NC400 Cooling

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Chris Adams

Re: NC400 Cooling
« Reply #20 on: 6 Jun 2012, 09:09 pm »
Brief update.

I decided to vent the amps just to give the electrolytic caps a chance to live a little longer. I thought about drilling holes but didn't want to, so I raised the top with some aluminum stand offs. Now there is a vent all around the top edge that can be closed anytime I like.




teetee

Re: NC400 Cooling
« Reply #21 on: 6 Jun 2012, 09:33 pm »
Can you measure the top cover temp again with amp vented?

Chris Adams

Re: NC400 Cooling
« Reply #22 on: 7 Jun 2012, 12:01 am »
Can you measure the top cover temp again with amp vented?

Sure. I measured the top and the large heat sink on the SMPS.

Top is still about 20F warmer than room temp. Heat sink is 10F cooler than it was with the top on, no venting. So the venting has reduced the large heat sink temp by 10F whereas removing the top completely reduced it by 20F.

If anyone is thinking about drilling holes to vent heat, the best area may be directly over the big sink.

By the way the standoffs are .25 inches. If you didn't want to drill but wanted better venting, just increase the length of the standoffs.

bhakti

Re: NC400 Cooling
« Reply #23 on: 7 Jun 2012, 12:44 am »

If anyone is thinking about drilling holes to vent heat, the best area may be directly over the big sink.


I would just add - think about drilling intake air holes to create air flow.  Maybe on the bottom cover.

Chris Adams

Re: NC400 Cooling
« Reply #24 on: 7 Jun 2012, 02:25 am »
I would just add - think about drilling intake air holes to create air flow.  Maybe on the bottom cover.

Good point!

medium jim

Re: NC400 Cooling
« Reply #25 on: 7 Jun 2012, 02:43 am »
Bigger heat sinks or aluminum bars/plates on the top of the amp to draw off the excess heat.

Jim

jtwrace

Re: NC400 Cooling
« Reply #26 on: 7 Jun 2012, 02:45 am »
Bigger heat sinks or aluminum bars/plates on the top of the amp to draw off the excess heat.

Jim

This is a great source for that.

http://heatsinkusa.com/

cab

Re: NC400 Cooling
« Reply #27 on: 7 Jun 2012, 03:28 am »
Heat sink for the ncore amp in on the bottom of the module so the best you can do is mount it to the case. There are two heat sinks on the smps which can be added to as long as they are kept electronically separate.

medium jim

Re: NC400 Cooling
« Reply #28 on: 7 Jun 2012, 03:46 am »
Heat sink for the ncore amp in on the bottom of the module so the best you can do is mount it to the case. There are two heat sinks on the smps which can be added to as long as they are kept electronically separate.

Mount some fanned heat sinks to the sides of the case to wick heat away.  Aluminum is a heat magnet and even in this setup, should draw heat away from the electronics.

Jim

Rclark

Re: NC400 Cooling
« Reply #29 on: 7 Jun 2012, 08:38 am »
Brief update.

I decided to vent the amps just to give the electrolytic caps a chance to live a little longer. I thought about drilling holes but didn't want to, so I raised the top with some aluminum stand offs. Now there is a vent all around the top edge that can be closed anytime I like.





 I like that. But JT keeps saying heat is not an issue, even in a closed box, so why then are we still concerned with heat and drilling holes, etc?

 Is even 120 degrees going to bother a capacitor designed to be in such a predicament? Certainly they are used in amps that must get a lot hotter. Do you think you will somehow vaporize the electrolytic fluid faster? What is the boiling point of that stuff anyway?

jtwrace

Re: NC400 Cooling
« Reply #30 on: 7 Jun 2012, 11:02 am »
But JT keeps saying heat is not an issue, even in a closed box, so why then are we still concerned with heat and drilling holes, etc?
I'm just regurgitating what Bruno has said many times already.  If he's not worried, I'm definitely not worried. 

bruno

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Re: NC400 Cooling
« Reply #31 on: 7 Jun 2012, 12:01 pm »
At low power the FET temperature is very nearly equal to the temperature of the mounting base.

Capacitor lifetime works as follows: the manufacturer gives a baseline lifetime at a given temperature and under rated load conditions. From that baseline, lifetime doubles for every 10°C reduction in temperature. Rated ripple current is usually taken to contribute 10°C to temperature, so no or very low ripple current constitutes another doubling of lifetime. Running the capacitor at a lower than rated voltage once again multiplies lifetime by a factor that goes up fairly quickly with dropping voltage.

The baseline lifetime of the caps on the NC400 is given as 2000 hours at 105°C. At idle or during normal listening (i.e. low ripple current) and 60°C we can thus multiply lifetime with a factor 2^((105-60)/10+1)=45. Expected lifetime works out as 90000 hours, or just over 10 years of continuous operation. At that point the capacitor will go out of spec, but not fail outright.

