Need NC1200 owners input

[muslhead]

Not trying to recreate another VTV build quality bashing thread but i noticed something after forgetting to turn off my amps after using them. I went back the next day and noticed they were hot to the touch (114 F) after being powered on for ~12 hours. Normally i turn them off after use so i was surprised to find them running this hot. My previous icepower PSAudio Stellar would be cool to the touch (and why i was ok to leave them on) and only get this hot after running them for a lengthy period at 50-75% of max (i know they are a different module). I tried reading the nc1200 spec sheet but couldn't find one for idle temp. Additionally, I am not sure it's the module or power supply that is causing the heat (or some other component possibly).
Firstly is this something I should be concerned with if my normal usage pattern is to turn them off after i am done using? Clearly heat is your enemy and will reduce life of all internal components. Do other owners (non VTV brand) amps exhibit this behavior?
Based upon the questionable build quality of VTV amps, could this be, at least partially, due to this factor and something i can address with him?
Was planning on just using until purifi comes out with a higher power module and just replace then. Just now not sure they will last long.
Input anyone?

 

[AnalogSteph]

I tried reading the nc1200 spec sheet but couldn't find one for idle temp. Additionally, I am not sure it's the module or power supply that is causing the heat (or some other component possibly).

What they do have is a spec for idle losses.
Typ 15 W, max 17 W for the NC1200 plus 9 W for the SMPS1200A700. So about 26 W, plus whatever the input buffer needs. That should be roughly the equivalent of a traditional 30-50 wpc integrated AB amplifier, or an office PC from about 2011.

Can you make out which areas of the case are getting warm in particular?

Photo seem to indicate a half-decent amount of slots for ventilation on the bottom, a bunch of thin ones around the perimeter of the back panel, and a lot of itty bitty holes on the top (lots of metal, not very much hole area at all). I don't think Steve @ Gamers Nexus would be particularly enthused. The case seems to rely in part on thermal radiation; I imagine thermal resistance would be reasonably high. So I wouldn't be surprised if it runs noticeably warm in the long run.

I guess the takeaway is that while Class D amplifiers are efficient, making them high power drives up the power dissipation again, particularly in idle. I can see why one may be tempted to use them with switchable or modulated supply rails (à la Class G/H).

 

[muslhead]

no, unfortunately, the case does a decent job of distributing the heat so i cant tell where it is coming from. The VTV case is riddled with holes in the bottom and on top with nothing along the sides, back or front. Other than living with it or placing a fan to increase air flow, i am stuck
I have heard other nc1200 builds don't have a high idle temp. I could be wrong but was hoping those that do in fact know, would provide their experience to narrow down the possible causes.

 

[echopraxia]

Not trying to recreate another VTV build quality bashing thread but i noticed something after forgetting to turn off my amps after using them. I went back the next day and noticed they were hot to the touch (114 F) after being powered on for ~12 hours. Normally i turn them off after use so i was surprised to find them running this hot. My previous icepower PSAudio Stellar would be cool to the touch (and why i was ok to leave them on) and only get this hot after running them for a lengthy period at 50-75% of max (i know they are a different module). I tried reading the nc1200 spec sheet but couldn't find one for idle temp. Additionally, I am not sure it's the module or power supply that is causing the heat (or some other component possibly).
Firstly is this something I should be concerned with if my normal usage pattern is to turn them off after i am done using? Clearly heat is your enemy and will reduce life of all internal components. Do other owners (non VTV brand) amps exhibit this behavior?
Based upon the questionable build quality of VTV amps, could this be, at least partially, due to this factor and something i can address with him?
Was planning on just using until purifi comes out with a higher power module and just replace then. Just now not sure they will last long.
Input anyone?

114F just from idling overnight is really hot. A well-built Hypex NC1200 amplifier should be cool to the touch (<85F) even after idling overnight, as seen here (a photo I received a while ago from @March Audio, who (re)built my NC1200 mono-block amps):

As you can see, surface temperature is <30C aka <85F. So if yours is idling at 114F, something is probably very wrong Sorry I can’t offer much help otherwise, but others here can perhaps give more detailed technical advise than I.

 

[muslhead]

Thanks.
That temp you show is more like what i experienced with my PSAudio icepower amps.
So, if its not the module (we have same module) does anyone know what could be potential cause? Case, perhaps?

