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845 Single to "Another Dimension Scale"
It retains the unique heat of the 845 without muddying the contours of the sound image
The KR 845 is designed to "use up" the scale of the 845 single with the precision and design of current production.
845output tubeIt is one of the representative of the world that "rings with voltage". The 845 single A class with a fixed circuit pushes the scale without losing density, and can produce core energy while making the sound field larger. The KR 845 is positioned as a model that reorganizes the 845 with a modern design.
There are two keywords in terms of structure. One is a new ribbon filament, and the other is a patented structure with 32 cathodes. While keeping in mind the pure A-class output range (20-26W class) that can be aimed at with the 845, it is made with a strong awareness of the stability and practicality of operation. It is assumed that it will be supplied in matched pairs.
In the world of 211 amplifiers, it is common to talk about designs that aim for the 20-26W class with pure A-class. The KR211 is also distributed on the premise of 211 single/211 amplifiers in that range, and is treated as classic 211 compatible.
Precautions for use
The KR 845 has a filament of 10 V (±5%) / 1 A. If you plug it into a typical 845 amplifier (assuming 10V/3.25A) as it is, the filament power supply will remain on the "3.25A assumption", and the actual measured heater voltage may be higher. The upward runout of the heater voltage is detrimental to lifetime and stable operation, so please adjust it by adding a series resistor so that it can be within 10V±5% in actual measurement.
| Pure A-class output (approximate) | 20~26W |
|---|---|
| Filament voltage | 10V（±5%）/1A |
| Basic characteristics (amplification rate) | 5.3 |
| Representative Action Points (A1 Class) Va / Ia / Vg | 650V / 90mA / -68V |
| Representative action points (A1 class) | 4.0mA/V / 3.0kΩ |
| Maximum current | 140mA |
| Maximum plate voltage | 1250V |
| Maximum plate loss | 100W |
| THD (Approximate) | <0.1% |
When replacing the standard 845 with the KR 845 in the Audion Black Shadows (845 SET), you can clearly improve both the handling of low frequencies and the perceived volume, ultimately achieving a 'SUBLIME' tightness. However, initially you may struggle with flashover, and adjustments including proper setup and protective circuits are necessary. This is not plug-and-play; once you adjust for the KR 845, returning to the standard 845 will also require recalibration.
In the Thöress 845 monoblocks (equipped with KR Audio 845), the low end becomes cohesive with warmth, power, and thickness, allowing even difficult-to-drive speakers like the Harbeth M40.1 to play with plenty of headroom. Rather than tightening through so-called 'absolute damping,' it creates a strong foundation while maintaining band connectivity, giving a sensation of the entire sound weighing solidly on top. As a result, the sound image extends well into the lower frequencies with a sense of presence and realism.
