Deciding between Purifi, Nilai, NC502MP or NC500x?

Hi All, 

This is my first post in the forum and I want to thank you all for allowing me to be here. 

I would like to ask your help in deciding what class D amplifier to buy. I need help deciding among the different options: Purifi, NC502, NC500X, Nilai, etc. 

I am new here, but I am not new to audio. Let me introduce myself. I became an audiophile more than 20 years ago. During my journey, I had many speakers such as the Danley SH50, Triangle floor standers, Triangle bookshelves, PSBs, NHTs, Tyler Acoustics, and some custom made horn speakers with Jabo horns. I also had many tube (SET, DHT, Push and pull) and solid state amplifiers, custom made and commercially available ones.

Around 2015, I had to do a radical downsize due to moving overseas, and I sold all my equipment.

Now, that I am based in north Virginia, I am finally rebuilding my system. My system is very humble at the moment. I have a MacBook feeding (with Audirvana) a Mini DSP Flex (via USB). The Mini DSP Flex sends high pass with some PEQ to Fosi V3, and also sends an open signal to a Rythmik L12 subwoofer. Fosi feeds main speakers, NHT C3 (85db, 6ohm).

My listening room is around 230 sq ft, and my listening position is 10 feet from speakers. I mostly listen around 70-75 db with peaks of 80-85db, this is measured with a sound level meter at my listening position. So, considering listening position distance from speakers, I do not need a lot of watts for my type of listening, but I would appreciate some headroom in watts for peaks.

On a subjective side, the NHT C3 are bright, but that can be tamed with some PEQ. Also on a subjective, personal, level, I listen to a lot of jazz, outlaw country, soul, indie rock, folk, progressive rock, among other more obscure musical genres.

Now, I am looking at the many Purifi stereo offerings from respected manufacturers (such as Boxem, Buckeye, VTV, Audiophonics, March Audio, etc) but I am wondering if with my current setup I would be able to even to listen the sound character differences between an Hypex Nilai, a Purifi or a NC502 based amplifier. I know the Purifi and the NIlai have a much better Sinad. But, I would also like to know how they sound from some of you who may own them or have listened to them.

Also, somehow, the ability to change op amps in some of the Purifi amplifiers (Audiophonics, VTV, Apollon, March Audio)  interest me because I can tune a bit the sound signature. 

I am only upgrading from the Fosi because I would like to experience this new, supposedly much better, generation of Class D amplifiers. 

Any help, ideas, comments, thoughts, numbers and/or calculations, are highly appreciated.

Thanks!

Alan Brain

I suggest you might want to put the Rogue Audio DragoN amps (stereo & mono blocks) on your list. They use the Ncore modules but also have a tube (12AU7) per channel so you get a bit of a tube favored sound.

Hi Eric, 

Thanks for the suggestion. The Rogue Audio Dragon seems very interesting with that tube buffer.

As much as I will eventually change my current speakers for Danley horns or something like Clayton Shaw´s Caladan open baffle, and that will necessarily entail upgrading all the components in the chain, I am not in that stage yet. For now, the Rogue Dragon is beyond my budget. But I will put on my list for later, for sure.

I went with VTV for my Purifi.  At the time, my choice was based on price, form factor and input buffer.  I liked the op-amp choices, starting with Sonic Imagery 995 for about 6 months before upgrading to the Weiss op-amps.  I also liked the use of through-hole components on the input stage (I like to tinker). All the connections & wiring are solid with upgrade options, and iirc you might be able to go off-menu with upgrade options/specifications if that's of any importance to you.

I would look more at features, power, build quality and looks.  Find the model that suits your needs best. I don't think you will really hear a  difference between the amps per se. They all operate in a similar manner and have distortion below the threshold of hearing. At that level, a few db of SINAD is pretty irrelevant. 

Kii Audio just switched the internal amps of their speakers from a proprietary Bruno designed NCore type amp to a Purifi based design. They aren't claiming the newer models sound better and didn't change the model name or the published specs. 

That said, there are some differences that may make a difference to you:

The Purifi and Nilai are designed to work with 2 ohm loads, the others aren't - if my memory serves me correctly.

If you want to play around with op amps/buffers, that's another consideration of which model you might want. 

The newer power supplies for the newer models are superior to the older ones. 

The March Audio and Apollon are regarded at forums where they discuss this stuff as having very good build quality. 

