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Why NCx500 isn't necessarily an upgrade

Bjorn

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We are in the age of chasing THD numbers in electronics. And while it's certaintly good with low distortion numbers, let me explain why using NCx500 modules or any other newer class D modules isn't necessarily an upgrade. And also why Vera Audio hasn't considered several of new class D modules that been released or are about to be released.

Let's look at a THD+N measurement of our Vera Audio P400/1000 with NC500 modules first. Showing both channels in 4 Ohm:
THD+N 4 Ohm.jpg


The NCx500 module comes with an integrated buffer, and here's our measurement with it:
NCx500 Hypex buffer_THD+N.png


As can be seen here, the distortion up till 20W is higher with NCx500. Above that they are very similar and I should mention here that NC500 modules can vary some and lately they have become better as well. Also note that there's less power with NCx500 before the distortion rises. With 0.002% distortion, our P400/1000 with NC500 has an increased output power of about 90W.

So with the standard Hypex buffer, this isn't an upgrade and there's a loss of power. If we however, bypass the internal buffer and use the Vera Audio buffer instead, we acieve better numbers.
THD+N_4Ohm_1KHz.png


While the distortion measurement has improved, we also need to ask ourselves if this an audible improvement. We would need a blind test to verify this, but he chances are probaly very slim for most and have the loss of output power.

We believe if there's desire to hear smaller details as well as possible, the first step would be speakers with lower distortion and acoustic treatment to achieve a clean impulse/ETC response and remove resonances in the time domain of the room. Both of these have a very audible difference. Horn loaded compression drivers of high quality and planar/magnetic drivers achieves something that other speaker drivers don't in this area. Chasing lower and lower distortion numbers from amps, and avoiding upgrading the speakers and not do something about the acoustics could very much be a waste. We need to focus on the bigger areas first.

Vera Audio has emphasized areas like great cooling, long life span, high build quality combined with several nice features in our amps. We also offer 5 years of warranty. And our amplifiers have extremely low distortion. Chasing even lower numbers here is not the way to go in our opinion.

That being said, if someone wanted us to still build the P400/1000 with the NCx500 modules combined with our own developed buffer we could certainly do it. They fit right in the present chassis. Perhaps it gives some an ease of mind, knowing the distortion numbers are better. But don't expect to hear a difference in a blind test. Upgrading to for example the coming Vera Audio Coherence 12 speaker will give you much more insight into the recordings. A super clean wavefront with a diffraction free cabinet and drivers with very low IMD.
IMG20240216133341 (Medium).jpg
 

Purité Audio

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Bjorn, off topic sorry, but have you posted preliminary measurements of the ‘Coherence’ loudspeaker and I have managed to miss them?
Thanks,
Keith
 

NTK

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How come there is a reduction in power output when you switched from the Hypex buffer to the Vero buffer?

index.php

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tmtomh

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Very interesting, @Bjorn - thank you!

I have a pet theory about this. It's admittedly simplistic, but I have a hard time dismissing it, so I'm curious to see what others might think:

I am not one of those folks who criticizes ASR for "chasing SINAD." However, that said, I have noticed that to me, psychologically, THD+N measurements generate different feelings depending on whether they're expressed in % or dB.

For example, 0.005% THD+N seems very low and like a nice, round-number figure that I'm comfortable using as a benchmark.*

But if we translate into SINAD, we get 86dB - which for anything but speakers and AVRs is generally viewed here as somewhere between "mediocre" and "broken" depending on what kind of gear it is.

Even 0.002% THD+N - which "feels" excellent - translates to less than 94dB SINAD, which again is not bad but not considered great here except for AVRs, dongles, and perhaps very inexpensive amps or inexpensive combo products like streamer/DAC/amps.

Even if that 0.002% THD+N is for an upstream component like a DAC and gets magnified 10x by downstream gear, it's still 0.02%, which I think everyone would agree is still at least an order of magnitude below the threshold of human hearing.

Of course the percentage and dB scales line up nicely once you get to 0.001%, which equals 100dB SINAD. But still, I wonder if part of the issue is just that there's a perceptual mismatch between where the "intuitively good-seeming, round-number" threshold numbers are for SINAD dB vs THD+N percentage at levels above 0.001%.

Given the technology and production capabilities available today, a 94dB SINAD DAC can signify poor engineering and there is value in that information, for sure. I'm just talking about the actual audible performance.


(* Assuming that the noise component does not comprise the overwhelming majority of that measurement, in which case the noise could be an issue with sensitive headphones or if magnified by other gear down the line in the signal chain.)
 
