Volume settings on the Rio carbon
I'm afraid that there is not. What headphones are you using? I have found that when many people ask questions like that it is the headphones and not the player. People say that when using the 3.04 firmware (look in tips and tricks for this player), the volume is higher but I haven't noticed a difference personally.. When I put my Rio up to highest volume it would damage my hearing if I could put it up any higher and I can only hear people shouting when it is on full volume. Have you got another pair of headphones/earphones to try? You could buy some high ambient noise reduction earphones and this may help.
Hope this helps,