CHANGSTAR: Audiophile Headphone Reviews and Early 90s Style BBS
Lobby => DIY => Topic started by: shipsupt on July 25, 2013, 10:30:18 PM
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Sooner or later we need to get 'em off the bench and into a box! This thread to discuss the trials and tribulations of case work.
I've got a new project I'm starting and I have some ideas on what I want to do with the chassis on this one.
All of the chassis on my rack are moving towards being black cases with raw, brushed, or polished aluminum front panels. I'm finally considering the bling in addition to function!
The new project will have several components with wood bases with aluminum tops. I'm thinking to keep with the theme I want to try a black piano finish on the wood and then either a brushed aluminum or full bling mirror polish.
Anyone have any experience with doing this kind of wood finish?
I may cheat, I sent an inquiry to a local high end furniture refurbishment shop to see if they could do the finish work for me if I supplied the cut wood.
I'll also want to paint the exposed transformer covers in a matching gloss black. I "think" I can do this myself.
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You should take a look at users HighFlyin 's builds
http://www.head-fi.org/g/a/672159/post-pics-of-your-builds/
http://www.head-fi.org/t/85561/post-pics-of-your-builds/8130#post_7664351
..dB
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Wow that makes my Jonokuchi look like crap.
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I kinda wanna build one now
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His blog is pretty good too, you can see more of his impressive builds. Very inspiring.
http://www.diyaudioblog.com (http://www.diyaudioblog.com)
You should take a look at users HighFlyin 's builds
http://www.head-fi.org/g/a/672159/post-pics-of-your-builds/
http://www.head-fi.org/t/85561/post-pics-of-your-builds/8130#post_7664351
..dB
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didn't know where to post this but figured it was "stuff"
(http://www.audiocircle.com/image.php?id=85436)
a linear regulated sculpture from audiocircle http://www.audiocircle.com/index.php?topic=117605.msg1252530;topicseen#new
..dB
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So I want to drill some ventilation holes into the top plate of my Hammond chassis. This is for my CKK.
(http://i.imgur.com/xxv5QQH.jpg)
Holes are 6.35mm with 10mm between centers. They'll be right above the output transistors. This look ok? Is that a good amount? Think I should put some ventilation over the Vregs as well?
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Sometimes I wonder just how much ventilation actually helps... it's been a while since I've done the thermodynamics/heat transfer courses, but natural convection is incredibly slow. The random air movement in a room is probably stronger than anything that can develop from the heat. Putting additional holes at a cool section of the chassis may aid in developing a directional flow, but again it probably won't match the random air in the room. Now if there were a fan, things would be different.
I know in some cases a closed chassis with a heat sink would be more effective than vent holes. Just tossing ideas out.
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I already have heatsinks mounted on the output transistors. Little bitty ones though. With the top plate installed the chassis gets hot. Not Asgard hot, but hot enough to make me want to try to ventilate. I can place my hand on it for however long I want. With the top plate off, the amp stays quite cool.
Never took thermodynamics myself, but I imagine the chassis will still get hot even with holes. Hot air inside chassis -> Cool air outside -> Hot air flows outside to reach equilibrium. As opposed to the chassis just getting hot and cooling itself by just radiating heat.
Either way, it could just be an aesthetic thing :)p17
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Depends. I know Bryston ran into problems air cooling the BHA-1 w/ their original scheme versus just using the chassis as a sink. Where does the cold/cool air come in from? You can't have exit holes w/o intake for convection. Well, you can do anything, but....
Might want to do the inverse on the bottom panel to stimulate airflow from bottom to top and one side to the other. I would also make the intake holes on the bottom bigger as cooler air is more dense, and smaller holes on the exhaust might help accelerate faster moving hot air via a pseudo venturi effect. Now this is just for airflow. Ideally you'd want the hot components directly mounted to the chassis to optimize heat transfer so it can act as a heat sink, maybe w/ some added surface area foils somewhere the natural air flow can synergize w/ the heat sink's cycle for scavenging effects.
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That's certainly overkill for this application. This amp stays cool without the top on. I can't even feel heat emanating from the any components unless I touch the heatsinks directly. I don't need convection here, just need to make it a bit more open air. Think Magni, not Asgard.
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We know that hot air rises and causes convection, but the reality of it is that on a small scale the air hardly moves at all.
