Need NC1200 owners input

[March Audio]

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

https://www.homedepot.com/p/Gardner-Bender-Energy-Usage-Power-Meter-PM3000/300905368

 

[muslhead]

https://www.homedepot.com/p/Gardner-Bender-Energy-Usage-Power-Meter-PM3000/300905368

yah, i was going to grab something like that from amazon.

 

[March Audio]

BTW the P701 shown earlier running on 120v is using 28 watts at idle no music playing.

 

[muslhead]

thanks. that will be my reference point once my meter gets here and i can do my test.
How long was it idling for before you took the reading?

 

[muslhead]

Got my meter yesterday and plugged on of the mono's in and fired it up
The results were .... drum roll please ................. 27 watts.
Can we conclude its not the module or PS? What's left?

 

[NTK]

Got my meter yesterday and plugged on of the mono's in and fired it up
The results were .... drum roll please ................. 27 watts.
Can we conclude its not the module or PS? What's left?

Then it has to be ventilation and/or room air temperature.

Heat transfer is all dependent on temperature differences. We now know the amount of heat dissipated. We know the surrounding air temperature. The heat transferred into the room air is simply the difference between the temperature of the room air and the average skin temperature of the chassis, multiplied by the surface area, and multiplied by the convective heat transfer coefficient.

The surface areas of the March Audio chassis and the VTV chassis are almost the same. The amounts of heat released are the same. The only explanation left for the difference in skin temperatures is different convective heat transfer coefficients, which are highly dependent on air circulation. [The skin temperature depends on the room temperature too, but we can assume that it stays within a pretty narrow range around 20-25 deg C.]

When looking at the table in Engineers Edge, the convective heat transfer coefficients for forced convection, for low speed is 10 W/m^ K, for high speed is 100, and for free convection vertical plate is 5. If you double the heat transfer coefficient, you reduce the temperature delta by half. As an example, if initially you have a 30 deg C delta and an ambient temperature of 20 deg C, the skin temperature will be 50 deg C, which is quite hot to touch. Reduce the delta temperature by half, the skin temperature drops to 35 deg C, which is just slightly warm.

It seems you will need a cooling fan. If idle is already too hot, partying time may be a problem.
https://www.amazon.com/home-theater-cooling-fan/s?k=home+theater+cooling+fan

 

[muslhead]

Then it has to be ventilation and/or room air temperature.

Heat transfer is all dependent on temperature differences. We now know the amount of heat dissipated. We know the surrounding air temperature. The heat transferred into the room air is simply the difference between the temperature of the room air and the average skin temperature of the chassis, multiplied by the surface area, and multiplied by the convective heat transfer coefficient.

The surface areas of the March Audio chassis and the VTV chassis are almost the same. The amounts of heat released are the same. The only explanation left for the difference in skin temperatures is different convective heat transfer coefficients, which are highly dependent on air circulation. [The skin temperature depends on the room temperature too, but we can assume that it stays within a pretty narrow range around 20-25 deg C.]

When looking at the table in Engineers Edge, the convective heat transfer coefficients for forced convection, for low speed is 10 W/m^ K, for high speed is 100, and for free convection vertical plate is 5. If you double the heat transfer coefficient, you reduce the temperature delta by half. As an example, if initially you have a 30 deg C delta and an ambient temperature of 20 deg C, the skin temperature will be 50 deg C, which is quite hot to touch. Reduce the delta temperature by half, the skin temperature drops to 35 deg C, which is just slightly warm.

It seems you will need a cooling fan. If idle is already too hot, partying time may be a problem.
https://www.amazon.com/home-theater-cooling-fan/s?k=home+theater+cooling+fan

Thanks for doing that calculation. I had already concluded the simple solution would be a fan. The difference is you concluded it had to be air flow. I am not convinced yet that is IT. It could be but I think, Marchaudio knows something about this and could provide valuable insight. The reason for my skepticism is i doubt my room temp and or air flow is radically different than his when he took his temp on his amp. The temp difference is just too great, IMHO, to conclude its air flow/room temp. I am not saying it cant be, it just doesnt seem logical knowing my room and how hot my other components get. Dont get me wrong, i am not arguing, more just thinking out loud. I have found when something doesnt make sense, it probably isn't right. OTOH Occam's razor.

