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Apollon NCx500ST Stereo Amplifier Review
- Thread starter amirm
- Start date
It'll only make a difference if you have audible ground loop noise.
Yes - depending on the preamplifier, there is some small buzz in the signal.
If that is an analogue input pre-amp, the noise could be coming in on the input to that amp. Again - if this is the case, changing the cable between pre-amp and amp won't help.
So I got my amp today. It is blue. It looks nice. It makes my set up look wicked. I hooked it up and sound comes out of my speakers. I like the logo. It looks and feels “high end”.
The person over at Apollon who maintains the help line is great.
I bought the amp because it looked like pure funk in the pics and the ASR recommend.
I do have a slight buzzing from my speakers even when nothing is playing. Did some “hunting” and it seems to be when the hdmi out cable is connected to my “pre amp” which leads to a projector.
The person over at Apollon who maintains the help line is great.
I bought the amp because it looked like pure funk in the pics and the ASR recommend.
I do have a slight buzzing from my speakers even when nothing is playing. Did some “hunting” and it seems to be when the hdmi out cable is connected to my “pre amp” which leads to a projector.
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PloddyPastard
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Congrats. Also keeping an eye on this brand for next year.
However, I have read now on few occasions regarding the buzzing. Is this a common thing which might happen, and if it does, one has to accept?
Had the same issue with a Class A/B Amp - which I then returned and got a new one. With that, the buzzing was gone.
Edit: It was/is a full integrated all in one device
Thx
Ground loops are more often than not the cause of the buzzing (or other noise). They are more common in systems where the wiring is more complex (eg av systems where HDMI is going to / from AVRs and TVs/projectors etc.
When they occur they can be difficult to eliminate, and it depends on the exact setup how best to do it. But using Balanced interconnect for analogue connections is one way. Breaking the loop using USB isolators or TOSlink from PCs is another.
Thanks. I was given the following possible solutions from Apollon support (they are a wonderful resource):
1. Get a newer balanced preamp or avr.
2. Put the projector on a power conditioner.
3. Try another hdmi cable for the hdmi out leading to the projector.
None of these are guaranteed to work. Could be a lot of money and effort lost with no reward.
In my case I sit 11 feet away from my speakers. The slight buzz is only audible at idle if you get really close to the speakers. It gets worse if you increase the gain.
I like the look of the amp. It makes my set up look slick. I don’t really know if there is any audible difference compared to when it was not in my set up. Just my humble opinion but to me it’s like having a hellcat badge on my stereo system. I have the power.
I was more bothered by the lack of a power cable which you have to source yourself. I don’t like using non oem parts as they never fit right.
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I would like to clarify that the Apollon NCx500 ST amplifier is not responsible for the buzzing noise experienced in the system. We thoroughly troubleshot the issue through our live support chat system alongside the buyer and recommended a systematic approach of disconnecting and reconnecting the HDMI cables one by one.
Through this process, it was identified that the buzzing noise originates from the projector when it is connected to the AV receiver (AVR) via HDMI. When the projector is disconnected, the system performs flawlessly, remaining dead silent. This confirms that the amplifier itself is functioning perfectly and is not the source of the issue.
It’s worth noting that similar occurrences can arise due to ground loops or electrical noise introduced by other connected devices. For example, one of our previous customers encountered a similar issue caused by a TV program module connected via HDMI to the AVR. The source of the problem was traced to the module’s 12V DC switch-mode power supply (SMPS), which introduced unwanted electrical noise into the system. Once the customer replaced the small 12V SMPS with a higher-quality power supply, the buzzing issue was completely resolved.
In such cases, the noise or buzzing typically stems from one or more of the following factors:
1. Ground Loops: A ground loop occurs when devices connected via HDMI share multiple ground paths, causing unwanted hum or buzzing.
2. Power Supply Interference: Low-quality power supplies (e.g., SMPS) can introduce electrical noise that travels through the system.
3. HDMI Cable Sensitivity: HDMI cables can sometimes act as conduits for noise, particularly if the connected devices have grounding issues or inadequate electrical isolation.
To mitigate such issues, we recommend inspecting the projector’s power supply, ensuring proper grounding, and considering the use of high-quality HDMI cables or an HDMI ground loop isolator if necessary.
I hope this clarification provides a deeper understanding of the situation. If further assistance is needed, please do not hesitate to reach out.
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A low cost thing to try would be pseudo balanced RCA to XLR connectors between the AVR and Amp. They have to be wired with three connections in the wire as this one is. (Not with the screen connected to pin 3 at the amp end)
With this wiring:
I will give it a shot. Thank you.
I never had to use your solutions but hunting down the issues in someone's system...sometimes turning out to be as simple as an ancient but defective cable that worked for them previously (in their systems previous incarnation).
Genstruktur
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I also have a projector connected through hdmi to my receiver. I will try and disconnect this also and see what happends. Since i do not have any nocie while actually playing movies/music i do not feel this issue to be so substantial thou.
This is a review and detailed measurements of the Apollon NCx500ST stereo class D amplifier based on Hypex NCOREx NCx500 modules. It was kindly drop shipped from the member and costs 1,090.00€ (US $1,168) with standard opamp.
View attachment 310220
While the case is stamped aluminum, it is a heavily customized one with attractive side vents. You get to select your color of choice. The back panel is where you notice the high value add:
View attachment 310221
You have no less than four gain settings and even an LED brightness switch! FYI, I will have to confirm which op-amp is included with this sample.