A metal chassis is highly conductive however. So heat trapped inside is transferred to the chassis, spread across the entire body, and transferred to the outside air. The bigger the surface area, the more effective this transfer. Heatsinks basically add surface area and extend how far conduction takes heat away before air will convect it off the body (ugh that was a poorly structure sentence, whatever I'm sleepy you know what I mean).
So the weird thing about vents is that you are now removing surface area for conduction, and if the air isn't moving then you've replaced conductive metal with insulative air... which will actually increase your internal temperature. Granted, this all hinges utterly on whether or not you can establish sufficient airflow inside.
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That's certainly overkill for this application. This amp stays cool without the top on. I can't even feel heat emanating from the any components unless I touch the heatsinks directly. I don't need convection here, just need to make it a bit more open air. Think Magni, not Asgard.
If you don't need convection, then why drill holes? Even w/o holes you are getting convection which drives the heat transfer of a heat sink. The question is how to best maximize the effect. Or if it's not that big a deal and you just want o play around go for it. Just drilling a few holes on top will likely make it worse as Armaegis said.
The question of loss of surface area w/ holes is a good one w/o proper design as a heat sink. Size is largely irrelevant to the effects of convection, it's a matter of temperature and airflow, not size. If you take the chassis apart and mount it on a board open face, you'll get much better convection. Likewise, if you employ strategic holes along with fins that already have lots of surface area, the loss from holes will be minimal compared to the gain in air movement. If you really want to get it right, one has to design the chassis as a proper convection/transfer system. People forget that even though it is a gas, for aerodynamic purposes, air behaves as a fluid so fluidynamics are just as relevant. Just popping a few holes in the top is akin to pouring out a 1 gallon jug of water without opening a second pressure relief valve.
http://www.youtube.com/watch?v=aSCMbZ-UAcY (http://www.youtube.com/watch?v=aSCMbZ-UAcY)
Hot air creates a low pressure environment (essentially like a pseudo vacuum that wants to filled/replaced), but it does very little work without the higher pressure of cool air driving to take its place and fill the void. It's just like weather, except the chassis is acting like a mountain range separating the climes from interacting. That's how you get stagnation and potential for worse performance than no holes at all.
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How hot are we actually talking about? How long can you keep a finger on the heatsinks when you've just opened the top?
In my opinion the vent thingy if done correctly (you need an intake as well) may not help that much for lowering the temps on the transistors as it may help other parts to not get hot. That is - air will slowly flow to the exit holes and not spread around the whole chassis.
But as I said - what temps are we actually talking about? Anything below 50-60°C is okayish in my book.
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How hot are we actually talking about? How long can you keep a finger on the heatsinks when you've just opened the top?
In my opinion the vent thingy if done correctly (you need an intake as well) may not help that much for lowering the temps on the transistors as it may help other parts to not get hot. That is - air will slowly flow to the exit holes and not spread around the whole chassis.
But as I said - what temps are we actually talking about? Anything below 50-60°C is okayish in my book.
Exactly, to be done right you need a well thought out design for the whole system. Always think about the system as a whole and everything in it relative to each other.
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I can put my finger flat on the side of the heatsink indefinitely without pulling away. It's uncomfortable but not painful. At the 35mA bias at least.
I doubt the chassis would actually be hotter with these holes drilled. The area being removed would be miniscule in relation to the total surface area.
I'll say it again, with the top off this amp is quite cool. The air "inside" the chassis is not noticeably warmer than the ambient. The side walls are only marginally warmer than any other piece of aluminum sitting on my desk. In this scenario the amp seems to equalize to the ambient temperature very well.
Which makes me confused when you guys say that removing surface area will make it heat up. Keep in mind, there are no components or heatsinks coupled to the chassis. They're all just sitting inside coupled to their individual heatsinks. Removing the top is removing a ton of surface area and that's obviously not making it warmer. So I think the better question is, at what point does drilling enough holes (removing surface area) turn this into an open system (top off)? Putting the top on flush (no slits) seems to make this the chassis warmer as well. So I'm questioning whether more ventilation is really a bad thing.
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As I've said - north of 60 degrees Celsius is where you should worry. I think the holes won't change much thermodynamically, yet on the long run you might run into a dust problem.
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more science...
Removing the entire top allows free convection because there's nothing in the way. The hot air can rise and cool air can swoop in from the surroundings. The random air currents in the room are probably stronger than that due to the heat anyways.
With the top on but holes drilled, the effective area of the holes is actually much smaller than what you measure due to the boundary layer effect which slows down airflow as it travels around or across a surface. Also, if you don't have holes for cool air entry then the chassis acts like a vacuum to hold the hot air in.
