The state of the art class D AUDIOPHONICS HPA-S600NC and AUDIOPHONICS HPA-S400ET sound different, though there is a caveat here.

[ommadusk]

Hi,

I have both these amplifiers in my possession so I've been able to compare them. It's not blind tested. I originally got the NcoreX a couple of weeks ago and I had the Purifi held in customs for a time and I decided at the last minute to get the Purifi as well. It's common belief here that these two SOTA amps will sound the same. I decided to get compare them when I saw this post https://audiosciencereview.com/foru...0-class-d-amplifier-review.41007/post-1689271. Somebody at Audiophonics thinks they sounded different so that was enough to make me want to compare them.

There is a caveat. If anyone's been reading my posts lately I've been having a few issues with crackling, noise, and unbalanced sound in my speakers, and I have not completely determined that the NcoreX is not faulty. However these problems have been intermittent and they've not appeared for a few days. It may have been because I wasn't screwing the speaker wires in well enough. In short, I don't think that's relevant to the comparison but it might be.

Firstly, I found the NcoreX really good. I use stereo speakers for both TV and music. I takes me 4 minutes to take out the speaker wires and XLR cables so I'm not able to immediately compare and people don't rememeber sound very well that makes comparison difficult. But still possible. When I'm listening to dialogue on TV I can hear everything much better with the Purifi. There is a lack of detail with the NcoreX and there's a slight harshness to the sound. I play TV at a lower volume generally than I do with music. With music I can hear a difference as well and I prefer the Purifi.

That's it. I can hear a difference between the two amplifiers. I know it's not popular to say this. I prefer the Purifi over the NcoreX. Btw I don't claim I've got amazing hearing because I've got some hearing loss. The difference is obvious, especially when listening to dialogue on TV. Please bear in mind the caveat that I spoke of.

 

[antcollinet]

It's not blind tested.

So a reasonably pointless description of the differences you hear. I note also you said nothing about level matching. Even small differences in level can lead to significant disparities in perception of sound quality - and even if you measured levels you have no way of setting them to be sufficiently close after changing from one amp to the other, for your testing.

Then as you say there is significant delay between hearing one and then the other.


And before you say "the difference is like night and day" It always is until the test is properly controlled.

 

[ommadusk]

Of course there was no level matching, there I've said it!

 

[Jimbob54]

2 minutes of my life I will not get back. Thanks.

 

[soerenssen]

I noticed while listening to more demanding genres like hiphop or in Rumble from Skrillex (around 1 minute into the song), the KEF's woofers seem to be struggling and at some point they get muffled for a moment, followed by a popping sound, but then it goes away immediately. I don't know if it's the speaker or the NCx500 amp.
To my ears, the combination of the NCx500 and Denon x4800h sound harsh in pure direct mode. For a nice bass level, I have to crank up the volume quite a lot and at that level it's not enjoyable anymore. Vocals are fine, acoustic guitar is already a bit harsh, and as soon as there are lot of instruments playing at the same time (metal, even jazz), it's too much, I have to turn the volume down. So basically I'm changing the volume all the time during a song.
It would be nice to have a good enough single-volume experience, but I don't know what should be the best way to achieve that: an upgrade to Purifi or using EQ/DSP (Dirac) on the receiver?

Like you, I was also told by Audiophonics (and Apollon too) that Purifi sounds warmer, less harsh, more musical. In your case, since both amps are from Audiophonics, the op amps are the same between the NCx500 and the Purifi, so that cannot explain the difference that you hear.

 

[antcollinet]

I noticed while listening to more demanding genres like hiphop or in Rumble from Skrillex (around 1 minute into the song), the KEF's woofers seem to be struggling and at some point they get muffled for a moment, followed by a popping sound, but then it goes away immediately. I don't know if it's the speaker or the NCx500 amp.

If that is not in the song, it sounds like you are dumping too much power into the speaker (which speaker?). That amp can dump a hell of a lot of power. Not many speakers are up to what it can it do.

In any case, I'd back off on the volume a little until you know what is going on. If you value your speakers that is.

 

[soerenssen]

If that is not in the song, it sounds like you are dumping too much power into the speaker (which speaker?). That amp can dump a hell of a lot of power. Not many speakers are up to what it can it do.

In any case, I'd back off on the volume a little until you know what is going on.

KEF Reference 3 Meta

 

[MaxwellsEq]

Thanks for taking the time to share your experience. There is irrefutable evidence that a failure to match levels to within 1% create repeatable sound differences. So I'm sure you did hear a difference - in fact, I would expect you to hear a difference. So would I and I might agree with your preference.

 

[ommadusk]

Thanks for taking the time to share your experience. There is irrefutable evidence that a failure to match levels to within 1% create repeatable sound differences. So I'm sure you did hear a difference - in fact, I would expect you to hear a difference. So would I and I might agree with your preference.

The point I was making is that it's not just the volume.

 

[DearSX]

Any way you can get some measurements? Something like the free REW EQ computer app with a miniDSP microphone may be able to pick up distortion and frequency differences at a given volume.

Maybe try to get the wiring nice and tight and leave it alone. Maybe one set of wires from each amp and just disconnect it at the speaker not the amps to avoid messing with the sound.

