NC400 Cooling

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Chris Adams

NC400 Cooling
« on: 27 May 2012, 08:09 pm »
I've noticed some are concerned with venting their cases or not.

I built mono blocks using the same case Siliconray is selling. There are no vents in the cases, they are completely closed. I've had them running since about 3pm yesterday at low volume. Not soft enough to carry on a conversation, but not at my usual listeng levels. I have checked the case temp at various times and the room temp at the same time. The cases seem to run about 21-22F higher than the room temp. Last night before I went to bed the room had gotten to about 80F. The cases measured 102F. This morning the room had cooled to about 67F. Cases were 88F. This afternoon, room temp 73F, cases 95F.

So far, very consistent. The mono blocks have measured within 1 degree of each other every time.


poseidonsvoice

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Re: NC400 Cooling
« Reply #1 on: 27 May 2012, 08:41 pm »
Thanks for the empirical measurements Chris. Regardless...people will continue to have the 'heebeejeebees' regarding heat sink management with this amplifier. If so, drill some vent holes or use a thicker heat sink. But honestly, it is a waste, in most audiophile systems. The manufacturer has already made his recommendations in the instruction manual, and has stated that most metal based cases like the SiliconRay model you and I have chosen is enough. It is Class D done right after all! My speakers are 95 to 96 dB sensitive...I will hardly be taxing this amplifier.

Given the small draw in wattage from the wall, most can afford to keep this amp on...all the time.   :green:

Best,

Anand.

bhakti

Re: NC400 Cooling
« Reply #2 on: 27 May 2012, 10:21 pm »
Thanks Chris for the info!!

That is good to know they run relatively cool and sealed cases sure keep the bugs and dust out.

DS-21

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Re: NC400 Cooling
« Reply #3 on: 28 May 2012, 01:06 am »
Given the small draw in wattage from the wall, most can afford to keep this amp on...all the time.   :green:

Though one thing to consider is that while Class D is (when competently done) more efficient at delivering power, it's not necessarily more efficient at idling than an AB amp. Also, my experience with other Class D designs is that they actually get hotter when idling than under load. That may not be true of the NCores, but it's something to consider.

Steidl Guitars

Re: NC400 Cooling
« Reply #4 on: 28 May 2012, 02:14 am »
Just for fun, I ran my stereo box (2 amps, 2 PSs) through a cheap watt meter.  With no load, it drew ~30 watts; disconnecting the nAMPON line from ground dropped it to ~20 watts. 

I measured this only a few minutes after start up.  The draw seemed to be decreasing slowly over time; I quit after about 10 minutes, when it was about 28/18 watts, respectively. 

*Scotty*

Re: NC400 Cooling
« Reply #5 on: 28 May 2012, 02:29 am »
The case temperature does not equal what temperature the devices in either the power supply or the module are operating at.
 In the case of the switch-mode power supply, the MOSFET doing the switching is passing all of the power that the amp is using. It will be heat-sinked but it wouldn't hurt to have a line of perforations along the edge of the top and the bottom of the case to let some of the heat in the box escape making the heat-sinking more effective. If it is working correctly you should be able to touch the heat-sink for a long three count, if you can't touch it for a three count then the device is running to hot and its operational lifetime will have to de-rated due excessively high operating temperatures.
 If I were building one of these I would use heat-sink compound between the module and the aluminum case to facilitate heat transfer from the module to the aluminum floor of the case. It's easy, cheap to do and it also couldn't hurt the longevity of the amplifier.   
Scotty

poseidonsvoice

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Re: NC400 Cooling
« Reply #6 on: 28 May 2012, 02:43 am »
If I were building one of these I would use heat-sink compound between the module and the aluminum case to facilitate heat transfer from the module to the aluminum floor of the case. It's easy, cheap to do and it also couldn't hurt the longevity of the amplifier.   
Scotty

Scotty is absolutely right. If you want the heat sink that is bolted to the Ncore module itself to be improved/upgraded, add heat sink compond to the bottom prior to bolting it to your chassis. Makes for better thermal coupling.

+1

.
Though one thing to consider is that while Class D is (when competently done) more efficient at delivering power, it's not necessarily more efficient at idling than an AB amp. Also, my experience with other Class D designs is that they actually get hotter when idling than under load. That may not be true of the NCores, but it's something to consider.

I agree. But I was speaking of Ncore only. My other amp was an SDS 254 which was warmer just sitting there at idle than during play time. Regardless, I trust Mr. Putzeys advice regarding thermal mgmt with his design. Don't want my $1.5k investment to vaporize though...

Anand.

acousticimagery

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Re: NC400 Cooling
« Reply #7 on: 28 May 2012, 08:19 am »
Hi Guys

Just to give you some re assurance about closed cases. Both Mola-Mola and ourselves at ACOUSTICIMAGERY are using completely closed cases with the NC1200's.

At Munich I held my hand on the Mola-Mola power amps and I would say they were quite warm but not hot. Our own D400M UcD amps have slots top and bottom where the amp module is and I'd say that at idle both cases were about the same.

I think it's the SMPS which generates most of the heat. But, of course, our cases are machined from one piece of billet ally and so the whole case is one big heatsink.

