At a glance
Reference-class headphone amplifier with huge output power, ultra-low noise and uncompromising sonic fidelity.
At a glance
Headphone and active-speaker amplifier
The Niimbus US 5 is the improved successor to the acclaimed US 4 and US 4+. It combines a reference-class headphone amplifier and a high-end preamplifier in one compact unit – ideal for headphones, power amplifiers and active speakers.
Thanks to its sophisticated preamp stage, the US 5 drives not only headphones but also power amplifiers or active loudspeakers. Headphone and rear line outputs can be switched separately from the front panel.
Remote Control

A solid aluminium remote allows infrared control of motorized volume, mute, input selection and headphone / line-out switching.
Technology Highlights
Connections & Features
Package Contents
| Item No. | 1008070 |
| Inputs (analogue, stereo) | 1× XLR (balanced), 2× RCA (unbalanced) |
| Max. input level | +21 dBu |
| Input impedance | 10 kΩ |
| Line outputs (stereo) | 1× XLR (balanced), 1× RCA (unbalanced) |
| Line-out gain | –12 / –6 / 0 / +6 / +12 dB |
| Line-out max. output level | +21 dBu |
| Line-out output impedance | < 1 Ω |
| Power amplifiers | 4 discrete-design amplifiers, 8 transistors per channel |
| Nominal input sensitivity | +6 dBu |
| Amplifier gain | –4 dB unbalanced / +2 dB balanced |
| Pre-gain | –15 / –12 / –6 / 0 / +6 / +12 / +18 / +24 dB |
| Frequency response | 5 Hz – 250 kHz (–0.5 dB) |
| Balance | ±6 dB |
| Volume control | ALPS RK27, motorised (remote control) |
| Output impedance (headphones) | 0.1 Ω unbalanced / 0.2 Ω balanced |
| Damping factor (50 Ω load) | 500 unbalanced / 250 balanced |
| Dynamic range | > 135 dB (A-weighted) |
| Noise | < –104 dBu (A-weighted) |
| THD+N (1 kHz, 2 × 10 V into 100 Ω = 1 W) | < –104 dB / < 0.00063 % |
| THD+N (1 kHz, 2 × 4 V into 32 Ω = 0.5 W) | < –103 dB / < 0.00071 % |
| Crosstalk | –105 dB (1 kHz) / –103 dB (15 kHz) |
| Headphone outputs | 1× 4-pin XLR (balanced), 1× 4.4 mm Pentaconn (balanced), 2× 6.3 mm jack (unbalanced) |
| Max. output power (balanced, both channels driven, 1 kHz, THD+N < 0.1 %) | 1,750 mW into 600 Ω (32.4 V) 2,900 mW into 300 Ω (29.5 V) 6,500 mW into 100 Ω (25.6 V) 7,000 mW into 50 Ω (18.8 V) 5,600 mW into 32 Ω (13.4 V) 3,200 mW into 16 Ω (7.2 V) 1,600 mW into 8 Ω (3.6 V) 820 mW into 4 Ω (1.8 V) |
| Power supply | 2 toroidal transformers (25 W each), > 50,000 µF filter capacitance |
| Mains voltage | 230 V AC / 115 V AC, max. 50 VA |
| Enclosure | Front 10 mm / rear 3 mm aluminium, black anodised; case 2 mm sheet steel, powder-coated |
| Case dimensions (W × H × D) | 351 × 59 × 248 mm |
| Overall dimensions (W × H × D) | 351 × 82 × 275 mm |
| Colour | Black |
Manufacturer data (NiiMBUS US 5 / US 5 PRO manual, July 2024). All values RMS, unweighted, 20 Hz – 20 kHz, pre-gain set to 0 dB.