Review and Measurements of Hypex NC400 DIY Amp

[6speed]

I hope the speaker systems in use here are single-driver crossover-less types that have no phase distortion.

This will be one of four amps for a 4 way active system with DSP and a certain amount of FIR corrections.

 

[restorer-john]

John,
Why is this surprising to you? Much of the concept of these Class-D/SMPS-PS amplifiers is to reduce thermal issues and decrease PS size and cost.
They're designed to play music in your system and not heat the room of your lab. The engineering trade-off is obvious here and has been understood for many years.
Hypex makes no claims otherwise in either their amplifier module datasheets or the SMPS supply data sheets.
Dave.

Hypex make plenty of claims. What's surprising is people are not calling them out on their exaggerated headline power output numbers and bringing them to task for it.

It's either a 400W amplifier or it is not. If the modules cannot output 400W continuously, they are guilty of deceptive practices. If their own power supplies cannot deliver their rated power continuously, they need to make it very clear in the headline advertised numbers, not buried deep in the fine print.

Perhaps you want to give them a free pass by calling it an 'engineering trade-off', but I expect a whole lot better from a supposed science based forum where claims should be rigorously checked and commented upon.

 

[amirm]

Not quite true Amir. The PSU is inadequate, that is a given, but the modules themselves cannot dissipate the heat for continuous operation at even their rated maximum output. Their continuous rating is significantly de-rated accordingly, and that is with adequate heatsinking.

Were you quoting the power supply specs or the amp specs? I thought it was the former in the context of the latter.

 

[Deleted member 2944]

My own NC400 amplifier with the A400 SMPS supply measures 56VP-P at onset of clipping on the outputs. A quick calculation using a 4 ohm R reveals a power of 390 Watts. (Pretty darn close to 400 in my book.)

No, not "continuous." But no claim is made anywhere by Hypex their amplifiers achieve the power rating on a continuous basis.
And even the "400" is specified at a single frequency of 1kHz at 1%THD, and not over the full frequency range.

The reason Amir's measurements show less is because this particular amplifier has two modules ganged onto one power supply.
The advertised Hypex NC400 "kit" is specified as a monoblock where one SMPS600A400 supply powers one NC400 amplifier module.
So, there is a de-rating at work on this particular amplifier. Amir correctly surmised this during his test. Disconnecting one module and a repeat test would show something close to the 400 Watt rating.

My goodness.

Dave.

 

[restorer-john]

My own NC400 amplifier with the A400 SMPS supply measures 56VP-P at onset of clipping on the outputs. A quick calculation using a 4 ohm R reveals a power of 390 Watts. (Pretty darn close to 400 in my book.)

No, not "continuous." But no claim is made anywhere by Hypex their amplifiers achieve the power rating on a continuous basis.
And even the "400" is specified at a single frequency of 1kHz at 1%THD, and not over the full frequency range.

The reason Amir's measurements show less is because this particular amplifier has two modules ganged onto one power supply.
The advertised Hypex NC400 "kit" is specified as a monoblock where one SMPS600A400 supply powers one NC400 amplifier module.
So, there is a de-rating at work on this particular amplifier. Amir correctly surmised this during his test. Disconnecting one module and a repeat test would show something close to the 400 Watt rating.

My goodness.

Dave.

My goodness Dave, I can't seem to get through to you can I?

You enjoy your 'Hypex Watts' and I'll continue to test and confirm specifications the way it has been done (and regulated) for 40+ years.

 

[Thomas savage]

Just out of curiosity how are we defining continuous in this context as I'm guessing it does not mean forever.

 

[Archmage]

Edit: Ok, I concede that restorer-john has brought up a realistic definition for 'continuous' in the following post. That's fine. But still, if this class of amplifier cannot meet the spec, then:

Based on actual usage:

If the Hypex amps, driven to just below clipping level at peaks, don't "thermal throttle" during playback of music of a higher-than-typical average amplitude, in a hotter-than-average room (say 35C ambient (95F)), then I'm fine with those "Hypex watts" - but it does look like 400w is overrating it.

If there are some temperature range limits in the instructions / white-papers, then perhaps some guidance toward additional heatsinking is warranted to keep within that temperature range for outlier cases.

