Note that this is a discontinued product. You may want to visit the brand's page here to browse their newer products.
What reviewers think
Bloggers and YouTubers have tried this product—so we've summarized their strongest opinions below. Links to full reviews follow.
Product Strengths
- Impressively natural midrange, described as silky, sweet, big, rich, textured, and haunting
- Excellent bass reproduction, deep, precise, and weighty
- Fluid and gentle sound with impressive layered depth and width
- Provides a warm, rich, muscular, and refined sound, enhancing older recordings
- Simple design with high-quality components and reliable build quality, built to last
- Lacks features such as digital inputs, phono stage, balanced connections, and subwoofer output
Product Considerations
- Low power output (25W) may require efficient speakers, although it exceeds this in practice
- Runs warm and requires good ventilation
- Speaker terminals can be a little difficult to use with certain types of spade connectors
- A review mentioned a thumping sound on speakers upon power-up, but this was considered a possible defect warranting return
Comparisons (according to reviewers)
- Vs Pass XA25: INT-25 has a simplified front end of the INT-60 machine, integrating the XA25 power amp and preamp
- Vs Pass INT-60: INT-60 is more powerful and neutral, INT-25 has better tonal balance, smoother sound, and superior bass performance (with proper speaker matching)
- Vs Exposure 3010S2 monoblocks: INT-25 has more detail, fluid sound, and deeper—more controlled—bass, but Exposure has more power and easier speaker interaction
- Vs Exposure 3010S2D Integrated Amplifier: INT-25 provides more detail and fluidity, more faithful and convincing bass, and more seductive female vocals
- Vs Luxman 590AXII: Luxman is more detailed with a thinner mid-bass, INT-25 has more warmth and body, giving it more humanity and muscularity
- Vs Vinnie Rossi L2i SE: INT-25 has more muscle, warmth, and glow, the L2i SE is more clean-sounding, with super refinement and silence
- Vs Line Magnetic 219ia: INT-25 has a similar sound signature, but with more 'muscle' and no maintenance, as well as more texture and bass
Takeaway: The Pass Labs INT-25 is a high-quality, simple-to-use integrated amplifier with a musical and engaging sound. Its strengths in the midrange and bass make it a great choice for listeners who value warmth, texture, and a fatigue-free listening experience.
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INT-25
reviews
Manufacturer details
- Type: Stereo
- Gain (dB): 29/35
- Volume control: 63dB (1dB steps)
- Remote: yes
- Inputs: 3
- Outputs: 0
- Power Output /ch (8 ohm): 25 Watts
- Power Consumption (W): 200
- Standby Power Consumption (W): <1
- Dimensions (W x H x D): 17 x 17.375 x 6
- Weight: 49 LBS
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.
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Brand highlights
Taking a step back to look at reviewers' thoughts of the brand's entire lineup—not just this product—what stands out most is the following:
- They design their products with a minimalist approach, focusing on essential components and avoiding unnecessary features in the signal path.
- Pass Labs emphasizes high-quality parts and meticulous assembly over brute force design, resulting in components built to last for decades.
- Their amplifiers often exhibit a sound signature with both detail and a touch of warmth, providing a musical and engaging listening experience.
- The company's components are often fully class-A, or run deeply in class A territory, known for its excellent linearity and lack of distortion.
Select products
INT-25
- Positioning: The entry-level integrated amplifier in the Pass Labs lineup, offering a more affordable option with high-quality sound.
- Description: Features simplicity and high-quality Class A amplification, making it ideal for small rooms or setups where space is limited. It features a minimalist design with fewer components in the signal path, which enhances speed and stability compared to more complex models like the INT-250. This makes it a great choice for those with a moderate budget who prioritize sound quality over power output, as it offers 25 watts per channel and is best suited for efficient speakers.
X350.8
- Positioning: The high-powered stereo amplifier positioned as the most powerful Class A/B amplifier in the Pass Labs lineup.
- Description: Delivers 350 watts per channel, providing ample power for larger rooms and more demanding speakers. It offers a superb and accurate representation of recordings, with a focus on holistic design rather than just specifications, setting it apart from smaller models like the X250.8.
XA200.8
- Positioning: A premium monoblock amplifier in the Pass Labs lineup, designed for high-end audio systems.
- Description: Delivers 200 watts of pure Class A power, providing exceptional sound quality and headroom for complex musical passages. It stands out with its high current capability and lack of microprocessor-controlled bias schemes, unlike the more affordable XA100.8.
XS300
- Positioning: The flagship monoblock amplifier in the Pass Labs lineup, representing the pinnacle of their amplifier technology.
- Description: Offers 300 watts of Class A power with separate power supply and amplifier chassis for lower noise, making it the top choice for those seeking the best in music reproduction. It features a higher-power constant-current source and single-ended bias current, which lowers distortion and enhances harmonic control compared to other models like the XA200.8.
