OK, since everybody wants to pick apart everything I say: why doesn't someone answer his question?
I'm tired of the frustration of not being able to say ANYTHING without people nitpicking me apart.
You all win...
I won't be coming to TalkBass anymore because I don't need the grief...
The resistor and capacitor here are not an LC filter. The resistor and capacitor are in line from the signal to ground. Maybe I should have put quotes around the word "blocks." When the tone pot is at 250K Ohms it is effectively stopping the audible effect of the capacitor.
I think it's kind of big. With the .047uF you're at half volume at 600Hz and half of that at 1200Hz. With the .1uF you're at half volume at 400Hz and half that at 800Hz.
The last two samples here are .047uF and .1uF:
http://www.youtube.com/watch?v=3I62Xfhts9k
Since the resistor blocks the signal from getting to the cap, I don't think you would hear any difference.
Even if you could, you would be counteracting the changes since the 500K resistor would cut fewer highs and the .1uF cap would cut more highs.
Ever thought about upgrading your current bass?
New pickups and preamp (if it's active) should fix your lack of high frequencies and it would be cheaper.