A portable device reliant solely on smartphone power, the diminutive nature of a "small DAC" leads to issues like weakened dynamics, diminished detail, and limited power output, all stemming from the constraints of the power source. Liberating a smartphone decoding earphone amplifier from this reliance on phone power is a straightforward method to immediately invigorate its sound performance, breaking free from power supply limitations. This concept is not lost on audiophiles like myself, and it underscores the necessity for audio brand designers to grasp this fundamental principle. This recognition has given rise to a new category in the market known as the "big DAC," namely a smartphone decoding earphone amplifier featuring an independent battery power source. A notable example of this innovation is exemplified in products like the Audirect BEAM 4. A notable characteristic of this product is its departure from an overly stylized approach. In contrast to typical small tail devices found in the market, which often exhibit intentional thickness or mid-low frequency emphasis, the sound signature of the BEAM 4 is relatively neutral and organic. Particularly noteworthy are the purity of the mid-to-high frequencies and the overall natural, enduring listening experience, which transcends the typical boundaries associated with standard small tails. This neutral design approach carries a degree of risk. Without a sufficiently robust sound foundation and strong quality, it could potentially lead to sharpness in the high frequencies and stiffness in the overall frequency response.
Enhanced battery current output capability should notably contribute to improving performance in these areas compared to direct power supplied by the phone. While the BEAM 4 maintains a neutral sound profile, it does not come across as thin; instead, it exhibits a moderate thickness in the mid-low frequencies. Furthermore, it demonstrates commendable speed and dynamics within the mid-low frequency range. It's essential to acknowledge that despite its satisfactory performance, this does not equate to the standards set by high-end music players, where a noticeable gap still exists. However, when compared to small tail products reliant on direct phone power, the BEAM 4 offers significant advantages in these aspects.
With its commendable current output capability, the BEAM 4 offers robust headphone driving power. It's crucial to disregard the promotional claims from various brands and not solely rely on listed headphone output power figures. Actual headphone driving performance is contingent upon the power supply system and the design of the analog amplification circuit. In this regard, the BEAM 4 holds a competitive edge. Most earphones available on the market should have no issues with driving and can meet basic power requirements, even though perfection isn't guaranteed. The device's relatively neutral style simplifies the headphone pairing process, alleviating concerns about compatibility between headphones and the small tail—a rarity in this category. However, in the case of over-ear headphones, it's advisable not to expect exceptional performance unless using a portable model specifically optimized for portability. Although such headphones may reach satisfactory volume levels, they often lack dynamic range. If compact size is a high priority for your DAC/AMP, perhaps limiting choices to original Apple products or models small enough to snugly fit in a shirt pocket alongside the phone, then the BEAM 4 may not fit the bill. While the BEAM 4 is considered one of the most compact models among small DAC with an independent battery, it remains notably larger than regular small tails powered directly by the phone. At a weight of 62 grams, portability is not a major concern. However, if size isn't a key factor for you, the Audirect BEAM 4 currently excels in user experience when compared to other small tails with an independent battery power source, offering a markedly improved sound experience over models powered by the phone. Particularly in terms of price, the BEAM 4 stands out as a top-tier product in the market, undoubtedly delivering exceptional value for its performance ratio.

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