Good Class D amps ??

[Matias]

I have a W4S STI-500 mk.2, which uses a pair of Icepower 125ASX2 in bridge mode and a custom buffer. Having owned and tested different powerfull class AB integrateds in my system before, I miss nothing in sound quality and have lots of pros in heat, power consumption and price. Love them.

[Matias]

18 hours ago, jmpsmash said:

 

So it has been decided. I will get the NC500 w/ Sonic Imagery opamp from Nord.

 

And my current NC400 has already been fixed. Super fast shipping from Hypex arrived from Netherlands in less than 2 days and swapping in the new module only took 10 mins. Now it is being burn in around the clock. It will take a week for it to match the hundreds of hours that I have on the other channel.

 

After the NC500 arrives and burned in, I can do a comparison. And I will need to find a new home for the NC400. I am tempted by the ST-10 too actually.

 

 

Also check out the Apollon NC800 SL which is also opamp+NC500 based.

https://www.apollonaudio.com/apollon-hypex-nc500-class-d-amplifier-nc800-sl/

[Matias]

I prefer the stereo version because:

- The components separation is practically the same (separate output stages, buffers, power supplies all a few centimeters apart should not interfere with each other);

- I already have longer 2.4m speaker cables (and they have better liquidity in the market, easier to buy/sell);

- Needs only 1 power cable so that I can spend more in a single cable than spending half in 2 power cables.

 

As for Nord x Apollon, there is also the chassis design, which one considers is prettier than the other. Very relevant! ?

[Matias]

On 11/29/2018 at 8:58 PM, jmpsmash said:

 

I ended up getting the monoblock from Nord. They are quite comparable. They are pretty much just the same ideas with the same components in the input stage (Sparko regulator and Sparko/SI op amps). Interesting that you think the Apollon has better layout, the only difference i see is the orientation of the power supply. they have the opposite orientation and the Nord one ended up with shorter cabling from IEC to PS and from PS to the input stage board.

 

And I ended up ordering yesterday the Apollon NC800 SL with Sparkos opamp, but I am going to test the SI from a friend as well.

[Matias]

2 hours ago, jmpsmash said:

 

Very interested to know what you think the differences are. Took me a while to decide on which one to get and at this point I am still not sure if getting the SI is the right choice. the Sparkos are $80 each.

 

Unfortunately it is going to take a long time until I can test both opamps in my system. But I really do not expect anything different from what is already described in both Nord and Apollon websites: Sparkos warmer and more laid back, Sonic Imagery leaner and higher clarity. System matching is to the owners' taste. I tested the Nord with Sparkos and it sounded excellent in my system.

[Matias]

Nord has a new Mk.2 version now of the NC500 amp, with different buffer board and opamps:

https://www.nordacoustics.co.uk/copy-of-nord-one-se-nc500

[Matias]

27 minutes ago, Ralf11 said:

I'd really like to know how the Nords compare against PS Audio's Stellar Gain Cell amps...

 

I understand that the PS Audio Stellar amplifiers are based on the new ICEpower AS modules: 2 x 300AS1 on S300, 1 x 700AS1 on each M700, plus their custom buffer. I read that currently the best ICEpower module is the 1200AS. And also that both Apollon and Nord sell both nCore NC500+discrete opamps and ICEpower 1200AS, and both say that the best sound quality is the NC500.

Having said that, of course the ideal would be to test all options in the same system. I would very much like to read such a shootout review.

 

PS: Apollon also has a "PRO" buffer board that accepts the larger opamps from Sparkos or Sonic Imagery, but not the smaller DIP8 versions, although they said not be night and day difference.

[Matias]

3 hours ago, GeneZ said:

 

Gain Cell is a means to adjust the volume of a preamp, sans a typical attenuator.  Rather than attenuate the full signal of a signal like a volume control does, the gain cell adjusts the output voltage of the preamp to raise and lower the volume.  Its not a variable resistive device like a volume control.  That's how I understand it.  Paul McGowan explains it in this video.

 

https://www.youtube.com/watch?v=xFdZRLwUI0Y

 

It makes a lot of sense for integrated and preamplifiers, anything with volume control. But the Stellar power amps do not have volume controls. So the gain cell has fixed gain.

