The Drop + xDuoo TA-84 review sample was kindly provided free of charge. I didn’t receive monetary or any other kind of compensation and I don’t use affiliate links. The price of the amplifier is $399 and is available exclusively from Drop.
Drop + xDuoo TA-84 Review
Drop has established several fruitful partnerships over the last decade or so and crafted numerous high-caliber headphone amplifiers, which have garnered various accolades. However, it’s worth noting that all of their previous models were either solid state or tube hybrids. Therefore, the Drop + xDuoo TA-84 marks a significant milestone as their inaugural all-tube headphone amplifier, featuring an OTL topology.
OTL topology
The collaboration between Drop and Chinese manufacturer xDuoo has resulted in the creation of the amplifier, known as Drop + xDuoo TA-84. xDuoo, with their extensive expertise in tube amplifiers, has employed the Output Transformerless (OTL) topology in this amplifier, effectively managing the signal without the need for a transformer. This design choice significantly reduces distortion.
In the preamp phase, the TA-84 utilizes dual ECC82 tubes, while the power amp phase runs on dual EL84 pentodes. These tubes generate high impedance, low current, and high voltage signals. However, for headphones or speakers, it is necessary to convert these signals into low impedance, high current, and low voltage signals. This conversion can be achieved through the use of output transformers or coupling capacitors, each method having its own advantages and disadvantages.
In the case of the TA-84, xDuoo has incorporated their specially designed capacitors in the power amp section to perform this conversion. These capacitors are not only exceptionally quiet but also impressively linear. However, since they directly output from the power tube, the amplifier’s output impedance is relatively high. As a result, it is best suited for use with high impedance headphones starting from 100Ω and higher.
One of the key benefits of the OTL topology is that it allows for low distortion and high linearity. Additionally, it provides a sound that closely resembles the character of the output tubes, without any interference from a transformer.
Stepped attenuator
The Drop + xDuoo TA-84 features a stepped potentiometer with 21 defined steps, each with a specific resistance value. This design ensures exceptional precision, reliability, and channel balance in the output level. Additionally, the gain switch at the back allows you to find the ideal setting for your preferred headphones or powered speakers. With a 16dB difference between low and high gain, you can easily customize the audio experience. The 21 steps provide ample room for fine adjustments without sudden volume jumps. However, it is worth noting that the rotating action of the potentiometer may feel slightly stiff and lacks smoothness.
Onboard DAC and preamp
In addition, the xDuoo TA-84 is equipped with a built-in USB DAC featuring the ES9018K2M DAC chip. This exceptional chip supports input sampling rates of up to 32bit/384kHz PCM and DSD256, ensuring high-quality audio reproduction. Moreover, the TA-84 boasts a preamplifier line output for both the line input and the onboard USB DAC. This convenient feature enables users to enjoy the warm tube sound with their preferred active monitors. However, it is important to note that the headphone and preamplifier outputs are active simultaneously, meaning that plugging in headphones will not mute the preamp.
Appearance
The Drop + xDuoo TA-84 amplifier boasts a sleek, oblong shape with precise measurements of 26.8×16.3×11.6 cm. While it stands tall, it remains narrow and compact, allowing for versatile placement as long as sufficient height clearance is available. Crafted from a full aluminum alloy construction, the chassis exudes a refined elegance with its smooth black finish. Notably, the amplifier is impeccably manufactured, devoid of any sharp edges or corners.
Embracing a simple and minimalist design, this amplifier embodies the timeless appeal of a classic tube amplifier. The tubes are prominently positioned at the front, while the power transformer is securely enclosed within a box at the rear. Conveniently, all four tubes are easily accessible and can be effortlessly replaced when needed.
The front panel maintains a clean and uncluttered aesthetic, with the volume control knob centrally located. Beneath it, a status red LED and a 6.35mm headphone jack add to the amplifier’s functionality. On the rear, you will find the AC input plug, power on/off switch, voltage selector switch, USB type-C input, RCA line input, RCA preamp output, as well as gain and input selector switches.