 

[NTK]

Thermal design can make a difference too. But I think in this case the effects should be secondary. One question -- how uniform is the temperature of the VTV case? Are there small hot spots and cool elsewhere?

 

[echopraxia]

It seems you will need a cooling fan. If idle is already too hot, partying time may be a problem.

I wouldn't say it's necessary, since March Audio's P701 design idles quite cool (< 30C / 85F, see above), without the need for any cooling fan. Perhaps you mean to say a cooling fan is the easiest fix in OP's case (e.g. versus a complete rebuild with a totally different case and airflow design)?

I'm know very little about hardware/cooling design. But I can confirm that the entire case surface of March Audio's amps feels quite cool to the touch when left idling over night (and in fact, even when playing loudly for hours they only start to feel warm, and rapidly cool down once idling again). And as far as I can tell, there is no secret stealth fan inside

 

[muslhead]

Thermal design can make a difference too. But I think in this case the effects should be secondary. One question -- how uniform is the temperature of the VTV case? Are there small hot spots and cool elsewhere?

The temp is pretty consistent across all surfaces at least nothing notable to the touch. The bottom, as you would expect, is hotter than the top due to less air flow.

 

[Worth Davis]

I use some really cheap USB 120mm fans, I put one on receivers and amps, this is in Houston, tx so ambient audio closet temperatures get hot anyways.
nice fan: https://www.amazon.com/gp/product/B078PX4575/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1
cheap usb fan: https://www.amazon.com/gp/product/B00MWH4FL4/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1

To be clear - in houston if you buy a hot receiver it will fry itself sooner than normal, so its best to move a little around your audio gear

 

[NTK]

People in this forum are probably more familiar with electricity than thermal/fluids, and I'll use the electrical analogy. Heat flow is analogous to electricity flow. Temperature is to voltage, heat flow is current, and conductivity/convection heat transfer coefficient is conductance (reciprocal of resistance).

If the heat flow (current flow) and thermal conductance (electrical conductance) are fixed, the temperature difference (voltage potential difference) will be fixed just like it is with Ohm's law. Therefore, if the room temperatures are the same, convection is the same, heat dissipations are the same, the average skin temperature of the cases must be the same. There is little way around it. There is little difference in the geometries between the 2 cases. Neither one has any slots or fins to increase the area for convection heat transfer, just like you have with heat sinks.

Here is my quick look at the thermal aspect of the March case and Ghent case:

The March case (the picture is a P122, but I am pretty sure they use the same case) is 2 pieces -- the upper part is single piece machined aluminum, and the bottom part is a flat plate. The majority of the heat leaves the NCore and PS modules from the bottom and transfers to the bottom plate. There are 6 screws attaching the bottom plate to the top, and there mating surface areas are where the heat gets transferred from the bottom plate to the rest of the case. Being a single piece part, heat conduction in the top cover is good, and should therefore evenly and efficiently distribute the heat all around. Thus, I will expect the March case will have good temperature uniformity.


The construction of the Ghent case is quite different. It has a front and a back end plates. The top and bottom are extruded aluminum pieces. This assembly does not lend to good thermal transfer between the parts, especially between the top and bottom pieces. I'd expect the bottom plate to be significantly hotter than the front and back plates. The top plate can get some of its heat from the natural convection of the modules through air circulation inside the case. But still, the "averaged" skin temperature between the 2 cases should be similar.


At least we know that the Hypex modules seem to be in spec. Time to take out the IR cameras to look at thermal profiles (and thermal movies to see how the profiles evolve too) .

