HPBA-2

Current-drive balanced headphone amplifier

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Reference listening systems: the sound how it is, not how it should be. Audio heaven in a pocket: Fully balanced professional headphone amplifier, especially designed for mid-high impedance - sensitivity headphones.

The reference headphone amplifier, which has now reached the Second Generation (Mk II), has been designed to faithfully reproduce the most subtle nuances contained in the musical message with the maximum detail and sobriety.

Two independent channels, based on the 'current-driving' principle, featuring independent power supplies, 'shunt' regulation stages, for best channel separation and wider stereo image, fully differential (balanced) circuitry for improved linearity, dynamic response and definition, making the membrane much more prompt to signal solicitations. Virtually immune to interference and noise, even in difficult environments.
256-step double-balanced volume control, totally analog but digitally controlled, based on binary-weighted resistive ladders, 16 relays and 0.5dB precision for each step, which can be operated from the front panel knob or IR remote.

Current drive: in the dynamic transducers, it's the current flowing through the voice coil which produces the magnetic field which interacts with the magnetic field of the magnet in the driver that causes the diaphragm to move back and forth. Thus a constant current amplifier has several advantages over the usual constant voltage amps: A current source amplifier delivers a precise current to the voice coil of the loudspeaker driver, ignoring the series impedance elements in the circuit, including the wire, connectors, the inductance of the voice coil, the resistance of the voice coil versus temperature, and so on, delivering higher accuracy and linearity.

Features

  • Fully differential solid state high definition circuitry
  • Dual Mono construction for improved separation and stereo image
  • Based on the 'Current Drive' priciple, eliminates major distortion and interference effects
  • Two filtered and regulated independent power supplies, common-mode filtering chokes for a vanishingly low noise floor
  • High-speed, totally analog processing
  • 'shunt' regulators made with all discrete components
  • Entirely balanced signal route for improved noise rejection
  • 3 mains toroidal-core transformers, independent for logic and analog stages, dramatically reducing interferences, featuring high-permeability M1 core, double-isolation (Class F - 155C) wire, double shielding: electrostatic shield between primary/secondaries, and electromagnetic shield through a mu-metal foil wrapped around each transformer
  • 256-step precision binary-weighted resistive ladders volume control, with gold plated contact relay switching
  • 4-layer MIL-std. p.c.b. with doubled copper deposit, cutting trace resistance in half, improves signal integrity
  • Ruggedized stainless steel 1U high chassis, rackmount or desktop version
  • Frequency response absolutely flat over the entire audio range and beyond, featuring linear phase response

Technical specifications

  • Frequency response: 1.5Hz—850KHz (-3dB)
  • C.M.R.R., 1kHz: ≥70dB
  • Signal/noise ratio at 20dB 22Hz/22KHz 300Ω terminated: ›100dB
  • Maximum output level (300Ω) : +11.5dBm (can be modified on request)
  • Input impedance: 20kΩ
  • Output impedance: 164Ω
  • Min. load impedance: 200Ω
  • Dimensions (W x H x D) inches : 17.72 x 1.73 x 8.66
    mm: 450 x 44 x 220
  • Net weight: 6.2kg (13.67 lbs)
  • Shipping weight: 8kg (17.64 lbs)

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