I have a question.
I ripped a mono CD to my pc (it was dual mono of course, because of the redbook standard).
With an audio editor I then removed one of the channels and saved a single channel mono wav file.
I now want to convert that single channel mono wav file to mp3 to the highest quality possible.
If I use 320 cbr, all the 320 kbps would be used for that only channel right?
It would be like the equivalent in terms of quality of a "640 kbps mp3 stereo file right?

Thanks in advance.

As an easier alternative, you could have taken the mono-rip and encoded directly to MP3. Joint stereo is the default with pretty much every preset.

http://wiki.hydrogenaudio.org/index.php?title=Joint_stereo

That was a lot of work for what will be essentially no tangible benefit, since Lame's use of joint stereo will pretty much accomplish the same thing by simply feeding it the file as ripped from the CD.

The answer to the first question is yes.

The answer to the second question is that it would be comparable to a 640 kbps mp3 stereo file if you had encoded the source in dual channel mode (provided there was such a bitrate, excluding the free format option). Looking at it another way, you will probably not be able to distinguish a mono file encoded at 160 kbps (or even -V0) from one encoded at 320 kbps. In the case of a killer sample, I would wager that the extra bits wouldn't provide much improvement.

Nope!

With Joint Stereo the MP3 encoder knows that you have redundant information and this is all taken into account. You'll get essentially the same results with encoding your dual mono file to joint stereo as with encoding mono-to-mono. (I'd actually prefer the true-mono MP3 because it will be properly identified as mono, whereas the joint stereo file will show-up as stereo.)

When you encode a true-stereo file with joint stereo, the redundant information is also taken into account. This means that you don't need twice the bitrate for the quality a stereo file to equal that of a mono file. (If you had a special case such as an English language soundtrack on the left channel and a French language soundtrack on the right, then there would be no redundant information and joint stereo would not be an advantage.)

And at these high bitrates, there would be no audio quality difference between 320 and 640kbps anyway. Both would sound identical, and with most files they would both sound identical to the uncompressed original...