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A-2500 Single-Ended Triode 211 or 845 monoblock amplifier



Transparency, purity, and presence – with real drive and bass! The 211 and 845 tubes finally reveal their true musical potential. Meet the A-2500 pure SET monoblocks!



We and many other audiophiles around the world have been asking for many years, and at last, KS Park found time to address requests for a SET amp using 211 or 845 power triodes! We got both!!

The A-2500 SET monoblock power amps use the customer’s choice of the famously musical 211 or 845 power tube. Both versions give the user 20 watts per monoblock of pure SET bliss. The input tube is a double triode (a 6CM7 for the 211 and 6DR7 for the 845 – not interchangeable) and the rectifier in both versions is the well-known, great-sounding and reliable 5R4.

The lucky few who have heard field-test samples, as well as first purchasers in Asia and Europe, have been deeply impressed by the A-2500 sound –  all the “transparency and presence” of the 211 and 845, “dead quiet”, “amazing drive and dynamics!” Not to mention feedback that these “‘little'” beauties are models of elegant industrial design“.

The A-2500s are sure to please and become highly-treasured components of your audio system!


Key Features

  • The A-2500s are single-ended triode monoblock power amplifiers. Each monoblock provides 20 watts of pure Class A, continuous power with either the 211 or 845 tube.
  • Point-to-point hard-wired circuitry
  • Fixed bias” for 211 and 845; easy to adjust bias point on top of chassis. To provide constant current (bias) monitoring for the power tubes, Allnic uses an analogue current meter to provide extremely accurate monitoring of the 211/845 tube. The meter makes it exceptionally easy to see the status of the tube at any time and to respond immediately to any variation in bias by use of the top-mounted bias control screw. The meter offers a simple, unambiguous indication of the tube’s status compared to conventional LED bias monitors.
  • Powerful Driving Circuitry. Allnic believes in the importance of using high-quality, low noise and powerful driving circuitry in all its amplifying devices. Off-the-shelf design is not a part of the magic of these amplifiers. Tubes and transformer characteristics are closely matched to complement each other to achieve the most accurate and satisfying sound. In the A-2500s, we employ a new old stock (NOS) 6CM7 (for the 211 power tube) and a 6DR7 (for the 845 power tube) triode as the input tube for the choke-transformer driving circuit. The listener can easily hear and even “feel” the differences between these designs and other, more conventional ones. Please imagine, as you listen to the A-2500s, its sound compared to the sound of an amplifier using conventional, for example, 6SN7, 6922, 12AU7 or 12BH7s.
  • Custom-made “fits all” 845 tube socket
  • Direct-heated Vacuum Tube Rectification. The A-2500s use a 5R4 full-wave rectifier tube rather than a semiconductor diode in the rectification circuit. This provides both sonic benefits and improved protection for the 211/845 power tubes.
  • “Full Engagement” Output Transformers. Conventional output transformers use pre-set secondary windings to accommodate 4, 8 and 16 ohm loudspeaker loads. However, these conventional transformers utilize only one secondary winding at a time, while the other secondary windings remain “idle”. This approach has two adverse effects. First, the output transformers are not working at their maximum efficiency, reducing their output relative to their potential. Second, the “idle” windings are not actually “idle”; they are subject to parasitic oscillations, producing their own “signal”. This undesirable electrical information is additive to the transformer’s output, distorting the amplified signal going to the loudspeaker. Allnic’s “Full Engagement” transformers address these issues by having 4 independent, secondary windings that are always fully connected, never “idled”. This means that all secondary windings are always connected to your loudspeakers, regardless of which output switch position you use (4 ohms or 8 ohms or 8 ohms or 16 ohms, depending on the factory configuration you have selected). The result is that there is neither a loss of transformer output efficiency, nor the introduction into the output signal of distortion from parasitic oscillations of the secondary windings.
  • Large Nickel/FeSi Core Output Transformers. As with our other models, Allnic uses very large output transformers (105 mm) with nickel, mixed with FeSi, cores. This provides for higher inductance with fewer windings than other designs can provide and results in the great benefit of an extremely wide range of output frequencies.Analogue Power Tube Current Monitors.
  • As are all Allnic Audio products, the A-2500s are fully RoHS (EU Reduction of Hazardous Substances regulation) compliant in construction and materials.

Technical Specifications

·     Output Power: 211 or 845: 20 watts


·     Total Harmonic Distortion: 0.3% at 5W/1KHz
·     Frequency Response:  

20Hz – 20KHz, +/- 0.5dB


·     S/N Ratio: -80dB (CCIR, 1KHz)
·     Damping Factor:  

4 at 8Ω load at 1KHz


·     Voltage gain:  

+28dB (211 version); +26dB (845 version)


·     Input Impedance: 100KΩ (single-ended, unbalanced)


·     Input Sensitivity: 0.7V for maximum rated power
·    Fuses:  

IEC Mains: For 110 – 120V AC regions 5A, 250V, 20mm slow-blow; For 210 – 230V AC regions: 3A, 250V 20mm slow-blow.

0.5A, 250V, 20mm slow-blow (211/845 protection)



·     Tubes (per chassis): 211/845 X 1 (power tube)

6CM7 X 1 for 211 version; 6DR7 X 1 for 845 version (input stage)

5R4 X 1 (rectifier) TUBES ARE NOT INTERCHANGEABLE BETWEEN 211/845 VERSIONS (except 5R4 rectifier)


·     Dimensions: (W x D x H) 440mm (17.3 inches) x 370mm

(14.6 inches) X 260mm (10.3 inches)

·     Weight: 20Kg (44.1 lbs) net per monoblock.

25Kg (55 lbs) shipping weight per monoblock

Product Support

A-2500 Manual 21-07-2022


Coming soon!

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