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KR AUDIO 300B(WE Clone)Direct Heat 3-Poleoutput tube
The core of the 300B, the "sense of reality in the midrange", is more visible and powerful in modern design.
What I expect from the 300B is not a production of sweetness, but a natural alignment of the vocal presence, the luster of the strings, the core of the piano, and the vanishing of the hall tone. The KR AUDIO KR300B is organized in the direction of improving the information outlook without losing the contours of the sound image without losing the character of the 300B. It is suitable for those who are looking for a type that does not get tired even after listening to it for a long time, but does not diminish the heat of the music.
The core of the structure is located in the ribbon filament. In addition, it introduces a unique patented design called "32 cathodes", which has a high vacuum level (10^-8 Torr) and a low grid current (up to 2.0 μA). The idea of making it easy to stabilize the state even after the sound is included from the beginning, and it is designed in a way that does not make the 300B a "consumables with large hits and misses".
In terms of numbers, you can see the skeleton that realistically uses up the 300B. The filament is 5V (±5%)/1.2A and the amplification factor is 3.9. The maximum rating is 550 V plate voltage, 120 mA plate current, and 50 W plate loss. Typical conditions for A1 class are plate voltage 450 V, plate current 100 mA, grid voltage -90 V, mutual conductance 6.2 mA/V, and plate resistance 630 Ω. While it is easy to assemble within the framework of a 300B compatible amplifier, it is essential to check the heater capacity (1.2A margin) and bias conditions. If this is right, both the cohesion and life of the sound will be stable.
| Filament voltage | 5V（±5%） / 1.2A |
|---|---|
| Basic characteristics (amplification rate) |
3.9 |
| Representative Action Points (A1 Class) Va / Ia / Vg | 450V / 100mA / -90V |
| Representative action points (A1 class) | 6.2mA/V / 630Ω |
| Maximum current | 120mA |
| Maximum plate voltage | 550V |
| Maximum plate loss | 50W |
The review emphasizes a well-balanced sound centered on transparency. Through proper break-in, any harshness is smoothed out, giving a strong sense of airiness in the midrange. The low frequencies are not exaggerated in quantity but maintain the necessary punch and density, providing a solid foundation. The high frequencies are described as naturally settling without stimulating, retaining the character of the source material.
The product also receives high marks for craftsmanship, with references to the physical quality of the appearance and the base. It is noted that the product offers a sense of reliability and ease of use in daily operation.
