Source: Corporate website, Last Accessed: 2021/01/27

The INT-25 embodies all the innovation that kept the X and XA amplifiers at the forefront of high-end audio, but -being a smaller stereo Class A amplifier at a lower price- it 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, the company says.
Simpler and fewer gain stages improves speed and stability according to Pass. 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 700W/40A 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 Pass' favorite NOS complementary FETs in common-source mode/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 but no line level output. The XA25 amplifier section is direct coupled requiring no DC servos or frequency compensation.
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, the company states.
INT-25 yields 2x25W at 8 Ohm loads and offers volume control through a 63dB stepped attenuator (with 1dB steps. A remote control is included.

For more information: https://www.passlabs.com/

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