Soundcheck / normalising plugins?

[peanutismint]

I'm using my RockBox iPod in work to provide in-store music, but keep having to alter the volume on our amplifier as all of my single MP3s are different volumes.  I know RockBox supports ReplayGain, but I have yet to find a free Mac program which will allow me to analyse and write replaygain info to my files.

Are there any plugins for Rockbox which will perform the task of keeping the output volume at a normal level?

[nls]

no such plugin exits and as you note this is exactly what replaygain was designed for...

a google for "mac mp3gain" gives this link
http://homepage.mac.com/beryrinaldo/AudioTron/MacMP3Gain/
it does however modify the files (just like the regular mp3gain) and doesn't use the tags.

[Lear]

Play supports tag-based ReplayGain. I think it even writes tags as Rockbox wants them.

[peanutismint]

Genius! Will give both a try.  It would appear I didn't Googlesearch very hard, but I promise I did! :-D

[Zardoz]

seeing as its for a workplace, you could use a pre-amp or microphone pre-amp to normalize the outputs to the (power amp/amp before the) speakers, and just have them in place and forget about settings on your (rockboxed of course!) player.
As in use a dedicated piece of hardware to do it for you. Do you have to pay royalties on what you play in store? We do here...