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Bjorn

Bjorn

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Bjorn, off topic sorry, but have you posted preliminary measurements of the ‘Coherence’ loudspeaker and I have managed to miss them?
Thanks,
Keith
Nothing yet. Should happen shortly.
 

delta76

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There are two things at ASR:
- people applaud high sinad as it is a very good indicator of good/clean engineering
- people are more pragmatic when it comes to recommending amp, while sinad is important, power, price, availability and reliability are as important.
Both are valid and not mutual exclusive
 
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Bjorn

Bjorn

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How come there is a reduction in power output when you switched from the Hypex buffer to the Vero buffer?

index.php

index.php
Good point. I'm afraid these pictures are not super accurate in the way they are portrait. And I apologies for not mentioning this and possibly comparing something slightly inaccurate. I'm going to need our engineer Armand to show these more accurately.

Here we have zoomed in on the NCx500 with the Vera Audio buffer, and we see that the limit is actually 500W.
THD+N_4Ohm_1KHz_higher resolution.png
 

Ron Texas

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Here's my take on electronics. Noise is a problem if you can hear it. The worst offenders are inexpensive active speakers, especially when used near field. The next group is efficient passive speakers. My Crown XLS 1502 with its sub ASR SINAD of 76 dB does not produce audible noise through my very inefficient LS50's unless I put my ear 2" from the driver. As for distortion, speakers have so much more distortion than electronics that it's unlikely anyone will hear distortion from electronics. One highly regarded active monitor was torn down here. The chip amp in it was found to have a SINAD in the 75 to 80 dB range. Remember that amplifier is directly connected to the driver so there is no attenuation from a passive network. The worst kind of distortion which one will ever get from an amplifier is clipping. It is audible, annoying to the point of causing a headache and can damage loudspeakers. So, make sure you have enough power and don't fuss over having the highest SINAD on the block.
 
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Bjorn

Bjorn

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What's audible is dependend on several factors. Obviously age and hearing plays a major role. Something I think some older audiiophiles make a mistake at, is judging what's audible in their years instead of what the threshold is for a young person. We are all in the same boat here and gradually loose hearing as we age.

Then we have the room acoustics, which I talk about a good deal but probably mostly to deaf ears here at ASR. But those who has heard a super clean impulse/ETC in a room knows how much this means in relation to hearing details or "resolution". It completely exceeds any difference between decent amps and super low distortion amps. And the same goes for speaker designs IMO.

And if acoustics and speakers holds great quality, it does also become a lot easier to hear differences in electronics. I've very much disagree with those who say we can't hear distortion from elecontrics. I'm confident we need a SINAD much higher than at 80 dB under good conditions, but I'm not sure where the limit is. Whether it's 95 dB, 100 dB or 105 dB or even higher for the youngest. But I'm also confident that when you reach about 105 dB, any possible improvement would be so low that almost no one would be able to distinguish it in a blind test. I'm open to be proved wrong ;)
 

tmtomh

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What's audible is dependend on several factors. Obviously age and hearing plays a major role. Something I think some older audiiophiles make a mistake at, is judging what's audible in their years instead of what the threshold is for a young person. We are all in the same boat here and gradually loose hearing as we age.

Then we have the room acoustics, which I talk about a good deal but probably mostly to deaf ears here at ASR. But those who has heard a super clean impulse/ETC in a room knows how much this means in relation to hearing details or "resolution". It completely exceeds any difference between decent amps and super low distortion amps. And the same goes for speaker designs IMO.

And if acoustics and speakers holds great quality, it does also become a lot easier to hear differences in electronics. I've very much disagree with those who say we can't hear distortion from elecontrics. I'm confident we need a SINAD much higher than at 80 dB under good conditions, but I'm not sure where the limit is. Whether it's 95 dB, 100 dB or 105 dB or even higher for the youngest. But I'm also confident that when you reach about 105 dB, any possible improvement would be so low that almost no one would be able to distinguish it in a blind test. I'm open to be proved wrong ;)

Is there any scientific literature documenting age-related changes in noise sensitivity? I'm no expert, so I'm only familiar with age-related changes in high-frequency sensitivity (and midrange sensitivity for folks with clinical hearing loss and/or of very advanced age).
 
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Bjorn

Bjorn

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Is there any scientific literature documenting age-related changes in noise sensitivity? I'm no expert, so I'm only familiar with age-related changes in high-frequency sensitivity (and midrange sensitivity for folks with clinical hearing loss and/or of very advanced age).
I haven't seen studies related to exactly to this but since hearing is gradually lost with age for all (to different extends), I would think the likelihood of also being able to distuinguish lower distortion becomes more difficult.
 

tmtomh

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I haven't seen studies related to exactly to this but since hearing is gradually lost with age for all (to different extends), I would think the likelihood of also being able to distuinguish lower distortion becomes more difficult.

That makes sense, but I think we still need to see if we can find any actual information.
 
