Does the Phillips MP3 player have a "line-out" jack? Since you didn't mention it, I doubt it does. But if it has one, try that instead of the headphone jack. It should help.
If not, the headphone amp idea is valid. Several years ago, I had a problem with an XM Radio's line-out not being loud enough in a vehicle. I'd have to crank it up to hear it, and then I'd invariably forget to turn the volume back down before switching sources. I'd end up blowing out my eardrums with FM/AM/CD. So, I bought a
Boostaroo at the local Radio Shack. It solved the problem quite nicely. It boosted the gain enough so that the XM's volume was very close to the "built-in" sources. I couldn't detect any impact to sound quality - but that was XM Radio. And since it's from Radio Shack, it's easy to return if it doesn't work out.
If I could remember where it was, I'd offer to just send it to you as I don't use it any more...
Good luck!
