"digital" type amplifiers from the GCA line, which had flexibility in the number of channels or number of watts per channel desired. 2014–present In recent years the company has grown dramatically in size, product range, and presence. The DirectStream DAC, launched in 2014, brought unique technologies to a DAC field crowded with similar chip-based solutions. Designer Ted Smith created a DAC based upon an FPGA (field-programmable gate array) which would allow owners to download and install no-cost firmware/OS upgrades which improve the unit's performance over time, and ensure that it does not become obsolete. As of July, 2019, the company has offered nine OS upgrades; recent ones have been named after "fourteeners", Colorado peaks which top 14,000 feet in height. The most recent of these is "Snowmass", released in November, 2018. The DirectStream also converts all inputs to DSD for processing; in Snowmass, signals are converted to 20 x the nominal SACD rate (56.338Mhz) and then converted back down to quad rate DSD (11.2896 MHz), with the output stage being a passive low-pass filter. Thousands of DirectStream DACs have been sold, with many in use in recording studios and as reference components by reviewers. Sprout, a compact integrated amplifier featuring a phono stage, Bluetooth, and a headphone amp, was introduced in a Kickstarter campaign in 2014; subsequently, thousands of units were sold. In 2018 a second generation unit, Sprout100, was introduced; the name reflected the increased power output of 100 watts/channel into 4 ohms. Other improvements included a fully asynchronous DAC that can handle 384/24 PCM or double rate DSD; dedicated subwoofer output; optional bass boost; high-quality, metal remote control; analog RCA inputs and outputs; and a TOSLINK optical input. Since 2015, PS has released three amplification products designed by industry veteran Bascom H. King, under the line name of BHK Signature. During more than 40 years in audio, King has designed products for Infinity, Marantz, Conrad Johnson, Constellation, and Audeze, among many others, and the BHK Signature line represents the culmination of all his experience and knowledge. The BHK Signature Preamplifier input stage features two 12AU7 dual triode vacuum tubes, which act as a zero-feedback balanced input amplification pair. Volume is controlled by a combination of an input stepped attenuator, built around the highest quality passive components for coarse volume adjustments, after which the actual gain of the vacuum tube is controlled, for finer steps. The control is designed