 

[March Audio]

Hypex thermal design note.

https://www.hypex.nl/img/upload/doc/an_wp/AN_Thermal_design.zip

 

[muslhead]

Thanks, Alan
I wasnt even considering the power loss in my concern since i didnt know it could be as much as 20-25% in worst case conditions (if i am interpreting the docs you included correctly).
I was thinking more about reliability and mtbf increase due to high temps.
Is there anything else i am missing?.
The way i see it, my choices are
1. a new amp (that didnt have this problem),
2. a fix of current amp to correct its problem(s) 3.
3. Using a cooling device when the amp is in use (ie a fan)
4, Just live with my bad buying decision and replace when it craps out?

 

[CDMC]

Thanks, Alan
I wasnt even considering the power loss in my concern since i didnt know it could be as much as 20-25% in worst case conditions (if i am interpreting the docs you included correctly).
I was thinking more about reliability and mtbf increase due to high temps.
Is there anything else i am missing?.
The way i see it, my choices are
1. a new amp (that didnt have this problem),
2. a fix of current amp to correct its problem(s) 3.
3. Using a cooling device when the amp is in use (ie a fan)
4, Just live with my bad buying decision and replace when it craps out?

5) Return to seller since defective.

 

[muslhead]

#5? Past my 30 day trial period.
Under what pretext are they defective?
I did not see any spec (thanks, Alan) they did not meet (no spec for idle temp).
There is no spec for bad workmanship.
I dont want to make this a witch hunt and take the higher ground. I made the decision to purchase and did not return within my grace period.
If they are defective, i have no problem asking to return. As of now, i dont see what is defective.
Based upon what you know and what the specs are, what is out of spec?

 

[echopraxia]

#5? Past my 30 day trial period.
Under what pretext are they defective?
I did not see any spec (thanks, Alan) they did not meet (no spec for idle temp).
There is no spec for bad workmanship.
I dont want to make this a witch hunt and take the higher ground. I made the decision to purchase and did not return within my grace period.
If they are defective, i have no problem asking to return. As of now, i dont see what is defective.
Based upon what you know and what the specs are, what is out of spec?

I don’t know if there is a Hypex-published spec for idle temperature, since that depends on the quality of the product’s overall cooling design (which is outside of Hypex’s control).

On one extreme, a build could theoretically liquid cool with a heat pump down to below room temperature. On the other extreme, another build could run so hot during idle that the electronics internally burn out within a few days.

It’s hard to know where to draw the line between outright defective, vs just a really low quality cooling design. The reference point I provided above at least shows what’s possible with a passively cooled build. Whether the difference between that and yours qualifies for classification as “defective” is not something anyone can definitively answer, I suppose. (Though I do think most here would agree that running that hot while idle is not okay for amplifiers at this price point.)

 

[NTK]

With a 25 W idle loss, I don't think a case temperature of 45 deg C is too excessive. Below are my back-of-the-envelope calculations.

The dimensions of the case are width, w = 8", length, l = 11", and height, h = 3.25". When the amp has reached steady state, the heat generated equals to the heat dissipated. From Engineers Edge the convective heat transfer coefficient for free convection of a vertical plate in air is ~5 W/m^2 K. The top surface is horizontal and should have a lower convective heat transfer coefficient, but I'll err on the high side here.
https://www.engineersedge.com/heat_transfer/convective_heat_transfer_coefficients__13378.htm

I'll ignore the bottom surface, and the surfaces participating in the convection heat loss are front and back, left and right, and top. The total surface area is 2*width*height + 2*length*height + width*length = 211.5 in^2 = 0.136 m^2. With a heat dissipation of 25 W, the average temperature rise is 25 / (0.136*5) = 36.6 deg C.

Thus, my estimated case temperature is actually higher than what you have measured with your amp. (May be because there is more air movements than purely natural convection and/or the bottom surface did help and/or the numbers used are a little off.) Given these numbers, blowing a little bit of air at it should lower the case temperature to a comfortable to touch level.

 

[echopraxia]

With a 25 W idle loss, I don't think a case temperature of 45 deg C is too excessive. Below are my back-of-the-envelope calculations.

The dimensions of the case are width, w = 8", length, l = 11", and height, h = 3.25". When the amp has reached steady state, the heat generated equals to the heat dissipated. From Engineers Edge the convective heat transfer coefficient for free convection of a vertical plate in air is ~5 W/m^2 K. The top surface is horizontal and should have a lower convective heat transfer coefficient, but I'll err on the high side here.
https://www.engineersedge.com/heat_transfer/convective_heat_transfer_coefficients__13378.htm

I'll ignore the bottom surface, and the surfaces participating in the convection heat loss are front and back, left and right, and top. The total surface area is 2*width*height + 2*length*height + width*length = 211.5 in^2 = 0.136 m^2. With a heat dissipation of 25 W, the average temperature rise is 25 / (0.136*5) = 36.6 deg C.

