At a glance
- Device type
- Headphone amplifier
- Amplifier technology
- Solid-state
- Headphone outputs
- 4-Pin XLR, 4.4 mm, 2× 6.3 mm
- Built-in DAC
- No
- Power
- 5.6 W @ 32 Ω · 2.9 W @ 300 Ω
NiiMBUS US5 Pro
Reference-class headphone amplifier with huge output power, ultra-low noise and uncompromising sonic fidelity.
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At a glance
- Device type
- Headphone amplifier
- Amplifier technology
- Solid-state
- Headphone outputs
- 4-Pin XLR, 4.4 mm, 2× 6.3 mm
- Built-in DAC
- No
- Power
- 5.6 W @ 32 Ω · 2.9 W @ 300 Ω
Niimbus US 5 PRO
Reference headphone & active-speaker amplifier with 256-step relay volume control
The Niimbus US 5 PRO is the refined successor to the acclaimed US 4 and US 4+ headphone amplifiers. It shares the core engineering of the US 5, while adding an ultra-precise 256-step volume control implemented via reed relays.
Enjoy a compact, outstanding-sounding headphone amplifier and a high-grade preamplifier in one unit. The sophisticated preamp function allows direct connection to power amplifiers or active speakers. Headphone and line outputs can be enabled/disabled separately from the front panel.
Premium multi-purpose design
A reference-class headphone amplifier plus a fully capable preamp stage: ideal for headphone rigs, power amps, or active speakers. Headphone and line outputs can be switched independently from the front.
Remote control
A beautifully machined, solid remote lets you control volume (256 steps), mute, input selection, plus headphone and line-out via infrared.
Technology highlights
- Perfect volume control: 256 precise steps via reed relays.
- Ultra-low noise: very low internal gain – self-noise is practically inaudible.
- High output voltage: 60 V internal operating voltage – ideal for high-impedance headphones.
- High output power: massive headroom – perfect for low-impedance and planar/magnetostatic headphones.
- High damping factor: extremely low output impedance for a strictly linear frequency response.
Features & connections
- 3 analog stereo inputs: 2× RCA (unbalanced), 1× XLR (balanced)
- Pre-Gain: –15 … +24 dB for perfect matching between source and headphones
- Motorized volume control and manual balance knob
- 4 amplifier stages: 7000 mW Pmax @50 Ω, 32 V RMS @600 Ω
- Headphone output monitoring (DC & clipping)
- Headphone and line outputs individually switchable
- Headphone outputs: 1× 4-pin XLR (bal.), 1× 4.4 mm Pentaconn (bal.), 2× 6.3 mm (1/4") (unbal.)
- Line-out: 1× RCA (unbal.), 1× XLR (bal.), adjustable level ±12 dB
- 2 toroidal transformers, > 50,000 µF filter capacitance
Package contents
- 1× Niimbus US 5 PRO
- 1× User Manual
- 1× Remote Control
Technical Data
| Item No. | 1008071 |
| 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 | Reed relay attenuator, 256 steps of 0.4 dB, 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.
NIIM-US5-PRO
Data sheet
- Device type
- Headphone amplifier
- Amplifier technology
- Solid-state
- Built-in DAC
- No
- Power into 32 Ω
- 5.6 W @ 32 Ω
- Power into 300 Ω
- 2.9 W @ 300 Ω
- Headphone outputs
- 4-Pin XLR, 4.4 mm, 2× 6.3 mm
- Balanced output
- Yes
- Inputs
- 2× RCA, XLR
- Output impedance
- 0.1 / 0.2 Ω
- Pre-amp output
- Yes
- Product type
- Headphone amplifier
