Apollon NCx500ST Stereo Amplifier Review

[Apollon Audio]

I have noticed that the top plates of my pair of Apollon NCx500ST's DO get warm/hot to the touch, even at idle if left on for a couple of hours, would it be a smart move for the long term health of the product to get some type of active cooling solution, like one of the "AC Infinity" products?

The capacitors in these amplifiers operate at a lower temperature compared to those in a Pass Labs X5 amplifier, further highlighting the superior efficiency and thermal stability of the NCx500ST design. I encourage you to measure the capacitor temperatures after extended amplifier operation. Notably, no active cooling is required to maintain optimal performance.

It is entirely normal for the enclosure to feel warm during operation. This indicates that it is effectively dissipating heat as designed. Constructed from pure aluminum, the enclosure functions as a heatsink, efficiently transferring internal heat to the exterior, ensuring optimal thermal management and system stability.

I have yet to see an amplifier capable of continuously delivering 500 watts at 20kHz while generating such a minimal amount of heat. This demonstrates the exceptional efficiency and advanced thermal management of the NCx500 design.

 

[Carlton80@0]

I have noticed that the top plates of my pair of Apollon NCx500ST's DO get warm/hot to the touch, even at idle if left on for a couple of hours, would it be a smart move for the long term health of the product to get some type of active cooling solution, like one of the "AC Infinity" products?

Can’t hurt to have active cooling for components. Especially if they are in a rack. I assembled a 2u cooling device from there separate offering.

 

[Extreme_Boky]

I must respectfully correct your assumption. This topic has been previously discussed, and the performance of the NCx500ST amplifiers has been thoroughly analyzed. With over 1,000 units sold worldwide, there has not been a single case of overheating reported.

Furthermore, I have conducted extensive testing, demonstrating that even under continuous high-power output, the module temperatures remain well within the normal operating range when mounted to a 3mm thick enclosure. It is important to highlight that my tests were performed using a 1kHz and 20kHz sine wave, which imposes significantly greater stress on the amplifier than real-world music signals, which are dynamic in nature.

The top cover was REMOVED during the testing you performed.

With the cover closed, you should load the output with the real-world load (resistive and a bit of capacitive load in parallel), and then let it run for an hour. You do not need to feed any input signal....

THEN -> measure the bottom plate temperature.... and, in particular, measure the chokes' temperature.

That will give you a good idea of what a random customer will face in real life.

 

[Overseas]

The top cover was REMOVED during the testing you performed.

.

Wow

 

[Matias]

Oh, yes, running minutes of full power with the top cover open is the unrealistic part. Close it and then it becomes exactly like a common use case? Makes no sense either way.

 

[maver1ck]

The top cover was REMOVED during the testing you performed.

With the cover closed, you should load the output with the real-world load (resistive and a bit of capacitive load in parallel), and then let it run for an hour. You do not need to feed any input signal....

THEN -> measure the bottom plate temperature.... and, in particular, measure the chokes' temperature.

That will give you a good idea of what a random customer will face in real life.

I would say random customer will have trigger connected so device is basically turned off when not in use.

 

[Apollon Audio]

The top cover was REMOVED during the testing you performed.

With the cover closed, you should load the output with the real-world load (resistive and a bit of capacitive load in parallel), and then let it run for an hour. You do not need to feed any input signal....

THEN -> measure the bottom plate temperature.... and, in particular, measure the chokes' temperature.

That will give you a good idea of what a random customer will face in real life.

Do you not think we have thoroughly tested this amplifier under various conditions, including with the cover on? We've been in this business since 2012, with thousands of amplifiers sold worldwide. This model offers exceptional performance at a highly competitive price, serving as a cost-effective and compact alternative to our larger, more expensive units. Given its value, what more would you expect at this price point?

