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
Magazine reviewers and YouTubers have tried this product—so we've summarized their strongest opinions below.
How useful are hifi reviews? We consider them useful for three things: (1) Surfacing new products you should demo in person at a dealer. (2) Learning which products reviewers unanimously praise as the best they've ever heard (this means they probably are legitimately great). (3) Identifying a product's unique attributes that satisfy your idiosyncratic needs and tastes. Beyond that, we discount what reviewers say because they heap praise on everything—rarely being negative for fear of souring relationships with manufacturers. Further, they seldom have more than a couple products on-hand at once, relying on their imperfect memories to compare to past products.
Video Review
Compared to their other products
We think it's helpful to understand how this product fits into the brand's full lineup (below). To learn more about these products, visit the brand's page.
I/50 Integrated Amplifier
- Positioning: The entry-level integrated amplifier in the Audio Research lineup.
- Description: Offers a compact design with a powerful all-tube amplification circuit, making it ideal for small to medium-sized rooms. Features optional DAC and phono modules, providing flexibility for various audio sources, unlike the more specialized power amplifiers in the lineup.
VT80 SE Stereo Amplifier
- Positioning: A mid-range stereo amplifier, offering a balance between performance and affordability.
- Description: Uses KT150 tubes for a robust output, suitable for diverse speaker setups. Provides a fully balanced design, unlike the I/50, and is more powerful.
Reference 160S Stereo Power Amplifier
- Positioning: A premium stereo amplifier, designed for serious audiophiles.
- Description: With its dual GhostMeters and advanced auto-bias technology, provides superior soundstage and detail. Offers more power and flexibility than the 80S.
Reference 330M Monoblock Power Amplifier
- Positioning: The flagship monoblock amplifier, representing the pinnacle of Audio Research's engineering.
- Description: Combines groundbreaking technology with an all-tube signal path, offering unmatched control and dynamic range. Surpasses the 160M MKII in power and sophistication, making it the ultimate choice for those with no budget constraints and a desire for the best possible sound.
See all the brand's products
Read the reviews
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An excellent review of a great product
/
Publisher
/
3/1/2022
An excellent review of a great product
Publisher
/
3/1/2022
Reference 750 Sel
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Manufacturer's notes
The Reference 750SEL monoblock amplifier continues the story begun decades ago with the introduction of the Reference 600; that is, the pursuit of a full-scale vacuum tube amplifier with enough power to drive any speaker, and to provide a musical experience unlike any before it.
Manufacturer Specs
- Power Output: 750 watts per channel continuous from 20Hz to 20kHz
- Power Bandwidth (-3dB points): 15Hz to 150kHz
- Frequency Response (-3dB points at 1 watt): 1 Hz to 200 kHz
- Input Sensitivity: 4.6V RMS Balanced
- Input Impedance: 200K ohms Balanced
- Output Taps: 4, 8, 16 ohms
- Output Regulation: Approximately 0.5dB 16 ohm load to open circuit
- Overall Negative Feedback: 13dB
- Slew Rate: 20 volts/microsecond
- Rise Time: 1.5 microseconds
- Hum & Noise: Less than 0.2mV RMS
- Power Requirements: 105-130VAC 60Hz (200-270VAC 50Hz)
- Power Consumption: 2100 watts at rated output, 2400 watts maximum, 800 watts at "idle"
- Tubes Required: 8 Matched pair KT150 Power Output; 1 6550WE Regulator; 1 6H30 Regulator Amplifier; 1 matched pair KT150 Driver; 1 6H30 follower
- Dimensions: 13.5" (34.3 cm) W x 23" (58.4 cm) H x 20.8" (52.8 cm) D
- Weight: 170 lbs. (77.2 kg) Net; 395 lbs. (180 kg) per pair shipped weight
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Average Price
$75,001-$100,000
Used Products
110
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Brand Popularity
100
of 600+
Badges
Top 50 Brand
Top 250 Brand
Products
15
Founded
1970
Our take on the brand
Audio Research is a hifi brand that has stayed committed to tube technology while many competitors moved to solid-state designs. The brand is known for its use of KT150 power beam tetrodes and hybrid power supply designs that blend tube amplification with solid-state regulation.
Brand Page
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Used
Audio Research
What if you spend a bit more?
Relentless 800
195500
195500
/
2
Reviews
Dan D'Agostino
Dan D'Agostino is an ultra-premium hifi brand distinguished by its unique copper heat sinks with holes and distinctive circular green-lit VU meters that give their amplifiers a steampunk aesthetic. Their amplifiers feature proprietary "Super Rail" technology that maintains high voltage for front-end transistors, while their three-chassis Relentless Preamplifier uses 30-pin interlocking connectors to eliminate wiring anomalies.