 

[muslhead]

People in this forum are probably more familiar with electricity than thermal/fluids, and I'll use the electrical analogy. Heat flow is analogous to electricity flow. Temperature is to voltage, heat flow is current, and conductivity/convection heat transfer coefficient is conductance (reciprocal of resistance).

If the heat flow (current flow) and thermal conductance (electrical conductance) are fixed, the temperature difference (voltage potential difference) will be fixed just like it is with Ohm's law. Therefore, if the room temperatures are the same, convection is the same, heat dissipations are the same, the average skin temperature of the cases must be the same. There is little way around it. There is little difference in the geometries between the 2 cases. Neither one has any slots or fins to increase the area for convection heat transfer, just like you have with heat sinks.

Here is my quick look at the thermal aspect of the March case and Ghent case:

The March case (the picture is a P122, but I am pretty sure they use the same case) is 2 pieces -- the upper part is single piece machined aluminum, and the bottom part is a flat plate. The majority of the heat leaves the NCore and PS modules from the bottom and transfers to the bottom plate. There are 6 screws attaching the bottom plate to the top, and there mating surface areas are where the heat gets transferred from the bottom plate to the rest of the case. Being a single piece part, heat conduction in the top cover is good, and should therefore evenly and efficiently distribute the heat all around. Thus, I will expect the March case will have good temperature uniformity.
View attachment 82385

The construction of the Ghent case is quite different. It has a front and a back end plates. The top and bottom are extruded aluminum pieces. This assembly does not lend to good thermal transfer between the parts, especially between the top and bottom pieces. I'd expect the bottom plate to be significantly hotter than the front and back plates. The top plate can get some of its heat from the natural convection of the modules through air circulation inside the case. But still, the "averaged" skin temperature between the 2 cases should be similar.
View attachment 82384

At least we know that the Hypex modules seem to be in spec. Time to take out the IR cameras to look at thermal profiles (and thermal movies to see how the profiles evolve too) .

now you got me interested. Dont have thermal cameras but i have an ir temp gun where i can easily take temps across the case and map out the findings. Not worried about the actual temp since the gun is only within a degree or two, but rather the gradient across each surface and the difference between top and bottom.

 

[echopraxia]

But still, the "averaged" skin temperature between the 2 cases should be similar.

OP here has noticed very high surface temperature on the top (not just the bottom), so are you sure the average temperature will be the same? I had experienced this as well with my VTV amps.

Are you factoring in potential differences in airflow velocity and location?

For example, for a PC, moving a case fan from one location to another could help the PC run significantly cooler, and this has nothing to do with surface area or power consumption (because these have not changed at all, in this example case). Rather, improved cooling will be because the airflow was channeled over the hottest parts (rather than the cooler regions, which will transfer little to no heat into the high velocity airflow).

 

[muslhead]

Quick and dirty temp measurements on top, bottom and sides showed uniform temps within +/- 2 degrees of average.
Top average (rounded) = 114F
Side average (rounded) = 117F
Bottom average = 127F
I did not measure front or back.

This seems more like a difference in cases, no? While it does not rule it out, maybe VTV build issues aren't necessarily THE problem (maybe just a contributor). Basically same size case, same materials and similar(?) venting should not give this different results though

 

[March Audio]

People in this forum are probably more familiar with electricity than thermal/fluids, and I'll use the electrical analogy. Heat flow is analogous to electricity flow. Temperature is to voltage, heat flow is current, and conductivity/convection heat transfer coefficient is conductance (reciprocal of resistance).

If the heat flow (current flow) and thermal conductance (electrical conductance) are fixed, the temperature difference (voltage potential difference) will be fixed just like it is with Ohm's law. Therefore, if the room temperatures are the same, convection is the same, heat dissipations are the same, the average skin temperature of the cases must be the same. There is little way around it. There is little difference in the geometries between the 2 cases. Neither one has any slots or fins to increase the area for convection heat transfer, just like you have with heat sinks.