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Used
Pass Labs
What if you spend more?
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With the inclusion the new tube cage, the transformer cover was raised 2" to allow the cage to fully protect any KT-120/KT-150 tube. The resulting metal work and power supply changes have yielded our quietest Nautilus yet. Many still love the sleek lower profile look of the Classic Nautilus and as such we allow you to order your Nautiluswith the original metal work style or the Rev 2. The Classic Nautilus will additionally save you $1000 on the purchase.
The Story of the Nautilus is born of the same process that brought the Zions. We set out to build my private amps apart from ampsandsound. These were to be mine without branding and never to leave for demos. All too often, my own listening space was sacrificed for the need for demo stock. I chose the HK Cit II as my inspiration point. From that seed came my own Cit II Monos build on turrets just like the best amps of the golden age.
The Nautilus brings the dual-mono layout onto a single chassis. We started with our most versatile circuit, the Mogwai, and went about creating two separate amps that share a single chassis. 2 Power Transformers, Separate Power Supplies, Chokes, and input transformers. The amps are built with separate turret boards, with the shared component being the input tube, volume control, and outputs.
The Nautilus is a classic and decidedly prosaic design, as it employs turrets and point-to-point wiring & there is no silicone, ICs, or regulators. We consider this a standard-bearer of purest audio with an American sensibility. The Nautilus is built in a way few modern amplifiers are. This is not due to intrinsic inferiority, but rather it is impossible to rush and is incredibly expensive to produce.
The Nautilus has been described as a tube integrated amp for personal audio users. We mean by this, the Nautilus allows for five separate impedances to be selected for system matching and has a pair of 8ohm 5 way binding posts. The speaker vs. headphone output is selected with a small toggle switch on the back of the amp.
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Product Strengths
- Five individualized outputs with different impedances
- Custom wound ultra-high quality output transformers provide excellent frequency extension and a flat response
- Engaging audio components offer superior sound quality using proven theories, solid engineering, and quality manufacturing, all taking place in the USA
- Brings out the very best qualities in all of the headphones tested, providing the best presentation ever heard from the Aeolus
- Build quality is a step-up from other amplifiers
Product Considerations
- The most expensive quarter inch plugs you can get, have locks on them, which can be annoying
- Unplug headphones before switching to speaker outputs
- Weighs around 68 pounds and around 93 pounds shipped in its large pelican style case—it is heavy
- Can clip when used with speakers if pushed too hard
Comparisons (according to reviewers)
- Nautilus sounds better than the ZMF Pendant Headphone Tube Amplifier and the Mogwai OG Tube Amplifier in every regard
- Nautilus is even more comprehensive and expressive through the powerful, well-controlled, tonal density that is detailed and rich in nuance—it has more extension and top-notch resolution
Takeaway: The Nautilus seems to be a versatile amplifier that brings out the best in headphones and speakers. It's built with quality parts and offers a lush and detailed sound experience for audiophiles who want to enjoy music to the fullest.
Video review
Our take on the brand
Double the Performance Trouble-free, noise-free, and double the power of traditional 300B amps. Made possible by patented circuit design. A New Classic We’re proud to continue a legacy of quality, American manufacturing with innovative new features. Ships with Tubes The 91E ships with new production 300Bs, the most popular electron tubes in the world. Made in the USA.
Product Strengths
- New patented design SCS (source current steering) allows the amplifier to have a fabulous bottom end without affecting the glorious midrange
- Proprietary noise reduction system eliminates noise that can be inherent in a single-ended design
- Circuit protects the 300Bs and keeps them in their safe operating range, so there is no chance of damaging the tube or having a shortened life
- More power from this amp than a traditional 300B, it's the difference in presentation
- It has Bluetooth, phono stage (moving coil and moving magnet), and wireless remote control
Product Considerations
- Instructions could be a little clearer about installing the 300Bs
- More warm-up is needed for each listening session than originally allowed
- The 91E was designed for operation with Western Electric manufactured 300B electron tubes
- The brands and specifications of the capacitors, resistors, transformers, internal wires, RCA jacks, switches, and binding posts are not disclosed
Comparisons (according to reviewers)
- Vs WE 91A: 91E retains what's best about the early WE 91A—its delicacy, bloom, openness, and tonal magic—and adds modern improvements
Takeaway: The Western Electric 91E is a uniquely designed amplifier providing great sound with modern features like Bluetooth and remote control, pushing what a 300B tube amplifier can achieve. It's a great option for audiophiles wanting to step up from other tube amplifier sounds.
