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Review and Measurements of Hypex NC400 DIY Amp

Julf

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All good here? Bought this used and I don't really know what I'm looking at

The speaker output leads are pretty bad, forming an enormous loop antenna.
 

Julf

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Looks like an nc400 old module(red caps) with a smps 600 power module. Only one nc400 module, I think you get a mono amp

Yes, definitely mono(block).
 

HeavyMantra

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The speaker output leads are pretty bad, forming an enormous loop antenna.

Can you simplify this for me

How big of an issue is it?

And yes, I bought a pair of course

The cables are Bertram proxima 2 silver if that matters
 
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Julf

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Can you simplify this for me

I can try. Bruno (the designer) has been pretty clear about how the output wires should be twisted together (just like the mains power wires in your amp) pretty tightly (even to the degree that they should not exit the output connectors in opposite directions) in order not to form an antenna that feeds into the feedback circuit.

How big of an issue is it?

Hard to say without measuring.

The cables are Bertram proxima 2 silver if that matters

All that matters is sufficient cross section (and the twisting). Those cables don't look very thick - what is the point of a non-circular cross section?
 

HeavyMantra

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I can try. Bruno (the designer) has been pretty clear about how the output wires should be twisted together (just like the mains power wires in your amp) pretty tightly (even to the degree that they should not exit the output connectors in opposite directions) in order not to form an antenna that feeds into the feedback circuit.



Hard to say without measuring.



All that matters is sufficient cross section (and the twisting). Those cables don't look very thick - what is the point of a non-circular cross section?

Thanks, most of these terms are new to me. The first time looked inside an amp was yesterday! Do you mean that the flat, silver looking cables should be twisted together?

The issue would be some kind of hum or interference? Can it be fixed by twisting the cables?

Have gotten what seems to be a good deal for the pair (about 1000 euro) but since I'm not tech savvy I don't want to buy something home-built if it could have big issues
 

Eirikur

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Can you simplify this for me

How big of an issue is it?

And yes, I bought a pair of course

The cables are Bertram proxima 2 silver if that matters

Looks like some sort of FM/VHF antenna wire is used towards the binding posts, pretty thin at that:
1575374656442.png


Also, seems the XLR connector is only half-connected (red) and possibly not even properly grounded (yellow).
1575376418601.png

Perhaps a more knowledgeable Hypexpert can comment on this.

This is the schematic approach for the DIY Hypex nCore NC400, notice the twisting as @Julf mentioned
1575376731750.png
 

Julf

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Thanks, most of these terms are new to me. The first time looked inside an amp was yesterday! Do you mean that the flat, silver looking cables should be twisted together?

Yes, except you would be better off with normal, round copper cables.

The issue would be some kind of hum or interference?

Noise or even high frequency oscillation (causing amp to run warm).

Can it be fixed by twisting the cables?

Yes.

You might be OK, but it is definitely against the recommendations of the designer.
 

HeavyMantra

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Yes, except you would be better off with normal, round copper cables

You might be OK, but it is definitely against the recommendations of the designer.

Thanks a lot. I think I'll go ahead and seal the deal and fix this later
 

HeavyMantra

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Looks like some sort of FM/VHF antenna wire is used towards the binding posts, pretty thin at that:
View attachment 41248

Also, seems the XLR connector is only half-connected (red) and possibly not even properly grounded (yellow).
View attachment 41250
Perhaps a more knowledgeable Hypexpert can comment on this.

This is the schematic approach for the DIY Hypex nCore NC400, notice the twisting as @Julf mentioned
View attachment 41255
Thanks, is the XLR not being connected and grounded something that could be fixed easily?
 

Julf

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HeavyMantra

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I've asked the seller about these things, hopefully I will know more soon including what the silvery flat cable is. I hope to be able to go ahead with the deal and fix any issues.
 

Julf

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I've asked the seller about these things, hopefully I will know more soon including what the silvery flat cable is. I hope to be able to go ahead with the deal and fix any issues.

Hopefully you don't get any flowery BS about how the silver cable is somehow better...
 

HeavyMantra

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Hopefully you don't get any flowery BS about how the silver cable is somehow better...

I probably will. I haven't read much about the cable conflict but I know it exists and that I won't prioritize really fancy cables even if it they were better

But you're saying it's worse than a copper one even?
 

Julf

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But you're saying it's worse than a copper one even?

The material is OK (but not better either), the shape and thickness/gauge are the issues (besides the twisting).
 

Julf

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So good to know. Is it only the flat silver one that has this problem?

Yes, and even there the only problem (again apart from the twisting) is a slightly larger output impedance / lower damping factor, so nothing major.
 

HeavyMantra

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Thanks for the help, I went ahead and bought them. The minimal design is worth some potential hassle
 

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veeceem

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I have the new NAD M22 Version 2. it's a custom NC400 board/layout made exclusively for NAD using NC500 output. It's an incredible amp.

View attachment 25100
Are the RCA/XLR connectors on this amp soldered directly into the PCB? It seems that way to me :/
Btw, it seems that the 2 smaller board are the amp modules? What about the bigger PCB which the connectors are soldered into?
 

6speed

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@HeavyMantra I would want to get the AC cable away from the SMPS transformers and inductor, which is as simple as tying it down between the SMPS and NC400. Also get the speaker cable going to the black binding post away from the output inductor, which is as simple as turning it to exit the screw-down connector the same direction as the other speaker cable.
 
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