Review: Unison Simply 845 -An Integrated Tube Amplifier

Review: Unison Research Simply 845 is an integrated amplifier - The New Simply 845 ranks at the top of Unison Research’s line of integrated tube amplifiers
5/5 - (1 vote)


Tube amplifiers, with their vintage charm, occupy a special place in the world of hi-fi. The Unison Research Simply 845 is a testament to the enduring appeal of tube technology. This Italian-made amplifier rekindles the magic of tubes in a market dominated by transistor amplifiers. In this review, we delve into the world of the Unison Research Simply 845 to explore its distinctive sound, craftsmanship, and the unique experience it offers.

Tech specs

  • Type-integrated tube amplifier
  • Tubes 2 x 845 selected, 4 x ECC82/12AU7 selected
  • Class Pure class A
  • Output stage topology Single-ended
  • Maximum power 23W
  • Bandwidth 20Hz-50kHz, +0dB; -1dB @ 12W
  • Feedback level 14 dB
  • Output impedance 6 Ω
  • Input impedance 47 kΩ/100pF
  • Inputs 4 line level
  • Outputs 1 tape, 1 subwoofer
  • Power consumption 300VA
  • Sizes Without packaging: 37 cm x 26cm x 57 cm (LxHxD) 14 1/2 x 10 1/4 x 22 1/2  inch
  • Weight 30,5 kg – 67 Ibs
  • Mains fuses 5x20mm – 6.3 AT       100V-120V5x20mm – 3.15 AT     220V-240V

Build Quality and Design

Unison Research is synonymous with high-quality hi-fi, and their Simply 845 exemplifies this reputation. The amplifier’s thick-walled double-box design not only promises but delivers something extraordinary. Craftsmanship takes center stage, with hand-carved applications made from local cherry and walnut wood adorning the amplifier’s chassis. However, the true craftsmanship is hidden beneath the surface, where the Italians wind their own mains and output transformers, vital components for the amplifier’s sound quality.

The build quality and design of the Unison Research Simply 845 are nothing short of exceptional. These aspects are integral to what sets this tube amplifier apart in the world of high-end audio.

Craftsmanship: Unison Research is renowned for its commitment to craftsmanship, and it is evident in the Simply 845. The amplifier’s chassis exudes quality, featuring thick walls and a double-box design that promises exceptional durability and performance. What truly distinguishes this amplifier is the meticulous craftsmanship that goes into its construction. Unique, hand-carved applications made from locally sourced cherry and walnut wood adorn many of Unison’s amplifier models, including the Simply 845. These applications not only add an aesthetic touch but also reflect the brand’s dedication to preserving traditional craftsmanship.

Component Quality: The amplifier’s internal components are carefully selected and of the highest quality. Unison Research takes pride in hand-winding its own mains and output transformers, which are crucial for sound quality. These transformers, typically concealed in vibration-proof metal enclosures, are a testament to the manufacturer’s commitment to excellence.

Visual Appeal: The Simply 845 is visually striking, with its glowing tubes, specially designed chassis, and transformer housing at the back. The amplifier’s tubes, particularly the 845s, emit a beautiful warm glow when in operation, adding to its visual charm. However, it’s important to note that these tubes can get extremely hot, and caution is advised when handling the amplifier.

Size and Weight: The Simply 845 is substantial in both size and weight. With a depth of over half a meter, it towers over most audio racks, making it a dominant presence in any room. The amplifier’s weight, approximately 30 kilograms, further emphasizes its robust build. Its size and weight, while indicative of its high-quality components, can make handling and placement a challenging task.

In summary, the Unison Research Simply 845 excels in build quality and design. Craftsmanship, high-quality components, and visual appeal are all integral to its identity. While its substantial size and weight may pose logistical challenges, they are a testament to its durability and the quality of materials used in its construction. This amplifier is not only a sonic delight but also a visual statement of high-end audio craftsmanship.

Comparison with Competitors

When comparing the Unison Research Simply 845 with its competitors in the world of high-end tube amplifiers, it stands out as a formidable contender. One distinguishing factor is its use of the single-ended triode design, featuring the 845 power tubes. While some competitors may opt for push-pull designs for higher efficiency, the Simply 845’s commitment to single-ended triode technology results in a more direct and transparent sonic presentation. This design choice emphasizes the amplifier’s technical excellence and its ability to convey audio with exceptional clarity and warmth, setting it apart from many other amplifiers in its class.

