9
GENERAL INFORMATION
The NIIMBUS HPA US 4+ is a stereophonic headphone amplifier designed to drive low-, medium- and
high-Z loads (16...600 ohms) as usually represented by high-quality headphones.
Because of its four built in amplifiers and the 4-pin XLR socket on the front it is also best suited to connect
balanced headphones.
Due to its specific, highly variable, low-noise and low distortion circuit design especially optimised for
dynamic and orthodynamic headphones, the NIIMBUS HPA US 4+ fulfils even highest demands.
Features:
-1 x stereo balanced inputs with gold-plated Neutrik XLR connectors
-2 x stereo unbalanced inputs with gold-plated full metal premium RCA connectors
-All three inputs selectable on the front panel
-PRE-GAIN = switchable input gain in eight steps -15/-12/-6/0/+6/+12/+18/+24 dBr
-Balanced and unbalanced stereo line outputs with RCA resp. XLR sockets,
gold plated, pre-post fader assignable
-Independent channel design
-Volume control with 256 steps of 0.4 dB through reed relay attenuator
-Balance control
-Remote controlled and motorized volume control, input/output selection, mute
-High-Quality op-amps in the signal path
-High-quality MKP capacitors in the signal path
-0.1 and 1% metal film resistors throughout the unit
- 4 Discrete-design power amps with 8 transistors per channel
-Output management: headphones active / line-out active / both active / none active (mute)
-2 x 6.3 mm (1/4”) silver-plated Neutrik headphone outputs
-1 x 4-pin XLR socket, gold plated for balanced headphones
-delayed relay-based headphone output during power on / instant cut-off for power off
-2 x toroidal transformers, 25 + 25 W
-Large filtering capacitors in the power supply (> 50.000 uF)
-Switchable ground lift
-Rugged steel case with metallic coating
-Solid, 10 mm aluminium front panel
With its dimensions, the NIIMBUS HPA US 4+ ensures optimum flexibility combined with high output
power. During design, high emphasis was put on operational safety even when the unit is operated
inappropriately.
The NIIMBUS HPA US 4+ is equipped with safety circuitry and internal filters to prevent damage to the
connected headphones due to DC voltages at the outputs, overload, over temperature and high-
frequency overload beyond the audible range.
THE CASE
of NIIMBUS HPA US4+ is made of 2 mm sheet steel and a thick 10 mm aluminium front panel.
This choice of material ensures high mechanical stability and resistance whilst maintaining a high
optical and haptic quality.
