Hypex NCx500 Class D Amplifier Review

[DonH56]

PIM (passive intermodulation) has gotten a lot more attention recently as dynamic range has increased. It used to be mainly an issue considered for antennas and exposed transmission line connections. Now, audio loads are a problem, and there are lots of other examples as 100+ dB dynamic range in systems (audio through RF/mW) is more prevalent.

 

[Rick Sykora]

I guess measuring heat after a certain amount of time with a certain amount of power; I honestly don't know either.

Power draw at idle is another option, as PMA has pointed out.

You have tried several modules and you know about the need of heatsinks, so even if that is not particularly accurate, I'd trust your word.

All in all, this gives an indication about how well you can stack components on top of each other or if the amp will need a fan or not.

are you asking to ensure whatever amp you buy is sufficiently cooled or are you planning to build one?

 

[Vacceo]

are you asking to ensure whatever amp you buy is sufficiently cooled or are you planning to build one?

I'm aiming at buying a multichannel amp.

 

[Rick Sykora]

I'm aiming at buying a multichannel amp.

Ok, thanks.

My short answer depends on the ambient conditions. If you are placing the amp in a cabinet with limited airflow, unless the amp has cooling, would buy a (temperature-controlled) cooling fan. This is regardless of the amplifier class. If Class D, the fan will run much less frequently. If you want to discuss further suggest you open a new thread or PM me. Want to keep our moderators happy!

P.S. If you are wondering which kind of fan to buy, something like this: https://www.acinfinity.com/componen...ponent-cooling-blower-system-rear-exhaust-17/

 

[AndreaT]

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 .

And yet, no penalty for doing the job right. So, I gather, either speakon connections or a torque instrument to be verified for the first few days by re measurements of torque to compensate for strands “channeling” or readjusting to the pressure of the screw

 

[droid2000]

this is retardedly difficult. how hard is it to attach speaker wires to speakers?

good reason why this whole industry is fucked

 

[AndreaT]

this is retardedly difficult. how hard is it to attach speaker wires to speakers?

good reason why this whole industry is fucked

Hard enough that Amir has shown it makes a difference.

 

[Sokel]

The sure thing after this review is that I cleaned with contact spray and tightened everything to the point of no return

 

[Piere]

Good gold plated banana plugs and sockets/binding posts usually perform flawlessly and without distortion. But stay away from bare copper contact transistions. Those are mostly the culprit! Don't screw bare copper wire! Solder it! Or use ferrules with a good quality crimping tool.

 

[Sokel]

Good gold plated banana plugs and sockets/binding posts usually perform flawlessly and without distortion. But stay away from bare copper contact transistions. Those are mostly the culprit! Don't screw bare copper wire! Solder them! Or use ferrules with a good quality crimping tool.

I use locking bananas,gold plated and everything but I wanted to be sure after that.
I even measured all after cleaning,for about my 3m cables was 0.2-0.3Ω so ok I guess.

 

[RndmLstner]

Good gold plated banana plugs and sockets/binding posts usually perform flawlessly and without distortion. But stay away from bare copper contact transistions. Those are mostly the culprit! Don't screw bare copper wire! Solder it! Or use ferrules with a good quality crimping tool.

Can you be more precise as to what contacts you're referring to? Re screw bare copper! Solder it!

 

[Piere]

Previous page:

Really something to take care of! Surely at these low levels of distortion. When I once measured a low sitortion CA amp I noticed distortion harmonics at very low level (below -120 dB) that looked like a train of harmonics going beyond 20 kHz at the spectrum view. Very similar to the typical cross-over distortion profile of a standard class-AB BJT amp. The dummy load was connected to the amp's binding post by screwing the bare copper wire directly underneath the binding posts. To my amazement the distortion disappeared when I tightened te binding post a lot more firmly. What was going on here? Well the thin oxide of the bare copper together with the gold plating of the binding posts acted as small Schottky rectifier diodes! By tightening the posts more firmly I went trough the copper oxide destroying the small diodes. Lesson learned: Stay away from pure copper regarding loudspeaker interconnect transitions!

I do not say it will be the case here, but these unexpected mechanisms can play havoc!

A good banana interconnect should be no more than some tens of milliohms. And most industrial from Mouser/Farnell, costing a few bucks, will do. Expensive WBT's perform no better but are anyway ok mostly.

 

[walt99]

The sure thing after this review is that I cleaned with contact spray and tightened everything to the point of no return

I think better than cleaning would be to apply something like ‘Deoxit’ to prevent oxidation. This is where tin plated copper is better than straight copper wire.
I use this stuff even on gold/gold plated contacts, I believe it helps. Unless the contact is air tight it will oxidize..

 

[Sokel]

I think better than cleaning would be to apply something like ‘Deoxit’ to prevent oxidation. This is where tin plated copper is better than straight copper wire.

I have both with oil and without,usually I apply the former to raw copper I'm about to fasten everywhere is needed.
Bananas are soldered,so I just spayed the one without oil as sometimes dirt sticks to the later after sometime.

 

[Piere]

I think better than cleaning would be to apply something like ‘Deoxit’ to prevent oxidation. This is where tin plated copper is better than straight copper wire.
I use this stuff even on gold/gold plated contacts, I believe it helps. Unless the contact is air tight it will oxidize..

Problem with the cheaper Chinese speaker binding posts and bananas is that they are not properly gold plated, but just gold flashed with a very thin submicron layer of gold. This is only useful for storage and display. Those look the same as the properly gold plated ones. Properly done, first a layer of nickel is plated and after that a 1 - 2 mills thick layer of gold. Without the nickel plating the gold will diffuse away into the copper/brass body. And you still have the oxidation problems. Quality industrial ones from Mouser etc. don't suffer from this. Imagine: 40 amps continuous through 0.1 ohm due to oxidation and dirt will heat a 160 watts! Your binding posts will melt very quickly!

 

[PeteL]

We have come full circle when the main subject on a product review on ASR is the loss of power and fidelity trough connections.

 

[Piere]

We have come full circle when the main subject on a product review on ASR is the loss of power and fidelity trough connections.

Very true! Then we have come to the ultimo amp with any measurable distortion! Amir's mission completed!

 

[pantherluv]

We have come full circle when the main subject on a product review on ASR is the loss of power and fidelity trough connections.

Which is why I use soldered lugs for speaker connections

 

[droid2000]

Which is why I use soldered lugs for speaker connectionsView attachment 258318

That looks legit. I think I'm gonna switch from bananas to that.

 

[Piere]

That looks legit. I think I'm gonna switch from bananas to that.

That is already an old way of doing: Use spades instead of bananas. But don't screw the bare wire into them, there are versions out there with set screws to hold the leads. Crimp or solder them!