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Our Summary
Product Strengths
- Exceptional sound quality right away that continues to improve
- Capable of uncompressed dynamics at both loud and soft volumes, micro and macro, and doesn't harden or distort when playing loud
- Can handle big scale, orchestral, beautiful music to really raw, crazy metal music, all played convincingly at loud and soft levels
- New details are revealed without being hyper-analytical, sterile, or harsh
- Built like military materiel
Product Considerations
- Each monoblock weighs 145kg, so owners will welcome assistance when receiving it
- Inputs are on balanced XLR only, while the solid copper speaker terminals are designed for spade lugs, not 4mm bananas
- The Breguet watch dial-inspired meter's 'time-keeping' is less accurate
Takeaway: The D'Agostino Relentless 800 reproduces a wide range of music genres with detail and dynamics, offering an immersive and enjoyable listening experience. It brings out the best in music.
Video review
Our take on the brand
Dan D'Agostino is an ultra-premium hifi brand distinguished by its unique copper heat sinks with holes and distinctive circular green-lit VU meters that give their amplifiers a steampunk aesthetic. Their amplifiers feature proprietary "Super Rail" technology that maintains high voltage for front-end transistors, while their three-chassis Relentless Preamplifier uses 30-pin interlocking connectors to eliminate wiring anomalies.
Visit our
Relentless 800
page
Product Page
KMA i800
139995
139995
/
1
Reviews
Krell
Krell is a hifi brand whose amplifiers use iBias technology to operate in Class A up to full power without excessive heat, while maintaining the ability to double power output as speaker impedance halves. Their amplifiers feature XD technology for better control over speaker drivers, and modern models like the K-300i include Bluetooth, HDMI, and streaming features for contemporary audio setups.
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Our Summary
Product Strengths
- Delivers 800W of class-A power regardless of the speaker load
- Features XD technology that lowers output impedance, resulting in more control over the speaker drivers and improved soundstage depth
- Employs Sym-Max technology to significantly reduce second-order harmonic distortion, bringing out more detail and improving the sense of timing and pacing
- Has a power supply consisting of 5400VA of transformers and 188,000µF of filter capacitance for substantial power delivery
- Offers protection against excess direct current, short circuits, and voltage sags—brown outs
Product Considerations
- It may be too much power for some users
- High idle heat dissipation at 890 btu/hr per channel
Takeaway: The Krell KMA-i800 is a powerful amplifier with technologies that aim to provide a clean and controlled sound. Its high power output helps to improve sound quality even at average listening levels.
Video review
Our take on the brand
Krell is a hifi brand whose amplifiers use iBias technology to operate in Class A up to full power without excessive heat, while maintaining the ability to double power output as speaker impedance halves. Their amplifiers feature XD technology for better control over speaker drivers, and modern models like the K-300i include Bluetooth, HDMI, and streaming features for contemporary audio setups.
Visit our
KMA i800
page
Product Page
Telos 4800
260000
260000
/
1
Reviews
Goldmund
Goldmund is a Swiss hifi brand known for its "mechanical grounding" technology, which reduces vibrations through heavy, precisely engineered components, and its proprietary Telos amplifier technology that significantly reduces intermodulation distortion. The brand appeals to audiophiles who prioritize pure sound reproduction, focusing on musical realism through minimalist design and high bandwidth circuitss.
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Our Summary
Product Strengths
- Designed to drive even very low-impedance loudspeakers without compromising distortion levels
- Delivers unmatched sound clarity and power with a maximum power output of 1050 watts RMS at 8 ohms and a total harmonic distortion (THD) of only 0.005% across 20 Hz to 20 kHz
- Features a damping factor of 600 at 1 kHz and output floor noise of less than 3 μV, delivering an impeccably clean and detailed sound free from unwanted background noise
- Ensures maximum thermal security and short-circuit protection with fully analog circuitry from input to output and an automatic shutdown feature
- Equipped with analog and digital inputs, including RCA and XLR connectors
Product Considerations
- A preamp is required to supply input switching and any processing needed before sending signals to the Telos 4800 to power the speakers
- As a mono power amp, two units are required for a stereo setup, increasing the overall cost significantly
Takeaway: The Telos 4800 is designed to meet the needs of any audio system and delivers unmatched sound clarity and power. With impeccable specs, it offers a high-end performance for audiophiles.