Here is my quick look at the thermal aspect of the March case and Ghent case:

The March case (the picture is a P122, but I am pretty sure they use the same case) is 2 pieces -- the upper part is single piece machined aluminum, and the bottom part is a flat plate. The majority of the heat leaves the NCore and PS modules from the bottom and transfers to the bottom plate. There are 6 screws attaching the bottom plate to the top, and there mating surface areas are where the heat gets transferred from the bottom plate to the rest of the case. Being a single piece part, heat conduction in the top cover is good, and should therefore evenly and efficiently distribute the heat all around. Thus, I will expect the March case will have good temperature uniformity.
View attachment 82385

The construction of the Ghent case is quite different. It has a front and a back end plates. The top and bottom are extruded aluminum pieces. This assembly does not lend to good thermal transfer between the parts, especially between the top and bottom pieces. I'd expect the bottom plate to be significantly hotter than the front and back plates. The top plate can get some of its heat from the natural convection of the modules through air circulation inside the case. But still, the "averaged" skin temperature between the 2 cases should be similar.
View attachment 82384

At least we know that the Hypex modules seem to be in spec. Time to take out the IR cameras to look at thermal profiles (and thermal movies to see how the profiles evolve too) .

Indeed, as I mentioned earlier the Ghent case won't transfer heat into the other panels from the base plate very efficiently.

@muslhead if you are interested I am happy to make the same offer to you as I did to echopraxia to rebuild your modules into our cases.

 

[muslhead]

Indeed, as I mentioned earlier the Ghent case won't transfer heat into the other panels from the base plate very efficiently.

@muslhead if you are interested I am happy to make the same offer to you as I did to echopraxia to rebuild your modules into our cases.

thanks, i will shoot you a mesasge or email

 

[boXem]

By which physical principle does a cool case indicate proper cooling of what's inside? Asking for a friend...

...cut...

Here is my quick look at the thermal aspect of the March case and Ghent case:

The March case (the picture is a P122, but I am pretty sure they use the same case) is 2 pieces -- the upper part is single piece machined aluminum, and the bottom part is a flat plate. The majority of the heat leaves the NCore and PS modules from the bottom and transfers to the bottom plate.

This is partially wrong, the coils dissipate a lot, and the SMPS1200 FETs are not on the bottom but on the side. So a lot of heat is transferred to the air inside the box.

There are 6 screws attaching the bottom plate to the top, and there mating surface areas are where the heat gets transferred from the bottom plate to the rest of the case. Being a single piece part, heat conduction in the top cover is good, and should therefore evenly and efficiently distribute the heat all around. Thus, I will expect the March case will have good temperature uniformity.
View attachment 82385

There are only 6 points to transfer the heat from the bottom plate to the cover, contact surface is quite low, I don't understand how you come to the conclusion that there will be a good temperature uniformity.

The construction of the Ghent case is quite different. It has a front and a back end plates. The top and bottom are extruded aluminum pieces. This assembly does not lend to good thermal transfer between the parts, especially between the top and bottom pieces. I'd expect the bottom plate to be significantly hotter than the front and back plates. The top plate can get some of its heat from the natural convection of the modules through air circulation inside the case. But still, the "averaged" skin temperature between the 2 cases should be similar.
View attachment 82384

Again not following your logic, I am not sure the contact surface between top and bottom is very different from the other case, but I am sure that it more homogeneous.

Hard for me to conclude that one is better than the other from these pictures, the only thing I am sure is that they have the same weak points.

 

[NTK]

By which physical principle does a cool case indicate proper cooling of what's inside? Asking for a friend...


This is partially wrong, the coils dissipate a lot, and the SMPS1200 FETs are not on the bottom but on the side. So a lot of heat is transferred to the air inside the box.

There are only 6 points to transfer the heat from the bottom plate to the cover, contact surface is quite low, I don't understand how you come to the conclusion that there will be a good temperature uniformity.

Again not following your logic, I am not sure the contact surface between top and bottom is very different from the other case, but I am sure that it more homogeneous.

