MM11645 for Aleph5?

[kslim]

Hello,

I am trying to build a stereo Aleph5 (a single box) using MM11645 (link below). Would you know 12'' of this would suffice the one channel of A5(150W)? The link says that 0.8C/W, which I heard is based on 3'' lenth.

I can go 15'' if needed, which will be side length of the box. I prefer 0.2C/W to have some room to tweak R19. My constraint, however, is the size of the box. I am not sure how this C/W scales with increasing length, ie are they just divide by length/3 ?

Also anyone knows price of this sink, when I just buy 2 pieces of 12'' to 15'' ?

Thanks very much, and here is the link.

http://www.mmmetals.com/extrusions/drawings/MM11645.jpg

[Nelson Pass]

The 3 inch figure has better thermal resistance per inch
because the efficiency tapers off as the sink gets longer.

a 15 incher would do a channel, I think.

[Brian Donaldson]

Hey, that's the extrusion I used for my Aleph 2+ I used 4 sections 10" tall (fins vertical) per monoblock. At 50 v rails 4 amp bias over 16 fets per channel it runs 165 deg F.

http://www.diyaudio.com/forums/attac...&postid=263089


Price... 2 years ago 8 feet cost me $450

you could get away with 8" tall 2 pieces side by side on each side safely.

[kilowattski]

Kslim,

I would recommend this extrusion. http://www.mmmetals.com/extrusions/drawings/MK62430.jpg . Two sections 12" long cost me $120 a year ago. The C/Watt is .6 per 3" and you do not have to piece together 2 sections for each channel of your amp, which makes for less machine fabrication. Also, the sink you picked has a base thickness of .2" which when threaded, is not alot of thread for a decent size screw when building your chassis. The one I recommend has a base of .3" which is better. It is up to you but IMHO the above would be a better choice. Best of luck with whatever sink you choose. Here are a couple threads where I have some pictures of these exact sinks I used in a chassis for my Zen IV project.

Zen IV Progress Report

Zen IV Progress Report

[kslim]

Oh well, the reason I am planning 12 to 15 inch section for each channel is because I prefer slimmer rectangular shape to the popular cubic shape. I dont mean the super slim shape, but my height constrain is 8'' maximum.

Both Brian and Kilos' design to me are kind of too tall or at least not slim, which is great looking in its own way. But I want slimmer box with deeper depth to compensate the reduced height. But then I might be constraining too much for a class a amp.

I agree with Nelson that 15'' should do it especially if I populate 6 FETS to some smart way. But not sure if I can meet 0.2C/W. Then maybe I will have to cancel A5 and start A3

[kilowattski]

Kslim,

Don't give up on the Aleph 5 just yet. There are other heatsink manufacturers out there. I understand that Conrad Heatsinks are very good and the MF35-151.5 (13.7795" long by 5.9646" high) at ~ $40 USD per sink (you only need 2) just may fit the bill. Their URL is http://www.conradheatsinks.com/welcome.htm . They are in Austrailia but I seem to remember hearing that a few members here in the states have used them. Have a peek at this thread just got new heatsinks from Conrad and you will see they are top quality heatsinks and fast delivery.

[kslim]

Oh those look very good. Thanks Kilo.

[Brian Donaldson]

Deeper and shorter will give lower R theta for the same total lenght of extrusion. If yo put 3 of the extrusions 7" tall, you could burn 400 watts for 2 sides (42" total extrusion)