Video review
Our take on the brand
Goldmund is a Swiss hifi brand known for its "mechanical grounding" technology, which reduces vibrations through heavy, precisely engineered components, and its proprietary Telos amplifier technology that significantly reduces intermodulation distortion. The brand appeals to audiophiles who prioritize pure sound reproduction, focusing on musical realism through minimalist design and high bandwidth circuitss.
Visit our
Telos 4800
page
Product Page
Eric Encore
174965
174965
/
2
Reviews
Engstrom
Named after a great Swedish choir conductor, ERIC is our no-compromise statement power amplifier. Fully balanced and transformer-coupled, it was created to drive even the toughest loads. ERIC uses separate power supplies for input and output stages and DC filaments. While the original model launched in 2016 used rare and specially designed T-100 power output tubes, the urge for even more power and refinement could not be ignored. Further R&D led to 845 power output tubes, an evolution so electrifying it earned the title ENCORE. The sound digs deeper, spreads wider and peers farther into the Scandinavian soundscape. Weighing in at 65kg per monoblock, the ERIC ENCORE is a titan of the industry in both size and sound.
Engström is a Swedish hifi brand that handcrafts amplifiers with a minimalist Nordic design, featuring fully balanced, transformer-coupled circuits and no negative feedback to preserve natural sound dynamics. Their amplifiers, which use KR Audio's T-100 power tubes, are known for creating an expansive, three-dimensional soundstage with what audiophiles call a "Scandinavian Sound"—characterized by open, detailed, and natural sonic qualities.
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Our Summary
Product Strengths
- Crisp, tight rhythms are allied to a sonorous, close-focused view of vocals
- Capable of bags of detail and definition, while bathed in a lovely warmth
- Massive bass weight is available, with fabulous rosiny bite to the low strings, silky violins, and the feeling of space and air around the performers
- Big, substantial sound makes the most of remasters, bringing out all the character of vocals
- Focus and warmth contributes to a solid, three-dimensional soundstage, and remains clean and tight when cranked
Product Considerations
- The precious bottles should never be left unattended or used without the purpose-designed glass hood installed
- The amps' thermal characteristics may be a problem in a globally-warmed English summer
- Each amp draws 430W from the wall
Comparisons (according to reviewers)
- Vs Dan D'Agostino Relentless Monoblocks—the ERIC Encores are more expensive per watt
Takeaway: The Engström ERIC Encore Mono Power Amplifiers offer a captivating and enthralling presentation that challenges old clichés about valve amps. One should hear them if given the chance, for they sound glorious.
Video review
Our take on the brand
Engström is a Swedish hifi brand that handcrafts amplifiers with a minimalist Nordic design, featuring fully balanced, transformer-coupled circuits and no negative feedback to preserve natural sound dynamics. Their amplifiers, which use KR Audio's T-100 power tubes, are known for creating an expansive, three-dimensional soundstage with what audiophiles call a "Scandinavian Sound"—characterized by open, detailed, and natural sonic qualities.
Visit our
Eric Encore
page
Product Page
What else competes at this price?
Momentum M400 MxV
79950
/
Released
2021
Dan D'Agostino
The company's inaugural creation, the Momentum Mono Amplifier, served as the foundation for its product line. The Momentum M400 MxV Mono Amplifier, the latest iteration, enhances the iconic design to new heights. Incorporating techniques and topologies from the Relentless Mono Amplifier, the Momentum M400 MxV models represent the pinnacle of Momentum circuitry evolution. The new model name, MxV, signifies Mass times Velocity—the fundamental equation for Momentum, a recognition that resonates particularly with individuals having a physics background.
Dan D'Agostino is an ultra-premium hifi brand distinguished by its unique copper heat sinks with holes and distinctive circular green-lit VU meters that give their amplifiers a steampunk aesthetic. Their amplifiers feature proprietary "Super Rail" technology that maintains high voltage for front-end transistors, while their three-chassis Relentless Preamplifier uses 30-pin interlocking connectors to eliminate wiring anomalies.
Expand Details
Our Summary
Product Strengths
- Exquisite aesthetics with a sleek design and a power meter that glows green
- Delivers a smooth and satisfying sound
- The sound is described as 'louder' and more powerful
- Said to be able to drive any speaker to its maximum output
- Upgrades are retrofittable to earlier Momentum models
- Balanced input only
Product Considerations
- Runs warm
- The scale on the power meter is essentially uncalibrated
- Requires a return to the factory for MxV upgrades on earlier Momentum Models
Comparisons (according to reviewers)
- The Momentum M400 MxV incorporates technology from the Relentless line and gets very close to the Relentless sound regarding space and depth
- The Momentum M400 MxV is smaller and lighter than the Karan Acoustics POWERa mono
- The Momentum M400 MxV is smaller and lighter than the D'Agostino Progression M550 Mono amplifier
Takeaway: The Momentum M400 MxV monoblock is a beautifully designed and powerful amplifier that delivers a smooth and satisfying listening experience. It incorporates technology from the flagship Relentless model, making it a top-tier choice for audiophiles.
