Purifi Class D

[jaytor]

It is nice to have the option to be able to tailor the sound with different input buffers, particularly for a product designed for the DIYer. Although the all-in-one approach is certainly simpler for the less-experienced builder and is more likely to deliver a consistent result. 

[Jud]

So if what I think is happening is indeed happening (your speakers have a lot of high end response, not so much deep low end, and the Nilai may show you that pretty starkly, more so than the Linn - and perhaps more so than the amp the speakers were tuned with by the manufacturer), then yes, you could play around with pre-amps as a hit-or-miss sort of frequency equalizer. But why not simply solve the problem directly with software frequency equalization?  You wouldn't have to take a hit selling the Nilai, and you'd have a frequency response tailored individually for your speakers and room.

 

You'd need a calibrated measurement mic, which you can get very inexpensively ( https://www.minidsp.com/products/acoustic-measurement/umik-1 ), and from there it's up to you whether you want to learn to do software equalization yourself for free ( https://www.roomeqwizard.com ), or pay someone to do it for you ( for example, https://www.dirac.com/live/ or https://accuratesound.ca/digital-room-correction-drc-calibration/?gclid=EAIaIQobChMI48nRgeWJ_wIVJRh9Ch3P0QWaEAAYASAAEgIOn_D_BwE ).

[mocenigo]

3 hours ago, leManu said:

Sadly the Nilai500 doesn't offer any replaceable opamp, so that's not an option. 

 

to be honest, replacing opamps only makes a difference if they are used in extreme conditions or you are using one well within its operating range, vs barely within (that’s why replacing the 1612 with a 1656 in the Purifi buffers may have an effect) vs outside it.  I infer that the Nilai500 has a very integrated design and in that case replacing the opamp would probably decrease performance.

 

3 hours ago, leManu said:

 

I feel like one of the main difference in sound that I experience is the lack of decay.  Notes just disappear so quickly that the sound is dry and lack texture, thus warmness.

 

Interesting, but this should never happen unless one of the two amps is broken by design. The disappearance of clearly audible sounds- as opposed to very subtle cues - is just not possible. So it was probably your previous amp that added some midrange bloom. It is legit to prefer it, it just is not hifi in my book. Or no longer, as the bar has been raised significantly.

 

3 hours ago, leManu said:

 I was never a fan of tubes, but again I was wondering if adding a tube pre amp or external tube buffer would give me back some of the warmth by adding decay to the sound.  And better imaging too.  But maybe I should just sell it and try another Hypex with opamp options...

SS opamps will not give you more decay and bloom, AFAIK - I do not know any that does that intentionally.

 

Or you could do what I have done. When I know (numbers do not lie - and they go way beyond the reductive SINAD, mind you) that a device is superior (and the numbers are not those on the price tag!) I let my brain burn in. In fact, now I cannot stand amplifiers with too much midrange bloom, and anything with more than a tiny little of warmth added will in fact make me sick. Clarity and purity of sound is still an acquired taste, nowadays.

[PYP]

55 minutes ago, Jud said:

So if what I think is happening is indeed happening (your speakers have a lot of high end response, not so much deep low end, and the Nilai may show you that pretty starkly, more so than the Linn - and perhaps more so than the amp the speakers were tuned with by the manufacturer), then yes, you could play around with pre-amps as a hit-or-miss sort of frequency equalizer. But why not simply solve the problem directly with software frequency equalization?  You wouldn't have to take a hit selling the Nilai, and you'd have a frequency response tailored individually for your speakers and room.

 

You'd need a calibrated measurement mic, which you can get very inexpensively ( https://www.minidsp.com/products/acoustic-measurement/umik-1 ), and from there it's up to you whether you want to learn to do software equalization yourself for free ( https://www.roomeqwizard.com ), or pay someone to do it for you ( for example, https://www.dirac.com/live/ or https://accuratesound.ca/digital-room-correction-drc-calibration/?gclid=EAIaIQobChMI48nRgeWJ_wIVJRh9Ch3P0QWaEAAYASAAEgIOn_D_BwE ).

