Don't know if you guys are interested, but uploaded a Swoopshare link to the infamous "Fatboy.wav" file. Hard to find anymore, and maybe less relevant now that the mp3 encoders are reduced to a few that are better quality than the ancient versions.
 
http://www.swoopshare.com/file/04d4499b803fbceb8b18fe626392d3cd/fatboy.wav.html
 
Fatboy is a wave file meant to destroy conversion to mp3. Sounds like a dumb ring modulated clip, but designed to test your mp3 settings to the breakdown limit.
 
Most are aware of the psychoacoustic model in mp3 translation dealing with selective frequency rejection from soft to loud. This where the encoder has the biggest problem dealing with processing the file without throwing in unwanted artifacts.
 
Fatboy modulates up and down enough to stress settings to crashing unwanted debris into the converted file.
 
Not perfect, since one size does not fit all conversion scenarios, but convert Fatboy to mp3 with your settings and do an A/B comparison.  If Fatboy.mp3 sounds like crap, your conversion settings are probably taking a hit as well.
 
John

Guys,
 
Please forgive if the link to Fatboy diverts to brainless crap hijacks. Mozilla redirects to some idiot shoe sale. IE seems to stay on track. Don't know what is happening to Swoopshare. Just trying to get the file to those who may want it.
 
John
 
(edit...)  Tried the link again, and we are progressing. Redirect is no longer shoe sales. Now it's toner cartriges.

codamedia
I've used sound forge for years - but it's a rather expensive solution for just making MP3's.
 
Learning the command line for lame is well worth it. I know the command line scares a lot of people (and many don't even know it exists) but it is very powerful. Also - I know this is taboo for many, but if you use iTunes you have a free converter right there.
 

Yeh. I would never have bought SF just as an MP3 converter but for the specific use I mentioned it's one of a small number of programs that will do the job perfectly. Of course it's an audio editor first which is why I have it.
As you mentioned also, iTunes is great for batch conversion of waves to mp3s. I know a lot of folks hate iTunes but I have it and QuickTime Pro installed on my daw and they've never caused any problems.

For years I used LAME setup via the external config route, but a while back I bought this Sonnox tool and found it perfect for everything I need, especially for adding the various MP3 tags:
http://www.sonnoxplugins.com/pub/plugins/products/codec/codectoolbox.html
Only £35.

Lots of good advice, tools for conversion. Downside to Sonnox may be the inability to update the mp3 encoder at will. But then again, on occasion still using Adobe Audition 1.5 Fraunhoffer as it recedes into the black hole of antiquity. Can't update nothing in Audition.  Still works well however, as long as 32 bits are supported.
 
Think that any more refinements to mp3 are on paper more than can be heard.
 
Good feedback that the Sonnox works well.
 
Tip on a really good free mp3 tag software. MP3tag. Does it all and the important ability to do less, as in blanking out brainless fields that only clutter the tag. Have used this for years.
 
http://www.mp3tag.de/en/
 
Another go to tool, which unfortunately doesn't work in win 8 and up. MP3 Gain. Think I keep XP alive just to use this. SoundForge down for a couple days, but here's a link:
 
http://sourceforge.net/projects/mp3gain/
 
This sets a volume level of the mp3 file without processing the file (mp3 to wav and back to mp3) and thus not degrading it any further. Does a great job with batch conversion.
 
My workflow has successfully been to render a project to stereo wave. Convert to mp3 with whatever LAME GUI container of choice.
 
Normalize to a constant level with MP3Gain. Edit the tag with MP3tag.
 
Finished product ready to send to all my millions of fans and groupies.
 
John