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That makes sense.
I could try to work around and drill some intake holes in the bottom but since it's already in a completed state it would be a PITA. Since RudeWolf mentioned it, I think the dust is more likely to limit this amp's life than heat. I'd leave the top off if it wasn't for the exposed mains wiring TBH.
Changing subjects, what would be the easiest way to get my hands on an acrylic top plate?
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Are you in the US? If so, you can spec one with Tap Plastics. Easy.
http://www.tapplastics.com (http://www.tapplastics.com)
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Finally got around to boxing up the Eddie Current Monolith.
Sounds great. Dead quiet background. :)p4
(http://img.photobucket.com/albums/v152/shipsupt/mono_zpsae69695b.jpg)
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nicely done !
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LOL. Did you make the cap-coupled or transformer-coupled version?
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I built both.
While I was waiting for the transformers to arrive I threw a couple of caps in. The up-side to the cap coupled build is it can be done very cheap. It seemed more than bit bright, lacked any weight, and sounded a bit tinny. It's pretty neat what can be done for so little money, but...
The transformer build kicks ass in every way. Everything filled out and the low end came to life. I'd say it still leans slightly to the bright side, but a few EQ clicks has things sounding how I like things. Everything is much more natural sounding, especially the mids and upper mids. It's really open and airy (with or without the 800's) and remarkably fast/dynamic. This is one of those amps that would catch peoples ears on a short listen, say at a meet.
It's sounding better with the 800's than I expected, as in very good. Stop the music and it's dead quiet; you can crank the volume to the stop and it's black. I'd really like to try some orthos with it, but I've got none left.
I'm pretty impressed for a $250 Darkstar amp.
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nice work! is that a Hammond walnut chassis?
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Thanks, and Yessir. It's not a bad case but a few things about it...
1. The aluminum is basically sheet like, so when milling the work tends to want to ride up the tools. Easy to make mistakes if you don't have the tool speed right.
2. If, like me, you mount your boards, transformer, etc... to the bottom plate, you have to wire things up with enough slack to remove the cover/top (the part with the wood sides) which will have all the switches, XLRs, LED, Pot etc.. mounted to it. This was sort of interesting to do and had me worried that I'd end up with a wire laying somewhere that would create noise in the circuit... but everything turned out fine. Obviously not quite as easy as having everything mounted to a single piece and a having a simple cover plate to open.
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Finally got back into the shop! I should have this Millett DCPP amp buttoned up soon if the fasteners I ordered show up soon. Spent today getting the top plate machined on the mill. Back plate tomorrow and then I can start mounting everything.
(http://img.photobucket.com/albums/v152/shipsupt/photo1_zpseefabeb8.jpg)
(http://img.photobucket.com/albums/v152/shipsupt/photo3_zps8b6e16d5.jpg)
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looks beautiful. that looks like quite the drill press.
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It's one of those cheap mini-mills. I had some training and experience doing machine work early in my career, so I'm pretty comfortable with doing manual machine work. You just need to be patient; it takes a little longer but you can get the job done.
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That's one serious bit! 1-1/4"? Is that the Grizzly clamping kit in the background?
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drill baby drill!!
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Not quite... 27mm. It is pretty big, but working with aluminum is so easy you can get away with crazy bits like that one.
The kit came from a UK outfit similar to Grizzly, so I'm guessing its the same kit re-branded.
That's one serious bit! 1-1/4"? Is that the Grizzly clamping kit in the background?
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It was a little too late to start testing tonight, but the chassis work is finished and the wiring is terminated. It'll need a little clean up after testing, but since I'm "working from home" tomorrow I'm sure I'll find a little time to get it hooked up to the variac and put some voltage to it. With any luck, and lack of magic smoke, I'll have some impressions tomorrow night. I plan to drive some speakers with it before I hook it up to the Floats.
I'm pretty happy with the chassis since it was essentially all stuff I had laying around, so the whole build was done for pretty cheap.
I'll take more pictures, my phone died after this first snap.
(http://img.photobucket.com/albums/v152/shipsupt/photo_zpse78adf58.jpg) (http://smg.photobucket.com/user/shipsupt/media/photo_zpse78adf58.jpg.html)
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:-DD Well done ship!
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No rubber or foam padding to reduce microphonics on the tube hole edges? I'd recommend a gasket.