[jtwrace]

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.

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!

Yes!   

[genjamon]

I just finished assembling mine this week. I had not attached the front or top panels of the chassis, so open air situation. I also used silver thermal compound between amp modules and chassis to improve thermal conductivity to chassis.

After an hour of listening the first night, I put my hand over power supply and amp module to see how hot they were. I was surprised how much heat was coming off the amp module. I touched one of the capacitors with my finger, and It was warm enough that I didn't want to keep my finger there more than a few seconds. I don't have equipment to measure surface temps.

Does this fit with others' experiences?

The next day, I plugged one of the monoblocks into the wall using my Kill-A-Watt meter to determine power requirements. With the ampon muting engaged, the amp was using 13 watts. Turning muting off, but without any playback, it consumes 18 watts. that's for a single monoblock.

[jtwrace]

I just finished assembling mine this week. I had not attached the front or top panels of the chassis, so open air situation. I also used silver thermal compound between amp modules and chassis to improve thermal conductivity to chassis.

After an hour of listening the first night, I put my hand over power supply and amp module to see how hot they were. I was surprised how much heat was coming off the amp module. I touched one of the capacitors with my finger, and It was warm enough that I didn't want to keep my finger there more than a few seconds. I don't have equipment to measure surface temps.

Does this fit with others' experiences?

The next day, I plugged one of the monoblocks into the wall using my Kill-A-Watt meter to determine power requirements. With the ampon muting engaged, the amp was using 13 watts. Turning muting off, but without any playback, it consumes 18 watts. that's for a single monoblock.

It's fine.  As posted above from Bruno.

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.)

[undertow]

FAILED POWER SUPPLY! SMPS600

You guys can believe what you wish, however I guess opening my mouth gave me some payback.

ONE of the 2 power supplies failed that I just installed within about 3 days.

I believe it was a weak or faulty relay and probably from being on the heat helped kill it even earlier than it would have failed. Of course 90% of the time something like this happens within 30 days of an electronic being installed.

I have a new power supply already installed, the old one went back to Hypex so in any case I am back with dual mono and some fast customer service.

They do get hot, I don't believe the heat is a good thing, and I don't believe you should think its the best option putting the NC400 in the case without decent cooling and believe it IS getting extra heat kickback from this power supply raising the temp. more than necessary.

Anyway, I have a vented chassis, and I have considerable space keeping the amp reasonably cool. We may never know why this first power supply failed, I just think its worth the extra precautions to not trap too much heat on these power supplies and in turn transferring it back to the NC400 modules.

And no it was not just a fuse that burnt out on this SMPS600 power supply 

[poseidonsvoice]

FAILED POWER SUPPLY! SMPS600

You guys can believe what you wish, however I guess opening my mouth gave me some payback.

ONE of the 2 power supplies failed that I just installed within about 3 days.

I believe it was a weak or faulty relay and probably from being on the heat helped kill it even earlier than it would have failed. Of course 90% of the time something like this happens within 30 days of an electronic being installed.

I have a new power supply already installed, the old one went back to Hypex so in any case I am back with dual mono and some fast customer service.

They do get hot, I don't believe the heat is a good thing, and I don't believe you should think its the best option putting the NC400 in the case without decent cooling and believe it is not getting extra heat kickback from this power supply raising the temp. more than necessary.

Anyway, I have a vented chassis, and I have considerable space keeping the amp reasonably cool. We may never know why this first power supply failed, I just think its worth the extra precautions to not trap too much heat on these power supplies and in turn transferring it back to the NC400 modules.

And no it was not just a fuse that burnt out on this SMPS600 power supply 

Let us know what Hypex says regarding the reason for the catastrophic failure, overheating or otherwise.

Anand.

[undertow]

Honestly, I don't know that they will say anything.

I made an RMA return and the unit is fixed. Beyond that they may not even keep track of it at this point, and it could be I am sure pointed to anything.

However, I will say this, the unit gets pretty hot so point was I feel better with it staying cool not stuffed in an undersized cigar box.

[persisting1]

My UcD 400 case got warm, but not overly hot. How hot are these units getting? Do these run much hotter than the older Hypex amps?

[undertow]

I don't know they are any hotter than any amp, including hypex products. I do know they put out more than enough heat to not trap them in a completely un-ventilated sealed metal box is what I am saying. It builds up quite a bit of pressured heat in there from what I can tell as your basically creating your own mini sauna if its a sealed box which I have seen many built like that on here, they should be fine with some vents in my opinion.

[ChrisPa]

I'll let you know when my enclosed sealed ncore monoblocs break down. They've been powered up continuously since 21st April so far

[jtwrace]

I'll let you know when my enclosed sealed ncore monoblocs break down. They've been powered up continuously since 21st April so far

I agree.  If Bruno who is much smarter then me isn't concerned, then I'm not. 

[cab]

I put these nifty cpu heatsinks on my smps heatsinks because my cases are rather small and I thought it couldn't hurt.... They seem to help....

