Hypex NCx500 Class D Amplifier Review

[USER]

I use screw terminal locking banana plugs. The screws sometimes come loose. I checked and they were tight. But under instrumentation I could see that wiggling the wiring caused good few dB change at higher power. So I tightened them to death and result was much improved performance:

It seems that at this level of performance SpeakON connectors are worth it. If I recall correctly, Benchmark was aware of this when they made their AHB2.

 

[amirm]

It seems that at this level of performance SpeakON connectors are worth it. If I recall correctly, Benchmark was aware of this when they made their AHB2.

Indeed. John had mentioned this to me as the SpeakOn is also PCB mounted so has even lower impedance. Come to think of it, I measured the AHB2 with SpeakOn connectors!

 

[Streamc]

OK, I investigated the cause of excess distortion at higher power. I had noticed that with buffer setting distortion had gone down which should not have been the case. I noted on the graph that my dummy load connection may need revisiting. Indeed that was the case. I use screw terminal locking banana plugs. The screws sometimes come loose. I checked and they were tight. But under instrumentation I could see that wiggling the wiring caused good few dB change at higher power. So I tightened them to death and result was much improved performance:

Due to lower distortion, we could eek out some more power at 1%THD so I updated the max and peak measurements as well:

As I expected, the impact here is lower due to much less current travelling through the wiring terminal. Still, we get closer to state of the art. As an aside, I verified that the Purifi measurements were with high gain (re-ran that measurement as part of testing the wiring).

Finally, the lowered distortion exists at all frequencies:

View attachment 257942

The buffered results would likely get a bit better as well. I will see if I can re-test those.

These results show the Hypex NCx500 to be even more remarkable than my original testing showed!

Is this contributed to Purifi amp?

 

[Rottmannash]

Is this contributed to Purifi amp?

It appears the 2nd graph compares the new Hypex module with the Purifi and shows the Hypex with lower distortion until appx 50 watts then the Purifi emerges victorious, albeit with lower max power.

 

[amirm]

Is this contributed to Purifi amp?

What is? If you are asking if Purifi measurements could be better, answer is no. The connections were optimized then. I remeasured it today but did not update the graph as it was the same as before.

 

[Whitecanhifi]

It should go without saying, but you ‘poll’ for members is purely a confirmation bias and wholly undermines the foundations of all these reviews.

 

[mdsimon2]

What is? If you are asking if Purifi measurements could be better, answer is no. The connections were optimized then. I remeasured it today but did not update the graph as it was the same as before.

I assume by referring to Purifi here you mean this amp - https://www.audiosciencereview.com/...easurements-of-purifi-1et400a-amplifier.7984/ and not the recently reviewed @Buckeye Amps Purifi 3 channel amp -> https://www.audiosciencereview.com/...ds/buckeye-3-channel-purifi-amp-review.40293/ which showed a similar increase in distortion at high power levels?

Any chance you still have the Buckeye Purifi amp to remeasure?

Michael

 

[amirm]

No, I sent the Buckeye back already.

 

[ozlegend]

Hello Rod, I'm sure many members here would be interested in your experience in speaker design, so I would suggest to take the comments about your Hypex NCore DIY amp posted with a grain of salt (although she wasn't pretty) and stick around.

Is that a highway to the?

Ah, excellent!


JSmith

Thanks for your kind words, I did not find the adverse comments upsetting but rather irrelevant and this was what I was arguing against as logically and politely as I could. They were irrelevant because the build prettiness had very little impact on the sound quality. I am sorry if people were offended by the lack of prettiness but I thought I had made clear it was DIY for personal use (to design better speakers) and not a commercially available amp.

My main point was that to my ears at least the NCx500 modules were a significant upgrade in sound quality to previous Hypex and other amps I had built - and this concurs with amirm's measurements. Also that as he has found subsequently the modules are more than capable of driving speakers to high output levels from current DACs (such as the Topping E50 I recently bought) with their built-in buffer.

(Regarding the 'prettiness" of the very many amps I have built it depends on the amp's complexity, the casing space available and the time I have, all of which were difficult with my current NCx500 amp build. Each module requires 3 separate voltage supplies so the 4 amp modules needed 24 voltage wires from the 2 SMPS as well as the balanced signal wires to and speaker leads from each module - and all had to be packed into a limited space as time over the Christmas/New Year break only permitted me to modify an existing dual MP502MP amp casing that already had the metal work done, the most time-consuming part of a build. By soldering directly onto the module's connector pins (which some people find distressing for some reason though I agree it is not for everyone) it also reduces contact resistance and over time - the sort of thing amirm subsequently found a problem when measuring the modules at high power).