Thus, my estimated case temperature is actually higher than what you have measured with your amp. (May be because there is more air movements than purely natural convection and/or the bottom surface did help and/or the numbers used are a little off.) Given these numbers, blowing a little bit of air at it should lower the case temperature to a comfortable to touch level.

Out of curiosity, how do you think March Audio achieves such low idle temperatures then?

 

[NTK]

Out of curiosity, how do you think March Audio achieves such low idle temperatures then?

Hard to tell. May be because where you placed your amp is very well ventilated. A good test is to measure the idle AC power consumption, if you have something like a Kill-A-Watt. Then we can be sure how much heat is generated during idle.

 

[restorer-john]

5) Return to seller since defective.

I'd hardly call 45 degrees C after 12 hours idling defective. I have plenty of amplifiers that sit around 50 degrees C idling along and closer to 60 in summer, especially directly over the power stage or voltage regulator stages. When you run them hard, you'd better not touch the top panels for more than a second...

Junction temperatures on devices are rated to 150 degrees C, sometimes 200 degrees, so that is at least 110 degrees C above ambient.

I'd be much more concerned the heatsinking is adequate for full power continuous testing. If it's 45 degrees at idle, we know it will skyrocket at maximum rated power. That's what I'd be testing.

I was going to suggest the Kill-A-Watt also. At idle, measure the consumption- you know pretty much all of that is going up as heat.

 

[muslhead]

Out of curiosity, how do you think March Audio achieves such low idle temperatures then?

Oh, come on. We all know electricity flows backwards on that side of the equator. Jeeesh

 

[March Audio]

Out of curiosity, how do you think March Audio achieves such low idle temperatures then?

A few things to consider. The case surface area and the ventilation. The case will need to be more than a certain size to keep temps adequately low. Also the module heatsinks are mounted on the base plate, need use of heatsink compound there. It also depends on how well the other surfaces, sides and top, are thermally connected to the base as to how much heat they will dissipate. Not an issue in our case design.
Also the output inductor gets warm so without appropriate ventilation it will warm the case. Oh also aluminium has better thermal conductivity than steel.

Which Metals Conduct Heat The Best?
Common metals ranked by thermal conductivity
Rank Metal Thermal Conductivity [BTU/(hr·ft⋅°F)]
1 Copper 223
2 Aluminum 118
3 Brass 64
4 Steel 17
5 Bronze 15

It's also possible that any particular module or psu is running hotter than normal. We have seen this a few times and rejected modules. As mentioned a mains watt meter can give you a clue on this. Temp and idle power consumption is something we test for.

As an aside people will perceive 45 deg as too hot and above 50 deg can burn.

 

[muslhead]

I'd hardly call 45 degrees C after 12 hours idling defective. I have plenty of amplifiers that sit around 50 degrees C idling along and closer to 60 in summer, especially directly over the power stage or voltage regulator stages. When you run them hard, you'd better not touch the top panels for more than a second...

Junction temperatures on devices are rated to 150 degrees C, sometimes 200 degrees, so that is at least 110 degrees C above ambient.

I'd be much more concerned the heatsinking is adequate for full power continuous testing. If it's 45 degrees at idle, we know it will skyrocket at maximum rated power. That's what I'd be testing.

I was going to suggest the Kill-A-Watt also. At idle, measure the consumption- you know pretty much all of that is going up as heat.

I dont have a kill a watt but what i can do while i find one is run it hard and measure temp then.

 

[restorer-john]

I dont have a kill a watt but what i can do while i find one is run it hard and measure temp then.

Not sure what Kill-A-Watt style products cost for you, but here they are only about $20-$30. They are a great little tool and you'd be wise to grab one.

You really can't run an amplifier like that "hard" enough in a normal domestic situation to really heat it up. You'll destroy your speakers and ears. Proper testing would require some serious dummy loads and test gear.

 

[muslhead]

ok, i'll grab one, test and report back
Thanks for everyone's input

 

[March Audio]

Thanks, Alan
I wasnt even considering the power loss in my concern since i didnt know it could be as much as 20-25% in worst case conditions (if i am interpreting the docs you included correctly).
I was thinking more about reliability and mtbf increase due to high temps.
Is there anything else i am missing?.
The way i see it, my choices are
1. a new amp (that didnt have this problem),
2. a fix of current amp to correct its problem(s) 3.
3. Using a cooling device when the amp is in use (ie a fan)
4, Just live with my bad buying decision and replace when it craps out?

The electrolytic capacitors are the items that are going to life. The biggest factor in this life is temperature. It's difficult to predict what this life will be as there are a number of variables, but a simple rule of thumb is that life halves every 10 deg c rise in temp.