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Tårns 2Diffseries Headphones Amplifier – Description
The Tårns 2Diffseries is a fully discrete, class AB headphone amplifier designed according to power-amplifier principles rather than simplified op-amp conventions. Its architecture is symmetrical, differential, and series-driven, with clearly separated stages for voltage gain, error control, and current delivery. The design is optimized primarily for 32 Ω headphones, while remaining fully capable of driving loads from low-impedance IEMs to high-impedance dynamic headphones.
The input stage is AC-coupled using a 4.7 µF capacitor paralleled with 22 nF, providing DC isolation while maintaining wide bandwidth and good RF rejection. A 50 kΩ potentiometer serves as the volume control, offering high input impedance and compatibility with modern DACs. Small compensation capacitors ensure stability and suppress ultrasonic interference without affecting the audio band.
Voltage amplification is handled by a fully discrete differential stage, symmetrically biased and degenerated for linearity. This stage provides moderate open-loop gain with excellent common-mode rejection and low transient distortion. Compensation networks using 100 pF and 220 pF capacitors define a controlled frequency response and ensure unconditional stability. In function and discipline, this stage is analogous to the VAS of a high-quality power amplifier, scaled appropriately for headphone use.
Biasing throughout the amplifier is carefully managed using diode reference strings and resistor networks, ensuring stable quiescent currents and proper thermal tracking. This approach minimizes crossover distortion while avoiding the thermal instability often found in simpler discrete headphone designs.
Between the voltage amplifier and the output stage, an intermediate driver section provides isolation and current buffering. Series resistors (27 Ω and 47 Ω) decouple the stages, preventing reactive loading and preserving linearity. This contributes significantly to the amplifier’s stability when driving real headphone loads and long cables.
The output stage employs a fully discrete complementary Diamond Buffer. This topology uses a symmetrical four-transistor arrangement forming a classic diamond follower, operating at unity voltage gain and providing current amplification only. The Diamond Buffer isolates the voltage gain stages from the load and enables the amplifier to deliver high current into low-impedance headphones without stress. Biasing places the stage in controlled class AB operation, with 10 Ω emitter resistors providing thermal stability, current sharing, and further reduction of crossover artifacts.
Thanks to the Diamond Buffer output stage, the amplifier achieves very low output impedance (below 1 Ω), excellent damping of headphone drivers, and peak output currents in excess of 100 mA. This allows clean, controlled drive of 16–32 Ω headphones, while higher-impedance models are driven primarily by available voltage swing rather than current limits.
Power is supplied by ±10 V symmetrical rails, locally decoupled with 100 nF ceramic capacitors for high-frequency stability and 220 µF electrolytic capacitors for energy storage. This supply arrangement provides ample headroom for modern 2 Vrms sources and balanced operating margins without unnecessary voltage stress or heat dissipation.
Overall gain is moderate and sensibly chosen, making the amplifier compatible with real-world sources while preserving usable volume control range and low noise. Typical output power is on the order of 50–150 mW into 32 Ω, which is more than sufficient for any realistic listening level while maintaining low distortion and wide dynamic headroom.
Stability is treated with the same rigor as in a full-scale power amplifier. Local feedback, compensation networks, emitter resistors, and series isolation ensure the circuit remains stable with reactive loads, capacitive cables, and wide-bandwidth signals. This level of discipline is uncommon in headphone amplifiers but critical for long-term reliability and consistent sonic performance.
In summary, the Tårns 2Diffseries headphone amplifier is a serious, reference-grade design characterized by a fully discrete signal path, differential symmetry, a properly implemented Diamond Buffer output stage, high current capability, low distortion, and excellent thermal and electrical stability. It represents a miniature high-end power amplifier, correctly scaled for headphones, prioritizing engineering correctness over marketing-driven specifications.
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