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The BorderPatrol P21 EXD is a high-end push-pull 300B tube amplifier delivering 20 watts per channel into 8 ohms. It features a 17" x 13.5" x 13.5" copper chassis with a wooden plinth available in rustic mahogany, ash, cherry, or maple. The amplifier is hardwired point-to-point and uses multi-section, split-bobbin output transformers with carbon-film resistors and DC filament supplies for the 300B tubes, rectified by Schottky diodes. Uniquely, it employs interstage transformers to couple the driver tube (6C45pi) to the 300B output tubes, avoiding coupling capacitors and global negative feedback, which enhances linearity, voltage output, and phase accuracy. The P21 EXD uses speaker taps for 4 and 8 ohms, with 8 ohms preferred for dynamic performance. It includes an external power supply unit with tube rectified, choke input filter high voltage supplies for independent feeding of the 300Bs, driver tubes, and bias supply, plus filament supplies. This design results in superior voltage regulation, noise rejection, and bass performance. The amplifier is praised for its neutrality, honesty, dynamic capability, and natural tonality, making it suitable for high-efficiency loudspeakers (recommended >87dB/W). It weighs approximately 35.2 lbs and is regarded as a musical and engaging amplifier with excellent resolution and detail retrieval.
Amplification power output and characteristics
Size, weight, and appearance
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Estimated price (community-sourced)
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The closest alternatives on specs, description and the systems they turn up in, with the specs they share set side by side.
The Montille EL84's power @ 8ω is 15W against the P21 EXD's 20W, its input sensitivity 1.0V RMS against 1.2V RMS, and its weight 12.2 kg (27 lbs) against 15.88 kg (35 lbs). Both share input impedance (100Ω).
The Sapphire 300B's power @ 8ω is 18W against the P21 EXD's 20W, its input impedance 55Ω against 100Ω, its input sensitivity 1.3V RMS against 1.2V RMS, and its weight 15 kg (33 lbs) against 15.88 kg (35 lbs).
The V20's power @ 8ω is 24W against the P21 EXD's 20W, its input impedance 35.4Ω against 100Ω, its input sensitivity 0.4V RMS against 1.2V RMS, and its weight 22 kg (49 lbs) against 15.88 kg (35 lbs).
The Stereo 300 MkII's power @ 8ω is 30W against the P21 EXD's 20W, its input sensitivity 0.1V RMS against 1.2V RMS, its weight 26 kg (57 lbs) against 15.88 kg (35 lbs), and its depth 330 mm against 342.9 mm.
Canary Audio M90
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