At the end of the day, its ok to just go with the one you prefer, but measurements can help make it more clear what is working and what is not. One option is to also connect one amp to the pre with RCA and the other XLR. Both are should sound about the same objectively.

 

[antcollinet]

KEF Reference 3 Meta

So first thing Id say is your amp is capable of more than double the power your speakers are specified for.


Second - is your normal setup driving the amp from your Denon?

is it possible you are driving the RCA outputs from the Denon into clipping? Have you checked the gain staging with the output voltage capability of the Denon? Or it might be you need such a low voltage out of the Denon to keep the volume at a low level, that you are running into dynamic range problems there.

What is your source into the Denon?

 

[soerenssen]

If that is not in the song

Hmm, I think it's in the song actually (Skrillex: Rumble). At 00:18 the bass goes away, I just listened to it on my headphones.

 

[antcollinet]

The point I was making is that it's not just the volume.

A level difference that is small won't be heard as a volume difference, it will be heard as a sound quality difference. A large level difference will sound both as volume and sound quality.

 

[soerenssen]

So first thing Id say is your amp is capable of more than double the power your speakers are specified for.


Second - is your normal setup driving the amp from your Denon?

is it possible you are driving the RCA outputs from the Denon into clipping? Have you checked the gain staging with the output voltage capability of the Denon? Or it might be you need such a low voltage out of the Denon to keep the volume at a low level, that you are running into dynamic range problems there.

What is your source into the Denon?

Wiim Pro into the Denon, pre-outs via RCA-XLR to the stereo NCx500. This is my current setup for both stereo and HT.
I tried with both 25dB (2.67V required)) and 31dB (1.5V required) gain, I didn't hear any difference but the Denon gets very hot above the heat sink if the power amp is set to 31dB gain.

 

[soerenssen]

is it possible you are driving the RCA outputs from the Denon into clipping?

I don't know. How could I check that?

 

[ommadusk]

I noticed while listening to more demanding genres like hiphop or in Rumble from Skrillex (around 1 minute into the song), the KEF's woofers seem to be struggling and at some point they get muffled for a moment, followed by a popping sound, but then it goes away immediately. I don't know if it's the speaker or the NCx500 amp.
To my ears, the combination of the NCx500 and Denon x4800h sound harsh in pure direct mode. For a nice bass level, I have to crank up the volume quite a lot and at that level it's not enjoyable anymore. Vocals are fine, acoustic guitar is already a bit harsh, and as soon as there are lot of instruments playing at the same time (metal, even jazz), it's too much, I have to turn the volume down. So basically I'm changing the volume all the time during a song.
It would be nice to have a good enough single-volume experience, but I don't know what should be the best way to achieve that: an upgrade to Purifi or using EQ/DSP (Dirac) on the receiver?

Like you, I was also told by Audiophonics (and Apollon too) that Purifi sounds warmer, less harsh, more musical. In your case, since both amps are from Audiophonics, the op amps are the same between the NCx500 and the Purifi, so that cannot explain the difference that you hear.

I didn't ask Audiophonics if there was a difference, I was only going on what somebody working there told you. Perhaps consider getting the Purifi to compare them.

 

[antcollinet]

but the Denon gets very hot above the heat sink if the power amp is set to 31dB gain.

That doesn't make any sense: How does the denon know what the external amp gain is (Other than you set a lower volume on the Denon). Are you able (as a test) to turn off the Denon internal amps?

How are your RCA to XLR cables wired?

What output do you have from the Wiim to the Denon?

Are you able (as a test) to drive the amp direct from the Wiim analogue output? Make sure volume is minimised first.

 

[soerenssen]

I didn't ask Audiophonics if there was a difference, I was only going on what somebody working there told you. Perhaps consider getting the Purifi to compare them.

They don't have the 1ET7040SA that I prefer for the KEFs.
And only Buckeye offers it with a properly sized PSU but I'm in the EU so warranty could be problematic.

 

[soerenssen]

That doesn't make any sense: How does the denon know what the external amp gain is (Other than you set a lower volume on the Denon). Are you able (as a test) to turn off the Denon internal amps?

How are your RCA to XLR cables wired?

What output do you have from the Wiim to the Denon?

Are you able (as a test) to drive the amp direct from the Wiim analogue output? Make sure volume is minimised first.

Wiim Pro -> optical cable -> Denon
RCA-XLR cable: https://www.amazon.de/dp/B001389G5I
Denon is set to pre-amp only for the fronts.
Wiim's 2V analog output is not working for some reason, I tried (enabled from the app, but no sound).

 

[ommadusk]

Any way you can get some measurements? Something like the free REW EQ computer app with a miniDSP microphone may be able to pick up distortion and frequency differences at a given volume.

Maybe try to get the wiring nice and tight and leave it alone. Maybe one set of wires from each amp and just disconnect it at the speaker not the amps to avoid messing with the sound.

At the end of the day, its ok to just go with the one you prefer, but measurements can help make it more clear what is working and what is not. One option is to also connect one amp to the pre with RCA and the other XLR. Both are should sound about the same objectively.

I'm screwing the speaker wires in as tightly as possible. I don't have the microphone and I'm not going to do any more comparing, I've done enough. Sorry about that.

P.S. I'm using 10 gauge speaker wire so I expect the connection is good.