The March Audio buffer got a rave review from Bruno himself. Said it was better than his. 

4 hours ago, flowcharts said:

I went with VTV for my Purifi.  At the time, my choice was based on price, form factor and input buffer.  I liked the op-amp choices, starting with Sonic Imagery 995 for about 6 months before upgrading to the Weiss op-amps.  I also liked the use of through-hole components on the input stage (I like to tinker). All the connections & wiring are solid with upgrade options, and iirc you might be able to go off-menu with upgrade options/specifications if that's of any importance to you.

 

 

I am very interested in the VTV Purifi, exactly due to that ability to tinker around with op amps and also because it is in the US and it has a warranty. On top of that, Warren, the owner, seems to be a first class act dealing with his products.

Thanks for sharing your experience, It is good to know that the VTV Purifi connections and wiring are solid. I was also looking at the Audiophonics HPA-S400ET but the case may not be tall enough to accommodate the adaptors needed to use API op amps such as the Weiss and others. Could you let me know what speakers you have? what was your previous amplifier? and what improved from your previous amplifier, if anything, when you changed to the VTV Purifi?

I think for my current needs, 200-250 watts is more than enough.  I usually listen at a distance of 10 feet from the speakers. So, per my calculations, to reach around 85db at the listening position (using my 85db speakers), I need around 20 watts. But, to properly handle those for 8-10 db peaks over those 85 (to get to 95db), I would need around 200-250 watts. And that is where the Fosi V3 struggles a bit, with the peaks. 

Regarding op amps, I am not fully sure that all op amps make a difference. I clearly heard a difference when I replaced the stock op amps in my Fosi V3, with MuseS02. There was a significant reduction in db in all frequencies above 10-11Khz. But, keeping an open mind on both sides of the debate of listening vs measuring (numbers), my experience could be explained by the Muse op amps not having the right specs for the job in the Fosi, which will confirm that op amps do make a difference in sound. Even though that difference may have been created by a serious mismatch. And even though when some people make actually love the sound that mismatch created.

I had many tube amplifiers, and I know very well through my own experience, that tubes do change the sound of a tube amplifier, regardless of the amplifier being push pull, DHT, SET, triodes or pentodes. Even changing a rectifier tube will make a evident difference.

I believe there is space for both visions (measurements vs listening experience) to live together, side by side. 

43 minutes ago, firedog said:

I would look more at features, power, build quality and looks.  Find the model that suits your needs best. I don't think you will really hear a  difference between the amps per se. They all operate in a similar manner and have distortion below the threshold of hearing. At that level, a few db of SINAD is pretty irrelevant. 

Kii Audio just switched the internal amps of their speakers from a proprietary Bruno designed NCore type amp to a Purifi based design. They aren't claiming the newer models sound better and didn't change the model name or the published specs. 

 

That said, there are some differences that may make a difference to you:

 

The Purifi and Nilai are designed to work with 2 ohm loads, the others aren't - if my memory serves me correctly.

 

If you want to play around with op amps/buffers, that's another consideration of which model you might want. 

 

The newer power supplies for the newer models are superior to the older ones. 

 

The March Audio and Apollon are regarded at forums where they discuss this stuff as having very good build quality. 

 

The March Audio buffer got a rave review from Bruno himself. Said it was better than his. 

Yes, I think you are 100% right. Once SINAD goes over 96db there is not much difference. Actually, distortion due to clipping becomes more important. 

You are also right in that some features may be relevant for my specific case. Surely, not the 2 ohm capability. My current speakers are 4-6ohm. And even if I change them at some point, I doubt I will get speakers that are close to 2 ohm.

Sure, I love to tinker with the sound. So, I would benefit of being able to do that, in that case the clear winner is the VTV Purifi with its Custom buffer that allows API and DIP8 op amps without much struggle. 

Aesthetically, I do not have much preferences, not for now at least. 

When you mention the newer power supplies, you are referring to the power supply that comes with the Nilai kit? or which one?

Be wary of class D with speakers that have good treble transient response, you will find yourself chasing treble gremlins from other components in the system. Nothing wrong

with that if you have the time and money. Apollon is a brand frequently recommended for having good input circuit options

On 1/14/2024 at 8:05 AM, davide256 said:

Be wary of class D with speakers that have good treble transient response, you will find yourself chasing treble gremlins from other components in the system. Nothing wrong

with that if you have the time and money. Apollon is a brand frequently recommended for having good input circuit options

Could you be more specific and describe what type of "treble gremlins" might be introduced?