In terms of power output, the Simply 845 surprises with its ability to deliver nearly 25 watts per channel. This wattage is notably generous for a single-ended triode amplifier, making it more versatile and capable of driving a wider range of speakers compared to some competitors with lower power ratings. While single-ended triodes are often associated with limitations in bass control and speaker compatibility, the Simply 845 manages to mitigate these concerns to a great extent, further enhancing its competitive edge. Its combination of technical excellence, robust power output, and the unique sonic characteristics of single-ended triode amplification position it as a strong competitor among high-end tube amplifiers.


Usability is a crucial aspect of the Unison Research Simply 845 tube amplifier’s design, ensuring that audiophiles can fully enjoy its exceptional sound quality without unnecessary complexity. One of the amplifier’s usability highlights is its strategically positioned input selector switch, located on the upper deck behind a protective grille. This thoughtful placement allows for a direct and efficient signal path, minimizing interference and preserving audio purity. With four high-level inputs to choose from, users have the flexibility to connect multiple audio sources, making it easy to switch between different inputs seamlessly.

Additionally, the amplifier offers two types of outputs, catering to various audio system configurations. The inclusion of an unregulated “tape out” allows users to connect external headphone amplifiers, meeting the needs of headphone enthusiasts who wish to incorporate the Simply 845 into their setup. The regulated preamplifier output further enhances usability by accommodating external devices like active subwoofers or other audio components. These practical features contribute to the amplifier’s versatility, ensuring that it can seamlessly integrate into a wide range of audio systems, both traditional and modern.

However, it’s important to note that while the Simply 845 excels in usability for audiophiles seeking straightforward, high-quality sound, it offers limited adjustment options compared to more complex amplifiers. This streamlined approach aligns with the amplifier’s focus on audio purity and simplicity, catering to users who prioritize sonic excellence over extensive customization. For those seeking a user-friendly and sonically superior amplifier, the Simply 845 provides a harmonious balance between technical excellence and ease of use.

Technical Excellence

The Unison Research Simply 845 is a prime example of technical excellence in the realm of tube amplifiers. At its core lies the single-ended triode design, a classic and revered technology in the world of audio amplification. This design, utilizing the 845 power tubes, showcases the amplifier’s commitment to preserving the authenticity and purity of audio signals. The precision engineering and craftsmanship behind this design are evident in the amplifier’s remarkable performance.

The amplifier’s ability to deliver nearly 25 watts per channel is a testament to its technical prowess within the realm of single-ended triodes. This power output is notably generous for a triode amplifier, defying the conventional notion that such amplifiers are inherently limited in power. The Simply 845’s technical excellence becomes apparent in its capacity to handle a wide range of music genres and listening preferences without restrictions, even during dynamic and bass-rich passages. Its capacity to offer both transparency and power underscores its technical superiority in the world of high-fidelity audio.

Practical Features

The Unison Research Simply 845, while primarily focused on delivering exceptional sound quality, also offers a set of practical features and considerations that enhance its overall usability and convenience for audiophiles:

Input Selection: The Simply 845 includes a well-placed input selector switch on its upper deck, accessible behind a protective grille. This positioning optimizes the signal path, ensuring a short and direct connection between your audio source and the amplifier. There are four high-level inputs available, providing flexibility for connecting multiple audio sources, such as CD players, turntables, or digital audio sources. This versatility allows you to switch between different sources with ease and precision.

Output Options: The amplifier provides two types of outputs. The first is an unregulated “tape out” that can be used for connecting external headphone amplifiers, making it convenient for headphone enthusiasts to integrate the Simply 845 into their audio setup. The second output is a regulated preamplifier output, which can be utilized for connecting external devices like active subwoofers or other audio components. This feature enhances the amplifier’s versatility and compatibility with various audio systems.

Optimized for 6 Ohm Speakers: The Simply 845 is optimized for use with 6-ohm speakers. While more demanding speakers can also be used, Unison Research has tailored this amplifier to work seamlessly with speakers of this impedance. This focus on compatibility ensures that the amplifier performs optimally with a broad range of speaker options, provided they match the recommended impedance.

