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Old 29th December 2009, 05:12 PM   #1
Eric is offline Eric  United States
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Default To Anodize or Not...

Hi Everyone,

After a long delay and many interim projects, its time to finish building my set of 100w Aleph-X amps for my basement theater (I am building 5 monoblocks). I have everything I need now except for the heat sinks. I have chosen to use this sink from MM Metals:http://www.mmmetals.com/extrusions/drawings/MM11645.JPG

Each monoblock will produce 100w and will need to dissipate 300w. The MM11645 is rated to 0.8c/w per 3" length, so I am planning on using four 10" lengths per chassis to achieve approx 0.06c/w per completed chassis.

So my question is this: should I have the extrusions black anodized or should I leave them a raw aluminum? How much radiative capacity do I lose if I leave then raw? I'm wondering if the cost of anodizing them is worth it...

Thanks,
Eric
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Old 29th December 2009, 06:17 PM   #2
massimo is offline massimo  Italy
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10 - 15 % minimum.
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Old 29th December 2009, 07:29 PM   #3
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dunno if the "black body" is worth that much % wise, check some heatsink mfrs sites to see what they say about it.

IF you get it anodized you want to make sure that it is "nickel sealed" or an equivalent process - tell the anodizer that it is going to get [u]hot[/i]. Most straight dyes used in anodizing will turn color(s) over time - black notoriously turns purple.

Also you have to use the mfr's engineering data to derate heatsinks WRT length when used with natural convection.

FYI

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Old 29th December 2009, 08:09 PM   #4
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Conrad Heatsinks - Technical Details
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Old 29th December 2009, 08:21 PM   #5
Eric is offline Eric  United States
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Hmmm... The Conrad page indicates 5-8% for black coating (though they don't call it anodize). 8% on a chassis rated for 0.06c/w is barely 0.005 - doesn't seem like its enough to bother with.
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Old 29th December 2009, 08:39 PM   #6
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Quote:
Originally Posted by Eric View Post
Hmmm... The Conrad page indicates 5-8% for black coating (though they don't call it anodize).
Nope, they specifically say it's "powder coated". In other words, covered in paint!

Black anodizing should result in about a 15 - 20% more efficient heatsink than plain aluminium
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Old 29th December 2009, 11:18 PM   #7
Eric is offline Eric  United States
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15%-20% seems more worth while. Thank, EH!
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Old 29th December 2009, 11:31 PM   #8
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It'll look better too.
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Old 30th December 2009, 03:38 AM   #9
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I have both types of Heat sinks... the same M&M profile used on Aleph 2's.

I had to "arrange" the heat sinks to hide anodizing flaws but it worked out.
The cut edges are RAZOR sharp.

The power coating on the Conrad's that I also have for an Aleph J project look nicer,
and the corners are rounded a bit so I won't cut myself like I did while constructing,
and moving around the Aleph 2's.

Unfortunately Conrad doesn't make a tall profile and depending on how your output
devices are mounted, you may not be able to use two horizontally stacked pieces,
and I'm not sure that is the best way to use heat sinks.

I'm pretty sure the Conrads are cast and not extruded,
the back plate is thicker than the M&M sink. (2 to 3 mm's)
Click the image to open in full size.

I used 2 sections of M&M per side 9" tall on the Aleph 2's.
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File Type: jpg Aleph2.jpg (98.3 KB, 287 views)
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Old 30th December 2009, 09:29 PM   #10
dms is offline dms
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Default 5 channels of class A

Eric,
I built an Aleph 4, and am in the process of building 2 Aleph 30's to run the 2 front speakers in my stereo/surround system. Let me warn you about the heat generated by one Aleph 4. I use a fan in the room next door, and route the air under the amp which lives in a purpose built wooden rack. The blower is a 220 volt running on 110 to slow it down and make it quieter. The heat from the one amp eventually warms my 16 x 19 foot basement. I figure with the additional 2 Aleph 30's, I will have to close off the furnace grates that feed the room when I have the amps on. With 5 amps, you will have to actively manage the heat or it will run you out of the room. I am near Chicago so I get 7 months of cold weather and the basement is always cool, until I turn on the Aleph!
Good luck
Don
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