Hard for me to conclude that one is better than the other from these pictures, the only thing I am sure is that they have the same weak points.

In the grand scheme of things, neither case is highly optimized for heat rejection. Otherwise, they will have fins all over.

My comparison was between the 2 designs. The March case uses 6 screws to attached the top and bottom parts together. The March top cover has machine tapped threaded holes and well defined contact surface areas.

For the Ghent case, the top and bottom parts are only in incidental sliding contacts -- basically they are just touching each other with no control of the contact pressure. The grove and slot are for the purpose of positioning only. The bottom part, which receives the majority of the heat, is attached to the front plate and the back plate, each with 2 self tapping screws. The top is similarly attached to the front and back plates. The only reliable heat conduction paths are for the heat to travel from the bottom part to the end plates, and then from the end plates to the top. There are only 2 attachment points from the bottom part to each end plate. The contact areas are smaller than the March case and are less well defined. Also, not insignificantly, the Ghent design uses self tapping screws. This increase the variability in the compressing force from the screws (aka screw preload). Translating a screw tightening torque into a screw preload is already highly variable (easily ±25% uncertainty, and depends on the materials, material hardness, thread surface roughness, thread profile tolerances, lubrication, etc.). With self tapping screws, the preload variability just goes sky high. Therefore, the contacts between the end plates and the top and bottom parts for the Ghent case is very poorly controlled, from the point of view of thermal conduction.

Therefore, one should be able to expect much better consistency from March, and overall, the March case is, IMHO, clearly the better of the 2 designs for thermal considerations -- certainly from the point of view of transferring and distributing the heat from the Hypex modules to the amp case.

It should be noted that the Hypex DIY NC400 kit also uses Ghent cases. But they only have half the idle heat dissipation as the NC1200 + SMPS.

 

[boXem]

In the grand scheme of things, neither case is highly optimized for heat rejection. Otherwise, they will have fins all over.

My comparison was between the 2 designs. The March case uses 6 screws to attached the top and bottom parts together. The March top cover has machine tapped threaded holes and well defined contact surface areas.

For the Ghent case, the top and bottom parts are only in incidental sliding contacts -- basically they are just touching each other with no control of the contact pressure. The grove and slot are for the purpose of positioning only. The bottom part, which receives the majority of the heat, is attached to the front plate and the back plate, each with 2 self tapping screws. The top is similarly attached to the front and back plates. The only reliable heat conduction paths are for the heat to travel from the bottom part to the end plates, and then from the end plates to the top. There are only 2 attachment points from the bottom part to each end plate. The contact areas are smaller than the March case and are less well defined. Also, not insignificantly, the Ghent design uses self tapping screws. This increase the variability in the compressing force from the screws (aka screw preload). Translating a screw tightening torque into a screw preload is already highly variable (easily ±25% uncertainty, and depends on the materials, material hardness, thread surface roughness, thread profile tolerances, lubrication, etc.). With self tapping screws, the preload variability just goes sky high. Therefore, the contacts between the end plates and the top and bottom parts for the Ghent case is very poorly controlled, from the point of view of thermal conduction.

Therefore, one should be able to expect much better consistency from March, and overall, the March case is, IMHO, clearly the better of the 2 designs for thermal considerations -- certainly from the point of view of transferring and distributing the heat from the Hypex modules to the amp case.

It should be noted that the Hypex DIY NC400 kit also uses Ghent cases. But they only have half the idle heat dissipation as the NC1200 + SMPS.

These are interesting details.
There are a few things not aligning in my mind:
- if March case cools better by conduction, I would expect it to be hotter in the same conditions, seems not to be the case (pun not intended but self appreciated)
- as already written, the SMPS1200 and the NC1200 dissipate a good proportion of heat in the air, and in this situation a higher thermal mass and lower surface of vents may not be an advantage.
- as you write, both cases are not optimized for cooling, they even have an insulation layer between themselves and what they are supposed to cool. How can one be much better than the other?