Pass Labs
INT-25 Integrated Amplifier
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Features
25 Watts per Channel: Provides 25 watts of power per channel into 8 ohms, suitable for a variety of speakers.
Combination of XP-12 Preamplifier and INT-25 Amplifier: Integrates the highly regarded XP-12 line-level preamplifier with the INT-25 amplifier for a seamless all-in-one solution.
Symmetrical Circuitry: Ensures balanced and accurate audio reproduction, capturing fine musical details.
High-Quality Components: Meticulously selected components contribute to the amplifier's exceptional sound clarity and dynamics.
Precise Volume Control: Features precise volume control for fine adjustments to suit individual listening preferences.
Balanced and Single-Ended Inputs: Offers single-ended (RCA) inputs for flexible connectivity options.
Musicality: Known for its musicality, the INT-25 amplifier allows listeners to fully immerse themselves in the nuances of their favorite music.
Minimalist Design: Boasts a clean and minimalist design that reflects Pass Labs' commitment to simplicity and performance.
Robust Build Quality: Crafted with attention to detail and high-quality materials for a durable and long-lasting amplifier.
Efficient Loudspeaker Compatibility: Ideal for use with sensibly efficient loudspeakers, providing engaging and detailed sound reproduction.
Reliable Performance: The INT-25 amplifier is designed for reliability and long-term performance, requiring minimal adjustments.
Exceptional Transparency: Delivers exceptional transparency and clarity, allowing the listener to hear every detail in the music.
What's in the Box?
Warranty
The Pass Labs INT-25 is an integrated amplifier and a harmonious fusion of power and precision in a single chassis. The INT-25 combines the exceptional performance of the XP-12 line-level preamplifier with the robust power of the XA25 amplifier, resulting in a formidable all-in-one solution for audiophiles. With its pure Class A topology and 25 watts per channel output, this integrated amplifier delivers breathtaking clarity and dynamics, effortlessly driving a wide range of speakers. The INT-25 features precise volume control and input selection, along with a host of connectivity options including balanced and single-ended inputs. Its sleek, minimalist design embodies Pass Labs' commitment to both aesthetics and audio excellence, making it a standout choice for those seeking uncompromising sound quality and convenience in one exceptional package.
Dragon Cable Recommendation: we recommend pairing the INT-25 amplifier with our award-winning Silver Dragon Interconnects. The Silver Dragon Interconnect is one of our best-selling cables at Moon Audio. Sold in Pairs, it is our top-of-the-line silver conductor-based interconnect. With a braided geometry and amazing shielding, this interconnect is a remarkable solution where noise isolation is key. The Blue Dragon Power Cable is also recommended to provide the cleanest and unbridled power to your high-end amplifier.
The INT-25 amplifier sports a brand-new design by Pass Labratories, inspired by the over fifty years of Nelson Pass' expertise of power amplifiers and the progression of combining sound, style, and performance. The INT-25 carries on the same legacy of beauty, in both the machine and the joys of listening to music.
The INT-25 is a Class A amplifier with 26dB of gain, amazing noise and distortion measurements, and much more. Inside the box you'll find the remote control, power cord, and spare fuse. The speaker binding posts can accept spades, banana plugs, or bare wire.
On the front of the amplifier, you'll find the large volume control, a volume digital meter, and buttons for on/off, mute, and three input options for external audio gear to connect to your system.
Design Elements of the INT-25
Pass Labs crafts FET amplifiers characterized by robust output stages, expansive heat sinks, and substantial power supplies. Utilizing premium components in uncomplicated linear configurations, these amplifiers are meticulously assembled and evaluated. Their performance is exemplary, both in measurements and auditory experience, with proven reliability. Through two decades of continuous innovation, the X and XA series have maintained their position at the pinnacle of high-end audio.
The INT-25 distills this legacy into a more compact form. This Class A stereo amplifier, offered at a more accessible price point, leverages reduced power demands to incorporate streamlined single-ended circuitry with a minimized component count in the signal path. Consequently, it eliminates degeneration—often referred to as "the other negative feedback"—across all stages.