 

[Prana Ferox]

Wouldn’t the speaker cabinet be the limiting factor in transportability of guitar amplifiers?

To some people every ounce and every inch counts, especially depending on how you're getting back and forth from practice / gigging.

For bass, most of the really hifi profiler rigs I've seen, to the extent they drive a cab at all, seem to use FRFR PA speakers with built in amplification and EQ. Impressive as this amp is, I suspect using it to push a passive cab would be a step back, and most FRFR passive cabs are complicated enough (hurting sensitivity) that you may want more than 500w.

 

[voodooless]

My main point was that to my ears at least the NCx500 modules were a significant upgrade in sound quality to previous Hypex and other amps I had built

That’s fine. You can have your subjective opinion.

and this concurs with amirm's measurements.

But no, it doesn’t. Amir’s measurements tell us nothing about how you feel the amps sounds to you. They are just hard and objectively measurements without any claims of audibility.

 

[pma]

It is good that the issue was found and it is good that we debated the strange rise in distortion plots here before. The loosen contact made the load nonlinear and of course in case of 4 ohm load, every milliohm of nonlinearity makes a difference in the distortion parameters of SOTA power amplifiers.

 

[pma]

Awesome the fix was so easy to rectify. Some days we can’t see the Forrest through the trees. In this particular case you did actually have a Screw loose!

It always seems to be “simple” after the real issue was found. But, as you can see, nothing is simple if you want to be accurate.

 

[pma]

Does this point to the need to employ a torque instrument when tightening speakers terminal? I love my Wiha! Would the same tightening improve the recently reviewed Buckeye performance?

In your (our) home setup, banana plugs of speaker wires may add up about 0.1% (-60dB) low order distortion and you (me, anyone) would not even notice. Measured. The sound may even drop out - and then you will notice it .

 

[Mnyb]

It always seems to be “simple” after the real issue was found. But, as you can see, nothing is simple if you want to be accurate.

Yes i see that sometimes in my day work complex perplexing symptoms simple root cause , but it can be a winding road to actually find it

 

[Sokel]

OK, I investigated the cause of excess distortion at higher power. I had noticed that with buffer setting distortion had gone down which should not have been the case. I noted on the graph that my dummy load connection may need revisiting. Indeed that was the case. I use screw terminal locking banana plugs. The screws sometimes come loose. I checked and they were tight. But under instrumentation I could see that wiggling the wiring caused good few dB change at higher power. So I tightened them to death and result was much improved performance:

Due to lower distortion, we could eek out some more power at 1%THD so I updated the max and peak measurements as well:

As I expected, the impact here is lower due to much less current travelling through the wiring terminal. Still, we get closer to state of the art. As an aside, I verified that the Purifi measurements were with high gain (re-ran that measurement as part of testing the wiring).

Finally, the lowered distortion exists at all frequencies:

View attachment 257942

The buffered results would likely get a bit better as well. I will see if I can re-test those.

These results show the Hypex NCx500 to be even more remarkable than my original testing showed!

Really glad you found the problem,I believe you suspected it cause there are other tests with amps a little earlier on where you point out that some results may be due to wiring.
Thanks Amir!

 

[Class D passion]

Ciao,

Ho trovato un video su YouTube relativo al Rouge Audio Design Studio N7-X di Hypex NCx500. Ha un bell'aspetto!

Perché ci pensi?

 

[Vacceo]

I might be getting something wrong with the graphs when I take them in comparison. These Hypex module seems to archive a slightly better SINAD than the Purifi module with a similar gain (around 27 db). The problem some of you are pointing out is the rising distortion that comes with rising power output. Am I reading it right?

 

[amirm]

Ciao,

I found a YouTube video about the Hypex NCx500 Rouge Audio Design Studio N7-X. It looks great!

Why do you think about it?

It is just two of the unit I tested here.

 

[amirm]

I might be getting something wrong with the graphs when I take them in comparison. These Hypex module seems to archive a slightly better SINAD than the Purifi module with a similar gain (around 27 db). The problem some of you are pointing out is the rising distortion that comes with rising power output. Am I reading it right?

Purifi has slightly lower distortion near its max power than NCx500.