Hi everybody !
I bought recently a cheap mpc on ebay. The mpc plays well but I want to 
add a bit volume on this. It looks like an Vandoren T20-T25 with a 
round chambre. The projection is ok, and the higher notes are good so 
too. The dark notes are correct and do not need to be better. On which 
charactéristic must I work ?
Thanks

PS : Just for information : I never did a job on any mpc before :-)

I would recommend you try making some temporary baffles first.  Use 
dental wax or poster hanging putty.  Use a pea-sized amount of putty to 
make a small baffle.  Start with a gentle arch shape that starts about 
7 mm from the tip and ends about 25 mm from the tip.  This will boost 
your sound without changing the tone a lot.

You can also get more volume by opening the tip.  This is much more 
difficult to do than adding a baffle.  First you need to get the proper 
measuring tools and learn how to use them.  There are several lists in 
the Files area of the Yahoo Mouthpiece Work Group site that will be 
helpful.  Some are lists of recommended tools, others are lists of 
steps you need to take to reface a mouthpiece.