The simplified architecture, featuring fewer gain stages, enhances both speed and stability. Operating at lower voltages enables the use of higher bias currents in gain devices, pushing them further into Class A territory. Advanced power FET technology supplants arrays of small parallel transistors with a single pair of industrial-grade devices, each rated at 700 watts and 40 amps. Equipped with a novel constant-current bias circuit that mitigates temperature fluctuations and is free from current-hogging concerns, these devices interface directly with speakers. This direct connection, devoid of ballast resistors, yields minimal distortion and optimal damping factor. The absence of degeneration further boosts efficiency and Class A operating current, facilitating extended Class A performance with low impedance and reactive loads.
At the amplifier's core, a straightforward front-end employs two pairs of Pass Labs' preferred NOS complementary FETs in common-source configuration, integrated into a current feedback (CFA) design. The preamplifier section presents a simplified, single-ended adaptation of its counterparts in the INT-60 and INT-250 models, featuring three line-level inputs without line-level output.
Every element in the audio chain, from the microphone to the speaker, imparts an enduring signature to the music. The XA25's amplification stage, being direct-coupled, eschews DC servos and frequency compensation, ensuring a transparent audio path. In keeping with Pass Labs' philosophy, the INT-25's technology and construction serve solely to enhance the listening experience. While it boasts impressive technical specifications, its true distinction lies in its subjective qualities. In a market where technically proficient products often lack vibrancy, this amplifier injects fresh vitality into musical reproduction.
Pass Labs and First Watt
Pass Labs and First Watt were founded by hi-fi legend Nelson Pass. After co-founding and later selling Threshold Audio, Pass began working out of his Auburn, California, home in the early 1990s to develop prototypes of single-ended Class A amplifier designs under the name Pass Labs. Pass Labs quickly became known for its commercially produced Aleph, X, and XA Series amps, and preamps. Pass later started First Watt as a passion project focusing on low-power amps for a niche audiophile audience. Today, Pass splits his time between the two companies, with production happening in Pass Labs' facility in Foresthill, California, USA. Some of Pass Lab’s most notable products include the HPA-1 Headphone Amplifier, their integrated amp series (featuring the Pass Labs INT-25, Pass Labs INT-60, and the Pass Labs INT-250), the Pass Labs XA25, and more. If you’re looking for a monoblock amplifier, stereo amplifier, integrated amplifier, or headphone amplifier, then Pass Labs has everything you need for your high-end audio. Visit passlabs.com for more info.
Features:
- Class A Operation: Utilizes pure Class A operation for pristine sound quality and low distortion.
- 25 Watts per Channel: Provides 25 watts of power per channel into 8 ohms, suitable for a variety of speakers.
- Combination of XP-12 Preamplifier and XA-25 Amplifier: Integrates the highly regarded XP-12 line-level preamplifier with the INT-25 amplifier for a seamless all-in-one solution.
- Symmetrical Circuitry: Ensures balanced and accurate audio reproduction, capturing fine musical details.
- High-Quality Components: Meticulously selected components contribute to the amplifier's exceptional sound clarity and dynamics.
- Precise Volume Control: Features precise volume control for fine adjustments to suit individual listening preferences.
- Single-ended (RCA) inputs for flexible connectivity options.
- Musicality: Known for its musicality, the INT-25 amplifier allows listeners to fully immerse themselves in the nuances of their favorite music.
- Minimalist Design: Boasts a clean and minimalist design that reflects Pass Labs' commitment to simplicity and performance.
- Robust Build Quality: Crafted with attention to detail and high-quality materials for a durable and long-lasting amplifier.
- Efficient Loudspeaker Compatibility: Ideal for use with sensibly efficient loudspeakers, providing engaging and detailed sound reproduction.
- Reliable Performance: The INT-25 amplifier is designed for reliability and long-term performance, requiring minimal adjustments.
- Exceptional Transparency: Delivers exceptional transparency and clarity, allowing the listener to hear every detail in the music.
What's in the Box?
- INT-25 Amplifier
- Stock Power Cable
- User Manual
FAQ
What is the power output of the Pass Labs INT-25 Integrated Amplifier?