[Matias]

6 hours ago, jmpsmash said:

 

He told me about it before I made my purchase. I didn't want to try something unreviewed so I got the mk1 version. He said there will be an upgrade path.

 

These amplifiers are extremely modular. Unscrewing the Nord buffer REV C board and plugging in the REV D board might even be user replaceable. And since the REV D has DIP8 small opamp socket as well as the larger opamp socket, users could upgrade the board first and the opamp later.

[Matias]

Hmmm seems my post was deleted, so here it goes again.

 

Mivera is selling the ICEpower 1200AS with Ghent's chassis for starting price of $799. Great price.

 

And one may buy 2 and use them in mono for 1.200W at 4 ohms.

 

https://www.miveraaudio.com/product-page/icepower-1200as2-amplifier

[Matias]

On 12/3/2018 at 12:55 PM, Matias said:

 

And I ended up ordering yesterday the Apollon NC800 SL with Sparkos opamp, but I am going to test the SI from a friend as well.

 

If someone suspects I am affiliated with Mivera that post above should make it very clear that I am not.

[Matias]

A week ago I compared my Wyred 4 Sound STI-500v2 integrated, based on 2 x ICEpower 125ASX2, against a friend's Nord NC500 stereo amplifier with Sparkos SS3602 opamps. Since I had no preamp, to make things comparable, I set the integrated to bypass the XLR inputs and used the Sabre based volume control of my Femto DAC for both. Volume was around 60-70 during the session with my Thiel CS3.7 speakers.

 

The STI-500 v2 is very good, but the Nord was a little better. Tonality was similar, but the Nord had a little better clarity specially on the mids and lows, which also extended a little lower with better control. Voices were also a little better defined and details and separation also a touch better. Highs were kind of similar imo.

 

It was not an big difference, but enough to justify an upgrade, in my case to the Apollon NC800 SL with the larger Sparkos SS2590 opamps . And also add a dedicated preamp too, probably a W4S STP-SE level 2. Compared to the price of such a preamp + power amp + cables combo, the W4S integrated has the better value though.

[Matias]

Isolate from the desk with IsoAcoustics products, they work great.

[Matias]

14 minutes ago, GeneZ said:

 

 

Definitive Audio Pro Monitor 800's?      Not to be done.

 

  ? Great little speakers for desktop if you have means for bass reinforcement. 

 

They are tiny and only have three legs built in. Too small for Iso Acoustics  (which I have)...............................

 

 ISO Pucks should do, 3 pairs: https://www.amazon.com/IsoAcoustics-Iso-Puck-Isolation-Studio-Monitors/dp/B06ZZ72LL6

[Matias]

I would really like to see NuPrime's measurements like the typical THD x power graphs by frequency, as ICEpower and hypex use. I could not find any measurements on their website or manuals... Not that I am an objectivist only but still I enjoy analyzing the differences. Specially with all the hype around the Evolution One.

[Matias]

@John769 I went the opposite direction, ordering the more expensive PRO opamps to get even higher performance and higher price. But I agree, the NC502MP based stereo power amplifier has a great price.

 

Prices from Apollon website:

- NC800SL (NC500 based - 2 x 400W at 8 ohms) with standard SI opamp - 1575 euros.

- NC800SL (NC500 based - 2 x 400W at 8 ohms) with PRO opamps - 1875 euros.

- NCMP700 (NC502MP based - 2 x 350W at 8 ohms) - 825 euros.

 

Plus optionals.

 

That is half the price for the 502MP. Never listened to them though...

 

 

[Matias]

18 minutes ago, esldude said:

https://www.audiosciencereview.com/forum/index.php?threads/review-and-measurements-of-nuforce-sta-200-power-amp.5039/

 

Measured results for a Nuprime amp.

 

Thanks. I was thinking more of the ST-10 and Evolution One amps. But Amir seems to have more entry level DACs and amps available to test in general. Maybe it is what people borrow him so he has not much of a choice in this.

 

Also the datasheets of both ICEpower and Hypex show power x THD for 3 frequencies: 100Hz, 1kHz and 10kHz. And usually the 10kHz one is differente from the others, so it is quite interesting to see how each module handles the frequencies differently. And Amir only measures 1kHz. Still I enjoy reading his measurements.

