Review and Measurements of Hypex NC400 DIY Amp

[DonH56]

Iv removed a post that seemed like a paid advertisement to me .

Guessing you were not the one paid...

Thanks for all you do, Sir Thomas!

 

[boXem]

I think it's my only viable option.

Which kind of filter doesn't affect the sound quality?

The problem is more to have a high pass filter adapted to your sub's low pass filter at 80 Hz. Do you have any data on this one?

 

[lucadoc]

Nope, by looking at the plate I could say that it's limited at 120hz...but I'm not sure


5)Low Level Filter Bypass - In = Filter in operation - Out = Filter Bypassed.
L.F.E. Position the filter is opened wide to allow the optimum performance from processor
6)Frequency Contour, set up so as to integrate with main loudspeakers.

 

[restorer-john]

That answer is not entirely correct. It only applies to class D amps with floating/balanced outputs.

Here's the OEM NC-400 output section for reference.

 

[Julf]

Here's the OEM NC-400 output section for reference.

Thanks! Clearly shows the output being ground-referenced, so not floating nor balanced.

 

[boXem]

Thanks! Clearly shows the output being ground-referenced, so not floating nor balanced.

To make things clear for everybody, this doesn't mean that it can be tied to something that is not floating: feedback is taken at both FBLH and FBLC. Tying FBLC to a fixed point would create a mess in the feedback structure.

 

[boXem]

For the curious ones, N5400 OEM schematics are available on the NAD M22 service manual, which itself can be easily found with whatever search engine.

 

[Julf]

To make things clear for everybody, this doesn't mean that it can be tied to something that is not floating: feedback is taken at both FBLH and FBLC. Tying FBLC to a fixed point would create a mess in the feedback structure.

Not sure about that, as FLBC is already tied through only 0.3 Ω (the 3 parallel 1 Ω resistors) to a fixed point - ground.

 

[boXem]

Not sure about that, as FLBC is already tied through only 0.3 Ω (the 3 parallel 1 Ω resistors) to a fixed point - ground.

I have to admit I didn't dig in further.
But...

 

[Julf]

I have to admit I didn't dig in further.
But...

Fair enough, problem is that without further explanation, the Hypex text could also mean "don't assume it is OK to connect the speaker return to whatever ground point".

 

[March Audio]

Fair enough, problem is that without further explanation, the Hypex text could also mean "don't assume it is OK to connect the speaker return to whatever ground point".

Yes, this is further clarified in the Purifi docs saying don't do that.

 

[Julf]

Yes, this is further clarified in the Purifi docs saying don't do that.

Would you happen to have the actual wording?

 

[meinhard57]

I thought the group might like to see the finished product - Hypex NC400 Full Dual Mono DIY Build, using the Ghent 300mm case. BTW - I am not bragging, just for info . I didn't like the binding posts that Ghent supplied, so I sourced some pure copper ones from AliExpress (took 3 weeks to arrive). Also, Ghent supplied screws that were too short for the LED board - had to go out and but some at the hardware store. Overall - no complaints - the Ghent case is really beautiful! There is another version of this same case that can be used to build a 3-channel unit (although it is a little tight). Total unit weighs in at 11.75 lbs.

View attachment Hypex-NC400-Ghent-DIY-6.jpg
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View attachment Hypex-NC400-Ghent-DIY-2.jpg

View attachment Hypex-NC400-Ghent-DIY-1.jpg

 

[boXem]

I thought the group might like to see the finished product - Hypex NC400 Full Dual Mono DIY Build, using the Ghent 300mm case. BTW - I am not bragging, just for info . I didn't like the binding posts that Ghent supplied, so I sourced some pure copper ones from AliExpress (took 3 weeks to arrive). Also, Ghent supplied screws that were too short for the LED board - had to go out and but some at the hardware store. Overall - no complaints - the Ghent case is really beautiful! There is another version of this same case that can be used to build a 3-channel unit (although it is a little tight). Total unit weighs in at 11.75 lbs.

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Nice!
A small improvement you could try to implement is to have the speaker cables connected to the boards in a way that avoids forming a loop. This would decrease the EMI inside the box. But I am nitpicking.

 

[Julf]

Nice!
A small improvement you could try to implement is to have the speaker cables connected to the boards in a way that avoids forming a loop. This would decrease the EMI inside the box. But I am nitpicking.

Not just nitpicking - Bruno has made it pretty clear that that is how it should be wired. The cables should definitely not go out in opposite directions.

 

[meinhard57]

Nice!
A small improvement you could try to implement is to have the speaker cables connected to the boards in a way that avoids forming a loop. This would decrease the EMI inside the box. But I am nitpicking.

Thanks for the comment - how would I do this? Is the issue the way the speaker cables are connected on opposite sides of the terminals? Or the length of the cables? I appreciate the input... Bob

 

[Julf]

Thanks for the comment - how would I do this? Is the issue the way the speaker cables are connected on opposite sides of the terminals? Or the length of the cables? I appreciate the input... Bob

The connection on opposite sides. Ideally the cables should go out towards each other. You want to minimize the loop area (especially near the circuitry).

 

[meinhard57]

The connection on opposite sides. Ideally the cables should go out towards each other. You want to minimize the loop area (especially near the circuitry).

Thanks. Hard to do with 12 AWG wire, but I’ll give it a shot. Bob

 

[boXem]

Not just nitpicking - Bruno has made it pretty clear that that is how it should be wired. The cables should definitely not go out in opposite directions.

Do you have a link where he explains why?
From my measurements on other Ncore, it was quite heavily impacting channel separation, I would be curious to learn if Bruno identified other effects.

 

[boXem]

Thanks. Hard to do with 12 AWG wire, but I’ll give it a shot. Bob

Well, 12 AWG on such a short length is just for bragging rights (very important when DIYing I must recognize).
If you have smaller gauge in a drawer, that will make your life easier.