The Pass Labs INT-25 Integrated Amplifier delivers 25 Watts per channel into 8 ohms. Despite its moderate power output, the INT-25 is designed to excel in driving high-quality speakers with precision and clarity. Its Class A operation ensures a clean and detailed sound signature, making it an excellent choice for discerning audiophiles who prioritize sonic purity.
What are the key features of the Pass Labs INT-25 Integrated Amplifier?
The Pass Labs INT-25 is packed with features that appeal to audio enthusiasts. It includes a fully balanced input stage and a discrete, direct-coupled FET output stage for exceptional signal integrity and low distortion. The INT-25 also features a high-quality volume control system, remote control operation, and a home theater bypass mode for easy integration into a multi-channel setup. Its compact size and elegant design make it versatile and suitable for a variety of audio systems.
Can the Pass Labs INT-25 drive difficult or inefficient speakers?
Yes, despite its modest power rating, the Pass Labs INT-25 is capable of driving a wide range of speakers effectively. Its Class A operation and high-current capability allow it to handle challenging speaker loads with ease. The INT-25 pairs particularly well with high-efficiency speakers that benefit from its clean and detailed amplification. Users can expect a dynamic and engaging listening experience, even with speakers that may be considered demanding.
Does the Pass Labs INT-25 require any special considerations for setup or maintenance?
The Pass Labs INT-25 Integrated Amplifier is designed to be user-friendly and relatively straightforward to set up. It does not require bias adjustments, as it is a self-biasing Class A design. However, users should ensure proper ventilation for optimal performance, as Class A amplifiers can generate heat. Adequate ventilation will help maintain the amplifier's performance and longevity. Additionally, it is recommended to provide sufficient space around the amplifier for airflow and to follow Pass Labs' guidelines for safe and optimal operation.
Who is Nelson Pass?
Nelson Pass, the man behind Pass Labs and First Watt, has been designing and building amplifiers for decades. His early passion, however, was speakers; at age 14, he started assembling loudspeakers. As a college student studying physics at the University of California-Davis, he co-founded a speaker company called PMA. He also worked for ESS, where he designed crossovers and enclosures. After college, with his interest having shifted toward amplifiers, Pass co-founded Threshold Electronics (now Threshold Audio). His achievements during the Threshold years include developing the first dynamically biased Class A amplifier circuit; developing a fully cascode audio power amplifier; and developing the STASIS stereo preamplifier and power amplifier. During the 1980s, Pass designed the Adcom GFA-555 amplifier. Later, after selling Threshold, he started Pass Labs in 1991 and First Watt in 1997. Pass holds several patents related to audio circuits.
How did Pass Labs make its name?
Pass Labs helped popularize solid-state, Class A power amplifiers. Pass Labs' first product, the Aleph 0 amplifier, operated as a single-ended Class A up to its 70-watt rating and in push-pull Class A at higher wattage. The Aleph series of amplifiers, some of the first solid-state amps that were said to be "tube-like" in sound, operated pure class A and contained internal circuitry using MOSFETs. The Aleph amplifiers had a unique appearance, a cube with heat sinks on all four sides, a solution to the heat generated by the class-A design. This can be attributed primarily to the specific MOSFETs used and the minimum number of gain stages that were implemented in the design. Pass Labs also developed the Super-Symmetry™ ("Su-Sy") circuit, which achieves exceptionally low distortion and noise levels. In 1998, Pass Labs released the X1000, the first amplifier using the patented SuperSymmetric™ topology. The X1000 achieved 1000 watts with high performance, local feedback, and only two gain stages: a cascaded differential pair of transistors and a large bank of complementary output followers. This groundbreaking design informed all subsequent Pass Labs amplifiers.
What else does Pass Labs make?
In 2002, Pass Labs unveiled the first XA amplifiers, combining the X and Aleph topologies into balanced single-ended Class A amplifiers with many of the characteristics of both the X and Aleph series. The current Pass Labs lineup includes Class A amps (XA and Xs Series), Class AB amps (.8 Series), line preamps (Xs and XP Series), phono preamps (Xs and XP Series), integrated amps (INT Series), and one headphone amp.
What is the relationship between Pass Labs and First Watt?
