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In Reply to: RE: Why would a ZERO rpm fan cause interference ? posted by Bob_C on August 18, 2014 at 15:05:59
Clearly there cannot be a zero rpm fan in a MAC Mini. otherwise why put it there? I doubt if the Mini can dissipate 10-15 W from the cpu alone without boilng out.
Follow Ups:
Yes, the fan is probably turning at a low speed. It just can't be heard. There are little apps for the Mac that allow one to see the speed of the fan.
"Yes, the fan is probably turning at a low speed"
Could be. But because fans use electricity and manufacturers want to get a good efficiency rating, it is now common for fan controllers to keep the fan powered off completely if possible and then run only at the speed actually required. In come cases, e.g. power supply fans, it is possible to physically see the fans and observe that, indeed, they do not turn under low load.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
Regardless of what is desired in theory, a small box like the Mini with a 15W cpu needs a running fan for safety. So Mercman is right.
Look at the size of any Class AB power amp that does 15W. Almost all heatsinks provided in fanless motherboards are under sized, presumably to cut cost. We don't really want cpu temperatures of 60 - 70 C in a closed enclosure, period.
"Regardless of what is desired in theory, a small box like the Mini with a 15W cpu needs a running fan for safety."
It's not a matter of safety, because if it were, there would be danger in the case the fan fails. There is (or should be) thermal management firmware and/or hardware to control power consumption. This can be done by underclocking, undervolting, shutting down redundant cores, etc...
I suggest looking at the power consumption of the device while it is idling. You will find that it may be very little. This can be easily done if one has access to the power source, e.g. using a device such as Kill-A-Watt to monitor power usage. (This won't work with battery powered devices such as tablets.) CMOS logic uses very little power when no signals are changing, such as when the system is idle. Even while playing music if there is no DSP involved CPU utilization will be a few percent and even when CPU utilization is higher much of the processor hardware will be idle (e.g. floating point vector processing, graphics processing). Obviously this depends on software.
My new Asus Transformer notebook/tablet runs windows 8.1 and has no fan. It runs at room temperature while reading PDFs or surfing the web. The only time it is warm is while charging the battery or playing video.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
You will not find this to be true, certainly not a couple of Watts as implied but tens of Watts.
I can see at all times voltage and current in my 12.5 V power supply.
My Mytek DAC uses 20 watts and doesn't have or need a fan.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
20W on the label. How much in use? There is not a single component that uses many Watts. Have you measured it? Try 10W on a 30W resistor and see how it burns.
You need to exercise some electronics common sense.
The measured power consumption of my Mytek DAC was a bit under the rated 20 watts. I measured it some time ago when I first got a Kill-A-Watt. I don't recall the exact figure, but my recollection is 18 watts.
The measured power consumption of my Asus T1000 tablet is 10 watts at the AC plug with the display on full brightness and wi-fi in use. In this mode the wall wort feels warm, but the tablet itself is well below body temperature. Power consumption at the wall plug increases to 12 watts while charging the battery and the tablet feels slightly warm. The tablet also feels warm while playing video, presumably because of significant graphic processing. This system runs Windows 8.1 with 2 GB RAM and an Intel Z3775 CPU at 1.46 Ghz.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
It's the distribution of power consumption that matters. There is no cpu requiring 15W when there is demand within a small area.
Fred,
I appreciate the terseness of your posts when I can understand them. Unfortunately, this was not the case here.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
If you cannot understand the concepts relating to heat density in a confined space and how this can be dealt with, then there is no point in any further discussion
My lack of understanding does not relate to engineering concepts of thermal management. It relates to my inability to decipher absurdly cryptic posts whose meaning is highly ambiguous.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
It's only ambiguous to you when you are unable to grasp practical engineering concepts.
"It's only ambiguous to you when you are unable to grasp practical engineering concepts."
Does this mean that you now accept the concept of thermal resistance? I know, it was years ago that we kicked that around but I still remember it because it was so unique.
Rick
Always accepted it. As I recall, you went from metal heat transfer to plastic, or thereabouts.
"Always accepted it. As I recall, you went from metal heat transfer to plastic, or thereabouts."
Excellent! I'm happy to stand corrected. It's such a useful and intuitive concept that I think it belongs in all audiophiles' mental toolboxes.
Rick
Exactly. Half the stuff he posts makes no sense.
> half
Give me rhythm or give me death!
Really? it runs hot as the new york subway platform in august.
I recently compared the Mytek to DACs cost 2 and 3 times as much.
The Mytek gives exactly $1595 worth of sound. But no more.
I haven't ever been on a NY subway in August, but my Mytek runs warm, not hot. There is no question of being able to hold my hand on the case for as long as I want. Hot would be like my amps, where that is not possible.
What were the DACs you compared and how did they compare?
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
Consider your self lucky then :)
Well the MyTek runs hotter than ANY other digital component I have ever seen.
Direct comparison were made to the following DACs:
SIM 380D (PCM) $4000
Bryston BDA-2 (PCM) $3000
Naim DAC $4000
Musical Fidelity M6 (PCM) $3000
Auralic Vega (DSD/PCM) $3500
Luxman DA-06 (DSD/PCM) $5000
Marantz NA-11S1 (DSD/PCM) $3500
To say the MyTek was a distant second would be the understatement of the year. In comparison, a very flat soundstage, dry treble, and less ambiance, by a country mile, actually.
I have said many times, considering the feature set, it is worth $1600, but no more than that. It does not belong in a reference system, and you are leaving a good amount of the recording ambiance on the table by using it.
Agree, the design is compromised.
I notice the constant slow speed of the fan in my laptop. The Mac Mini is pretty compact, so I bet it is also on. The little fan apps will let owner know what is happening.
As I posted earlier about my Mac Mini fan:
Can't do better than that Abe!
you can't hear the fan (over ambient and 4TB drives), but the electrical, acoustics, vibrational and audio effects on the output can be and is still there.
I have been trying to explain this to you for a long while.
I understand and agree Fred. No argument here.
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