There is some irony to temperature and class D. People expect class D to run cool. That would only be true if one substituted a class D power stage for a class A amp and kept the heat sink as it were. Of course it would run stone cold under those conditions. But the point of course is to cash in on the diminished heat output and reduce heatsink capacity until the final temperature is the same.

(Back to hiding. I'm not actively monitoring this forum, but I'd like to take advantage of the occasion to give three cheers to jtwrace for setting up this Circle and organising the listening tour.)

Chris Adams

Re: NC400 Cooling
« Reply #32 on: 7 Jun 2012, 01:05 pm »
Thanks, Bruno. Appreciate your time to comment on the subject very much. And I truly appreciate your incredible amplifier design that gets me so much closer to the music!

poseidonsvoice

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Re: NC400 Cooling
« Reply #33 on: 7 Jun 2012, 01:12 pm »
Welcome Bruno to AC!
:hyper: :dance: :drums: :rock: :bounce:

Anand.

Rclark

Re: NC400 Cooling
« Reply #34 on: 7 Jun 2012, 08:24 pm »
Wow, that just happened.  :D


 So with a closed box, if we listen to the amp constantly, never give it rest, in ten years we might have to check the caps and have a few replaced, if that. Sounds good to me.


orientalexpress

Re: NC400 Cooling
« Reply #35 on: 7 Jun 2012, 08:31 pm »
sweet,i don't need no stinking hole  :thumb:


lapsan

medium jim

Re: NC400 Cooling
« Reply #36 on: 7 Jun 2012, 08:35 pm »
Wow, that just happened.  :D


 So with a closed box, if we listen to the amp constantly, never give it rest, in ten years we might have to check the caps and have a few replaced, if that. Sounds good to me.

If you have decent hearing you will know when a cap goes bad.  However, what Bruno said was that after 90K hours caps might go out of spec....so after 10 years there may not be a need to change or service the unit, unless you do hear a change.

Jim

*Scotty*

Re: NC400 Cooling
« Reply #37 on: 7 Jun 2012, 10:25 pm »
I like the idea of possibly getting 15 years out of the caps by adding a few strategically placed ventilation holes. I also admit to occasionally being a belt and suspender man.
 A Centigrade to Fahrenheit conversion puts 60 degrees C at 140 degrees F.
If we can lower the caps temperature by even 8 to 10 degrees F we could possibly add 50% to the caps life expectancy.
Scotty

medium jim

Re: NC400 Cooling
« Reply #38 on: 7 Jun 2012, 10:29 pm »
I like the idea of possibly getting 15 years out of the caps by adding a few strategically placed ventilation holes. I also admit to occasionally being a belt and suspender man.
 A Centigrade to Fahrenheit conversion puts 60 degrees C at 140 degrees F.
If we can lower the caps temperature by even 8 to 10 degrees F we could possibly add 50% to the caps life expectancy.
Scotty

I like the way you think!

Jim

undertow

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Re: NC400 Cooling
« Reply #39 on: 8 Jun 2012, 12:46 am »
Well I did mention it in my thread on the dual mono setup, but here it goes... It is a dual mono so two power supplies in the case and this of course can add substantially more heat with 2 power supplies with each other... You can get a nice burn from the top plates of those power supplies.

Actually the Ncore itself I have no worry about, the NC400 bolted is a heatsink right to the case. But the power supplies get pretty hot. And they do transfer a lot of heat back INTO the NC400 being bolted to the same metal.

My suggestion is use Vented tops at a minimum and they then stay totally cool. Just me but especially when spending this kind of money, and easily making it bulletproof as I had to build it myself anyway, why not?

By the way I used Arctic silver 5, really good pure silver thermal heatsink compound. Its sold right at radioshack too. Cheap to order online, but with shipping you can get it locally from Rat shack just the same. It drops the temp about another 10 degrees. The NC400 stays cold with no issue.

"Further on the power supply.

You can melt cheese directly on that top plate for sure.

I have seen some posters using a "Stacked" Chassis.

This is great accept it seems they put the power supply on the bottom under a plate then put the NC400 on the top.

It defeats the purpose in my mind, they are adding at least 100 degrees to that NC400 heat sink even if the NC400 is disconnected and the power supply is just on.

Reverse it and put the NC400 on the bottom and the Power supply on the top to let the heat rise out of the case is the way to go, and in my opinion I highly suggest VENTED top plates at a minimum for the power supply it really does stay dead cool without transferring all that heat back to the NC400's heatsink in the case with it which is kind of against the whole purpose.

Or I guess you could just go with power supplies in one chassis and the NC400 in the other, I doubt that is necessary just saying."

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