Vocal Stripping is extremely difficult to achieve. All musical instruments produce sounds that vary in frequency. Vocals do too. How can you distinguish between the vocal sound at 600-900Hz and an instrument thats range covers 400Hz to 1kHz. You can't do it.
So you can EQ out the frequencies that the vocal covers. If you EQ that range out totally (ie. what you want - totally no vocals') you also EQ out instruments leaving a horrid gaping hole in your music.
So you got a choice. Little bit of vocal or big gaping hole.
Hope this helps.