Entertaining the idea of having a case milled for my Aleph J. What do you all think about top mounted heatsinks?
Partly inspired by the Mola Mola audio gear, they have very attractive top plates.
Partly inspired by the Mola Mola audio gear, they have very attractive top plates.
I don't think anyone wanted to answer your questions so I'll take care of it.
Just one question: Have you ever seen a power amp design with the heatsink arranged like this (especially in class A)?
Do you have an idea of what is commonly called convection?
I'm not here to shoot an ambulance, but to get you to figure it out for yourself.
Just one question: Have you ever seen a power amp design with the heatsink arranged like this (especially in class A)?
Do you have an idea of what is commonly called convection?
I'm not here to shoot an ambulance, but to get you to figure it out for yourself.
If you Google "heat sink fin orientation in natural convection" you can find several research papers that have studied this. Although upward fin orientation with the heat sink on its back is not the worst case, it is certainly not the best from a heat transfer standpoint. One paper says that a side mounted vertical orientation is 12% better. It would be even more so in your case as you show some of the fins to be partly buried. The worst case was found to be side mounted with the fins horizontal.
There is a lot to be said for this reasoning. 12% (if that is the correct number) is not a huge difference, and if the DIY'er does not find his/her own product to be esthetically pleasing, what's the point? I am, however, wary of the partially buried fins. Perhaps they could be longer.
You can probably cook on it. Go for it.
Attachments
People on this forum would be horrified / pass out with what I subject high dissipation projects to in Arizona (summer no less).
To date, I Avnet a single device fail and because of my work schedule I have a lot of listening time, I’m mean entire days worth during the week.
Build what you want to build they you want it to look. However, you do need to calculate your sink area and probably add some for the fact that they are not getting the benefit of proper orientation.
Anecdotally, my AJ is parked in a short 3U, and has been cooking for a tremendous number of hours over many, many years in a very warm room for much of the year. It only passes the 10 second test in the winter time.
Your idea is neat and different.
To date, I Avnet a single device fail and because of my work schedule I have a lot of listening time, I’m mean entire days worth during the week.
Build what you want to build they you want it to look. However, you do need to calculate your sink area and probably add some for the fact that they are not getting the benefit of proper orientation.
Anecdotally, my AJ is parked in a short 3U, and has been cooking for a tremendous number of hours over many, many years in a very warm room for much of the year. It only passes the 10 second test in the winter time.
Your idea is neat and different.
Clearly i need to do some more research and design creativity. The buried fins were purely an aesthetical choice. Since posting im thinking about some ways to use that area to the back of the case covering the heatsink to channel air through the fins.
I think i could live with 12%. Now 12% Plus the unknown inefficiency of buried fins, i may or may not loose sleep thinking about that ha.
Thank you for the insight
That’s a very attractive case and idea. It’s also a bad idea for a couple of reasons for this application because;
1) Class-A amplifiers, and Aleph specifically, run hot. The heatsinks need the fins orientated vertically so there can be fresh, cooler air drawn in at the bottom to replace the air that is heated by the heatsink which is rising up… Many people who have had cooling issues with thier amps have been able to fix it merely by rasing the amp off the shelf/floor by a single inch, to ensure a path for the air on the bottom to get to the heatsink. Top-mount heatsinks loose a lot of efficiency, as they can’t move the air.
2) Having anythning top-mounted on a project like this makes it a complete and total PITA to work on. The wires need to be long enough to remove the top and place it on the bench next to the bottom with the PSU and such, and it is completely inconvenient. As you’re thinking about it you’ll say, gee, that can’t be so bad… but it is.
I’ve been stupid enough to do something similar twice, and have been annoyed at myself ever since that it took me two times to learn the lesson! lol
Now, that said, the curves and cutouts you have drawn are gorgeous, im sure you can find a way to integrate that into the top and front and make an amazing looking amplifier!
🙂
1) Class-A amplifiers, and Aleph specifically, run hot. The heatsinks need the fins orientated vertically so there can be fresh, cooler air drawn in at the bottom to replace the air that is heated by the heatsink which is rising up… Many people who have had cooling issues with thier amps have been able to fix it merely by rasing the amp off the shelf/floor by a single inch, to ensure a path for the air on the bottom to get to the heatsink. Top-mount heatsinks loose a lot of efficiency, as they can’t move the air.
2) Having anythning top-mounted on a project like this makes it a complete and total PITA to work on. The wires need to be long enough to remove the top and place it on the bench next to the bottom with the PSU and such, and it is completely inconvenient. As you’re thinking about it you’ll say, gee, that can’t be so bad… but it is.
I’ve been stupid enough to do something similar twice, and have been annoyed at myself ever since that it took me two times to learn the lesson! lol
Now, that said, the curves and cutouts you have drawn are gorgeous, im sure you can find a way to integrate that into the top and front and make an amazing looking amplifier!
🙂
Who has real experience with top mounted heat sinks? If you have 100% buyin on the chart EUVL posted then heat source location, orientation and ventilation have a great deal to do with the heat sink’s efficiency. What about ventilation around the devices (holes drilled around the transistors in a top Mount heat sink?) or heat pipes integrated into the heat sinks (as passive cpu sinks do)…this is just a problem to be solved not a never-do situation
I have seen this article in the past but could not locate the link. I haven't found any two papers that came up with the same numbers, but all agree that side vertical is the best. I believe that the differences in their numbers are the result of different heat sink or test configurations. The fin thickness, length, and spacing all come into play.
I’m sure it could be done. And remember, even a small fan turning slowly and quietly makes an enormous difference in efficiency.
Personally, my biggest complaint isn’t the thermal hit, but the massive inconvenience of the top mounted devices.
Personally, my biggest complaint isn’t the thermal hit, but the massive inconvenience of the top mounted devices.
You sure are brave! haha. Thank you for sharing
My current chassis is a 5U. A safe side build as far as heat management. Building in a chassis of that size was great having the extra space to stretch out. I can appreciate the effort that went into making a 3u case work. As far as temperatures in that, yeah, shes a hot one.
Thank you for the insight.
That helped me better understand the conditions heatsinks need to operate optimally.
So, the inconvenience of top mounted parts. The idea is these heatsinks will not be mounted directly to the top plate. They will be mounted to the face plate with a bracket so the top can be lifted leaving the heatsinks in place. Still an uncomfortable situation being that the boards will still be underneath the heatsinks. Im working out a mounting solution to make that less obnoxious.
Thanks! I had fun drawing it up. Goals are = sexy amp + unique design haha.
I will continue to tinker with design and post my changes
Can you incorporate the curves and cutouts into the top/front somehow with ‘normal’ side-mount heatsinks? Your deign ideas are very attractive and would make a great looking amp.