INT-25

INT-25

At Pass Labs we build Fet amplifiers with excessive output stages, huge heat sinks and massive power supplies. We use the highest quality components in simple linear topologies, assembled and tested with care and subtlety. They measure well, sound great, and are reliable. Twenty plus years of ongoing innovation have kept the X and XA amplifiers at the forefront of high-end audio.

The INT-25 embodies all this and less. 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.

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.

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Technical specifications  

Class
A (Integrated)
Inputs
Three (3) RCA
Remote
Yes
Gain
26 dB gain
Output Power
25 Watts rms @ 8 ohms / 50 Watts rms @ 4 ohms
Distortion
0.1% @ 25 Watts, 8 ohms, 1 KHz
Class A Envelope
50 Watt peak for 2, 4 or 8 ohm load
Bandwidth
DC to -2 dB @ 100 KHz
Noise
Less than 150 uV output, unweighted 20 to 20 KHz
Damping Factor
500
Slew rate
100 V/uS
Input Impedance
48 Kohm
Peak Current
10 Amp output (200 Watt peak into 2 ohms)
Protection
Shutdown at 10 amps output
Idle Power draw
2.3 Amps @ 120 VAC (275 Watts)
Dimensions
17" W x 17.9" D x 6" H
Weight
51 lbs
Shipping Weight
56 lbs

Downloads  

Owner's Manual

CAD file

Spec sheet

Brochure