Getting a good read on the room interaction is a very good suggestion (although experienced ears can give a good idea of problem areas).  Personally, from there I would try some inexpensive acoustic treatments (or build your own if a DIYer and depending upon whether the room is shared-use).  Since you have two amps now, it would be an interesting experiment to try the treatments with both before anchoring them semi-permanently.  This approach does add a lot of variables at once, but these are key relationships (i.e., amp/speaker and speaker/room interfaces) to get right before adding more gear IMO.  

 

Perhaps you mentioned it earlier:  what didn't the Linn give you that you sought to improve?

 

 

[leManu]

1 hour ago, Jud said:

So if what I think is happening is indeed happening (your speakers have a lot of high end response, not so much deep low end, and the Nilai may show you that pretty starkly, more so than the Linn - and perhaps more so than the amp the speakers were tuned with by the manufacturer), then yes, you could play around with pre-amps as a hit-or-miss sort of frequency equalizer. But why not simply solve the problem directly with software frequency equalization?  You wouldn't have to take a hit selling the Nilai, and you'd have a frequency response tailored individually for your speakers and room.

 

You'd need a calibrated measurement mic, which you can get very inexpensively ( https://www.minidsp.com/products/acoustic-measurement/umik-1 ), and from there it's up to you whether you want to learn to do software equalization yourself for free ( https://www.roomeqwizard.com ), or pay someone to do it for you ( for example, https://www.dirac.com/live/ or https://accuratesound.ca/digital-room-correction-drc-calibration/?gclid=EAIaIQobChMI48nRgeWJ_wIVJRh9Ch3P0QWaEAAYASAAEgIOn_D_BwE ).

That's a good suggestion, I will do this in the next days.  Thanks. 

[leManu]

14 minutes ago, PYP said:

Getting a good read on the room interaction is a very good suggestion (although experienced ears can give a good idea of problem areas).  Personally, from there I would try some inexpensive acoustic treatments (or build your own if a DIYer and depending upon whether the room is shared-use).  Since you have two amps now, it would be an interesting experiment to try the treatments with both before anchoring them semi-permanently.  This approach does add a lot of variables at once, but these are key relationships (i.e., amp/speaker and speaker/room interfaces) to get right before adding more gear IMO.  

 

Perhaps you mentioned it earlier:  what didn't the Linn give you that you sought to improve?

 

 

Power!  Linn was trying hard to push active system at that time, using one amp per channel.  So they are a bit under-powered by modern standard when using them alone (80W/Channel/8 Ohms, 28.5dB gain).  My speakers sensitivity is 86dB, so not that easy to drive loud.  I even had to put the Nilai in high gain mode to achieve interesting power results.  Actually I should probably have bought 2 mono blocks.  I might even do it if I manage to tune it in for my liking.

 

I'll try EQ before getting into room acoustic treatment.  But maybe I'll end up there.

[leManu]

1 hour ago, mocenigo said:

 

to be honest, replacing opamps only makes a difference if they are used in extreme conditions or you are using one well within its operating range, vs barely within (that’s why replacing the 1612 with a 1656 in the Purifi buffers may have an effect) vs outside it.  I infer that the Nilai500 has a very integrated design and in that case replacing the opamp would probably decrease performance.

 

 

Interesting, but this should never happen unless one of the two amps is broken by design. The disappearance of clearly audible sounds- as opposed to very subtle cues - is just not possible. So it was probably your previous amp that added some midrange bloom. It is legit to prefer it, it just is not hifi in my book. Or no longer, as the bar has been raised significantly.

 

SS opamps will not give you more decay and bloom, AFAIK - I do not know any that does that intentionally.