I ended up getting an Apollon NCx500 Stereo. I had Apollon and VTV as strong options. At the end, as much as the custom VTV buffer would let me use the Weiss discrete op amp if needed, a friend of mine told me his experience with Stacatto op amps and Sparkos op amps, both able to fit in the Apollon amplifier without much modifications. So, with the need to fit big discrete op amps such as the Weiss no longer factoring in, and taking account the aesthetics, I decided to go for the Apollon. It should arrive in one week or so. I will post my impressions here. 

4 hours ago, Allan F said:

 

Could you be more specific and describe what type of "treble gremlins" might be introduced?

Glare, peakiness that less capable amps masked because of slower transient response or poorer linearity in the treble region. Magnepans are very unkind to treble problems

Just a short update. The Apollon NCx500 arrived yesterday. Packing was not the best, but maybe customs changed it. Surely, customs opened the box so that is a possibility. When I opened the box, the amplifier was only protected with a very thin paper and nothing else. Surely, it had some styrofoam corners but that was all. Not impressed by the packing to be sincere.

I hooked it up immediately and started listening, testing the different gain settings. I tried them all but the highest. Having the 2 volts coming out of the Mini DSP Flex, I mainly listened to a lot of music in the third setting, one before the highest. The first two settings did not provide enough power to make a real difference. The first and second were close to the max power (regardless of distortion) provided by the Fosi V3. 

It is all subjective below and, surely without a doubt, it is all specific to my case. So, in that sense, my comments only apply to my specific situation and pertain to my experience with less than 10 hours with the amplifier. 

Pros:
- Soundstage became 20-30% wider horizontally
- Instruments were easier to discern in space. 
- Bass became louder and tighter. 
- Background is really dead.
- No hum and no noise when turning the amplifier on or off. Surely, if the amplifier is turn on or off in the right sequence with regards to the other components.

Cons:

- Soundstage depth got reduced. 
- Frequencies around 10khz to 15khz became more prominent. They are not louder than before, but probably due to the higher Sinad they are easier to discern.
- Frequencies from 80hz to 300hz, the midrange, are somehow lost in the soundstage. This did not happen with the Fosi V3. Still, too early to even confirm this properly. I will play with some PEQ in the Mini DSP and see what I can do. Some songs that have a prominent midrange eq, around 80 to 300hz, do not have that problem. I should say that the portrayal of voices by this particular amplifier, in my short experience, is not too pleasant to my ears. And knowing my friends, many of them who are talented musicians and also listen to a lot of music, they will share my opinion. I did spend a couple of hours moving the speakers closer to the back wall, and away from the wall, as well as placing them further apart or closer to each other (to reinforce that center midrange image), but this sound signature did not change much.

I will listen further to the amplifier with the higher gain setting and report back. For now, unexpectedly, I find myself in the side of those who want to go by the numbers, or the efficiency of Class D, but find that regardless of the great measurements performance, some Class D amplifiers simply do not produce a pleasant sound. And when I say pleasant sound, I am clearly being 100% subjective to what I like. Because, beyond the numbers there is that learned experience, that develops into taste.

Until now, and this is still very early, I would dare to say that regarding the critical frequency range of 80hz to 300hz, where most voices fall, the Fosi V3 with its stock op amps sounds better (in my system, in my room and for my ears and for my mind) than the Apollon NCx500. 

I truly hope that as I further experiment with the Apollon gain settings, speaker position, and even PEQ in the Mini DSP, that statement above will radically flip to the other side.

Sincere subjectivity...

do try a fast tube pre in front of the amp. The experience I had was that SS pre + class D was unpleasant in mid range

On 1/13/2024 at 10:38 AM, firedog said:

The March Audio and Apollon are regarded at forums where they discuss this stuff as having very good build quality. 

Another highly regarded manufacturer is boXem,Audio, located in Luxembourg.

3 hours ago, davide256 said:

do try a fast tube pre in front of the amp. The experience I had was that SS pre + class D was unpleasant in mid range

Yes, thanks, I will surely try that. I wonder if a Schiit Saga would be enough to smoothen and flesh out the midrange. 

I already tried even the highest setting and it did not improve much. 

9 minutes ago, alanbd said:

 

Yes, thanks, I will surely try that. I wonder if a Schiit Saga would be enough to smoothen and flesh out the midrange. 

