(I’m not sure how to type or use this forum, so bear 
with me)
File size before (a 6minute vinyl recording, 24.8 MB):
File size now (another 6-minute vinyl recording, 14.6 MB):
The highest “Sample Rate”, “Quality”, and experimenting with different "Bit Rate Mode"s.
(why can’t I show more links to be more descriptive? even just 2 more?)
To painstakingly type this out:
Export Audio
Format: MP3 Files (like before)
Sample Rate: 48000 Hz
Bit Rate Mode: Average (I’ve tried all of them, and they still resulted in 14 or 15 MB)
Quality: 320 kbps
The “Best” Quality Preference setting:
(another painstaking endeavor; my nerve-damaged right hand)
Sample Rate Converter: Best Quality (Slowest)
Dither: None
(on both options)
In short… it doesn’t sound as “full” as before (and the resulting file doesn’t sound the same as on Audacity itself, like it did before) . And it bothers me, as a music lover (and I’ve used MP3s both times).
Can you help me find out how I can bring back the previous quality? Thank you.
~Neo
Before and after what?
NONE OF THIS will explain a significant quality difference…
kbps is kilobits per second. There are 8-bits in a byte so divide by 8 and then multiply by 60 to get kilobytes per second.
Your 6-minute file should be about 14MB. But maybe one of the files has embedded artwork?
MP3 is lossy compression but 320kbps is the “best” MP3 setting and it’s generally very good, and often you can’t hear a difference between a good MP3 and the uncompressed original.
When you open an MP3 in Audacity (or any normal audio editor) it gets decompressed. If you re-export as MP3 you’re going through another generation of lossy compression and SOME “damage” accumulates. If possible you should compress ONCE as the last step.
Joint Stereo makes more efficient use of the bits than regular stereo so you can get smaller files (lower bitrates) or higher quality. The part that makes it joint stereo (L/R to M/S) and back is lossless.
One of your files is very-slightly louder than the other. If that’s the peak level, you can push the peaks up to 0dB, or near 0dB. (MP3 compression often boosts the peaks a bit, so you might want to normalize for -1dB peaks before exporting to MP3.)
Dither won’t be applied to MP3. And dither (or the lack of dither) isn’t audible under normal listening conditions anyway unless you’re making 8-bit files. It’s a very-minor mostly-theoretical thing. The “rule” is to dither when downsampling the bit-depth, but MP3 doesn’t have a bit depth.