INTRODUCTION & FEATURE

In the vacuum tube amplifier world, 845 is one of the most loved and trusted kinds of power tubes because of the sonic maturity that this tube brings. However, to exploit all the strengths of the 845 tubes is not really easy.

Our engineering team has spent nearly 15 years researching, testing and developing a wide variety of 845 vacuum tube amps ranging from push-pull to single end circuits, including power amps and integrated amplifiers. The power of our 845 vacuum tube amplifiers is various from 20w to 90w. Eagle 845 is one of the latest official models in the 845-tube amp family that ThivanLabs has researched and developed since the 2000s.

Eagle 845 inherits and comprehensively promotes the achievements of ThivanLabs 845 tube amplifier research and testing. The amp uses two 845 tubes for the power stage and 12AU7, 6SN7, 6V6 tubes for the pre stage. This latest model is a single-ended design with the output power 22W (Class A). The single-ended design achieves the Eagle 845 a soft, refined yet poised timbre, good speaker control and full warm bass. The amplifier is extremely easy to pair with different speakers.

When paired with our Eros speaker models, they bring an impressive musical stage, fully demonstrating the strength of the sound characteristics of the 845 tubes, which is the stability of sound, the detail and sophistication of the timbre and the fullness of all sound range. Eagle 845 is really like a professional artist who has undergone a rigorous process to reach perfection, technical virtuosity to express the best emotions in music.

The optimal circuit design for the amplifier’s 845 tubes has achieved an utmost outstanding effectiveness in reproducing the sound naturally and in a greatly high-fidelity level. Almost all genres of music from orchestra classical music, ensembles, chamber music, solo instruments, international vocal music, to Vietnamese lyrical music are excellently performed.

For classical music, a system with Eros-9 Ultra loudspeaker driven by Eagle 845 optimally reproduced a wide, full sound stage, natural instrument sounds, and clear sonic background. Moreover, the movement of sound in the space is very realistic, very close to the actual performances in the auditorium.

For vocals, the image is clear, detailed, smooth, warm. The singer’s emotions are expressed realistically, especially for emotional romantic songs.

For musical instruments, in addition to the detail and completeness of the instrument’s sound, it also retains its naturalness, not being exaggerated. Good recordings will show this difference very clearly.

The materials and parts used for the amp are all selected with utmost care and Eagle-845 is optimally assembled by Point-to-point method with strict quality control by ThivanLabs. This results in a very high durability and a working stability of the amp, which build up a long life of the product.

Eagle-845 totally utilizes output transformers (OPTs) researched and manufactured in-house by ThivanLabs. This is also the strength of ThivanLabs’s vacuum tube equipment, which brings a unique natural sound quality.

The output transformer (OPT) is a very important component to transmit audio energy from the tubes to the speaker, arguably the most important in the engineering design of a single ended tube amplifier. We have accumulated a lot of practical experience through an over 15-year process of directly designing and manufacturing output transformers with tens of thousands of products until now with many different electronic product types to achieve the best specs and most optimal quality of ThivanLabs OPTs. ThivanLabs currently research and manufacture almost all types of transformers such as Toroidal Core, C-core, EI for various amplifier types including Single Ended, Push Pull, OTL etc with output power from 3W – 400W.

The Output Transformer (OPT) has been specially designed and engineered by ThivanLabs with a “no compromise” criterion to achieve the best sound with the 845 tubes. As a result, the official OPT total weight of almost 11kgs, the heaviest and largest OPTs used for the 845 amp in the world. This has created an extended frequency range from 8Hz – 38kHz with low distortion without using feedback that makes the sound less emotional and negatively affects music quality.

Using small OPT has truly more negative results for the reproduced sound. If a small output transformer (OPT) is used, the ferromagnetic core will also be small. Then the low frequency sonic signals of 20-30Hz passing through the small iron core are not loaded enough and attenuate this frequency range, leading to a weak and thin bass. To deal with the weakness of the small OPT and get better specs, some engineering designs use as much feedback as possible to improve bass frequencies. However, although applying more feedback possibly gets good measurements, it is not the best way to solve the core of the problem and influence the reproduced sound in a negative way. Accordingly, the bass sound will often stiffen, no longer preserving the original naturalness. Using a small OPT means the copper wire wound on it must also be small and this makes the coil impedance high, leading to a remarkable signal loss of the OPT. As a consequence, dynamics and details of the sound get lost, especially in the climax segments of the music.

Therefore, the use of large OPT is the best way to get the best sonic signal transmission. Although this way increases the production cost and the weight of the Eagle 845 to nearly 60kgs, it definitely deserves its value in getting the best sound and music. In this case, the weight really represents the value it brings to the sound.

Another outstanding advantage of Eagle 845 is the use of Interstage Transformer (IT). This is also the strength of the tube amplifiers engineered by ThivanLabs. A special Interstage Transformer is designed for the driver stage for 845 tubes, which provides low impedance for the driver stage, bringing up a super well control of the power tubes. The use of IT provides a very good control for all operating power levels from low to high. As a result, the sound truly matures with an extremely good balance and poise whether played at high or low volumes. This is very evident in the sound stage that Eagle 845 reproduces very wide and deep, so airy as well as a clear image of the sound and a natural timbre.

The Eagle-845 is a large step forward in the series of 845 amps we’ve researched and developed over the past 15 years. This amp offers great sonic value for audiophiles who always seek for the purest and most natural, highest fidelity beauty of the sound and listen to music because of the beauty and emotions it brings to the listeners.

The difference in amp models released in 2022 is the integration of a sound mode selection feature including standard dynamic (Standard/Dynamic) and high dynamic (Dynamic/High Dynamic). The sound mode selector is located on the front of the amplifier for convenient use. This feature gives players a more varied and enjoyable music experience. Based on the common sound standards of ThivanLabs audio equipment, the sound always has been focused to get very good dynamics, whereby Standard (or Dynamic) mode has a very good dynamic in the most balanced whole sound. For High Dynamic (or Dynamic) mode, dynamics are enhanced. Accordingly, the sound is wider and more spacious. Depending on sound preferences and music genres, users can choose their favorite mode.

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