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R&S RTB2004 noctua fan questions/feedback

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alonsojar:
Hello,
My Rtb2004 is reaching its end of warranty and I'm considering to replace the Sunon stock fan by a Noctua NF-A8 FLX.
The Sunon is not probably too noisy, but the fan is running at 1.750 1.850 rpm after some minutes working and never goes down no matter what I do, so very close to its maximun 2.000rpm. It looks like voltage control is not designed to get a wide actuation range on this device.
On the other hand the replacement seems easy and not very expensive...

Anyone did replace the fan and could share the experience?

The Noctua on the specs overpasses the Sunon not only in reduced noise (16.1 vs 20.4 dBA at 2000 rpm), but is also offering more airflow and static pressure at the same rpm (I mean without any Low Noise cable installed).
 
There is a small concern about the current consumption that in the Noctua is 0.84 watts while the Sunon is 0.54W (a 50% more). I'm asking myself if it'll be safe to plug it to the motherboard in the long term. 

Perhaps the Notcua watts figure is the worst case with the Ultra Low noise adapter resistor plugged in ??
What do you think?

Thanks in advance!!
J.Alonso

alonsojar:
Thank you Peter,

I've read this thread time ago. The guy said that the noctua nf-a8 was not making any noticeable difference for him and finally installed a bigger fan requiring a mod. This is far away from my intend and I'm probably  less ambitious (and lazy) regarding noise.

I'm just asking for people who really installed a noctua 80mm or similar and their experience in the long term.
Cheers
J.Alonso

Rydda:
Well I'm the guy.
And I am still running my 'upgraded' RTB. My reasoning for the modification was basically:
- the Sunon fan was no better or worse than several Noctua fans I tried.
- every replacement still sounded like a small fan running at high speed. Not a sound I enjoy.
- the noise could be lowered by lowering the speed of the fan, but every attempt to lower the speed resulted in an increase in the pcb temperature.

For me, it was not meaningful to pursue that path.
But since this is an extremely subjective topic, it might be different for You.

IMO it is almost impossible to draw any conclusion from information online how you yourself will experience the noise from an instrument. One example: I have been considering an upgrade to the MXO4. This has an audible noise level according to R&S of 34dBA and is described as 'whisper quiet' in every review. The RTB2004 had an audible noise level of 28dBA (also according to R&S), so just judging from these figures, the MXO4 would be 6dB louder than the RTB. And I know how I hated the noise from the RTB. 

/Ola

alonsojar:
Hi Rydda,
Your considerations are very reasonable and useful for me.
In my case I tested the scope noise using a phone app placed 10cm in front of the screen on the bench. Probably not the best instrument nor placement, but with the room silent it measured 28 dB and with the scope on running normal fan speed (say 2.780 rpm reported by scpi command) around to 40 dB. Too much? I don't know....

I've ordered the Noctua NF-A8 and will report the results. A small reduction or even a change in tonality could be enough for me.
In the worst case I'll use it in other project (like my nge103b power supply that you reported to have a noticeable  improvement). It will take some weeks because I'm waiting also for the molex connector used in the mainboard (micro-fit model if I'm not wrong) that I also ordered and will delay due to holidays season.
Tnx
J. Alonso

pdenisowski:

--- Quote from: Rydda on July 19, 2023, 02:26:58 pm ---I have been considering an upgrade to the MXO4. This has an audible noise level according to R&S of 34dBA and is described as 'whisper quiet' in every review. The RTB2004 had an audible noise level of 28dBA (also according to R&S), so just judging from these figures, the MXO4 would be 6dB louder than the RTB. And I know how I hated the noise from the RTB. 

--- End quote ---

I've used both scopes (RTB and MXO4) in my very quiet office for hundreds of hours.  If I have my back turned to my bench, I can't tell from three meters away if either one of them is on. I've worked in test and measurement for over 25 years (15 at R&S and 10 with another major company) and the MXO4 is one of the quietest instruments I've ever used.

I'll see if I can do a side-by-side test sometime next week (I only have an MXO4 at the moment), but as you say, the annoyance caused by noise is a very subjective thing.

It would be interesting to do an audio frequency analysis of the noise from the two instruments:  I'm not sure it's safe to assume that the audible noise from all instruments has the same (Gaussian, White) frequency distribution, so it may be the case that some types of fan noise are more annoying than others simply due to the spectral distribution of that noise.  For example, a fan with a lower overall dBA might be more pyschoacoustically annoying because it has higher frequency audio components.  Just a thought :)

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