guys are:
- Is it true that the Empeg won't play 48khz MP3 files well, resulting in distorted playback?
- Is it true that the issue is that the DAC is a CD-player DAC which can only accept 44.1khz properly?
- Does anyone know of any other hardware-based MP3 players that will have the same problem?
- Can anyone think of other situations where a 48khz MP3 file will play back poorly on other kinds of equipment?

Thanks!