Case Fans

[mypasswordis]

Anyone ever tried them? If so, what setup worked best and how quiet were they? I've been thinking up logistics of the SRM212 I'm recasing with the new HV power supply. Thinking about using a small 40mm fan since the heatsinks I will be attempting to use (same ones as what I'm attempting to put in the mini Dynalo) aren't that big and I want to crank it to 10mA. I'll be using one per channel so 2 total and each will be dissipating around 11-12W. Guesstimating 4C/W rise on the sinks (no specs stated in the listing) that's around 75-80C on its own  If it's 5C/W then it's really bad times.

Edited April 30, 2017 by mypasswordis

[luvdunhill]

Check out some recommendations Nelson Pass had on using fans, and a simple circuit to feed them at a very low level.

[mypasswordis]

Thanks! Not sure where I should be looking, on his website or his diyaudio posts? I did find a thread with someone using a Noctua fan in a heat tunnel on an F5: http://www.diyaudio.com/forums/pass-labs/206756-f5-turbo-circuit-boards-36.html He gets to use a big fan which means low rpm and thus a lot quieter, but the 40mm doesn't seem too bad from reviews. There's even an adapter to slow the fan speed down from 4500 to 3700 rpm so I don't have to mess with PWM or voltage divider or something. 

[luvdunhill]

It's posted on the first page of the "Babysitter construction help" thread.

[mypasswordis]

Ooh, found it. Since it's single ended, once it reaches temperature there shouldn't be too much change so I can probably just set it and forget it. Might be interesting down the line to add code to my rpi server to automatically change pwm speed and manage bias levels based on temperature sensing presets for class ab. Also can make it remote controlled through web pages like with the vol ctrl. The srm212 is all about compactness and bang for buck.

[bbest]

On 01.05.2017 at 0:45 AM, mypasswordis said:

Anyone ever tried them? If so, what setup worked best and how quiet were they? I've been thinking up logistics of the SRM212 I'm recasing with the new HV power supply. Thinking about using a small 40mm fan since the heatsinks I will be attempting to use (same ones as what I'm attempting to put in the mini Dynalo) aren't that big and I want to crank it to 10mA. I'll be using one per channel so 2 total and each will be dissipating around 11-12W. Guesstimating 4C/W rise on the sinks (no specs stated in the listing) that's around 75-80C on its own  If it's 5C/W then it's really bad times.

Hello!

I use 140mm fan in my HTPC. Size makes matters and it is very low noise. You could choose fan with features: silence, quite or some thing like this. Size more important than firm/model. If worry about noise in power, you could use RC filter or make separate PSU+filter for all fans in your system.

Small fans more sound noisier. With big ones you could blow out more area hearing less noise and with bigger air flow.

[Dusty Chalk]

What he's trying to say is, bigger fans are quieter.  This has been my experience (from computers, not amps) as well.

If that's not viable with your amp, try using much lower speeds.  It doesn't take much to make a difference -- air flow vs. not air flow alone will help from keeping air trapped within your case, if the vent isn't on top.

My Supra++ has a case fan.  It's hardly audible.

[mypasswordis]

On 5/1/2017 at 3:54 AM, mypasswordis said:

 He gets to use a big fan which means low rpm and thus a lot quieter

 

Sadly I can't stick a nice big 80mm or 120mm fan in there as it is way too big for the case I want to use. Only a 40mm or possibly 50mm could be squeezed in, as the internal case height is 60mm and there's always additional stuff going on at the edges to hold everything together. The 40mm Noctua I was looking at, based on Marc's advice, is rated for 17.9 dBA and seems to get good reviews. It's also much easier to drill smaller holes in sheet metal  35mm or 1 3/8" seems to be about the max for normal unibits, just right for a 40mm fan. What's the best way to drill large holes bigger than 1 1/2 inch anyway? 

[luvdunhill]

Use a chassis punch, which is not cheap unless you find a used one.

[Pars]

^ And that won't work for thick panels. Not sure if a good hole saw would work?

[luvdunhill]

^ And that won't work for thick panels. Not sure if a good hole saw would work?

I wouldn't use a hole saw. Maybe a sacrificial forstner bit - just don't let Steve know - and only on aluminum and even then it isn't safe. The punch can work to about 1/4" thick aluminum.

[Kerry]

For aluminum, I could mill it for you

[swt61]

I have used hole saws to mount fans in steel computer cases in the past. I would just make sure to use a sharp hole saw and a drill with a handle, or if that hole saw catches, it'll dislocate your wrist.

[spritzer]

There are some gigantic circular hole saws on ebay and while being pretty shitty, they work ok for some light cutting.  I'd only use them on aluminum though. 

[mypasswordis]

18 hours ago, Kerry said:

For aluminum, I could mill it for you

Thanks, I might take you up on that soon!  Will shoot you a PM sometime in the next few weeks as I gather parts and figure everything else out. I only realized after I received it that the 50VA Antek HV transformers only have one HV secondary  need to order a big fat 100VA one 

Having intact wrists and fingers is a plus. 

[mypasswordis]

So a 40mm fan is pretty small. Definitely glad I didn't get a 50mm as it wouldn't fit in the case. Considering getting another 40mm tho...

[Craig Sawyers]

On 5/4/2017 at 11:31 AM, spritzer said:

There are some gigantic circular hole saws on ebay and while being pretty shitty, they work ok for some light cutting.  I'd only use them on aluminum though. 

Just picking up on this thread. I've used chassis punches, hole saws and (ugh) forstner bits depending on the size of the hole and thickness of the material. And only on Al. They key thing with hole saws and forstner bits is lots and lots of lube.

[spritzer]

Isn't that always the case?  It's all about the lube... 

[swt61]

3 hours ago, Craig Sawyers said:

Just picking up on this thread. I've used chassis punches, hole saws and (ugh) forstner bits depending on the size of the hole and thickness of the material. And only on Al. They key thing with hole saws and forstner bits is lots and lots of lube.

Wow, I would never have thought of using a Forstner bit on aluminum. Is aluminium softer? 

[Craig Sawyers]

-ium is an interesting thing though. Titanium, Lithium, Sodium, Calcium, Magnesium, Iridium, Curium etc etc.

Without the "i" those would be Titanum, Lithum, Sodum, Calcum, Magnesum, Iridum and Curum, which would be just silly

So Aluminium is completely logical 

[Dusty Chalk]

6 hours ago, spritzer said:

Isn't that always the case?  It's all about the lube... 

Reminds me of a joke a very clever girl engineer used to pick up a similarly clever guy engineer in college (yeah, that whole school were rutting like rabbits -- made it hard to concentrate on studying):

Girl:  "Do you smoke? "

Guy:  "Yes."

Girl:  "Use more lube."

[swt61]

Logical, yes. 'Merican, no. 

[mypasswordis]

The Trump administration seems to have overdosed on sodum...

Since I'm just drilling through alumin(i)um I'll try a hole saw for the next project, thanks. I can get away with just using a 1 3/8" step bit for a 40mm fan.