Understood. However, are you aware of the strain an amplifier experiences when outputting 500 watts of continuous power for five minutes at 20kHz? Is this a typical real-world use case? The most critical aspect here is that assumptions are being made regarding overheating. Have you come across any documented cases of overheating with our NCx500ST amplifiers, given the significant number sold worldwide?

 

[Apollon Audio]

Oh, yes, running minutes of full power with the top cover open is the unrealistic part. Close it and then it becomes exactly like a common use case? Makes no sense either way.

Running a continuous 20kHz sine wave for several minutes places an extremely high strain on the amplifier. Despite this, the amplifier performed exceptionally well, even with the modules mounted on a 3mm baseplate and without any forced cooling.

 

[Extreme_Boky]

Do you not think we have thoroughly tested this amplifier under various conditions, including with the cover on? We've been in this business since 2012, with thousands of amplifiers sold worldwide. This model offers exceptional performance at a highly competitive price, serving as a cost-effective and compact alternative to our larger, more expensive units. Given its value, what more would you expect at this price point?

Understood. However, are you aware of the strain an amplifier experiences when outputting 500 watts of continuous power for five minutes at 20kHz? Is this a typical real-world use case? The most critical aspect here is that assumptions are being made regarding overheating. Have you come across any documented cases of overheating with our NCx500ST amplifiers, given the significant number sold worldwide?

I am not sure what the point of your reply is..?? You haven't performed the test as I asked already. It is a simple test.

People on this forum complained about the high running temperature of this particular amp. It is a small amp with a folded sheet metal bottom plate, so it can't dissipate much heat.

Load the amp with a resistor and a capacitor in parallel. You say you have experience. Good. So, insert real-world typical speaker cables between the amp and load. Let the amp sit for a while. There should be no input signal. Then, measure the bottom plate temperature.

 

[Apollon Audio]

I am not sure what the point of your reply is..?? You haven't performed the test as I asked already. It is a simple test.

People on this forum complained about the high running temperature of this particular amp. It is a small amp with a folded sheet metal bottom plate, so it can't dissipate much heat.

Load the amp with a resistor and a capacitor in parallel. You say you have experience. Good. So, insert real-world typical speaker cables between the amp and load. Let the amp sit for a while. There should be no input signal. Then, measure the bottom plate temperature.

The bottom of the amp reaches 35-38 degrees celsius. What are you trying to prove?

An amplifier enclosure reaching 35 degrees Celsius (95°F) is generally not considered hot in the context of electronic devices. Here’s why:

1. Safe Operating Range – Most electronic components, including amplifiers, are designed to operate safely at much higher temperatures, often up to 60–80°C or more.
2. Human Perception – While 35°C might feel warm to the touch, it is well below any temperature that could cause discomfort or burns (which typically occur above 50°C).
3. Heat Dissipation – A well-designed amplifier naturally dissipates heat, and 35°C suggests effective thermal management without excessive heat buildup.

In summary, 35°C is a completely normal and safe operating temperature for an amplifier enclosure.

For those who are skeptical about the heat dissipation of this amplifier, we offer a Lux version featuring a 10mm thick aluminum enclosure with large ventilation openings on both the top and bottom.

One moment, please...

 

[Apollon Audio]

I just used an IR thermometer and the exterior case temp was 99.6f @ idle.

Not sure if that’s really that hot. Someone else said they were as hot as Class A amps, as a former Pass Labs owner I can tell you the heat difference between my X5 and these are an order of magnitude.

I never had any parts fail in that space heater, and it was 20+ years old, so I’m not sure why these would age prematurely.

One of our valued customers independently measured the amplifier's temperature and obtained the same readings, confirming that the enclosure reaches a maximum of 37,5°C. This further validates that the amplifier operates efficiently within safe thermal limits.

 

[antcollinet]

I am not sure what the point of your reply is..?? You haven't performed the test as I asked already. It is a simple test.

People on this forum complained about the high running temperature of this particular amp. It is a small amp with a folded sheet metal bottom plate, so it can't dissipate much heat.

