I assumed the adapter cable came with a resistor but I’ll confirm.
Fan sold as part of Dreamcast fan mod kit. Will check the box.
Yeah it might, depending on the kit. Some noctua fans (ULN models) come with an adapter too.
I linked to the 5V fan I installed in my post last fall in this thread (realize you’re in the UK though). The embedded video should start where Bob goes through the mod as well - not questioning your modding ability just pointing out for reference. It was a night and day noticeable difference when I installed mine.
For anyone just seeing this I’ve since gone back to the OEM PSU.
Me too, I used the 5v NF-A4X10. I got a friend to print me the parts.
It was way quieter without any additional adapter or resistor.
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Yes, A4x10 is the fan.
Here’s my mod:
https://www.instagram.com/p/CIVtV2gnGIf/
Here’s the noise: you should be able to equalise the volume on your phone with the volume of your Dreamcast power on beep and then compare the fan noise levels.
For me the noise is not much different than before.
Yours is definitely much louder than mine. I can’t even hear mine when it’s on and the only way I know its on is by feeling the exhaust.
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Oh wow ok. Glad it’s not as it should be.
Seller is happy to exchange for another.
Yeah mine is like that too. I can hear it if I’m close, but there’s no way I would notice it while playing.
Exchange what, the fan? I would hazard a guess that considering the quality of the fans noctua makes, exchanging the fan won’t make a difference. It’s probably very unlikely that the fan is bad.
Can you check the model number listed on the sticker of the fan? Maybe there was a 12v fan in a 5v box?
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I’ll double check.
My hunch is that the adapter cable with the resistor in is faulty. The fan itself seems fine.
I saw some mention of a resistor mod instead of removing the 12v rail, anybody try that or have any more info on it?
https://www.arcade-projects.com/threads/gdemu-testing-a-theory-re-heat.10474/
I’ve seen similar talk of the PSU still getting hot after removing the 12v rail on Reddit but it’s all anecdotal stuff.
I had read and seen something similar but didn’t have any suitable resistors handy, so I took 12V rail mod option as I could do it immediately.
Waiting on my replacement fan things, but right now exhaust air is quite warm.
Replaced the fan (they sent me one so I figured why not) and resistor/adapter cable and things sound… pretty much the same.
I decided to measure noise levels with the app dB Meter. I see 20dB difference between background noise and the fan hum. The fan box specs say level should be 17.9dB.
Can anybody measure their dB levels and let me know if it’s the same?
Different app (android), but mine seems to go from about 15-16dB to 35-36dB, so yeah about 20 difference.
It depends HUGELY on how far away my phone is from the fan grille though… and this 20dB measurement is with the phone’s mic sitting directly below the grille for max increase.
I can definitely hear it from a few feet away, but I feel like it’s a good balance between noise and effectiveness. I wouldn’t be able to hear it during gameplay.
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That’s great, thanks. I measured the same way.
So this fan isn’t as silent as I was expecting! If I ever have to open it up again I’ll pop in my original fan and measure its dB.
Now back to the gaming. I’ll crank the volume a little higher. 
If you’d like to make your own little Ultra-Low Noise Adapter like the one included with the ULN series of Noctua fans, you can just add a 50ohm resistor to the supply wire.
And if that doesn’t get you the results you like (too fast, or too slow), all you need to do is go up or down in the resistor value.
Thats the thing: my adapter cable already has a resistor fitted inline.
So yours is 20dB without a resistor?
Mine is 20dB with a resistor.
Yeah, no resistor in-line for mine. i just bought the fan and installed it myself.
I’m curious what the value of the resistor you have in there is. Would be pretty simple to replace it with a different value if you want.
Really hard to see the colours in that photo… what are they?