Accessories
The package comprises of the stock tubes, a standard power cord, and a premium 1m long USB type-C to A cable.
Operation
The amplifier is equipped with a delay starting function, which grants approximately two minutes for the tubes to warm up before it activates. It offers a straightforward operation, as you have the option to connect your preferred source through the line input or utilize the built-in USB DAC without any driver installations required.
Power output and noise
The xDuoo TA-84 delivers a rated output power of 44mW/100Ω, 83mW/300Ω, and 93mW/600Ω. While these numbers may seem low at first glance, they are not because the amplifier excels in providing the necessary voltage swing to drive high impedance headphones effortlessly.
During my testing, I paired the xDuoo TA-84 with various high impedance headphones including the Sennheiser HD8XX (300Ω), Sennheiser HD660S2 (300Ω), Sennheiser HD650 (300Ω), and the iBasso SR3 (150Ω). To my amazement, the amplifier exceeded my expectations by delivering excellent dynamics and an abundance of headroom. Even at just ¼ of the volume range on the high gain setting, the amplifier effortlessly drove all of these headphones, leaving no room for disappointment.
The noise floor of the amplifier is relatively low, although it is not completely silent. To hear any tube hiss or transformer noise, you will need to increase the volume above the halfway mark. It is important to note that the xDuoo TA-84 is not designed for use with low impedance, high sensitivity headphones, so discussing its behavior with such headphones is irrelevant.
To ensure proper heat dissipation, the amplifier features venting slots on both sides and at the bottom. While it does get warm during use, it does not become excessively hot. The volume knob remains cool to the touch, allowing you to safely position the xDuoo TA-84 in a rack. Just make sure to leave approximately 5 cm of clearance above the transformer and on both sides.
Tube talk
The package includes the stock ECC82 and EL84 tubes from the Psvane classic series. However, it seems that these tubes were made for bulk production without undergoing thorough quality inspection or matching. Unfortunately, both ECC82 tubes in the review sample were highly microphonic, and one of them even had a defect that caused heavy background hissing noise. Although the power tubes were fine, I decided to replace all four of them.
Fortunately, both types of tubes are commonly produced by various manufacturers and are reasonably priced. After researching prices and availability, I opted to order matched pairs of JJ Electronic tubes for both the ECC82 and EL84 variants.
Once I replaced the tubes, the amplifier became completely silent without any background hiss or microphonic noise. It worked flawlessly. Additionally, I found that the JJ EL84 power tubes were more dynamic, controlled, and technically potent compared to the stock ones. Therefore, I recommend trying out different tubes to maximize the amplifier’s performance.
It’s important to note that the xDuoo TA-84 is an all-tube amplifier, so it requires at least half an hour of warm-up time for the tubes to reach their ideal working temperature.
Before conducting any listening evaluations, I left the amplifier playing music for approximately 150 hours. This allowed both the tubes and capacitors to settle down and perform optimally.
Listening impressions
The majority of the testing was conducted using the line input of the Drop + xDuoo TA-84 amplifier, while less testing was done with the onboard DAC. My primary sources for testing were the Aune X8 XVIII and the Goldenwave Serenade DACs.
The xDuoo TA-84 exhibits exceptional sonic performance, making it an outstanding amplifier. It possesses a delightful and highly enjoyable sound signature that combines the enchanting qualities of tube amplifiers with the technical prowess of solid-state amplifiers in the same category.
The sound produced by the xDuoo TA-84 is slightly warm, rich, and harmonious, offering a remarkable level of musicality and an incredibly analog-like character. The timbre is natural, organic, and realistic, accurately reproducing the nuances of acoustic instruments and vocals with lifelike precision. It delivers the most vibrant harmonies and a wide range of overtones.
Not your grandfather’s tube amp
The xDuoo TA-84 amplifier adopts a contemporary approach in its tube implementation. Its audio circuit is meticulously engineered to maintain neutrality, avoiding excessive coloration or distortion of the measured frequency response. Unlike older tube amplifiers that tampered with the frequency response, muffled the treble, and emphasized the midrange and bass to create a syrupy, warm, and indistinct sound lacking control and definition, the TA-84 prioritizes accuracy and clarity.