Load the amp with a resistor and a capacitor in parallel. You say you have experience. Good. So, insert real-world typical speaker cables between the amp and load. Let the amp sit for a while. There should be no input signal. Then, measure the bottom plate temperature.

@Apollon Audio have already done all the tests necessary. Why should they do any more at the demand of (no disrespect intended) some random person on the internet. If they were to respond to such demands, they would be able to do nothing else.

 

[antcollinet]

The bottom of the amp reaches 35-38 degrees celsius. What are you trying to prove?

An amplifier enclosure reaching 35 degrees Celsius (95°F) is generally not considered hot in the context of electronic devices. Here’s why:

1. Safe Operating Range – Most electronic components, including amplifiers, are designed to operate safely at much higher temperatures, often up to 60–80°C or more.
2. Human Perception – While 35°C might feel warm to the touch, it is well below any temperature that could cause discomfort or burns (which typically occur above 50°C).
3. Heat Dissipation – A well-designed amplifier naturally dissipates heat, and 35°C suggests effective thermal management without excessive heat buildup.

In summary, 35°C is a completely normal and safe operating temperature for an amplifier enclosure.

For those who are skeptical about the heat dissipation of this amplifier, we offer a Lux version featuring a 10mm thick aluminum enclosure with large ventilation openings on both the top and bottom.

One moment, please...

I've just put my hand on the back of my TV at the point where all the electronics are.

It feels warm to the touch. If I were to guess, I would say it is in the region of 35 to 38C. And it's a plastic cover so with the higher thermal resistance, it is likely the internal temperature is higher than that of your amp.

Guess how worried I am.

 

[tmtomh]

It's important for products to be robustly designed and well-tested. And it's important for manufacturers and vendors to be honest and transparent. I think we can all agree on that, yes?

That said, I've kind of had it up to here with members accusing vendors and manufacturers of unsafe or substandard designs when they (the members) appear to have no reliable baseline of what the norm is, what is a safe level, what the rated operating temps of the internal components are, and so on. Not to mention that a couple of our members who do have some knowledge of that stuff tend to just egg on these other members when the target is small vendors of Class-D based amps.

This is the claim that started this latest round of "Yeah, but what about..." questioning of @Apollon Audio :

The amp modules are mounted on a bottom plate/sheet metal; there are two amp modules and an SMPS that apparently dissipate (someone did a calculation - around 60W (!!)) a lot of heat. That bottom plate ( 3mm?) is not sufficient to cool these modules down. The heat transfer between the bottom plate and the top cover is also questionable because there is simply not enough contact area between the two to transfer the heat.

The parts I've bolded are the core of the claim. No evidence has been presented that this claim is correct, or that the claim should even be taken seriously.

This is ASR and we should have open minds, so I'm not asserting that such evidence doesn't exist. But it seems to me that it's wrong to try to make Apollon reply to repeated accusations of improper cooling and improper testing, and implied accusations of dishonesty, based on a single, vague, evidence-free claim.

If @Extreme_Boky has data to back up this claim, they should provide it so folks can evaluate it. Otherwise, they and anyone else relying on their claim should kindly take a seat.

 

[Extreme_Boky]

1. The thread contributors reported high temperatures, sufficiently so to report their concerns. People can search for them... or not. It's their call.

2. Someone on this thread did total dissipation calcs - and came up with 60W. Is this calculation correct? No idea. Manufacturers do not state heat dissipation figures. These are top-of-the-line modules - I expect to see the dissipation figure clearly stated. If correct, the 60W dissipation is too much for that piece of sheet metal.

3. Amplifier manufacturers should provide those (total dissipation) figures, clearly stating the conditions under which the measurements were taken. They should also add the additional dissipation caused by TO220 regs, especially if loaded with boutique OPAmps that burn a lot of current.

 

[Apollon Audio]

1. The thread contributors reported high temperatures, sufficiently so to report their concerns. People can search for them... or not. It's their call.