Video review
Our take on the brand
In the world of audiophiles, there is purist group militating for simplicity in tube amplification systems focusing on the use of the tube designed in the early days of tube technology: the directly heated triodes of which the most famous is the 300B. I300 is built around a simple 300B push-pull without feedback which offers unequalled musiciality of this tube.
After the preamplification using an ECC82, the signal feeds a phase inverter (called Schmitt) followed by 6SN7 triodes sufficient to drive the 300B.
The power supply is another strong point. In addition to the fact that each stage has its own power supply, particular care has been taken with the 300Bs themselves.
As direct heated triodes, the heater is the cathode. This requires a very "clean" power supply with no less than seven separate power circuits.
As for all our devices, transformers are designed and manufactured in our workshop. The one dedicated to the power supply, uses a magnetic circuit EI M6X of a design which gives a very stable operation, without noise and with a reduced overheating.
The output ones use a double CV38 magnetic circuit built according to our standards. The I300 is the only integrated with such an output transformer.
A design mode that allows the device to appear much more powerful than its 10W may suggest!
As far as design is concerned, the I300 remains faithful to our range and has a compact design. The 2mm thick 304L chassis easily supports the weight of the other elements. For a better comfort of use it is equipped with a remote control.
Listening to the I300, it's all about accuracy, subtlety and musicality of the 300B which magnify your tracks. No doubt it will delight demanding audiophiles triode lover!
Product Strengths
- Wonderful mid-band presentation that comes from the 300B tubes
- Bass is extended and controlled
- Provides detail and insight into recordings without being piercing
- Soundstaging is wide, deep, and natural sounding
- Every stage in the amplifier has its own power supply, and particular care has been taken with the 300Bs themselves
Product Considerations
- The included remote is functional, but not in keeping with the quality of the amplifier itself
- It is very heavy, weighing 40kg
- The high polished chrome and gold accents may divide opinion
- Those looking for an amplifier that is absolutely neutral in its presentation may want to listen to something else
Comparisons (according to reviewers)
- Vs Merrill Thor amps, the Jadis I300, to the reviewer's ears, is a far superior amp for listening and putting a big grin on your face
Takeaway: The Jadis i300 is built superbly and delivers a balanced sound with detail and emotional connection, making it a joy to listen to. It is a refined performer across the audio spectrum and with all kinds of music.
Video review
Our take on the brand
Product Strengths
- Restores faith in humanity during an age dominated by digital devices
- Outstanding product crafted with high-quality metalwork, including a thick engraved panel, heat sinks that match the rounded edges, and internal components that are hand-soldered onto double-sided, 2 mm thick circuit boards
- Hybrid amplifier using a dual triode in the preamp stage and Mosfets in the output stage, offering the possibility to customize the sound by experimenting with different valves
- Offers unparalleled control over bass and extension, the mids are incredibly authentic, while the highs are enchanting in their golden glow, also boasts impressive attack, dynamics, and rhythm, along with remarkable speed
- Exceptional analogue amplifier primarily designed for high-quality sound through headphones—that also excels as a speaker stereo amplifier
Product Considerations
- Expensive
- Speaker declared power output is just 10W/8 ohms, which is enough to power a pair of medium-sensitivity speakers (88dB) in a small room if you don't push it too hard
Comparisons (according to reviewers)
- Vs Pass Labs XA30.8: Low bass was a bit bloomier, and that its virtual needle on the elasticity-to-damping metre sat slightly deeper in the elasticity zone
Takeaway: The Riviera Labs AIC-10 BAL is a high-quality, all-analog hybrid amplifier that works great with headphones and speakers and is designed for a very pleasurable listening experience, built with human hearing in mind. This is the right choice if one wants the best sound possible.
Video review
Our take on the brand
What competes at this price?
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Our Summary
Product Strengths
- Addictive sound signature, unlike any other amp, with otherworldly instrument and voice reproduction
- Delivers serious magic with Fleetwood Deville and Klipsch Heritage speakers, revealing obscure details and creating a massive soundstage
- Dynamics for days
- Combines the qualities of a nice SET amp without the downsides, like noise or tube replacement
- Exceptional build quality and design with high-quality parts
- Only has two RCA inputs, no XLR balanced connections
Product Considerations
- Heavy speaker cables can cause the amp to tilt
- The volume dial functions as a gain dial, which may be different than what some users are accustomed to
- May not be suitable for hard-to-drive speakers in the 85db range that dip into 2–4 ohms
Comparisons (according to reviewers)
- The AMP23R offers more texture, layering, mid-bass, and vocal presence than Nagra INT
- The AMP23R is more organic, ethereal, and dynamic than Kinki Studio EXM1
- It sounds better than the Vinnie Rossi L2iSE, so long as the speakers are easy to drive
- The Enleum has more delicacy and finesse than Pass Labs and Cary Audio
- The AMP23R stacks up with the finest gear such as ampsandsound Bryce monoblocks
- Pass Labs First Watt SIT-3 offers a bit more organic, warmer presentation
Takeaway: The Enleum AMP-23R is a small but mighty integrated amplifier with a unique and addictive sound signature, and it is built with high-quality components. It's a great choice for those with sensitive speakers looking for a reference-quality system in a compact package.
