The Sovtek 12AX7LPS is a Large Plate ? Spiral Filiment 12AX7 tube. This is the best offering from Sovtek yet. It is used by Mesa Boogie and is also used by many other smaller manufacturers. The spiral filament reduces hum in AC filament amps - while the larger plates allow for a more linear response. This is one of the finest modern production 12AX7 being made today.