 

I already tried even the highest setting and it did not improve much. 

Older tube pre-amps, like an Audio Research SP-16 would be what I would be looking at. Or something similar.

7 hours ago, alanbd said:

 

Yes, thanks, I will surely try that. I wonder if a Schiit Saga would be enough to smoothen and flesh out the midrange. 

 

I already tried even the highest setting and it did not improve much. 

Yea... no. Get something good. The Saga wont be a quality match for the class D resolution. Audio Research has always had good transient response for tube gear

but they are not cheap. A Decware pre might also be  a good choice

10 hours ago, davide256 said:

Yea... no. Get something good. The Saga wont be a quality match for the class D resolution. Audio Research has always had good transient response for tube gear

but they are not cheap. A Decware pre might also be  a good choice

I get it. Thanks. Let me see what I can find. What about Audio Research SP-8 or SP-10? are these also good choices? And what about a Conrad Johnson PV-5? 

35 minutes ago, alanbd said:

 

I get it. Thanks. Let me see what I can find. What about Audio Research SP-8 or SP-10? are these also good choices? And what about a Conrad Johnson PV-5? 

IF you can get an SP-8 or 10 or Conrad Johnson - great. The only reason I suggested an SP-16 is the tubes used are easy to find - 12AX7 tubes. Some of the others use esoteric tubes.

The Class D journey continues....

I was able to do a couple more listening sessions and the first fact is that I noticed that I develop listening fatigue way faster with the Apollon NCx500 than with the Fosi V3 or with my previous NAD 3020 D. 

I did further testing with all the gain settings in the Apollon but the sound signature did not change much.

I also played with the Parametric Equalizer in the Mini DSP Flex trying to bring out the midrange and further flesh out the sound. It did not work. The sound was better when I added anywhere from 3 to 5db around 200hz with a Q of 1.5 or so, lifting a bit the surrounding frequencies. But, not even that was able to fix the problem with the midrange. Surely, that EQ brought out the midrange, but it did not round the edges. The sound was still very harsh and flat in the midrange.

Then, a friend of mine brought a inexpensive Aiyima T8 Tube preamplifier, it only has one tube. I put the Aiyima in the chain right between the 2 volt output of the Mini DSP and the input of the amplifier. That worked much better even when the Aiyima had just the stock tube. It also made the soundstage smaller and the sound muddy. But, we are bringing a western electric 396A tube this Friday and that should work better in the Aiyima T8. I am just doing this test with the Aiyima to taste how the sound can improve. If it goes somehow well, I will have to buy either a tube preamplifier such as an Audio Research SP16 or Tube4hifi SP14, or even the Elikit TU-8500, which are all in my price range.  But, if what the Aiyima brings with the WE tube is not promising then I will just sell the Apollon. 

Something I noticed when I was listening with the Aiyima tube preamplifier in the chain is that despite the fact that everything got somehow muddy and the elements in the soundstage lost pinpoint accuracy, the sound was way more pleasant, engaging and non-fatiguing. So, that is something to think about. 

My friend also brought an Aiyima 08 Pro amplifier, no tubes. And we hook it up replacing the Apollon, without the tube preamp, just with the Mini DSP. The sound was way fuller (although not as accurate and clean as with the NCx500), the midrange was way more natural and full bodied.  If I need to choose, I would easily prefer to lose some of that defined imaging and horizontal separation in the soundstage that the NCx500 provides for a more natural midrange and a more non-fatiguing sound.

Just today, before packing the amplifier. I decided to reset my whole speaker position to zero and turn off the subwoofer. I followed the Sumiko method with Jennifer Warnes´Ballad of the Runaway Horse, as I have done several times. And, wow, what a difference. Surely, the edges are still there, but the center image is solid like a brick, and midrange is not recessed anymore. It is incredible how much change pays to properly position the speakers. 

Surely, there is still much to improve, to give a more 3d character to the center image and to smooth out those high frequencies, but having a solid center midrange that is good starting point. I will get the Western Electric 396A tube, and will do a test to see how far can tube preamplifier can take me. 

Now, that I am starting to see the real sound of this amplifier, I think it needs a good tube preamplifier that does not color a lot the sound, just softens the edges, gives presence, and leans a bit on the side of neutral (as opposed as super warm). 

I have an Apollon arriving today, thankfully I’ve already been thru the class D “teething” process with OA GaN monoblocks. Even though I lose transient response at frequency extremes, a MZ2 used as tube pre doesn’t bite/ grunge the way a SS Topping Pre90 did in mid range.

