Noctua

Noctua NF-A4x20 PWM, Premium Quiet Fan, 4-Pin (40x20mm, Brown)

Name: Noctua NF-A4x20 PWM, Premium Quiet Fan, 4-Pin (40x20mm, Brown)
Brand: Noctua
SKU: B0DSJ76SG5

Status: Noctua NF-A4x20 PWM: Unavailable on Amazon as of 2026-10-21 16:21 UTC. SpecPicks has no in-stock listing with matching specs on file; the search below lists current offers. eBay sellers may still list this model new or used.

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Bottom line: The Noctua NF-A4x20 PWM: 14.9 dB(A) max noise at full 5000 RPM tilt; main trade-off: brown and beige color scheme clashes in most builds.

Unavailable on Amazon as of 2026-10-21 16:21 UTC

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By Mike Perry, Founder & Editor-in-Chief · Listing data updated 2026-10-21

Mike Perry — Hardware researcher since 2014, focused on GPU performance across gaming, rendering, and local-LLM inference. Synthesises community benchmarks, manufacturer specs, and public forum data into actionable buying guides. About the author →

Pros & Cons

Pros

✓ 14.9 dB(A) max noise at full 5000 RPM tilt
✓ 20mm depth adds static pressure vs thin 40mm fans
✓ 4-pin PWM header control, no manual tuning needed
✓ OmniJoin adaptor set splices onto proprietary headers
✓ Rated >150,000 hours MTTF on the bearing

Cons

✗ Brown and beige color scheme clashes in most builds
✗ 20mm thickness won't fit slim 10mm fan brackets
✗ Low-Noise Adaptor drops peak speed to 4400 RPM
✗ 5000 RPM top end is still audible up close

Manufacturer description

The Noctua NF-A4x20 PWM is a 40x40x20mm cooling fan built for the cramped, noisy equipment most people want to quiet down: 1U servers, NAS enclosures, network switches, routers, and DVRs. Its A-series frame uses Flow Acceleration Channels and Advanced Acoustic Optimisation to push air at up to 5000 RPM while topping out at 14.9 dB(A) - quiet enough that a rack-mounted switch stops announcing itself from across the room. The 20mm depth gives it noticeably more static pressure than a standard 10mm 40mm fan, so it moves air through restrictive grilles and dense heatsinks that thinner fans…

SpecPicks Verdict

SpecPicks scored Noctua NF-A4x20 PWM using a rating × review-volume × price-fit model applied to published specs and reviews across the PC & gaming hardware category. Noctua's PC & gaming hardware lineup sits within the broader category mid-tier; price and specs are the deciding factors over brand loyalty here. Judge it on the specification table and the price rather than on sentiment: check the figures that decide your use case, then put it side-by-side with two or three close alternatives in the Compare tool before clicking through.

Common buyer scenarios for PC & gaming hardware of this kind: matching it to an existing build, replacing a failing part, or upgrading from a previous-generation equivalent. Check the spec table below against your current setup — particularly socket / form-factor / power-rating fields — and confirm compatibility on the retailer's listing before purchase. Prices and stock are set by the retailer and may have moved since this page was last updated.

Frequently Asked Questions

Will the NF-A4x20 fit my 1U server or NAS?

It fits any standard 40x40mm mounting pattern, but it is 20mm thick instead of the common 10mm. Measure your clearance - 1U servers, NAS enclosures, switches, routers, and DVRs are the listed target applications.

How loud is this fan actually?

Noctua rates it at a maximum of 14.9 dB(A) at its full 5000 RPM. The included Low-Noise Adaptor caps it at 4400 RPM for a quieter fixed setting.

Do I need a 4-pin PWM header to use it?

A 4-pin header gives you automatic speed control. On a 3-pin header the fan runs at full speed, though you can use the supplied Low-Noise Adaptor or the OmniJoin adaptor set for proprietary connectors.

What comes in the box?

Anti-vibration mounts, fan screws, an extension cable, a y-cable for running two fans off one header, the Low-Noise Adaptor, and the OmniJoin adaptor set.

Is it worth the price over a generic 40mm fan?

The >150,000 hour MTTF rating plus the 14.9 dB(A) ceiling are the differentiators. For a router or NAS you leave running 24/7, that math works out differently than for a one-off build.

Key Features

Premium quiet fan, 40x40x20 mm, 12V, 4-pin PWM, max. 5000 RPM, max. 14.9 dB(A), >150,000 h MTTF
Award-winning A-series design with Flow Acceleration Channels and Advanced Acoustic Optimisation frame for superior quiet cooling performance
40x20mm size ideal for 1U servers or replacing fans in network and storage equipment (routers, switches, NAS etc.) or other devices such as DVRs
4-pin PWM version for automatic speed control via 4-pin PWM fan headers, 5000rpm maximum speed (4400rpm with supplied Low-Noise Adaptor)
Includes anti-vibration mounts, fan screws, extension cable, y-cable and OmniJoin adaptor set for connecting the fan to proprietary fan headers

Full Specifications

Brand	Noctua
Model	NF-A4x20 PWM
Voltage	12 Volts
Material	Fibre-glass reinforced PBT
Dimensions	40x40x20 mm
Unit Count	1.0 Count
Noise Level	14.9 Decibels
Part Number	NF-A4x20 PWM
Material Type	Fibre-glass reinforced PBT
Cooling Method	Air
Number of Items	1
Vibration/Rumble	Yes
Air Flow Capacity	9.4 Cubic Meters Per Hour
Compatible Devices	Desktop
Power Connector Type	4-Pin
Warranty Description	6 year manufacturer’s warranty
Maximum Rotational Speed	5000 RPM
Item Dimensions L x W x H	1.57"L x 1.57"W x 0.79"H

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