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
- Round, colorful, and illumined sound.
Product Considerations
- Bass boom and splashy cymbals were noted.
Comparisons (according to reviewers)
- More convincing with the Børresen 05 Silver Supreme Edition loudspeakers and Synergistic Research SRX cabling, than with the Verity Sarastro II loudspeakers and Ansuz cabling.
Takeaway: The Thrax Spartacus 300B monoblocks are capable of producing gorgeous sound that is heavenly and convincing. It can seduce listeners with its audio quality.
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Spartacus 300
reviews

Manufacturer details
- Weight: 55kg
- Dimensions: 430x650x300mm
- Power Consumption: 380W
- Voltage: 115/230V 50/60Hz
- Max. input level: 4Vrms
- Output Power: 50W
- Gain: +16db
- Input impedance: 1.5k Ohm
- Output impedance: 0.5 Ohm
- Signal to Noise: 112db
- Frequency response: 20-20,000Hz +/- 1db
- THD @1W: 0.05%
Now for the first time you can actually hear what a 300B really sounds like and prepare to be amazed. Complimented by the finest nano-cystaline core output transformer, nano-crystalline choke power supply it really redefines tube amplification. Spartacus features one of the simplest possible signal paths with absolute zero feedback (wire-vacuum-wire-vacuum-wire).
To achieve simplicity while delivering exemplary performance, each device in the signal path had to be the best possible. The legendary 300B tube was chosen. They are the most linear amplifying devices and some of the very best audio tubes ever made. It is a fact that the distortion of triode vacuum tubes compared to solid-state devices is orders of magnitude lower. Apart from the low distortion level, the type of distortion they produce is a consonant 2...
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:
- Thrax designs its products with a "total system" approach, where each component (preamplifier, amplifier, speakers) is designed to work synergistically, optimizing the overall system performance.
- The brand blends tube and solid-state technologies in unique ways, leveraging the strengths of each to achieve a sound that is both detailed and musical.
- The design and aesthetic of Thrax products are meticulously crafted with high-quality materials like milled aluminum, offering a sophisticated and modern appearance.
- Thrax amplifiers are designed to perform optimally without negative feedback, maintaining tonal purity and offering high resolution at all power levels and loads.
Select products
St. Teres
- Positioning: Positioned as a high-performance stereo amplifier in the Thrax lineup.
- Description: Offers clarity and tone, thanks to its transformer-coupled hybrid design. Features a unique solar cell biasing technique for the output stage, which is not found in the Heros or Enyo, providing noise-free operation and dynamic sound.
Heros
- Positioning: A hybrid amplifier that combines tube sound with modern technology, positioned as a versatile option in the lineup.
- Description: Stands out with its fully differential architecture and transformer-coupled input and output, offering a compact yet powerful Class A performance. Unlike the St. Teres, it uses a single differential DC-coupled FET/Tube stage.
Enyo
- Positioning: A modular audiophile system, integrating multiple components into a single unit, positioned as a comprehensive solution in the lineup.
- Description: Excels with its modular design, combining a preamplifier, DAC, and power amplifier in one chassis, offering a clutter-free setup. Features a unique cathode feedback output stage and a fully differential architecture, unlike the Heros and St. Teres.
Our take on the brand
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Used
Thrax
What if you spend more?
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
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.
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
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
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
What competes at this price?
Our Summary
Product Strengths
- High momentum, dynamic span, effortlessness, and immediacy.
- Open and highly complex spatial frames with loads of air around sound sources, filled with colors securing a zesty, vibrant, moisturized, and articulated view.
- A unique blend of virtues—posh, elegant, euphonic, organic, fresh, and engaging—while showing detail and clarity.
Product Considerations
- Very hot and needs enough space for heat dissipation.
- The shiny chassis attracts dust and fingerprints and requires regular cleaning.
- Elongated narrow enclosures require deeper than usual shelves or floor placement.
- The review unit had an inactive balanced socket that paying customers won't see.
Comparisons (according to reviewers)
- Vs Trilogy 995R: Bass is shallower and not as beefy, but more elastic and complements the higher ranges instead of dominating.
- Vs Aavik I-880: PSE1605 trades some quickness for extra tone.
- Vs Enleum AMP-23R, Nagra Classic-INT, and AGD Production Vivace monos: PSE1605 trades some of its quickness and illumination for more tone and grounded perspective, but still scores very high on detail and clarity.
Takeaway: The Audio Phonique PSE1605 mono amps offer a unique listening experience with exceptional sound and a vibrant soundstage. If one appreciates a combination of elegance, detail, and engaging sound, the PSE1605 could be a great fit.
Video review
Our take on the brand
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
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
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
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
Questions? Ask the brand's dealers.
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