Video review
Our take on the brand
Dan D'Agostino is an ultra-premium hifi brand distinguished by its unique copper heat sinks with holes and distinctive circular green-lit VU meters that give their amplifiers a steampunk aesthetic. Their amplifiers feature proprietary "Super Rail" technology that maintains high voltage for front-end transistors, while their three-chassis Relentless Preamplifier uses 30-pin interlocking connectors to eliminate wiring anomalies.
Visit
Momentum M400 MxV
Page
Product Page
Reference 330M
90000
/
Released
2024
Audio Research
The Reference 330M puts you right there, and does not let you forget that you are listening to a living performance captured in time, just waiting to be unearthed with no potential left unrealized. The beauty, the emotion, the dynamics, the life are all there to conjure total immersion, whenever you want it.
Audio Research is a hifi brand that has stayed committed to tube technology while many competitors moved to solid-state designs. The brand is known for its use of KT150 power beam tetrodes and hybrid power supply designs that blend tube amplification with solid-state regulation.
Expand Details
Our Summary
Product Strengths
- Fully balanced design, handcrafted in the USA
- Employs a sextet of KT170 valves, ECC83, and 6H30, with hand-selected and matched valves
- Features Audio Research's 'Auto-Bias' circuitry and an internal hour meter for monitoring valve usage
- Aesthetically elegant design with unique 'Ghost Meters' which are LED-illuminated and can be dimmed or switched off
- Capable of delivering high power at low frequencies, controlling and driving speakers like a big solid-state amplifier
Product Considerations
- High price point
- Requires a 20A IEC cable (supplied)
- The bass control and sheer bass output of the Gryphon Audio Antileon EVO (solid state) could not quite be matched by the Reference 330M
- The unit use a variable speed fan, although it was essentially silent during testing, this may still present a point of concern for some users
Comparisons (according to reviewers)
- Vs Gryphon Audio Antileon EVO: The Gryphon Audio Antileon EVO (solid state) has slightly better bass control and output
Takeaway: The Audio Research Reference 330M is an intelligently engineered and beautifully styled amplifier that embodies the meaning of 'Reference' in sound quality. Its powerful valve design delivers excellent performance and is sure to be a conversation piece in any high-end audio setup.
Video review
Our take on the brand
Audio Research is a hifi brand that has stayed committed to tube technology while many competitors moved to solid-state designs. The brand is known for its use of KT150 power beam tetrodes and hybrid power supply designs that blend tube amplification with solid-state regulation.
Visit
Reference 330M
Page
Product Page
Reference 330M Monoblock
90000
/
Released
2024
Audio Research
Audio Research is a hifi brand that has stayed committed to tube technology while many competitors moved to solid-state designs. The brand is known for its use of KT150 power beam tetrodes and hybrid power supply designs that blend tube amplification with solid-state regulation.
Expand Details
Our Summary
Product Strengths
- Handcrafted in the USA
- Beautifully designed and superbly assembled
- Skillfully balances accuracy and romanticism, combining precision and beauty
- A powerful amplifier that controls and drives speakers effectively
- Provides panoramic vistas of large orchestras in grand acoustic spaces
Product Considerations
- Requires a 20A IEC cable (supplied)
- Bass output could not quite be matched by the Gryphon Audio's Antileon EVO
Comparisons (according to reviewers)
- Outdid the Audio Research Reference 160S, which performed superbly
- Outperforms the Audio Research 750SEL in every way
Takeaway: The product is intelligently engineered, superbly built, and elegantly styled, with a sonic standard that epitomizes the meaning of 'Reference'. It is a blindingly powerful valve-glow beacon of amplification excellence.
Video review
Our take on the brand
Audio Research is a hifi brand that has stayed committed to tube technology while many competitors moved to solid-state designs. The brand is known for its use of KT150 power beam tetrodes and hybrid power supply designs that blend tube amplification with solid-state regulation.
Visit
Reference 330M Monoblock
Page
Product Page
Apex
99000
/
Released
2022
Gryphon
Since its introduction in 2022, Apex has been hailed as the finest power amplifier ever created. Critics and connoisseurs have universally praised its combination of shattering power and sublime delicacy; its ability to drive any loudspeaker balanced with unimpeachable tonal neutrality. It has always been Gryphon's mission to achieve the highest possible audio performance in terms of sheer musicality, transparency and realism. With Apex Mono and Apex Stereo, Gryphon Audio Designs has elevated pure Class A power amplification a titanic leap above what was previously considered possible.
