I have heard so many good things about the Sovtek 12AX7LPS, but locally only the 12AX7LP is available. There should be no difference in sound only that the LP might hum in some amps. This is from Sovteks website: 12AX7LP $14.30 Great for DC on filaments. Used by VHT. 12AX7LPS $15.50 "S" Spiral filament for no hum with AC heaters. Used by Mesa Boogie And this is from tubeman.com: ...Please note, we currently don't have the LPS version with spiral filament for hum suppression in amps with AC filament supply, however in the vast majority of amps even with AC supply, the LP version will not hum. Will the LP-version hum in my amp?