Video review
Our take on the brand
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Our Summary
Product Strengths
- Very powerful amp with crazy headroom, capable of driving most headphones, including those that need a lot of power, and can grow with you as different headphones
- Delivers clarity, separation, detail, and impact, making every pair of headphones sound better
- Multiple impedance outputs allow dialing in the best sound for a given pair of headphones
- Super black background—very low noise floor
- A ton of different tubes can be rolled, including EL34s, KT66s, KT67s, KT88s, 6550s, and KT90s, making it very versatile and allowing customization of the sound to exact taste
Product Considerations
- Only one input via a pair of RCA connectors
- Requires a pre-amplifier or DAC with volume control if obtained without the volume pot
- May lack convenience features because of ampsandsound's minimalist philosophy
- Can be very heavy
Comparisons (according to reviewers)
- Vs Linear Tube Audio's Z10e: Z10e seemed more focused and brightly lit through the midrange
Takeaway: The Bigger Ben is a hugely versatile and powerful amplifier that could be an end-game amp, especially if you want to experiment with tube rolling. Its sound is detailed, clear, and engaging, making it a great choice for anyone who loves listening to music.
Video review
Our take on the brand
Our Summary
Product Strengths
- Wide and deep soundstage, with a depth extending as far as 70 feet in one test
- Music reproduction is natural and realistic, creating a sense of instruments and voices being present in the room
- High frequencies and cymbals shimmer and crash realistically
- Impeccably constructed and manufactured with original circuit solutions
- Capable of drama, delicacy, and danger which transcends reproduction — turning the act of listening into a full-fledged experience
Product Considerations
- Selector knob on top of the unit is difficult to access when the tube cage is installed
- Speakers need to be a good match for the amplifier's 23 watts of power
- Bass was shy and ill-defined when used with the Dynaudio Contour 60i speakers
Comparisons (according to reviewers)
- Compared to Conrad Johnson Premier 10 & 11A, the Simply 845 has a wider and deeper soundstage and better reproduction of high frequencies and cymbals
- Compared to PrimaLuna (top-of-the-line), the Simply 845 sounds better sonically
- Compared to Line Magnetic Audio LM-845iA Integrated Amp, the Simply 845 does delicate better
Takeaway: The Simply 845 is a revealing integrated amplifier that makes music sound magical and is an excellent choice, especially for horn speaker lovers. This amplifier transforms speakers into something wonderful and will enhance the music experience.
Video review
Our take on the brand
Our Summary
Product Strengths
- Refinement and smoothness in sound
- Exceptional build and finish, including exquisite woodwork
- Seductive midrange and overall musicality
- The Sinfonia has a romantic, addictive sound that's better suited to classical music
Product Considerations
- Not the last word in slam
- Needs careful system partnering to sound its best
- Dynamics were very good, although not exactly of the same caliber as with the ModWright preamp and amp
- When pushed to the extremes, during the most dynamic passages, the Sinfonia began to reach its limit—compressing gently and giving up some of the low frequency control
Comparisons (according to reviewers)
- Sinfonia offers a smoother, warmer, and more seductive sound, while the S6 amplifier sounds a little 'faster' and more linear
Takeaway: The Sinfonia is a fine amplifier with a beautiful build that delivers a refined and smooth sound. It's a good choice for enjoying music and will make your eyes smile with its hand-made Italian design.
Video review
Our take on the brand
Our Summary
Product Strengths
- Exceptional build quality and aesthetics
- Delivers a robust 40 watts per channel into 8 ohms
- Demonstrates remarkable frequency handling, extending from 17Hz to 63kHz (-2dB)
- Precise bias adjustment with built-in meter
- Superb control, power, and effortless flow
Product Considerations
- Relatively heavy at 30kg
- May require occasional tube maintenance
- Power output might not suit all speaker combinations
- A softer 300B glow was not present
Comparisons (according to reviewers)
- The Triode as amp offered a similar kind of finely grained nearly neutral sound as the Audionet
- No amp has bettered the Riviera Levante integrated amp in dimensional quality
- Parts cost plus the Evolution comes with two Western Electric 300Bs that run $1499 per matched pair on the open market, while the Triode TRZ-300W sports four Triode-branded 300Bs
Takeaway:
The Triode Evolution is a high-end tube amp that delivers music with power and clarity. Those who value musical authenticity and appreciate the warmth of tube amplification may find it a great fit.
Video review
Our take on the brand
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