Educating Myself About Fan Noise

It's very rare for an audiophile amplifier to have a fan. They use large heat sinks to avoid the fan noise. I only know of Hafler amps using a fan. Pro amps do too but that's all.

I believe my Mosecode 600 had a fan. I never heard it unless I was right in front of it. My HD sat.box has a fan--same thing---Altho at avs.com many complained of the fan noise from this very box--- as well as fan noise from dpl rear proj.tvs. and projectors. The first 2 projectors I owned were NOISY as hell. My 3rd wasn't,even tho it had a fan.So I guess it's 'how' this fan thing is implimented,along with which fan is chosen.

Thanks, already I am glad I finally asked this question. I think this Dynaco model has an interesting history and I like owning it (audio equipment becomes a hobby and a learning experience after all) but now I can see a little that other options won't necessarily run into this fan noise problem.

As I think about it, I think I read a review a few years ago of a Nakamichi item that had a fan that bothered the reviewer a bit.

Hi everyone

Apologies for hi-jacking/reviving this old thread but I'm in need of some fan noise education/help myself.

I've got a vintage Sumo 9+ amp that has been restored by Gas Audio/Sumo specialist Mike Bettinger. He gave the amp the works, new power caps, new ceramic caps, re-biasing, new input/output jacks, extensive break-in. I got the Sumo back recently and the music sounds great. The only downside is the rear fan that is used in the Sumo 9 Plus is very audible (greater than 30 db) when I'm listening to acoustic music or quieter passages of songs. It didn't bother Mike but it bothers me.

I sit about 9 to 11 ft away from the Sumo 9 Plus when I'm listening to music. I've tried putting it as far away as I could from me but I still hear the fan. Now one thing that did help was an extra sheet of sound absorbing material from Acoustipack (Sound proofing for PCs and servers). I draped the sheet over the rear of the amp and the fan just leaving some space though for air to escape from the sides. The noise went down by a little bit but still not enough.

Now I'm going to try to find a quieter replacement fan that still pushes enough air out to keep the Sumo operating a safe temp but should I not find a suitable replacement I had an idea.

I don't know if many of you remember the wood cabinets that were used to encase Phase Linear amps. It was a box that was an exact fit to the amp but had an open back. I was thinking about doing something similar. I would be encasing the Sumo in a wood cabinet with a bit of space on the sides, top and rear but leaving the back only partially open to allow for some air to escape as well as routing of power cord, ICs and speaker wire. Within the cabinet I would put acoustic dampening foam or carpet padding to muffle the sound.

Now I'm definitely open to suggestions as to how to combat the fan noise. The enclosure sounds like overkill and can be a bit costly depending on the quality of the box as well as sound proofing material. Plus I may have muffled the fan noise but now may be harming the Sumo with excessive heat. Also I'm hoping the acoutic material doesn't start emitting toxic fumes because of the heat.

Now if anyone has any fan suggestions for the Sumo 9+ I'm open to those as well. I'd like to get the quietest fan that can still push a decent amount of air. I was thinking about Yate Loon fans or maybe Nexus fans but I know there are tons out there in the market.

Well thanks so much everyone.

Can you put some rubber grommets between the fan housing and whatever it connects to?

I believe there is a separate fan cooling device for the PS3 that you might try. Low noise also fans exist (cost about $100+). The tendency is for manufacturers to use the cheapest fans possible in audio and computer gear ($20 fans).

I have done DIY upgrades to fans on equipment and managed to get a 20 db noise reduction. A noise factor can be the proximity to a grill - a fan without a fine grill or one with a grill that is one or two inches away will run much quieter. If you place something in a closed cabinet then you can also gain about 10 db in noise reduction but the fan may run more often due to the restricted air flow.

FWIW: The fan on the Panasonic PT-AE4000 projector is an example of a very quiet fan design. I highly recommend this projector. I cannot recommend this projector enough. A giant killer which blows away 10K projector systems from only a couple of years ago. Now is the time to get into projection and screens IMHO - as black levels have finally reached high quality at a reasonable price.

Greetings. Here is an update. It's been quite a learning experience with this fan and the amp.

First the fan currently in the Sumo 9 of mine is:

NMB - 3110MS-12W-B30-A00 - Axial Fan
Manufacturer: NMB
Newark Part Number: 34R2249
Manufacturer Part No: 3110MS-12W-B30-A00 RoHS Compliance :

Description Axial Fan
External Height:80mm
External Width:80mm
External Depth:25mm
Current Type:AC
Supply Voltage:115V
Fan Flow Rate:24CFM
Noise Rating:31dBA
Bearing Style:Ball
Power Connection Type:Lead Wires
Current Rating:90mA

This is an AC fan that runs full speed all the time. There is no drop in replacement from the sites I checked that could still push out around 24 CFM and have a db level less than 31dBA.

Srwooten. I took some rubber spacers I had and cut them and put them on the corners of each fan. This seperated the fan from the metal surface of the Sumo 9. This all but elminated the vibration noise caused by the fan. It was my biggest gain in decreasing the noise.

Now to Shadorne's post.

I haven't had much luck with PS3 coolers in general. They were temp controlled but when they came on they were loud to my ears and audible from my sitting distance. From looking @ the Neeko or Nikko fan I have with my PS3 it looks like a bunch of noisy 40mm fans. If you could send me any leads on low noise AC fans that you have used in the past I'm game. The only 80mm fan I found that could move more than 24cfm but have less than 31 dBA was from Noctua. I would have to mount this fan externally from the Sumo and power it seperately with an AC adapter since it is a DC fan. Really ugly.

Thanks for the lead on the projector. My uncle is in the market for a new one. I'd love to take it apart to see how the fan system works but my uncle would kill me.

Now I did apply some Acoustipack panels to the internals of the Sumo 9 and it helped marginally. I'm going to enjoy the amp for now and figure out what kind of enclosure I'm going to build around it.

Thanks

i passed on buying an ARC Ref 110 due to fan noise.

Eight years after the posts above, I want to thank jedinite24 for documenting so much information about the fan. I just bought a Sumo 9 without a prior listening test. The fan was definitely an issue. Having read it should be making 31dB of noise, I measured mine at 56dB. I think it may be getting old! Even a relatively loud new fan should be an improvement. It’s good to know the required specification while I look for one.
Thanks again.
PS my immediate solution to the fan noise problem was to put the amp in the basement, run speaker wires via the heating duct cutouts, and turn the amp on and off remotely using Google Home with a wifi smart plug. Despite that, my fan is actually so loud I can hear it faintly through the basement door. I think I’ll also add rubber grommets as suggested above. Thanks for that tip too.