 

Or you could do what I have done. When I know (numbers do not lie - and they go way beyond the reductive SINAD, mind you) that a device is superior (and the numbers are not those on the price tag!) I let my brain burn in. In fact, now I cannot stand amplifiers with too much midrange bloom, and anything with more than a tiny little of warmth added will in fact make me sick. Clarity and purity of sound is still an acquired taste, nowadays.

At the Montreal audio show in April a lot of people were raving about Artist Cloner system.  I really dislike it because I felt like all the music was overly warmth, liked played through those old "loudness" button in cheap amp. So I'm not a "warmth" seeker that much.
If my old amp was adding bloom in the midrange, which is very possible, would it also explain the superior soundstage I got from it?  I'll start moving my speakers around to see if the change of amplifier could have cause change of speakers/room interaction 

[PYP]

11 minutes ago, leManu said:

  I'll start moving my speakers around to see if the change of amplifier could have cause change of speakers/room interaction 

Good that you are willing to experiment!  Placement (including where you sit relative to the speakers) is a huge variable and alone might solve your issues.  Have fun!

[mocenigo]

1 hour ago, leManu said:

If my old amp was adding bloom in the midrange, which is very possible, would it also explain the superior soundstage I got from it?

 

Well, there are two things here.

 

A bit of H2 with inverted polarity can give the impression of a deeper soundstage (Nelson Pass even designed a toy circuit to play with that).

 

The second aspect is that IMD will increase the amount of apparent information associated to the signal, also slightly increasing the separation between two channels, resulting in a wider soundstage.

 

So, one may perceive a deeper and wider soundstage as a side effect of that touch of warmth.

 

 Roberto 

 

 

 

[taipan254]

5 hours ago, Jud said:

So if what I think is happening is indeed happening (your speakers have a lot of high end response, not so much deep low end, and the Nilai may show you that pretty starkly, more so than the Linn - and perhaps more so than the amp the speakers were tuned with by the manufacturer), then yes, you could play around with pre-amps as a hit-or-miss sort of frequency equalizer. But why not simply solve the problem directly with software frequency equalization?  You wouldn't have to take a hit selling the Nilai, and you'd have a frequency response tailored individually for your speakers and room.

 

You'd need a calibrated measurement mic, which you can get very inexpensively ( https://www.minidsp.com/products/acoustic-measurement/umik-1 ), and from there it's up to you whether you want to learn to do software equalization yourself for free ( https://www.roomeqwizard.com ), or pay someone to do it for you ( for example, https://www.dirac.com/live/ or https://accuratesound.ca/digital-room-correction-drc-calibration/?gclid=EAIaIQobChMI48nRgeWJ_wIVJRh9Ch3P0QWaEAAYASAAEgIOn_D_BwE ).

Agree

 

if I were to go down this path I’d talk with @mitchco and / or explore purchasing Acourate and a calibrated measurement mic to develop a hi res convolution filter. 

[taipan254]

Also @leManu pls make sure you built the amp properly. In particular you want to make sure your left and right speaker terminals on the amp correspond to the correct polarities. Otherwise the speakers could be out of phase, which could def make the speakers sound thin. 
 

Here’s a construction video for your reference. 
 

 

[PYP]

interesting comparison of three class d amplifiers.  Comments regarding Purifi vs. Nilai at 1:04:17 and then conclusions section at the end.

 

https://alpha-audio.net/2023/01/january-29-2023-1030-cet-live-stream-review-three-times-class-d-hypex-purifi-icepower/

 

 

[Allan F]

17 hours ago, PYP said:

interesting comparison of three class d amplifiers.  Comments regarding Purifi vs. Nilai at 1:04:17 and then conclusions section at the end.

