NC400 THD+N vs Power

mgalusha · « **on:** 12 Aug 2012, 09:52 pm »

I had a few minutes today and ran a THD+N vs Power sweep on an NC400 into an 8 ohm load.

Noise dominates until about 3 Watts and then hovers around .001%THD until about 150W. This was with a standard 1kHz signal. Of course this doesn't come close to telling the whole story, it does show how low the distortion is until the power is pretty high. At the traditional 1% definition of clipping the graph shows roughly 250W into 8R. I use a non inductive load capable of handling over 4kW.

When I get a bit more time I'll pull 4 and 2 ohm graphs. I also looked at the FFT plot at 50W. The 2nd and 3rd harmonics were ~110dB below the fundamental and the 4th at about -120dB down and the rest buried in the noise floor. Basically the same as the 1W output.

mgalusha · « **Reply #1 on:** 13 Aug 2012, 02:03 am »

Two and four ohm loads.

dburna · « **Reply #2 on:** 13 Aug 2012, 02:42 am »

Hey -- is this my NCore?

mgalusha · « **Reply #3 on:** 13 Aug 2012, 03:04 am »

Quote from: dburna on 13 Aug 2012, 02:42 am

Hey -- is this my NCore?

The 8 ohm plot is indeed your amp. The 2/4 ohm plot is one of mine.

lowtech · « **Reply #4 on:** 13 Aug 2012, 06:05 am »

I wonder why published measurements differ from yours by such a significant amount. http://www.hypex.nl/docs/NC400_datasheet.pdf

JohnR · « **Reply #5 on:** 13 Aug 2012, 07:33 am »

Quote from: lowtech on 13 Aug 2012, 06:05 am

I wonder why published measurements differ from yours by such a significant amount. http://www.hypex.nl/docs/NC400_datasheet.pdf

They look pretty similar to me... the Hypex one is lower once you get below 0.001 but that could be simply noise floor. What difference specifically are you noting?

lowtech · « **Reply #6 on:** 13 Aug 2012, 01:39 pm »

Yeah, closer than I had originally thought. They appear to meet published spec.

a.wayne · « **Reply #7 on:** 27 Jun 2013, 02:08 am »

Quote from: mgalusha on 13 Aug 2012, 02:03 am

Two and four ohm loads.

Thanks for the effort and basically what is shown on the Hypex web site , with the effective sweet spot max at 100 watts regardless of load , (8,4,2) making 33 watts for best sonics ..

Rclark · « **Reply #8 on:** 27 Jun 2013, 04:53 am »

I doubt a human being could perceive any change in sonics with these amps. There's no audible "sweet spot", there's no spot on the dial where it's suddenly better than before. The SQ remains utterly consistent. This is something you have to experience.

Julf · « **Reply #9 on:** 27 Jun 2013, 11:03 am »

Quote from: a.wayne on 27 Jun 2013, 02:08 am

Thanks for the effort and basically what is shown on the Hypex web site , with the effective sweet spot max at 100 watts regardless of load , (8,4,2) making 33 watts for best sonics ..

That is what you see. What I see is a "sweet range" of 0 - 400W of "best sonics". I agree you probably shouldn't go much above 400 W "for best sonics"

jtwrace · « **Reply #10 on:** 27 Jun 2013, 11:05 am »

Quote from: Julf on 27 Jun 2013, 11:03 am

That is what you see. What I see is a "sweet range" of 0 - 400W of "best sonics". I agree you probably shouldn't go much above 400 W "for best sonics"

No doubt!

a.wayne · « **Reply #11 on:** 27 Jun 2013, 06:04 pm »

Quote from: Rclark on 27 Jun 2013, 04:53 am

I doubt a human being could perceive any change in sonics with these amps. There's no audible "sweet spot", there's no spot on the dial where it's suddenly better than before. The SQ remains utterly consistent. This is something you have to experience.

Broad sweeping statements huh, yes its not audible then why boast how low it is and shoot for more .

Frivolities aside

measure how much voltage is being used when listening I'm willing to wager the best percieved sonics is at the 33-100 watt range. This amp is at its best on speakers with high sensitivity 88db/w/m would be my assessment ...

Not best with super high or low sensitivity speakers ....

Regards

Rclark · « **Reply #12 on:** 27 Jun 2013, 07:21 pm »

Frivolity? That was a dead on accurate statement. The only sweet spot would be imagined, not heard.

a.wayne · « **Reply #13 on:** 27 Jun 2013, 07:32 pm »

Cake , eating, having ,
Yeah, so the same as the perception of Sound quality , imagined not heard, cant have it both ways, every system has a sweet spot..

Based on the Nc400 distortion spectra its best below 100watts , Measure the voltage, awaken .......

Rclark · « **Reply #14 on:** 27 Jun 2013, 07:59 pm »

Very true, it can be system dependent, but won't be the Ncore causing a sweet spot. On four separate pairs of speakers I've not been able to hear any difference at any volume excepting that I can't listen at full wallop for too long without attracting unwanted attention.

The amp is flat as a pancake. Quiet is just as refined and full bodied as it is when loud, same in between at moderate volumes. No difference. Try some

, you know you want to.

a.wayne · « **Reply #15 on:** 27 Jun 2013, 08:48 pm »

Contrary to your perception I'm not anti-D , I'm anti bad sound

so Yep , cant wait to place my order , hopefully some super NCore man will step up and help out with a demo , until then i'm on the fence , seeing the Rotels would shut down and the BelCanto's failed to excite ..

Rclark · « **Reply #16 on:** 27 Jun 2013, 09:17 pm »

I don't doubt that when you finally hear these tiny little beasts with their switching supply (the horror!), your ideas about modern day amp topologies will be expanded, and you'll be pretty happy. Cake indeed.

srb · « **Reply #17 on:** 27 Jun 2013, 09:38 pm »

I listened to the Ncores with the Salk HT2-TL speakers. Unfortunately, it was very apparent that they were a bit disappointing on the many vocals we listened to, as they rendered the vocals unnaturally thin and nasal compared to the AVA Synergy 450 and modified Naim amplifiers (both very good amplifiers in their own right) that got the vocals just right. They also were a bit shrill on super dynamic high frequency passages that the other amplifiers rendered without harshness.

The Ncores won for efficiency/power saving and a smaller enclosure, but were just lacking in sound compared to the other amplifiers. I was a little surprised after all the hype and for the fact that the Salk HT2-TL are probably fairly representative of a fair number of 4Ω, ~ 88dB speakers with conventional cone drivers and ribbon tweeters.

Class D amplifiers in general seem to have more variable results depending on the speaker type and load, and these were no different. I'm sure there are speakers that sound much better when paired with the Ncores, but these Salks were not one of them.

We all did agree that the little round Ncore modules were cute as a button, though. And that the Salk HT2-TL are very nice speakers.

I recommend an audition before purchasing.

Steve

Edited to correct the AVA amplifier model from Synergy 350 to Synergy 450

jtwrace · « **Reply #18 on:** 27 Jun 2013, 09:40 pm »

This is not a review thread, please keep this thread on topic.

Rclark · « **Reply #19 on:** 27 Jun 2013, 09:52 pm »

Given the sudden placement of this "review" and my own experience with these amps, I found the points humorous. And experienced the total opposite, on several speakers including my own Magnepans. Vocals are live, in your room, highs are beautifully rendered, often breathtaking.

I've already convinced three other people, who've posted here as well, I can quote them, to build Ncores and they blew their other amps away.I've received no angry PM's or backlash threads, only thanks for the heads up.