I have some mixes on a podcast site with 500MB of free space. To fit all my mixes on it, I need to convert them to 48kbps. However, various configurations sound terrible to me: 44kHz Joint Stereo, 24kHz Mono, etc. Any suggestions?

96kb/s on 44.1khz stereo would be on average the best quality converter depending on what rate you play back. If for instance your playback rate is higher,. then so should your converted rate be, if how ever your rate is lower, to be able to hear the quality recording, keepp the rate s high as possible. Playback on the lower rates sounds terrible on air.

I don't understand what you mean by playback rate. All configurations are 48kbps. My question is about the best SAMPLE RATE and MODE. 44kHz Joint Stereo has a shimmering underwater distortion.

Are these mixes already lossy?
If so then no setting is best; try a few and pick the least crappy sound.

The newest are made in Mixmeister Fusion and I "Export to File", select 48kbps, and it defaults to 24kHz Mono, which sounds muddy. The older ones were made in Mixmeister Pro 6, and I earlier did an "Export to File", selecting WAV. The WAV files I convert using Media Coder, selecting LAME 44kHz Joint Stereo, but it has a shimmering underwater sound. Media Coder seems like a sophisticated free product, but it has such a vast array of options, I don't know where to start.

In my opinion, any file that is something other that straight voice under 96k or even 64k just isn't going to sound that great saved as an MP3. AAC+ files are good, but you can still tell that they're not as crisp/clean.

I got my podcast host to enable AAC+, and the mixes are now showing in the iTunes store. I am going to output from Mixmeister Fusion to WAV, then convert to 48kbps AAC+. Is it correct to assume this is better than outputting to 320kbps mp3 instead of WAV? What is the preferred intermediate step?

Going the WAV first I guess would be "best" for what it's worth.

As I do my vinyl in Adobe Audition 3 these days, I find that it helps to keep my initial WAV rip - clicks, pops, hiss, crackle and all - and work from a copy of it to make whatever I'm going to use on the station (usually 320/44 mp3.) Same is true for recent CD rips. That way if I need to redo something I have a good raw starting point, sort of like photographers used to keep their negatives in a cool, dry place.

With the price of media storage these days, it may be time to just start playing directly from processed WAV files.

Them WAVs still ain't filled up my 1.6TB DriveZilla