Pass Labs make some of the finest HiFi audio electronics in the industry. Continually on the "Reccomended Components" lists of Sterophile and The Absolute Sound you really need to hear the beautiful music making magic that PASS Labs products bring to any HiFi system.
Pass Labsis ahigh-end-audiocompany based in Auburn, California, United States founded by Nelson Pass, a well-known figure in the high end audio community.
Pass founded, and worked at, audio company Threshold, where he developed the Stasis series of amplifiers. These designs were later licensed to Nakamichi
Today Pass Labs makes amplifiers and, preamplifiers. Pass Labs is also a supporter of the DIY audio community and maintains an internet presence for this purpose.
The PASS Labs INT25 is a high voltage pure Class A integrated amplifier that has a simplified circuit topology to allow the immediacy and delicate details to shine through your system in a way that is natural and full.
PASS Labs INT25 design features
The INT-25 embodies is a smaller powered stereo Class A amplifier that takes advantage of the lower power requirements to have simpler single-ended circuitry and fewer parts in the signal path. This also allows elimination of degeneration, “that other negative feedback” in all stages.
Simpler and fewer gain stages improves speed and stability. Lower voltages means the ability to run gain devices at higher bias currents, more deeply into Class A. Newer power Fet technology replaces banks of parallel small transistors with a single pair of industrial devices, each having a 700 watt / 40 amp rating. With no current-hogging issues and a new constant-current bias circuit to compensate for temperature drift, they connect directly to the loudspeaker without ballast resistors for lowest possible distortion and highest damping factor. No degeneration also increases the efficiency and Class A operating current, allowing greater Class A operation into low impedance and reactive loads.
The simple front end circuit uses two pairs of our favorite NOS complementary Fets in common-source mode in a current feedback (CFA) configuration.
The preamp section is a simplified single-ended version of the one used in the INT-60 and INT-250 with three line level inputs and no line level output.
Everything done in the signal chain from the microphone to the loudspeaker, forever leaves an indelible mark on the music. The XA25 amplifier section is direct coupled requiring no DC servos or frequency compensation, neither adding too or subtracting from the experience.
As with all Pass amplifiers, the technology and construction are strictly in the service of the listening experience. The INT-25 measures superbly, but its subjective qualities are most special. In an industry where products with great specs are often found to be dry and boring, this amplifier breathes new life into the music.