Need to increase playback level

I am transcribing courtroom recordings with volume too low, even with sliders at maximum in TheRecord Player. My primary computer is Mac OS X.

My previous technique was to save the recordings as .wma, convert to MP3, open with Adobe Soundbooth on Mac, apply an effect to raise level, save back as MP3, then open with TheRecord Player.

Now I have Adobe Audition CS6, and when I do the same thing the MP3 file generates an error on attempt to open with TheRecord Player.

Any suggestions?

I can share enhanced MP3 file by Dropbox if helpful.

Update: Never mind. Got it to work.

Copied .wma to Mac, edited with Audition, saved as MP3 on Mac, copied file back to Windows, opened with TheRecord Player as expected.