Review and Measurements of Hypex NC400 DIY Amp

[kazsud]

Why would it be better?

I guess I'm wondering how they compare?

 

[maty]

I received mine last week from @Audiophonics. Very clean little power amp, goes all the way to the max power (datasheet gives 1.17V input fo it) without audible distortion. Excellent pairing with my ADI-2 DAC.

I liked it so much that I immediately ordered two PA-M250NC (NC250MP) instead!

I wanted more power for my 88db/8ohms speakers. By the way, the NC250MP has the lowest THD + N of the entire NCxxxMP line...

https://www.audiophonics.fr/en/powe...s-d-amplifier-ncore-2x250w-4-ohm-p-13545.html

by lida Y

[ Excellent value for money

I have a pair of NC-400 based mono kit (built by own) , Ucd3xMP amplifiers for my own. And I imported some NCore based amplifier for my friends.

This PA-S250NC is excellent!
- rigid body makes this well frequency reproduction balance though not easy to open top plate... I had to struggle with many screws...

This amplifier may use uniiversal amp chassi but better than most of amps in this price class or upper class.
- Well considered simple construction

Simple and it seems easy to maintain.
- Good sound from initial

I have checked with:

Source : 60000 tunes on NAS read by Win10 Pro 64bit rev1903 /foobar2000
DAC: XMOS ES9018K2M USB DAC (Headphone output to use volume knob)
Amp: this one
Speaker : All Accuton based 3way (built by own )
Accuton C173-6-191E woofer 17cm mid-bass
Accuton C50-8-044 Mid-range 50mm mid
Accuton C30-6-358 Tweeter

Bass is apparantly improved. Voice (Mid) range has distortion-less clear and smooth and silky high strings. ]

 

[VintageFlanker]

I received mine last week from @Audiophonics. Very clean little power amp, goes all the way to the max power (datasheet gives 1.17V input fo it) without audible distortion. Excellent pairing with my ADI-2 DAC.

I liked it so much that I immediately ordered two PA-M250NC (NC250MP) instead!

I wanted more power for my 88db/8ohms speakers. By the way, the NC250MP has the lowest THD + N of the entire NCxxxMP line.

@Audiophonics should really send these units (or their PA-S250NC/PA-S500NC) to @amirm for review. Sure, datasheets from Hypex already tell a lot of things, but I would be curious to see how these perform under Amir's testing methodology.

One question remains, though: Is there a way that the unbalanced nature of both PA-S125NC/PA-M250NC (RCA only) downgrade the performance somehow?

Perfect match with the ADI-2 DAC. The max input is rated at 1.66V (6.61 dbu), so I work with the +7dbu ref level. That way, I may deal with all the power available from - 96db to 0db!

 

[Matias]

One question remains, though: Is there a way that the unbalanced nature o both PA-S125NC/PA-M250NC (RCA only) downgrade the performance somehow?

Hypex usually strongly recommends in their datasheets their amplifiers to be implemented balanced. I am surprised that Audiophonics chose to ignore this and implement with unbalanced inputs only. I know the chassis is small but still.
Yes, this could downgrade performance...

For a small sized, desktop system I would go with the small chassis of Nord MP series:
https://www.nordacoustics.co.uk/nord-one-hypex-ncore-mpxxx-stereo-p

For example the NC502 stereo version has only 240mm width, both XLR and RCA and 2x 500W in 4 ohms.
https://www.nordacoustics.co.uk/product-page/nord-one-mp-nc500-stereo-power-amp

 

[VintageFlanker]

How much better is an AHB2 than NC400 mono blocks?

Both are "similar" distortion-wise (and probably in many others tests) but NC400 monoblocks definitely provide more power than one AHB2.

Two AHB2 bridged is another story... At another price.

Hypex usually strongly recommends in their datasheets their amplifiers to be implemented balanced. I am surprised that Audiophonics chose to ignore this and implement with unbalanced inputs only. I know the chassis is small but still.
Yes, this could downgrade performance...

For a small sized, desktop system I would go with the small chassis of Nord MP series:
https://www.nordacoustics.co.uk/nord-one-hypex-ncore-mpxxx-stereo-p

For example the NC502 stereo version has only 240mm width, both XLR and RCA and 2x 500W in 4 ohms.
https://www.nordacoustics.co.uk/product-page/nord-one-mp-nc500-stereo-power-amp

View attachment 32102

What Hypex says in the datasheet:

Balanced or unbalanced

All Hypex modules are completely balanced for optimal performance. The modules can be connected to an
unbalanced source. To do this correctly, please read our application notes: ‘Dealing with legacy pin 1
problems’ and ‘Amplifier signal input wiring’.

 

[Matias]

Yes, I read that, but in the NC400 datasheet:

9.4 Vastly preferred balanced setup: XLR input.
Regardless of whether the remainder of your audio system has balanced connections or not, the very best
way to wire the input of the NC400 is to leverage the advantage of its balanced input. You can get almost all
of the quality improvement afforded by balanced connections even with an unbalanced source, provided that
you have a balanced input.

9.5 Acceptable unbalanced setup
Having made sufficiently clear that there is, in fact, no reason why anyone should ever want to waste a
perfectly good balanced input by putting the module in a box with RCA inputs, it is likely that some will
persist. Two workable methods are given. The first uses differential wiring up to the rear panel to present a
normal unbalanced input to the outside world, the second uses an unbalanced cable as a floating quasidifferential
connection.

 

[Dominic]

If it's only a simple single click when unmuting I wouldn't stress over it too much.
There's a ghost in the machine.

I tested some more and realised that they both have the same issue with the clicking, and its the issue of a XLR connection click, the same click/pop noise when you connect the XLR from the amp to the preamp.