Cheers......John

TomS

Re: NC400 Cooling
« Reply #8 on: 28 May 2012, 10:50 am »
...
 If I were building one of these I would use heat-sink compound between the module and the aluminum case to facilitate heat transfer from the module to the aluminum floor of the case. It's easy, cheap to do and it also couldn't hurt the longevity of the amplifier.   
Scotty
I used heat sink compound for mine just because I always have for DIY power amps and supplies and figured it couldn't hurt. I haven't measured the temps but the small SR cases are just luke warm.

mgalusha

Re: NC400 Cooling
« Reply #9 on: 28 May 2012, 12:33 pm »
I also used thermal compound between the amp module and case, I couldn't help myself. :)

Chris Adams

Re: NC400 Cooling
« Reply #10 on: 28 May 2012, 01:27 pm »
Though one thing to consider is that while Class D is (when competently done) more efficient at delivering power, it's not necessarily more efficient at idling than an AB amp. Also, my experience with other Class D designs is that they actually get hotter when idling than under load. That may not be true of the NCores, but it's something to consider.

I have a pair of Tripath 300w mono blocks and noticed that they due run warmer at idle. I will check the NCores after idling  for a while and after a high volume listening session to see if there is a difference.

I'll pop the top and check the heat sinks on the SMPS 600.

Think I'll get some heat sink compound and check the case temp directly under the amp module both before and after compound application.

Chris Adams

Re: NC400 Cooling
« Reply #11 on: 28 May 2012, 02:25 pm »
I just checked room, case and SMPS heat sink temp. The SMPS heat sink temps were very difficult to read. They were jumping all over. I would say dissipating heat effectively. I could hold my fingers on the small heat sink for 10 sec. or more. Large heat sink, five seconds or more.

Room - 70F
Case directly over large heat sink - 92F
Small heat sink on SMPS - 88-125F
Large heat sink on SMPS - 92-130F

I decided to measure the screw top that held the hottest transistor on each heat sink.

Large - 143F
Small - 134F

Hottest component was large transformer @ 165F.

The shut down temp for overheating on the SMPS is 203F

I'm using a Metris infrared laser thermometer.

PeteG

Re: NC400 Cooling
« Reply #12 on: 28 May 2012, 02:35 pm »
Chris, thanks for the extra testing. After 20hrs the bottom chassis was just Luke warm (that works for me), I also like that I don't need to leave them on all the time like my Simaudio amp after 10-20 mins The Ncore's sound the same to me.

Chris Adams

Re: NC400 Cooling
« Reply #13 on: 28 May 2012, 04:03 pm »
I also like that I don't need to leave them on all the time like my Simaudio amp after 10-20 mins The Ncore's sound the same to me.

When I had Jason's I didn't notice a big difference between 20 mins and 20 hrs. Once mine are broken in (if they even need much of that) I'll do some comparisons. If there is not enough difference to my ears I'll consider installing a power switch. Just using the nAMPON at the moment.

I'm letting the amps run with the top off of one for a few hours to check SMPS heat sinks with maximum venting.


konut

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Re: NC400 Cooling
« Reply #14 on: 28 May 2012, 04:20 pm »
Would it not make sense to mount the boards "upside down" (screwed to the top) of a finned casework?

Chris Adams

Re: NC400 Cooling
« Reply #15 on: 28 May 2012, 05:04 pm »
Would it not make sense to mount the boards "upside down" (screwed to the top) of a finned casework?

Are you talking about the amp or SMPS. The amp is in direct contact with the bottom cover of the case and does not get that hot. I measured about 98-104F on the amp heat sink. Max allowable temp for amp is 194F.
The board of the SMPS comes in contact with the case at the four standoffs only. The hottest areas on the SMPS are the heat sinks and the large transformer. You would have to screw the heat sinks into the case to improve cooling.

Chris Adams

Re: NC400 Cooling
« Reply #16 on: 28 May 2012, 05:09 pm »
I found the temps to be lower with the top off for 2.5 hours. The laser thermometer was jumping around too much so I used the temp probe on my DMM. Temp on the large heat sink was 123F. Small heat sink was 131F

I put the cover back on and will check later tonight after it warms up again.

Chris Adams

Re: NC400 Cooling
« Reply #17 on: 28 May 2012, 07:12 pm »
Just checked the temp on large heat sink after top on for 2 hours, 143F. The top covers of both amps were 96.6F, so I believe the amp I measured was back to "normal" operating temp.

Temp increase with top on was 20F. Definitely runs cooler with the top off so I imagine some venting will also decrease internal temp. I don't know how much of a difference this makes long term. The amp with no venting is running well under temperature max levels.

I can imagine reducing the temps a bit could increase longevity, but by the time it fails, Bruno will have a new amp that will surpass this one. :wink:

*Scotty*

Re: NC400 Cooling
« Reply #18 on: 29 May 2012, 12:00 am »
Chris, were those temps taken with the amp just idling or during music playback when the amp was under a load.
Scotty

Chris Adams

Re: NC400 Cooling
« Reply #19 on: 29 May 2012, 01:40 am »
Chris, were those temps taken with the amp just idling or during music playback when the amp was under a load.
Scotty

Amps were playing at low volume and had been for approx 24 hrs when I first checked. Today still playing at low volume and on for approx 48 hrs when checked.