 

https://alpha-audio.net/2023/01/january-29-2023-1030-cet-live-stream-review-three-times-class-d-hypex-purifi-icepower/

 

For those interested in the Conclusion, it can be found at 1:39:13

[PYP]

2 hours ago, Allan F said:

 

For those interested in the Conclusion, it can be found at 1:39:13

These are just opinions, of course, but it was surprising that at least one reviewer commented on the Nilai vs. the Pass, which is their standard.  If the Nilai gets close to the Pass. especially at the Nilai's price point (OK, you do have to put it together), then it seems like Class D has indeed evolved and improved and that the economy of this kind of product becomes clear.  I don't know if the Nilai mono-blocks would have improved performance, but that would have been an interesting comparison.  

[barrows]

30 minutes ago, PYP said:

These are just opinions, of course, but it was surprising that at least one reviewer commented on the Nilai vs. the Pass, which is their standard.  If the Nilai gets close to the Pass. especially at the Nilai's price point (OK, you do have to put it together), then it seems like Class D has indeed evolved and improved and that the economy of this kind of product becomes clear.  I don't know if the Nilai mono-blocks would have improved performance, but that would have been an interesting comparison.  

My DIY build of the Hypex NC-400 amplifier had a tough act to follow: I compared it with my Pass Labs X 150.5, back and forth, over the course of about 8 months.  It was close, with each amplifier having some strengths over the other.  Ultimately the NC-400 won out for me due its lower noise floor, better detail retrieval, and more textured bass.

Note that with the Pass X.5 and now X.8 series amps, the circuitry and parts quality is all the same from model to model, they are just scaled up for more output power as you go up the line.

Loved the economy of running the NC-400 as well, the Pass idled at around 200 watts of power consumption.

[leManu]

On 5/22/2023 at 8:37 PM, mocenigo said:

The second aspect is that IMD will increase the amount of apparent information associated to the signal, also slightly increasing the separation between two channels, resulting in a wider soundstage.

 

So, one may perceive a deeper and wider soundstage as a side effect of that touch of warmth.

This is quite fascinating and disturbing (at least for me), and can maybe explain what I'm experiencing.  It sure ring a bell when I red that.

 

On 5/22/2023 at 4:55 PM, mocenigo said:

Or you could do what I have done. When I know (numbers do not lie - and they go way beyond the reductive SINAD, mind you) that a device is superior (and the numbers are not those on the price tag!) I let my brain burn in. In fact, now I cannot stand amplifiers with too much midrange bloom, and anything with more than a tiny little of warmth added will in fact make me sick. Clarity and purity of sound is still an acquired taste, nowadays.

That's what I'm trying to do right now,  I'm only playing the Nilai and will do so for a week.  Then I'll listen to my Linn again and see what I'll think then.  Maybe it's like an old shoe that your so used to that the new one feel weird?  But I'll see in a week and post my thoughts here again.

 

Thanks for your insight.

[mocenigo]

8 hours ago, Allan F said:

 

For those interested in the Conclusion, it can be found at 1:39:13

Sadly the conclusion are invalid. It does not seem to be a controlled test: not blind, volume not matched. So, they just were more impressed by the latest technology, and I guess they will be more impressed by the 1ET9040BA, and then by the next Hypex iteration and so on. 

[Jud]

3 hours ago, mocenigo said:

Sadly the conclusion are invalid. It does not seem to be a controlled test: not blind, volume not matched. So, they just were more impressed by the latest technology, and I guess they will be more impressed by the 1ET9040BA, and then by the next Hypex iteration and so on. 

Sadly your conclusion is invalid.

 

- The latest technology is the Purifi, not the Hypex.

 

- Their conclusions happen to be in line with the measurements (though the noise and distortion figures are so low for both Hypex and Purifi they may well be inaudible).

 

Edit: BTW, are you certain volume wasn’t matched? I believe there was a reference to the bother they went through to match volume.

[DuckToller]

Just to enlighten the discussion, afaik, the Hypex Nilai was introduced in the 2nd half of 2022, the PuRiFi Eigentakt in 2019.

[mocenigo]

54 minutes ago, Jud said:

Sadly your conclusion is invalid.

 

- The latest technology is the Purifi, not the Hypex.