If power is reduced during any real use case within reason, and no solutions are offered, then I'd consider restorer-john's point fully valid.

Edit: I had built some monoblock amps from Hypex UcD modules in the past, but I never tested them like this. I never noticed any thermal issues, but I also had plenty of headroom in my case.

 

[restorer-john]

Were you quoting the power supply specs or the amp specs? I thought it was the former in the context of the latter.

We have two very optimistically rated components (SMPS600 and NC400) vying for first place in the 'running out of power and SOA awards' An exercise in finger pointing if you ask me.

Just out of curiosity how are we defining continuous in this context as I'm guessing it does not mean forever.

Continuous RMS power from 20Hz-20KHz at a defined distortion level, both channels driven (if it's a stereo amplifier) into a defined impedance with 8 ohms being the defacto nominal. Other impedances can be stated in addition to 8ohms for further information. The standard FTC test is for a period of not less than 5 minutes, immediately after a preconditioning period of 1 hour at either 1/3 power or 1/5 power, depending on whether you want to be seen as serious or taking the easy way out.

We have these standards. All respectable manufacturers adhered to them and HiFi reviewers used them. JA still does as far as I am aware. Who's else is left?

 

[mitchco]

user notnyt over at AVS has been measuring amps for a while: https://www.avsforum.com/forum/155-diy-speakers-subs/1780914-measuring-amplifiers.html

 

[amirm]

Who's else is left?

Me!

As much as I like to be hard on gear in testing, I can't bring myself to sticking to those standards. Average music power is pretty low compared to continuous sine wave.

 

[Deleted member 2944]

You're holding Hypex to a performance specification that they make no claims to achieve. (In fact, they specifically say they can't.)
The continuous rating testing requirement is something YOU'VE applied to their product, and then you claim their specifications are exaggerated because they don't meet YOUR specification. Is that about it??
Classic!

Amir has surmised the correct reason this amplifier didn't achieve the 400 watt power rating and I've just confirmed it for you. But even a cursory look at the ratings of both the SMPS supply and the modules would reveal the issue. It's an SMPS600 (600 watt) supply and we have two NC400 (400 watt modules.) It should be obvious.
We would need (at minimum) an 800 watt supply in order to not de-rate the performance of these two amplifier modules paralleled onto the single supply.

I don't know how much clearer I can make it for you.

Dave.

 

[Thomas savage]

So we are lowering standards I guess you can take the man out of Microsoft but you can't take Microsoft out of the man.

 

[amirm]

So we are lowering standards I guess you can take the man out of Microsoft but you can't take Microsoft out of the man.

Well, the moment I settled for you as the moderator Thomas, that story was written!!!

 

[Thomas savage]

user notnyt over at AVS has been measuring amps for a while: https://www.avsforum.com/forum/155-diy-speakers-subs/1780914-measuring-amplifiers.html

Might have to delete this post as it seems to suggest amir did not invent amp testing online and we can't have that can we.

 

[Thomas savage]

Well, the moment I settled for you as the moderator Thomas, that story was written!!!

As I remember it no one else wanted to be associated with you..

 

[restorer-john]

You're holding Hypex to a performance specification that they make no claims to achieve. (In fact, they specifically say they can't.)

Well, drop the aspirational Peak Power rating and print what they can actually achieve according to standards. All commercial amplifiers have to adhere to that specification. Now I know why they peddle this stuff to DIYers, they can get away with it as it doesn't fall under the same consumer laws for complete amplifiers.

I can't bring myself to sticking to those standards.

Well, what shall we call these magic watts? Amir watts, Hypex watts? By all means do an additional EIA/EIAJ toneburst test like everyone used to do (see the Proton example above) to determine dynamic headroom/short term power, but don't abandon hard fought and won requirements put in place to ensure consumers got what they were paying for. Stand up and be counted Amir!

I do them all on my gear. Preconditioned, continuous, both channels, and single channels into various impedances and do both EIA and EIAJ toneburst tests. Single and both channels tells you a lot about the power supply capability. I don't do reactive (other than capacitive at high freq, low power) or power cube style tests as it's just too much to attempt without a magic box and too hard to plot manually.