The xDuoo TA-84 is an amplifier that maintains a strong and highly competitive technical performance. It offers a neutral and linear sound, ensuring that treble extension and clarity are not compromised. The audio produced by this amplifier is vibrant and full of energy, showcasing exceptional definition and remarkable detail retrieval. The bass is quick, precise, and well-controlled, with impressive layering. The mid-range is expansive, prominent, and clearly defined, devoid of any noticeable coloration.
Tube magic
The significance of tubes may be questioned by some. However, the truth is that tubes possess the remarkable ability to enhance even harmonics across the entire frequency spectrum. This results in a delightful and smooth sound that resembles analog characteristics and exudes a sense of musicality. Moreover, tubes contribute to a rich and powerful low-end, creating a visceral and full-bodied experience, while still maintaining excellent dynamics and physical impact. The mid and higher frequencies also possess a full-bodied and weighty quality, ensuring a cohesive sound without any loss of treble weight. The decay of notes is natural, with a timely fade that is neither too fast nor too slow, and each note is intricately sculpted, providing a holographic relief.
Within the same price range, certain solid state amplifiers possess a more technical character, offering superior transparency, clarity, intricate detail reproduction, and noteworthy bass impact. However, none of them can rival the intrinsic musicality, harmonious essence, and fluidity in music delivery exhibited by the xDuoo TA-84.
The Drop + xDuoo TA-84 stands out among its competitors as it delivers a truly immersive and rich sound experience. While some solid state amplifiers may offer comparable holographic properties, none can match the visceral and full-bodied sound of the TA-84. Its expansive soundstage creates an open and spacious listening environment, with larger-than-life images. While there may be solid state amplifiers that excel in imaging precision and positioning accuracy, none can rival the sheer holographic and majestic sound of the xDuoo TA-84.
Sonic bliss
The xDuoo TA-84 proved to be an exceptional performer when paired with high impedance headphones during my testing. However, one particular headphone stood out among the rest. The amplifier seemed to be custom-made for the Sennheiser HD8XX (as well as the HD800S), as it effortlessly delivered a visceral and rich texture, impactful bass, and an incredibly organic sound. The synergy between the xDuoo TA-84 and the HD8XX created a heavenly sonic experience. When coupled with a natural sounding DAC, such as the ones mentioned earlier, this combination offers a deeply satisfying and highly musical experience that can rival much more expensive setups.
The onboard DAC
The onboard DAC offers exceptional clarity, linearity, and transparency, making it a perfect match for the abundant power of the amplifier. It delivers impressive performance, especially when budget constraints are a concern. However, the xDuoo TA-84 takes scalability to a whole new level, and if you opt for a high-quality external source, you will undoubtedly experience even better results.
In the end
The xDuoo TA-84, Drop’s inaugural all-tube, OTL headphone amplifier, stands out as their most impressive product to date. Its musicality, captivating sound, and analog essence make it an exceptional amplifier, boasting competitive technicalities, remarkable tube rolling potential, and ample power to drive high impedance headphones. Crafted with precision and durability, featuring a top-notch onboard DAC and preamplifier output, the Drop + xDuoo TA-84 offers outstanding value and ranks among the finest OTL amplifiers on the market, all without breaking the bank. In fact, considering the current options available, you would need to spend at least twice the amount to find something marginally superior to the xDuoo TA-84. Therefore, I highly recommend seizing the opportunity and acquiring one before it becomes unavailable.
Copyright – Petros Laskis 2024.
+ Natural and organic timbre + Musical and engaging + Immersive and holographic soundstage + Technicalities and transparency + Low noise + Plenty of power for high Z headphones + Responds well to tube rolling + USB DAC and preamp output + Easily accessible tubes + Compact size + Build quality - Not recommended for low Z headphones - No coaxial digital input - Stock tubes - Stiff potentiometer - Headphones won't mute the preamp
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