 

- Their conclusions happen to be in line with the measurements (though the noise and distortion figures are so low for both Hypex and Purifi they may well be inaudible).

 

Edit: BTW, are you certain volume wasn’t matched? I believe there was a reference to the bother they went through to match volume.

*cough* the Nilai design comes AFTER the Purifi they tested.

 

Second, at that level the absolute levels of distortion and noise are only for bragging rights, they are not a meter of sound quality. In fact, the Purifi addresses also hysteresis distortion, and the Nilai documentation does not mention that, so they did not (otherwise they would mention it).

 

Third, Level matching procedure did not look well documented

 

And anyway this is a sighted test, so completely irrelevant for the tiny differences that there may be between these amps.

[Jud]

48 minutes ago, DuckToller said:

Just to enlighten the discussion, afaik, the Hypex Nilai was introduced in the 2nd half of 2022, the PuRiFi Eigentakt in 2019.

 

30 minutes ago, mocenigo said:

*cough* the Nilai design comes AFTER the Purifi they tested.

 

Second, at that level the absolute levels of distortion and noise are only for bragging rights, they are not a meter of sound quality. In fact, the Purifi addresses also hysteresis distortion, and the Nilai documentation does not mention that, so they did not (otherwise they would mention it).

 

Third, Level matching procedure did not look well documented

 

And anyway this is a sighted test, so completely irrelevant for the tiny differences that there may be between these amps.

Yes, I understand the Nilai iteration of the Hypex design came later, but Putzeys designed Purifi after Hypex. So I suppose one could think of either as the latest technology.

 

Do I suppose the amps really sound that different without hearing them for myself, and even then would I necessarily trust my conclusions? No.

 

But I believe there is a tendency to dismiss these listening impressions on the basis of a laundry list of the “usual suspects” (latest shiny thing, no volume matching), which in this case aren’t correct (volume matching) or arguable (latest tech). I just think, without arguing for the correctness of others’ sighted listening impressions, or even my own, that at least we should be careful about evaluating them on an accurate basis.

[mocenigo]

39 minutes ago, Jud said:

Yes, I understand the Nilai iteration of the Hypex design came later, but Putzeys designed Purifi after Hypex. So I suppose one could think of either as the latest technology.

 

in Italy we call this way or arguing “trying to climb a mirror” (with your bare hands, is implied) but you have my sympathy.

 

 

39 minutes ago, Jud said:

Do I suppose the amps really sound that different without hearing them for myself, and even then would I necessarily trust my conclusions? No.

 

But I believe there is a tendency to dismiss these listening impressions on the basis of a laundry list of the “usual suspects” (latest shiny thing, no volume matching), which in this case aren’t correct (volume matching) or arguable (latest tech). I just think, without arguing for the correctness of others’ sighted listening impressions, or even my own, that at least we should be careful about evaluating them on an accurate basis.

 

What seems clear to me is that Hypex put a discrete, optimised input buffer in the Nilai. If the test was conducted with the stock EVAL input board, performance may be different just because of that. Frankly, I did not double check which implementation of a Purifi amp they listened to, but from the images it is clearly the EVAL1. And there is anedoctal evidence that just replacing the OPA1612 with an OPA1656 on that board improves subjective impressions. I use a neurochrome Universal buffer and I can testify that it made a difference over the EVAL1z

 

I am quite sure that IF they can still hear a difference in a double blind test, then it is due to the input buffer.

[Jud]

18 minutes ago, mocenigo said:

 

in Italy we call this way or arguing “trying to climb a mirror” (with your bare hands, is implied) but you have my sympathy.
 

What seems clear to me is that Hypex put a discrete, optimised input buffer in the Nilai. If the test was conducted with the stock EVAL input board, performance may be different just because of that. Frankly, I did not double check which implementation of a Purifi amp they listened to, but from the images it is clearly the EVAL1. And there is anedoctal evidence that just replacing the OPA1612 with an OPA1656 on that board improves subjective impressions. I use a neurochrome Universal buffer and I can testify that it made a difference over the EVAL1z

 

I am quite sure that IF they can still hear a difference in a double blind test, then it is due to the input buffer.