(even my Dad gets test reports- this is one of his 'finds' I had to fix...)

 

[6speed]

As much as I like to be hard on gear in testing, I can't bring myself to sticking to those standards. Average music power is pretty low compared to continuous sine wave.

Agreed. If I were to bring an amp to market to compete with Hypex, then I would definitely side with @restorer-john and want to take a hard line to maintain my outrage. As it stands, Hypex publishes a ton of data that paints their DIY products in an honest light. What they did is take all the engineers aside and say "here is the power it outputs under differing circumstances." I don't understand the indignation that your grandmother has been deceived. Go test a commercial implementation of a Hypex product and see if it meets the FTC guidelines for continuous power, and if it is in disagreement with what that particular manufacturer has published.

Also keep in mind that the FTC guideline is a (now) response to corporate greed in order to provide a level playing field...and having oversimplified the matter does not reflect real world requirements. The NC400 and SMPS600 are available only to the DIY community. Validating any OEM implementation is another effort. I think the implied charter for this forum is great and am happy to see the recent interest in amplifiers, so I would simply ask the participants of this forum to come up with a reasonably sized collection of tests to run all amps through--I tried to establish a baseline once already here and would appreciate feedback from @restorer-john on how to standardize testing on this forum. The FTC guidelines are a good reference point, but they do not have to be followed, just acknowledged.

I feel like Amir's testing has produced results that validate what I would expect my non-standard implementation to provide given the supplied documentation. It meets my power/efficiency/footprint requirements, and Amir has confirmed what my ears tell me in that it also meets my distortion requirements.

 

[garbulky]

Well, drop the aspirational Peak Power rating and print what they can actually achieve according to standards. All commercial amplifiers have to adhere to that specification. Now I know why they peddle this stuff to DIYers, they can get away with it as it doesn't fall under the same consumer laws for complete amplifiers.



Well, what shall we call these magic watts? Amir watts, Hypex watts? By all means do an additional EIA/EIAJ toneburst test like everyone used to do (see the Proton example above) to determine dynamic headroom, but don't abandon hard fought and won requirements put in place to ensure consumers got what they were paying for. Stand up and be counted Amir!

I do them all on my gear. Preconditioned, continuous, both channels, and single channels into various impedances and do both EIA and EIAJ toneburst tests. Single and both channels tells you a lot about the power supply capability. I don't do reactive (other than capacitive at high freq, low power) or power cube style tests as it's just too much and too hard to plot.

(even my Dad gets test reports- this is one of his 'finds' I had to fix...)

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I agree with you John. At the very least we have to at least keep to the same standard that other amps are testing. Similar to AVR's that list their power ratings as 200X5 when in reality if you drive them all channels driven their power drops down to 40 watts a channel.
However for real world use, it would be useful to know how long the NC400 can output 400 watts of power.
Also what is limiting it? Is it the switching supply? Will a torroidal supply and large heatsink on the amp be able to sustain 400 watts continuous?

Also continuos ratings test can really separate well built amps from lesser robust units. When Stereophile does their test they encountered several amps that simply shut down, not able to stand up to the thermal load or whatever.

 

[amirm]

However for real world use, it would be useful to know how long the NC400 can output 400 watts of power.

As I noted, I am hesitant to test loaner equipment to such limits (thermal fault).

 

[6speed]

However for real world use, it would be useful to know how long the NC400 can output 400 watts of power. Also what is limiting it? Is it the switching supply? Will a torroidal supply and large heatsink on the amp be able to sustain 400 watts continuous?

It is too late and I am too lazy to go look at datasheets to hazard a guess...although I think a much (much) bigger SMPS and an over-abundance of cooling would be a good starting point. I think this should be part of the value of this forum. After standardizing the testing Amir does of an amp (that can follow the FTC guideline or another more realistic one of our choosing since we listen to music and not sine waves), I think it would be great to pick apart design choices that provide such limitations and how other choices might overcome them. Some manufacturers have used linear supplies with Hypex amp modules. Maybe they were not happy with a suggested SMPS and knew their linear supply was up to the task.