[DavidT]

Here are some measurements taken from my quad amp chassis, employing dual UCD 400 for bass, and dual NC 400 for the higher ranges. Cooling holes on lower  chassis, open top, user heat sinks for amps. One SMPS per amp pair (total of two SMPS)

Instrument: FLUKE 179 True RMS VM, using Type K thermocouple (TC)

Calibration: Boiling H2O @ 102 C ( 2 C correction required ), room air @ 21.5 C

Method: Amp at idle for 1 hr. Finger press TC bead against surface using a 0.5 mm thick coated fiberglass protective cloth until temp reading stabilizes. Record non-corrected data.

UCD 400

Output inductor: 46.0 C

Main electro-cap: 42.1 C

Blue T-Bar: 42.1 C

User heatsink: 37.7 C

non HS TO-220 devices: 71 C

NC 400

Output inductor: 46.5 C

Electro caps: 38.2 C to 52.7 C ( too hot to touch)

User heat sink: 34.3 C

SMPS 600

Main xfmer: 47.7 C

Small HS 36.0 C

Large HS original: 46.5 C

Large HS w/ user HS added: 38.2 C



BTW, all 4 amps output 190 WRMS into 8 ohms, both channels driven, just before clipping, with 120 vac line voltage

That is: 190W * 4 = 0.760 KW! Yowzer!

Regards, DavidT

[DavidT]

Follow-up to Previous Post (Past post shows temp data w/ cover off, also see this for measurement parameters)
 

Method:

Amp at idle for 6 hrs with vented cover installed. Cut power. Remove cord. Remove chassis cover. Check power supply rails @< 24 VDC. Press TC bead against surface with finger using a 0.5 mm thick coated fiberglass cloth until temp reading stabilizes. Record non-corrected data. All data taken within 3 minutes of cover removal.

Note:

The coated fine weave fiberglass cloth reduces errors due to the heat sink effect of the finger, as well as protects it from electrical shock and heat burns!

These data are less accurate than the previous data, because I did not wait as long as previously for temp stabilization. This is a trade-off between errors due to surface cooling and errors due to thermocouple time constant.

All temp measurements were done with the power turned off and the power cord removed. Power supply rails below 24VDC.

Room air: 21.6 C


UCD 400 ( most surfaces too hot to touch > 1 sec)

Output inductor: 54 C

Main electro-cap: 51 C

Blue T-Bar: NM

User heatsink: 53 C

Non HS TO-220 devices: 85 C


NC 400 ( most surfaces too hot to touch > 1 sec)

Output inductor: 55 C

Highest temp of 10 electro caps: 61 C

User heat sink: 42 C


SMPS 600 ( most surfaces too hot to touch > 1 sec)

Main xfmer: NM

Small HS: 49 C

Large HS original: NM

Large HS w/ user CPU style HS added: 50 C


My Conclusions:

This is a stunning amount of power capability in a very small and light weight package! Well done!

Surface temperatures appear normal for reliable modern gear to me, although I prefer about 10 C more thermal margin for even more extended reliability.

The user added CPU HS (e.g. designed for horizontal use) on the SMPS600 large HS brings it's temp down to about the temp of the SMPS600 small HS.

If the SMPS600 large HS raises in temp approximately the same as the small HS with the cover installed, then the original large HS would theoretically measure about,

   46.5*(49/36) ~= 63 C

The 85 C measurement on the UCD TO220's bothers me, but hey, my various UCD amplifiers have survived 6 summers just fine...


HTH, Regards,

DavidT

[bhakti]

DavidT - Thanks for the info!

Do you have any pics or links of the heat sink you are using on the power supply?

[DavidT]

Hello Bhakti,

I am using two of these CPU heat sinks on the SMPS600 large HS:

AAVID THERMALLOY 9000000958 (special) $1.39 ea. USD

http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_2150942_-1

DavidT

[OzarkTom]

Hello Bhakti,

I am using two of these CPU heat sinks on the SMPS600 large HS:

AAVID THERMALLOY 9000000958 (special) $1.39 ea. USD

http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_2150942_-1

DavidT

Wow, how can you afford those?

[DavidT]

quiet now , do not tell Judy, but I raided the kitchen piggy bank... (smile)

[undertow]

I ordered 8 of them as the minimum was 10 bucks anyway... Gonna load up the large plate on the SMPS with them. The left over whatever just put them for another project maybe down the road. Not bad for a slight reduction at only like 15 bucks shipped Ups Ground since they are self adhearing and horizontal mount. Actually the vents on my power suppies are right above so should get decent airflow over these heatsinks too.

[Don_S]

I have this in my music server. Big sucker. Too bad I can't see it. 

[Atlplasma]

A number of folks have raised concerns about heat build up. Any opinions on using a laptop cooling pad with the enclosure to absorb heat. Mono price has some on closeout for just a few bucks. The one issue would be if you left the amp on continuously. The cool pads are only good for 8 hours.