[Matias]

Actually 6.67kHz instead of 10kHz, no Edit button...

[Matias]

@GeneZ ICEpower ASP has quite a bit of THD in 6.67kHz compared to the newer ASX2 and AS, or the nCores. And they are still being sold today (Rotel RB-1091 and W4S SX1000R for example).

 

I decide on both measurements and listening. Just bought my Apollon NC800SL PRO a few weeks ago.

[Matias]

Nord (and Apollon) offer both SI opamps. The 2 larger pro ones are said to be a little better sounding. But seems like the pro opamps are temporarily unavailable.

[Matias]

@GeneZ what I meant about power x THD measurements are the graphs that both ICEpower and Hypex use on their datasheets.

 

They were done with Audio Precision equipment, using 4 ohms impedance (8 ohms too but I show 4 because it is more relevant IMO).

 

Blue line is bass (100 Hz), green line is mid range (1 kHz), red line are highs (6.67 kHz, sibilant area of the frequency spectrum).

 

All power graphs end up in a high rise until they reach 1%, which is normally the standard THD percentage that manufacturers rate their power in a given impedance.

 

The top graph is an older ICEpower 1000ASP. Notice how the bass line is descending, meaning the distortion is somewhat constant but in relation to the increasing power level, its percentage goes down. But the same does not happen to mids and highs: the distortion increases with more power. Specially highs are all over the place up to 0.2% mid power. Higher distortion in highs may be related to the bad reputation class D got until a few years ago (1000ASP was released about 2003?).

 

Next is the newer ICEpower 125ASX2 in stereo (SE mode),  not bridged (BTL mode). The mids green line is better behaved, low and closer to the bass blue line. The highs red line is also a lot lower, specially in low power, and always below 0.1%. All 3 lines reach 1% in a lot less power than 1000ASP, but that is not my point here. This module was released about 2011.

 

Next is the newest ICEpower 1200AS. Again all 3 lines are very well behaved with the highs red line reaching a maximum of 0.01% mid power, which is quite a big step in performance. This one was released in 2017.

 

And last in line is nCore NC500. All lines are very well behaved, reaching incredible 0.001% mid power, including the highs red line! This is seriously low THD, closer to DAC figures than regular power amplifier figures. Highs are 200 times less distorted mid power than 1000ASP! nCore NC500 was released about 2011.

 

Notice that this performance increase is NOT directly related to switching performance:

- ICEpower 1000ASP - 350 kHz idle

- ICEpower 125ASX2 - 450 kHz idle

- ICEpower 1200AS - 500 kHz idle

- nCore NC500 - 450 kHz idle

Even Hypex datasheet says: "Commonly expressed creeds that an amplifier’s suitability for high quality
audio can be read from these numbers (switching frequency in particular) are ill informed."

 

That is why I wanted to see the custom NuPrime amplifiers being measured this way, to see how they compare.

 

(I am not 100% sure about the release dates, correct me if I am wrong)

 

Then I see Stereophile's measurements of Bel Canto REF600M, and the THD 1kHz 8 ohms line (Fig. 4) is a lot higher and increasing gradually. This is deliberately designed and implemented on the buffer, because the power stage is lower as we saw on the raw NC500 graphs.

https://www.stereophile.com/content/bel-canto-eone-ref600m-power-amplifier-measurements

 

 

[Matias]

@GeneZ I agree, by no means I am 100% objectivist. Heck, my system has a lot of expensive power cords, fuses and tweaks. I totally agree with you that "how does it sound" is the golden rule. Still, those measurements are interesting and should tell part of the story.

 

And with NuPrime being so hyped lately, I wonder how much better their measurements could get than the already fantastic nCore NC500.

[Matias]

To be fair, even though I am curious to see THD measurements, truth is that big names like Nelson Pass and Dan D'Agostino do not care much about lowest THD. Instead they just design their amplifiers just sound good.

[Matias]

1 minute ago, crenca said:

 

I don't know about Dan

 

Hear it for yourself: 

 

[Matias]

That is why I find interesting to have lowest distortion on nCores and color at will with buffers and opamps to suit ones system and taste.