Heat Management: Given the nature of tube amplifiers, the Simply 845 generates a significant amount of heat during operation, particularly from its 845 tubes. To address this, Unison Research has designed the amplifier with a protective grille and a reflective false floor to redirect and dissipate the radiant heat away from the amplifier’s sensitive components. While the amplifier does emit a warm glow due to the tubes, it is important to exercise caution and avoid touching the tubes during operation due to their high temperatures.

Limited Adjustment Options: It’s important to note that the Simply 845 offers limited adjustment options compared to some modern amplifiers. This streamlined approach is intentional, catering to audiophiles who prioritize sonic purity and simplicity over extensive controls and customization. While some advanced users may appreciate the straightforward design, others may find it less accommodating for fine-tuning specific audio preferences.

Size and Weight: The physical size and weight of the Simply 845 should be considered as practical factors during setup and placement. With its substantial dimensions and weight of approximately 30 kilograms, the amplifier demands sturdy and well-ventilated support. Careful consideration of its placement is essential to ensure proper ventilation and safety.

In summary, the Unison Research Simply 845 incorporates practical features that enhance its usability and versatility. These features include input selection options, multiple output choices, optimization for 6-ohm speakers, and effective heat management to ensure safe and efficient operation. However, it is designed with simplicity in mind, offering limited adjustment options compared to more complex amplifiers. Its substantial size and weight should also be considered when planning its placement in an audio system.

Listening Experience (Sound Quality and Sound Test)

The Simply 845’s sound quality is breathtaking. It offers a unique clarity and purity, particularly in reproducing voices and acoustic instruments. The amplifier’s single-ended design allows it to excel in rendering fine details and nuances, making each note a captivating event. It provides an exceptional listening experience that sets it apart from traditional transistor amplifiers.

The Unison Research Simply 845 tube amplifier delivers a sound quality that is nothing short of captivating. It’s a unique listening experience that sets it apart from traditional transistor amplifiers and even some other tube amplifiers.

Temperament, Clarity, and Warmth: One of the standout qualities of the Simply 845 is its temperament, clarity, and warmth. Tube amplifiers, especially single-ended triodes like this one, have a distinctive character that can significantly impact the listening experience. The Simply 845 strikes a remarkable balance between these characteristics, providing a sound that is both engaging and transparent.

Interaction with Speakers: The amplifier’s interaction with speakers is a critical aspect of its sound quality. Unlike transistor amplifiers, where the speaker’s role is relatively straightforward, tube amplifiers like the Simply 845 introduce a more intricate relationship between the amplifier and the speaker. This interaction can vary significantly from amp to amp and from speaker to speaker. In the case of the Simply 845, it behaves exceptionally well-naturedly.

Balanced Sound: The Simply 845 manages to deliver a balanced sound even when paired with three-way floorstanding loudspeakers. It doesn’t allow any frequency ranges to excessively stand out or become recessed. This balance makes it easy to appreciate the amplifier’s qualities, particularly its ability to present voices with heavenly clarity and directness.

Instrument Reproduction: In addition to its prowess with vocals, the Simply 845 excels in reproducing acoustic instruments. Guitars and pianos, for example, come to life with exceptional purity and decay. The amplifier’s single-ended triode design makes it exceptionally impulsive and clear, preserving the subtle nuances of instrument performances.

Single-Ended Triode Magic: Single-ended triode amplifiers like the Simply 845 have their unique charm. They can reveal fine details and dynamics in music that may go unnoticed with other amplifier types. The warmth and richness of their sound can be beguiling, drawing the listener into the music in a profound way.

Power and Clipping: While tube amplifiers, especially single-ended ones, are often associated with limited power, the Simply 845 challenges this notion. With nearly 25 watts per channel, it offers substantial power for a triode amplifier. This means that it can handle a wide range of music genres and listening preferences without restrictions. It’s capable of delivering forceful and bass-rich music without distortion, even during dynamic passages.

However, it’s worth noting that single-ended triode amplifiers like the Simply 845 may have limitations on real speakers, especially in terms of controlling heavy bass membranes and ensuring precise start-stop responses. Despite this, the Simply 845 manages these limitations admirably and allows for an enjoyable listening experience, even with rock and electronic music.

In conclusion, the Unison Research Simply 845 offers a sound quality that is characterized by temperament, clarity, and warmth. It excels in rendering voices and acoustic instruments with exceptional transparency and purity. The interaction between the amplifier and speakers is harmonious, making it a versatile choice for a wide range of music genres. Its single-ended triode design introduces a unique charm that can be profoundly engaging for audiophiles seeking a distinctive listening experience.