Gryphon is one of the most respected high-end amplifier brands in the world. Its bass grip is phenomenal, thanks to an unusually high level of capacitance, which keeps everything tight and controlled, even with demanding speakers. Gryphon is also known for its bold, brutalist design—a look that a lot of people love. You’ll find their gear all over Europe and Asia, and the Diablo 333 is often considered an ‘endgame’ amp by those chasing the very best sound and aesthetics.
Expand Details
Our Summary
Product Strengths
- Delivers lots of current due to a new 2000VA toroidal transformer
- The Apex Stereo's ease of presentation was immediately obvious—it fully engaged the reviewer
- The amp exuded supreme self-confidence
- The amp simultaneously speeds things up and slows things down
- Superior speaker grip, improving organization, timing, and musical flow
Product Considerations
- Initial start-up can be alarming due to flashing error lights
- The size and weight (445 lbs) can make installation challenging
- It's gigantic and heavy, requiring special equipment and tools to handle its production
Comparisons (according to reviewers)
- Vs Boulder 2060: The Apex revealed more tonally saturated sounds
- Vs Boulder 2060: Apex cast a larger soundstage, and within those huge spaces, images were generally larger and more three-dimensional
- Vs Boulder 2060: Apex exposed more detail in the music
Takeaway: The Gryphon Apex Stereo is a powerful amplifier that brings music to life with a balanced and full sound at any volume. Its ability to reveal the resonant nature of instruments transforms listening sessions into immersive experiences.
Video review
Our take on the brand
Gryphon is one of the most respected high-end amplifier brands in the world. Its bass grip is phenomenal, thanks to an unusually high level of capacitance, which keeps everything tight and controlled, even with demanding speakers. Gryphon is also known for its bold, brutalist design—a look that a lot of people love. You’ll find their gear all over Europe and Asia, and the Diablo 333 is often considered an ‘endgame’ amp by those chasing the very best sound and aesthetics.
Visit
Apex
Page
Product Page
Reference
75552
/
Released
Avid Hifi
Possessing formidable power, unrivalled technology and a herculean appearance this amplifier delivers electrifying signals to your loudspeakers, transforming your music into a thrilling experience.
AVID Hifi is a brand known for its turntables featuring unique engineering like sapphire bearings and dual-stage clamping systems that improve bass grip and soundstage projection. The brand's design philosophy involves developing technology in their high-end models and then adapting it for more affordable products, with their components made from solid aluminum and speakers weighing 100kg for exceptional build quality.
Expand Details
Our Summary
Product Strengths
- Build quality is among the best, with all pieces fashioned from solid aluminum
- The system delivers an effortless and truly reference-level sound
- Produces deep and powerful bass that energizes the room with ease
- Offers stunning analogue playback with incredible soundstaging, holographic image, depth, and width
- Delivers music with startling clarity across all genres
Product Considerations
- The Reference Preamplifier lacks a remote, focusing on a purist design
- The Reference Three speakers are very heavy—weighing 100kg net
Comparisons (according to reviewers)
- The Avid Hifi Reference system performed similarly well with Fanfare for the Common Man, producing impressive bass and dynamics, compared to the YG Acoustics system with Boulder
Takeaway: The AVID HiFi Reference system is a top-tier system delivering exceptional sound quality and effortless power. It is designed to provide an extremely enjoyable and immersive music experience, making it a worthwhile investment for serious audiophiles.
Video review
Our take on the brand
AVID Hifi is a brand known for its turntables featuring unique engineering like sapphire bearings and dual-stage clamping systems that improve bass grip and soundstage projection. The brand's design philosophy involves developing technology in their high-end models and then adapting it for more affordable products, with their components made from solid aluminum and speakers weighing 100kg for exceptional build quality.
Visit
Reference
Page
Product Page
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
Magazine reviewers and YouTubers have tried this product—so we've summarized their strongest opinions below.
How useful are hifi reviews? We consider them useful for three things: (1) Surfacing new products you should demo in person at a dealer. (2) Learning which products reviewers unanimously praise as the best they've ever heard (this means they probably are legitimately great). (3) Identifying a product's unique attributes that satisfy your idiosyncratic needs and tastes. Beyond that, we discount what reviewers say because they heap praise on everything—rarely being negative for fear of souring relationships with manufacturers. Further, they seldom have more than a couple products on-hand at once, relying on their imperfect memories to compare to past products.
Video Review
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