Regarding “climbing a mirror” - 🙂 Thank you, what a wonderful expression!

 

I think you may be right about the input buffer in the Nilai, though I don’t have much confidence in double blind listening tests for reasons I’ve mentioned elsewhere in the forum.

[davide256]

On 5/22/2023 at 4:55 PM, mocenigo said:

 

to be honest, replacing opamps only makes a difference if they are used in extreme conditions or you are using one well within its operating range, vs barely within (that’s why replacing the 1612 with a 1656 in the Purifi buffers may have an effect) vs outside it.  I infer that the Nilai500 has a very integrated design and in that case replacing the opamp would probably decrease performance.

 

 

Interesting, but this should never happen unless one of the two amps is broken by design. The disappearance of clearly audible sounds- as opposed to very subtle cues - is just not possible. So it was probably your previous amp that added some midrange bloom. It is legit to prefer it, it just is not hifi in my book. Or no longer, as the bar has been raised significantly.

 

SS opamps will not give you more decay and bloom, AFAIK - I do not know any that does that intentionally.

 

Or you could do what I have done. When I know (numbers do not lie - and they go way beyond the reductive SINAD, mind you) that a device is superior (and the numbers are not those on the price tag!) I let my brain burn in. In fact, now I cannot stand amplifiers with too much midrange bloom, and anything with more than a tiny little of warmth added will in fact make me sick. Clarity and purity of sound is still an acquired taste, nowadays.

I'm getting the impression that you do not play/esteem any sort of wind or string instrument. Which escalate in price based on the strength of that warmth/timbre depth you are eschewing as much as technical capability.

[barrows]

IMO,  this test appears to be fine for a comparison within the given system context.  As the input buffers used on the Nilai are a discrete implementation, optimized for the Nilai, I would give the Nilai the theoretical edge there.  The difference with using discrete components vs. "using all in one" IC based circuits, is that a talented designer has much more flexibility in tuning the circuit for the task at hand.  In addition, Bruno Putzeys has mentioned in interviews that the Purifi Eval 1 input stage was not designed to be the best possible input stage for the Purifi module, and that he would do something different if were designing an input stage for the Purifi module if he were trying to make the "best" possible complete amplifier.

To get an idea what the "best" possible, Putzeys designed, input stage might look like, we could consider the input stage on the Mola Mola Kalugas (designed by Putzeys): this is an discrete based input stage, using his "single-ended/differential" circuit approach.  This design takes a balanced input, converts to single ended, and then back to differential to drive the module-in this process it also reduces overall input stage noise by 6 dB.  What approach does Hypex use with its discrete input stage on the Nilai... they do not really say: it might just be a discrete, single, opamp, style circuit, or it might be something else.

I find it a bit disappointing that more manufacturers are not getting a bit more creative with the commercial class D amps they design and sell.  I would like to see more Purifi based amps with unique input stage approaches, using discrete components, and even tubes.  I feel like there are a lot of cookie cutter builds out there, but few really well though out approaches.  It is clear that one can do better than just using a single opamp (circuit, IC or discrete) based approach, at least the DIY Neurochrome buffer is a bit better thought out than just a single IC, but where are the really cool, discrete input stage versions?  

On the Nilai's "newness", it is pretty clear if one believes Hypex's marketing materials on the Nilai, that it is indeed a new design-certainly based on what has gone before, but with refinements and improvements over Ncore.  What those improvements are... well we do not know.  But as with Purifi, it is likely that the improvements are in the control loop.  I am supposing that Hypex did not sit on their hands when the Purifi design was released.

I found the high frequencies are slightly more refined (more extended, and smoother) with Purifi vs Ncore-it is a small thing...  I wonder if Nilai has a similar improvement?