of 60 Hz (adjustable). Thus, connected equipment was provided with a precise 117V, 60 Hz power signal (in the US, other countries had units for their specific voltage and frequency) lacking noise from the utility company. The P-300 provided, in theory, perfect noise free power of the same specifications that the power company should be providing. Various additional "waves" known as "multiwave" were also provided. The P-300 is a historically important product in high-end audio as it helped redefine and popularize the Power Conditioner product category and spawned imitation. This even though companies such as Accuphase followed with their own concept of power regeneration (though not additional waves, i.e., "multiwave" which PS audio claims provide additional benefits). More powerful models of the P-300 were introduced including the P600, P1000, P1200 and P1000. The P-500 and P-1000 provided up to 500 and 1000 watts of "clean" power to connected equipment but with the penalty of generating a tremendous amount of heat in the process. Because Power Plants utilized a traditional analog class A/B stereo power amplifier they were only 50% efficient. This meant that for every watt delivered to the load, an identical watt of heat was generated, thus requiring massive heat sinks to dissipate the heat. On August 21, 2007, US patent 7259705 was issued to PS Audio for the design rights to a new efficient tracking power regenerator that improved efficiency from 50% to 85% based on the same principles of regeneration. That same year, PS Audio introduced the Power Plant Premier, the first of its new AC Regenerator products to utilize this tracking AC technology it patented. In 2010, the current generation of AC regenerators was launched and carry the model PerfectWave. For high end cables, PS audio offered the "Lab" cable line which was replaced by the "Lab II" line, which was replaced by the "XStream" cable line. Currently the power cable line is the PerfectWave Power Cable line. PS audio offered the PCA II preamplifier. This was discontinued and replaced with the GCP-200 preamplifier. Each had an optional phono stage and external power supply option. For amplifiers, PS audio offered the HCA-2 "digital" amplifier. This was a switching amplifier (many would call this a Class D Amplifier) that provide about 150 watts per channel. A more conventional amplifier, the Classic 250, provided 250 Watts per channel. These amplifiers were discontinued and the follow-on amplifiers were all