It seems the preamp mute button shut off the signal altogether, so when I unmute I get the click.

My other amps such as a Crown Xls2002 or my active monitor speakers seem to filter out this click when the XLR cable is connected, but the Hypex amps both get this feedback of the click/pop.

Is that something to do with the grounding of the device? I did notice one of the Hypex giving a hum though the speakers when the XLR was disconnected, I tried a couple of DACs and preamps and they all give the signal click when the XLR is connected to the Hypex.

 

[Dominic]

[QUOTE = "Julf, post: 218909, member: 17"] By "controller", do you mean preamp / source? Any pics of how the monoblocks are wired internally? Are they DC coupled? [/ QUOTE]

Preamp sorry yes, image attached of the offender, although the other one does it too but much quieter

 

[Julf]

Preamp sorry yes, image attached of the offender, although the other one does it too but much quieter

Thanks. The wiring looks OK, but there is no coupling capacitor on the input, so any DC on the output of your source will be amplified by the amplifier gain - this could cause the popping sound on turn-on/off.

 

[Julf]

For a small sized, desktop system I would go with the small chassis of Nord MP series:
https://www.nordacoustics.co.uk/nord-one-hypex-ncore-mpxxx-stereo-p

For example the NC502 stereo version has only 240mm width, both XLR and RCA and 2x 500W in 4 ohms.
https://www.nordacoustics.co.uk/product-page/nord-one-mp-nc500-stereo-power-amp

Don't the Nord ones use nC500s with some Nord-provided buffers instead of the hypex-provided ones on the nC400s?

 

[Julf]

Is that something to do with the grounding of the device? I did notice one of the Hypex giving a hum though the speakers when the XLR was disconnected, I tried a couple of DACs and preamps and they all give the signal click when the XLR is connected to the Hypex.

More likely DC on the output of your source.

 

[Julf]

Yes, I read that, but in the NC400 datasheet:

This should be mandatory reading for anyone in audio: The G Word, or How to Get Your Audio off the Ground.

 

[Dominic]

Thanks. The wiring looks OK, but there is no coupling capacitor on the input, so any DC on the output of your source will be amplified by the amplifier gain - this could cause the popping sound on turn-on/off.

Yes, that must be it! That's why these amps behave differently to my other commercial amps. Any guides available, or can you tell me what I need to do. I have all the necessary tools, soldering station, but now I just need the knowledge!
Thanks for the advice on this

 

[Julf]

Yes, that must be it! That's why these amps behave differently to my other commercial amps. Any guides available, or can you tell me what I need to do. I have all the necessary tools, soldering station, but now I just need the knowledge!
Thanks for the advice on this

I suggest you start by inserting DC filter capacitors (I would try with 2.2 μF polypropylene) in series with the inputs. What is your source?

 

[maty]

Curiosity.

Old NC400 (red caps)

New NC400 (black caps), like yours:

Maybe with a Wima MKP4 2.2 uF

[PDF] https://www.wima.de/wp-content/uploads/media/e_WIMA_MKP_4C.pdf

 

[Julf]

Maybe with a Wima MKP4 2.2 uF

As far as I know they are not in the signal path. The nC400 is DC coupled.

 

[Dominic]

I suggest you start by inserting DC filter capacitors (I would try with 2.2 μF polypropylene) in series with the inputs. What is your source?

Source is a crane song Avocet, changing speaker outputs or mute/unmute causes the clip.

Makes sense that commercial products have the filter that click/pop out.

Can it be done on the xlr line if it's in series, are there XLR DC filter accessories?

Or do I need to solder it inside, and in that case which pin does it go between?

Thanks again, much appreciated

 

[Julf]

Source is a crane song Avocet, changing speaker outputs or mute/unmute causes the clip.

As the nc400 has a fair bit of voltage gain (26 dB, or a factor of 20), even a small DC offset on the output will cause a pop.

Can it be done on the xlr line if it's in series, are there XLR DC filter accessories?

Or do I need to solder it inside, and in that case which pin does it go between?

Any "DC filter" would just be the same capacitors. You can put them in a separate small box with XLR ins and outs, but it is much easier to solder them to the input connectors - two capacitors per channel, one between pin 2 and the non-inverting input lead and the other between pin 3 and the inverting input.

 

[maty]

I wanted more power for my 88db/8ohms speakers. By the way, the NC250MP has the lowest THD + N of the entire NCxxxMP line...

Audiophonics-PA-S250NC-stereo-NC250MP-specs

https://www.audiophonics.fr/en/powe...s-d-amplifier-ncore-2x250w-4-ohm-p-13545.html

Audiophonics-PA-S500NC-stereo-NC500MP-specs

https://www.audiophonics.fr/en/powe...s-d-amplifier-2x500w-4-ohm-ncore-p-13344.html

********** UPDATE: The data was wrong. Corrected yet: 124 dB ************


* If the data are right *, SNR must be at max power and not at 1 watt -> Hypex NC250MP is the best option to listen to good/very good recordings with high DR at home.

With modern commercial music, badly recorded and DR < 10 dB, I suppose it will be quite difficult to appreciate differences between the two modules beyond the power.

Can someone verify the data? The PDF manuals with all specs are not available on the Hypex website.
https://www.hypex.nl/oem-audio-amplifiers/

 

[Dominic]

As the nc400 has a fair bit of voltage gain (26 dB, or a factor of 20), even a small DC offset on the output will cause a pop.



Any "DC filter" would just be the same capacitors. You can put them in a separate small box with XLR ins and outs, but it is much easier to solder them to the input connectors - two capacitors per channel, one between pin 2 and the non-inverting input lead and the other between pin 3 and the inverting input.

Thanks very much, very well explained, I guess I'll plan which option to go with then!