Reasons to Buy/Not Buy It

Reasons to buy the Simply 845 include its remarkable craftsmanship, distinctive tube sound, and the ability to create an immersive and intense listening experience. However, potential buyers should consider factors like the choice of speakers and the amplifier’s heat output.

Reasons to Buy the Unison Research Simply 845:

  1. Exceptional Sound Quality: The Simply 845 delivers audiophile-grade sound quality characterized by clarity, warmth, and an uncanny ability to convey intricate musical details. If your top priority is achieving an immersive and high-fidelity listening experience, this amplifier is an excellent choice.
  2. Single-Ended Triode Design: Its use of the single-ended triode design with 845 power tubes sets it apart, offering a transparent and direct sound signature that many enthusiasts find captivating. This design choice is a reason to buy if you value audio purity.
  3. Ample Power Output: With nearly 25 watts per channel, the Simply 845 provides ample power for a wide range of speakers, making it versatile and capable of handling various music genres and dynamic passages.
  4. Flexible Input and Output Options: The amplifier’s input selection options and multiple output choices cater to different audio setups, providing flexibility and convenience in integrating it into your system.

Reasons to Consider Alternatives:

  1. Limited Adjustment Options: If you prefer amplifiers with extensive customization and fine-tuning options, the Simply 845’s streamlined design and limited adjustments may not align with your preferences.
  2. Physical Size and Weight: Due to its substantial size and weight, the amplifier demands a sturdy and well-ventilated support system, which may be challenging for users with limited space or those seeking a more compact amplifier.
  3. Specialized for Audiophiles: The Simply 845 is tailored for serious audiophiles who prioritize sound quality above all else. If you are looking for an amplifier with additional features like built-in streaming or digital connectivity, you may need to explore alternatives with more comprehensive functionality.

In summary, the Unison Research Simply 845 is an ideal choice for audiophiles seeking top-tier sound quality and a genuine single-ended triode experience. Its limited adjustment options and substantial physical presence may not suit all users, particularly those who desire more customization or have space constraints. It is best suited for enthusiasts who prioritize the art of pure, high-fidelity audio reproduction.

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The Unison Research Simply 845 may offer just 2x 23 watts of power, but its impact on the world of hi-fi is disproportionate to its specifications. With the right speakers and a carefully selected setup, this Italian-made amplifier transforms music into a captivating and intense experience. Its craftsmanship, the allure of glowing tubes, and its exceptional sound quality make it a unique addition to the world of high-end audio.

Advantages of the Unison Research Simply 845:

  1. Exceptional Sound Quality: The amplifier offers remarkable audio quality characterized by transparency, warmth, and a capacity to reveal intricate musical nuances, making it a top choice for audiophiles.
  2. Single-Ended Triode Design: Its use of single-ended triode technology with 845 power tubes delivers a unique and direct sound signature appreciated by enthusiasts seeking sonic purity.
  3. Ample Power Output: With nearly 25 watts per channel, the Simply 845 provides substantial power, ensuring compatibility with a wide range of speakers and musical genres.
  4. Flexible Input and Output Options: The amplifier’s input selector and multiple output choices enhance its adaptability to different audio setups, offering convenience and versatility.
  5. Quality Craftsmanship: Handcrafted in Italy, the amplifier boasts exceptional build quality, and its aesthetic appeal is complemented by hand-carved wooden applications, reflecting meticulous craftsmanship.

Disadvantages of the Unison Research Simply 845:

  1. Limited Adjustability: The amplifier offers limited customization options, which may disappoint users who prefer in-depth control over their audio settings and adjustments.
  2. Size and Weight: Its substantial physical dimensions and weight can be challenging to accommodate in smaller spaces or setups, requiring sturdy furniture and ventilation.
  3. Specialized for Audiophiles: The Simply 845 is tailored for dedicated audiophiles and may not appeal to those seeking integrated features like digital connectivity or streaming capabilities.
  4. High Price Tag: The amplifier’s premium sound quality is reflected in its price, positioning it as an investment for serious audio enthusiasts with a generous budget.
  5. Heat Emission: Due to the nature of tube amplifiers, the Simply 845 generates considerable heat during operation, necessitating adequate ventilation and care to prevent accidental burns.