2. Someone on this thread did total dissipation calcs - and came up with 60W. Is this calculation correct? No idea. Manufacturers do not state heat dissipation figures. These are top-of-the-line modules - I expect to see the dissipation figure clearly stated. If correct, the 60W dissipation is too much for that piece of sheet metal.

3. Amplifier manufacturers should provide those (total dissipation) figures, clearly stating the conditions under which the measurements were taken. They should also add the additional dissipation caused by TO220 regs, especially if loaded with boutique OPAmps that burn a lot of current.

Your claim that people reported high temperatures is incorrect. A few of our valued customers in this thread simply noted that the amplifier case felt warm "hot" to the touch. Following this, one of our valued customers conducted an independent measurement and recorded a maximum case temperature of 37.5°C.

Like I've mentioned before this is purely a matter of human perception. While 37.5°C might feel warm, it is well below any temperature that could cause discomfort or burns. For reference, burns typically occur at 50°C or higher with prolonged contact. Many consumer electronics, including laptops and other audio equipment, often exceed this temperature during normal operation.

Furthermore, high-end Class D amplifier modules are designed for efficiency, and the measured dissipation levels indicate that the thermal management of the enclosure is functioning as intended. The design ensures that the amplifier remains within safe thermal limits while delivering optimal performance.

 

[NTK]

1. The thread contributors reported high temperatures, sufficiently so to report their concerns. People can search for them... or not. It's their call.

2. Someone on this thread did total dissipation calcs - and came up with 60W. Is this calculation correct? No idea. Manufacturers do not state heat dissipation figures. These are top-of-the-line modules - I expect to see the dissipation figure clearly stated. If correct, the 60W dissipation is too much for that piece of sheet metal.

3. Amplifier manufacturers should provide those (total dissipation) figures, clearly stating the conditions under which the measurements were taken. They should also add the additional dissipation caused by TO220 regs, especially if loaded with boutique OPAmps that burn a lot of current.

1. As with all electronics that generate heat, it needs to be placed in a location with reasonable ventilation. It doesn't matter how little heat the device generates, if it is in a fully insulated place and not allowed to dissipate the heat it generates to the outside, the termperature will not stop rising. Having huge heat sinks will not work, if the operating condition is to leave the amp on 24/7, as the heat sink cannot transfer the heat somewhere else and the temperature will keep rising, it just rises slower (inversely proportional to the thermal mass).
2. Per Hypex datasheet, each Nx500 dissipates max 5.8 W when idle, each SMPS1200A dissipates 9 W, therefore a total of ~20 W.
3. I see no heat sink on the op-amps, and no good heat condition path to dissipate heat, thus, if they generate anywhere close to the amount heat as the amp modules, they will fry themselves in no time, and we'll all know about it.

 

[Apollon Audio]

I am not sure what the point of your reply is..?? You haven't performed the test as I asked already. It is a simple test.

People on this forum complained about the high running temperature of this particular amp. It is a small amp with a folded sheet metal bottom plate, so it can't dissipate much heat.

Load the amp with a resistor and a capacitor in parallel. You say you have experience. Good. So, insert real-world typical speaker cables between the amp and load. Let the amp sit for a while. There should be no input signal. Then, measure the bottom plate temperature.

I believe there’s a misunderstanding here. The amplifier is made of aluminum, not standard folded sheet metal. Aluminum has excellent thermal conductivity, allowing for effective heat dissipation even in a compact design.

 

[antcollinet]

That said, I've kind of had it up to here with members accusing vendors and manufacturers of unsafe or substandard designs when they (the members) appear to have no reliable baseline of what the norm is, what is a safe level, what the rated operating temps of the internal components are, and so on.

This.

 

[antcollinet]

Is this calculation correct? No idea.

Then perhaps it is time to stop and be quiet, until you've got some evidence significantly more convincing than anecdote and "touch testing" to discuss.