9 hours ago, davide256 said:

I have an Apollon arriving today, thankfully I’ve already been thru the class D “teething” process with OA GaN monoblocks. Even though I lose transient response at frequency extremes, a MZ2 used as tube pre doesn’t bite/ grunge the way a SS Topping Pre90 did in mid range.

¨Teething¨ fits the bill. Having said that, once I managed to position the speakers in the right place (after three hours), the center image was very solid. 

I use the Mini DSP as a preamplifier since I can connect even the phone pre to the Mini via the analog input, and I can bluetooth to the Mini and also connect a USB to my laptop and use the DAC of the Mini. For now, it is more than enough. I would only add a ¨second¨preamplifier, a tube one, if the tests with the mini Aiyima T8 give promising results. 

Also, once I locked the speakers in position, since the midrange came alive, the frequency spectrum was way more balanced and so the major issues with harshness were gone. But, not the ¨teething¨, for that I need tubes. Even using the a PEQ curve in the Mini DSP will not solve it. 

The challenge, when the time comes, will be to find a tube preamplifier that round the edges, adds presence, give a bit of tube bloom and decay, without muddying too much the sound or cutting dbs at the extremes of the frequency spectrum. That is a tough bill, I was contemplating a Supratek pre but I would really prefer something small with a small footprint. 

2 hours ago, alanbd said:

 

¨Teething¨ fits the bill. Having said that, once I managed to position the speakers in the right place (after three hours), the center image was very solid. 

 

I use the Mini DSP as a preamplifier since I can connect even the phone pre to the Mini via the analog input, and I can bluetooth to the Mini and also connect a USB to my laptop and use the DAC of the Mini. For now, it is more than enough. I would only add a ¨second¨preamplifier, a tube one, if the tests with the mini Aiyima T8 give promising results. 

 

Also, once I locked the speakers in position, since the midrange came alive, the frequency spectrum was way more balanced and so the major issues with harshness were gone. But, not the ¨teething¨, for that I need tubes. Even using the a PEQ curve in the Mini DSP will not solve it. 

 

The challenge, when the time comes, will be to find a tube preamplifier that round the edges, adds presence, give a bit of tube bloom and decay, without muddying too much the sound or cutting dbs at the extremes of the frequency spectrum. That is a tough bill, I was contemplating a Supratek pre but I would really prefer something small with a small footprint. 

I’m waiting on an LTA Velo pre, should show up this month. And hopefully get closer to the Pre90 at frequency extremes. Nice thing about the Apollon amps is they also have RCA input

8 hours ago, davide256 said:

I’m waiting on an LTA Velo pre, should show up this month. And hopefully get closer to the Pre90 at frequency extremes. Nice thing about the Apollon amps is they also have RCA input

The LTA Velo looks great and probably sounds amazing.  So, you are using headphone amplifier as preamplifiers? I guess that the impedance is not an issue since you are using line level inputs in your real amplifier? and I wanted to ask you, what was your experience with the Orchard Audio Gan amplifiers? and did you order a Purifi, Nilai or NCx500 from Apollon?

Last night, I received the WE396A tube, non D Getter. I placed it in the tiny Aiyima T8 and the improvement in sound was nothing short of dramatic, all in all very positive. I lost significant focus in imaging, mainly in instrument separation and soundstage accuracy, but the sound became very pleasant. I also lost some dbs from 12Khz up, but I gain some dbs in the bass region  although probably the bass became a bit loser. The soundstage did not shrink horizontally, just lost some focus, but it gain a lot of depth. I am amazed by this tube. I have a GE 5 star triple mica, and a Russian 63n, tube coming to further experiment. 

Having said that, the midrange was the best i have been able to extract from the Apollon NCx500 and that may be enough to close the deal. I listened to some of my classic jazz favorites, (Hawkins, Webster, Quebec, Peterson, etc) and it was very a pleasant and long session. Long is important because I did not develop any sound fatigue. 

I will buy an Aiyima T8 (the same one I am using now) for now and relax a bit. And then later down the year, I will take the time to choose a very good tube preamplifier (or a headphone amplifier that serves as pre) but that has a small footprint.

In the meantime, I can gain some further body in the sound when I soon change my speaker cables from the incredible Duelund DCA16GA to the Duelund DCA20GA.