EDIT: the default TI OPA1612 op-amp was in this sample.
EDIT 2: turns the amp used Sonic Imagery op-amps (by mistake).
To make sure I didn't go mad given the combination of input types and four gain settings, I stayed with XLR testing.
If you are not familiar with the tests that are about to follow, please watch my video on understanding amplifier measurements.
Edit: just realized I left out the "n" out of the name on all the notations.
Apollon NCx500ST Amplifier Measurement
I started with the lowest gain setting:
View attachment 310222
While just a couple of dBs shy of the reference design, performance is good enough to easily land in our top 10 best amplifiers tested:
View attachment 310223
You need a ton of input voltage to get max power in this low gain setting so let's step up through the gain settings:
View attachment 310224
View attachment 310225
View attachment 310226
You can see the benefit of low gain in am amplifier for best noise performance especially since the dynamic range of the DAC improves as well with higher output.
Here are two SNR measurements:
View attachment 310227
I picked next to highest gain because it lets you drive it to max power with less than 4 volts on XLR:
View attachment 310228
In that reward, it would have been nice to have a different gain level optimized for 4 volts output from the source (here, we jump from 2.1 to 5 volts).
Notice how channel separation is also gain sensitive:
View attachment 310230
Frequency response is expectedly excellent and load independent:
View attachment 310229
Intermodulation is kept to very low levels:
View attachment 310231
View attachment 310232
This is one powerful amplifier:
View attachment 310233
View attachment 310234
View attachment 310235
The amp has a very robust protection circuit and did not mind at all being pushed way beyond clipping. This made it easy to measure with PowerCube:
View attachment 310236
An ideal amp would keep its voltage constant regardless of load. We almost have that at 4 ohm but at 2 ohms, the required current goes through the roof and output droops. Lest you get depressed about that, check out the amount of power you are getting:
View attachment 310237
For a moment, it produced 2.2 Killowatts on my 20 amp circuit! I should mention that I have modified these tests for burst rather than continuous power. With continues output, it is very easy to push the Powercube beyond its specs. The burst nature is the reason so much power was to be had at that 2 ohm load setting.
Anyway, the amplifier is extremely robust and doesn't care how difficult the load is.
Distortion is kept at a minimum at or below 1 kHz:
View attachment 310238
BTW, this test is also updated to have more frequencies represented than before (addition of 200 Hz).
Amplifier is stable on power up:
View attachment 310239
And is extremely quiet on power on/off:
View attachment 310240
Conclusions
The Apollon NCx500ST is a clear value added class D amplifier with lots of features compared to reference design. It gives up just a few dBs of noise performance but still manages to rank #6 in our list giving you confidence of transparency while producing copious amount of power. It is also easily sourced in Europe which is a benefit for many of our readers.
I am happy to put the Apollon NCx500ST amplifier on my recommended list.
Manufacturer Specifications:
Frequency Response: 0 – 70k Hz +0/-3dB
Low Distortion: THD+N – – 0.0002 % 20Hz-20kHz
High Input Impedance 50K
Signal to noise ratio: 137dB
Gain (dB) 12,8/20,5/27,5/29
Ultra High Damping Factor
High Current Output
Power rating: 675W @ 2ohm | 650W @ 4ohm | 380W @ 8ohm
Case Dimensions: 350mm depth x 90mm height (with feet) x 280 mm width
Weight: 2.9 kg
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Hi there! I have just boght this amplifier and are just waiting for it for delivery. A question. Wouldn´t it be interesting to "stress" the amplifiers a little bit more regarding the chosen volt. Instead om using the same amount of volt regardless amplifier a percentage of the amplifier would give a more fair conclusion? This amplifiera for example coudlt have been mesaured with this output, 14,14 volt RMS, if 10% of peakpower is used.
How would you connect four active crossover channels (2x tweeter, 2x midrange/bass) to two stereo amps? I wonder if it offers a benefit connecting the two tweeters to one amp and the two mid/bass chassis to the other one. Or is it better to treat it like 'usual': one amp - left speaker, one amp - right speaker?
If the amps are the same, then it is one amp one speaker.
Otherwise you are loading one amp (driving the bass) much more than the other, and hence limiting the total power you can get out.
On the other hand if you already have a beefy amp, you can use that for the bass, and get a much lower power, and ideally low noise one for the tweeters. Similarly if the amps you already have are different power ratings, you want to put the lower power amp on the tweeters.
Thank you!, makes sense to me, but will there be no disadvantage if one channel (driving the bass) is carrying much more load than the other channel driving the tweeter?
No. Most likely "two channels driven full load" will be limited by the power supply output current. Having one channel lightly loaded may allow the other to deliver a little more. Further more, the power supply will be less stressed, and there will be less heat into the enclosure.
Basically both amps get an easy ride - rather than one doing next to nothing and the other getting hammered.
fadetoblackbs
Member
Sorry if this is a silly question, but when this Amp states it has (for example) aprox. 300W at 8Ohms: is this power available at all 4 gain settings?
with a simplified model you can find the answer:
- the 300 watts power is the max power the amp can reach with a "decent" distortion (under 1% THD, as an example)
- the gain is something like "the amplification factor over the input"
so ... for a higher gain, you need less voltage at input to deliver that 300 watts and with a lower gain you need more voltage at the input (from the preamp / source)
normally, the product specifies the input voltage needed to reach the full power at every available gain.
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