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Ron Texas

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What's audible is dependend on several factors. Obviously age and hearing plays a major role. Something I think some older audiiophiles make a mistake at, is judging what's audible in their years instead of what the threshold is for a young person. We are all in the same boat here and gradually loose hearing as we age.
When I was young good electronics were very expensive and I had very little money. Now I am old and can't hear as well as I used to. High performance electronics can be had for a reasonable price and I have enough money to buy that stuff. Does this remind any one of the famous short story "Gift of the Magi"?
 
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Bjorn

Bjorn

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Bjorn, off topic sorry, but have you posted preliminary measurements of the ‘Coherence’ loudspeaker and I have managed to miss them?
Thanks,
Keith
Small teaser.

Threw them up here without working on placement and horns/TV are on the side. Sorry of the poor picture quality.
IMG20240304141928 (Medium).jpg


And they measure very well with no "room EQ". Perhaps a bit on the dark/bassy side here, but that's simpy a matter of tuning with shelves. 1/12 Oct. smoothing and right and left channels.

Høyre Coherence 12 V3.jpg


Venstre Coherence 12.jpg


Here from opposite side in the room with a flatter tuning.
Coherence 12 with diffusers.jpg
 

Purité Audio

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Decent!
I am going to have to get some sheep (skins).
Keith
 

Ra1zel

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But if we translate into SINAD, we get 86dB - which for anything but speakers and AVRs is generally viewed here as somewhere between "mediocre" and "broken"
Mediocre and broken but on ASR only, in any "secure" blind test transparent
 

restorer-john

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We are in the age of chasing THD numbers in electronics. And while it's certaintly good with low distortion numbers, let me explain why using NCx500 modules or any other newer class D modules isn't necessarily an upgrade. And also why Vera Audio hasn't considered several of new class D modules that been released or are about to be released.

Let's look at a THD+N measurement of our Vera Audio P400/1000 with NC500 modules first. Showing both channels in 4 Ohm:
View attachment 353984

The NCx500 module comes with an integrated buffer, and here's our measurement with it:
View attachment 353985

As can be seen here, the distortion up till 20W is higher with NCx500. Above that they are very similar and I should mention here that NC500 modules can vary some and lately they have become better as well. Also note that there's less power with NCx500 before the distortion rises. With 0.002% distortion, our P400/1000 with NC500 has an increased output power of about 90W.

So with the standard Hypex buffer, this isn't an upgrade and there's a loss of power. If we however, bypass the internal buffer and use the Vera Audio buffer instead, we acieve better numbers.
View attachment 353988

While the distortion measurement has improved, we also need to ask ourselves if this an audible improvement. We would need a blind test to verify this, but he chances are probaly very slim for most and have the loss of output power.

We believe if there's desire to hear smaller details as well as possible, the first step would be speakers with lower distortion and acoustic treatment to achieve a clean impulse/ETC response and remove resonances in the time domain of the room. Both of these have a very audible difference. Horn loaded compression drivers of high quality and planar/magnetic drivers achieves something that other speaker drivers don't in this area. Chasing lower and lower distortion numbers from amps, and avoiding upgrading the speakers and not do something about the acoustics could very much be a waste. We need to focus on the bigger areas first.

Vera Audio has emphasized areas like great cooling, long life span, high build quality combined with several nice features in our amps. We also offer 5 years of warranty. And our amplifiers have extremely low distortion. Chasing even lower numbers here is not the way to go in our opinion.

That being said, if someone wanted us to still build the P400/1000 with the NCx500 modules combined with our own developed buffer we could certainly do it. They fit right in the present chassis. Perhaps it gives some an ease of mind, knowing the distortion numbers are better. But don't expect to hear a difference in a blind test. Upgrading to for example the coming Vera Audio Coherence 12 speaker will give you much more insight into the recordings. A super clean wavefront with a diffraction free cabinet and drivers with very low IMD.
View attachment 353993

A 1kHz test is all you need? LOL.

What about low frequencies, intermediate frequencies and high frequencies? 20Hz-20kHz, worst case THD is what I want to see.

And that means an analyzer with a decent bandwidth (~200kHz). Oh, but the NCx needs a filter...

I agree totally, the 1kHz THD+N or SINAD wars are hilariously stupid.
 

pma

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As can be seen here, the distortion up till 20W is higher with NCx500.

I would say the difference is not in distortion, but in noise. You cannot distinguish it in THD+N plot. You might like to measure THD (without N) as a function of power, instead. REW software (even the free version) will let you find the difference, should it be either THD or N.

My suspect - the gain is the same in both cases??
 

restorer-john

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How about just measuring the residual noise floor in the audible bandwidth in the first place?

As you say, it will be the limiting factor in most cases where a competent design is used.
 
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