When he started Pass Labs, Pass did everything out of his home. In 1997, having outgrown the space, Pass Labs moved into commercial space in Foresthill, California. When Pass started First Watt, it was a "kitchen table" venture, with work once again happening in his home. In 2016, with production demands not leaving him enough time to pursue the vast array of yet-to-be-designed amps, Nelson handed the business end of First Watt over to Pass Labs. Pass Labs took over the building of First Watt amplifiers as well as marketing and distribution. There's a synergy between the two operations, in that Pass Labs gets to gather up some of the more interesting First Watt finds and repurpose them as more commercially viable designs. Today, Pass splits his time between First Watt and Pass Laboratories.
| Parameter | Specification |
|---|---|
| Physical Specifications | |
| Dimensions | 17" W × 17.9" D × 6" H |
| Weight | 51 lbs |
| Shipping Weight | 56 lbs |
| Warranty | 3-Year Limited |
| Technical Specifications | |
| Amplifier Class | A (Integrated) |
| Inputs | Three (3) RCA |
| Remote Control | Yes |
| Gain | 26 dB |
| Input Impedance | 48 kΩ |
| 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) |
| Audio Specifications | |
| Output Power | 25 Watts RMS @ 8 ohms / 50 Watts RMS @ 4 ohms |
| Class A Envelope | 50 Watt Peak for 2, 4 or 8 ohm Load |
| Total Harmonic Distortion | 0.1% @ 25 Watts, 8 ohms, 1 kHz |
| Frequency Response | DC to -2 dB @ 100 kHz |
| Noise | Less than 150 μV Output, Unweighted 20-20 kHz |
| Damping Factor | 500 |
| Slew Rate | 100 V/μs |
- JHJohn H.Verified BuyerRated 5 out of 5 stars10 months agoThe place to buy
Mac made it so easy and was so helpful it was like buying food at a fast food resturant.you will be treated with respect .
- JKJeffrey K.Verified BuyerRated 5 out of 5 stars4 years agoJe suis tres content!
For the past 35 years I’ve used tube amplification exclusively. In choosing a new amp for my secondary system I wanted to try something different. Pass Labs’ INT-25 has been a revelation for this Classical Music lover.
- RWRobert W. C. J.Verified BuyerRated 5 out of 5 stars5 years agoINT-25 Integrated Amplifier
This has to be one of the best solid state integrated amps on the market. 25 watts of class A amplification produces remarkable detail and sound quality. Paired with efficient speakers (in my case 93db) it produces volume that is more than sufficient to fill a large room without audible clipping at settings well below the max level. My sources go through a Chord Qutest DAC which has a "warm" filter I use for everything. The result is almost tube like. Simplicity is the order of the day here so if you're looking for a one box solution you'll have to look elsewhere. Three line level inputs and one speaker pair output. The appearance is one of elegant strength. The front panel controls are smooth in operation with a nice tactile feel. The lifting handles on the back panel will come in handy since this baby tips the scales at 50 lbs. One neat little features is the ability to turn off the volume display except for when the level is being adjusted. The remote has the feel of being carved from a single block of aluminum. A big thumbs up to Joe Pass and his design team. they have created a real gem!!
- RWRobert W. C. J.Verified BuyerRated 5 out of 5 stars5 years agoMine for life - the Pass INT-25
This has to be one of the best solid state integrated amps on the market. 25 watts of class A amplification produces remarkable detail and sound quality. Paired with efficient speakers (in my case 93db) it produces volume that is more than sufficient to fill a large room without audible clipping at settings well below the max level. My sources go through a Chord Qutest DAC which has a "warm" filter I use for everything. The result is almost tube like. Simplicity is the order of the day here so if you're looking for a one box solution you'll have to look elsewhere. Three line level inputs and one speaker pair output. The appearance is one of elegant strength. The front panel controls are smooth in operation with a nice tactile feel. The lifting handles on the back panel will come in handy since this baby tips the scales at 50 lbs. One neat little features is the ability to turn off the volume display except for when the level is being adjusted. The remote has the feel of being carved from a single block of aluminum. A big thumbs up to Joe Pass and his design team. they have created a real gem!!