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

I recently added the Noctua NF-A4x20 PWM to my server setup, and the performance of this 40x20mm fan has left me thoroughly impressed. Noctua's reputation for premium quality is well-deserved, and this fan is no exception.Firstly, the build quality is exceptional. The brown color may be unconventional, but it's a symbol of Noctua's commitment to quality. The construction feels robust, and the attention to detail is evident. This fan exudes durability, assuring me that it can handle continuous operation in a server environment.Now, let's talk about the noise level—or rather, the lack of it. This fan is remarkably quiet, especially considering its size. Noctua's focus on providing a quiet solution without sacrificing performance is evident here. Whether my server is working at full capacity or idling, the NF-A4x20 PWM operates silently, contributing to a peaceful and distraction-free environment.The PWM functionality is a standout feature. The fan's speed is dynamically controlled based on the system's temperature needs, ensuring optimal cooling without unnecessary noise. This adaptability is a game-changer for maintaining the right balance between temperature control and acoustics.Installation was a breeze, thanks to the included accessories and clear instructions. The fan integrates seamlessly into my server setup, and the 4-pin connector allows for precise control over its operation.The performance, reliability, and quiet operation make it a top-tier choice for anyone seeking a compact, high-quality fan for their server. In my book, it's a solid 5-star product, and I wouldn't hesitate to recommend it to anyone looking to add performance and lower the noise level of their server or PC.

Works well, fits right into the spot the old 40x40x20 mm fan went. That thing was noisy as heck on start up. Board inside the TEG-S708 has 3-pin fan port, so voltage line controls rpm, but this 4-pin from Noctua works just fine in the 3-pin port. Fan still changes rpm speed based on voltage line. Silent as heck. It does move less air than stock, but still enough air over the 10G switch heat sinks to cool it down. Laser readings on heat sinks were under 44C after couple hours of power on.

I don't write reviews here often, but this device really warranted it. We have an NVR for our security system and lately the fans just seemed to louder than usual. I did some research through YouTube and several mentioned replacing the fans for the unit we have and recommended these fans. I was a bit skeptical thinking would it really make that much of a difference and is this something I should even mess with.I decided to give it a try and all I can say is I wish I would have done this sooner. It was quite easy to remove the existing fans and the the new fans are all wired and come with their screws (the original screws were too small). I did have to shave a little plastic off the connector as it is too narrow for the existing. But just a blade from a box cutter did the trick. I connected them, screwed then in place and put the device back together. As soon as I powered up the device... I convinced they were not even working because it was completely silent. I used a flashlight and sure enough, the fans were turning. But they are insanely quiet! It's sad the equipment I purchased doesn't use a quality quiet fan such as this product. I cannot recommend these enough. Super easy to replace and just incredibly quiet.

Bought this to replace the stock fan in a MikroTik CRS310-8G+2S+. This noctua fan at max rpm is 1/4 the volume of the stock fan at idle temps. The difference is crazy. Airflow seems to be better to as the temps are lower at the same rpm compared to stock as well. High quality, excellent performance, and absolutely no noise.

Great upgrade to make my Mikrotik Router quieter.

Nice and quiet

Fast shipping, these are nice little fans for servers so quiet and makes my office nice to be in.

Very high quality but very low output at 5.5 cfm. I tried these in a Arista switch to replace the existing high airflow but ridiculously loud Sunon fans. They couldn’t do the job. Temps climbed above 50 deg C for the cpu. I chang d to the pwm version which puts out a bit more cfm but still not enough. Overall airflow was significantly lower and temps rose 15 to 25 degrees C across the board. Just not enough airflow. My solution ended up keeping the original fans and grounding the pwm input to slow the fans to their lowest speed of about 25% (CLI only allows going to 30%) and doing some creative baffling and sealing work to make sure the hottest component got enough air flow. The cooling on these units is brute force with not enough engineering going into the design and a few easy mods and changing air flow from rear to front resulted in temps in the 31 to 39 degree C range instead of the 41 to 49+ range with the Noctuas. 27 to 34 were the original temps with fans at 60 percent and 21 degrees ambient.They are really nice fans but make sure your equipment can tolerate the very low air flow. The other thing I’d like to see is having them available without all the accessories at a reduced price. It’s great to have all the options if you’re buying only one or two fans but if you need 3,4,or 6(in this case) you end up with 6 or 7 dollars worth of stuff for each fan left over that you have no need for. I’d also like to see them provide a 4 pin connector with pigtail for the pwm version so you don’t have to cut the fan connector off for solder in installation.I give them 4 stars because they are really nice fans and well documented (in other words, since you have all the data it’s your own fault if they are too anemic for the job). I’d give them 5 stars if the highest speed was about 20 cfm with the option to slow them down if need be. I estimate they are likely insufficient for most applications - the loud fans used in many rack mount equipment puts out up to 65 cfm.