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In Reply to: RE: Magnepan color recommendation posted by 4everyoung on July 07, 2017 at 03:07:51
The ribbon maggies reveal the grain in most class D amp's top end. However, there are several kinds of class D amps. NuForce and NuPrime (same engineers) use a 600khz sine wave modulation, while B&O and Hypex NCore and Ucd use 400khz triangle wave carriers. The top end of the NuForce amps is better, their midrange is impeccable. The top end is not on par with a good tube amp or a great SS class A amp. The lack of compression on the Devialet and other feed forward amps and on the NuForce/Prime is very impressive. Well executed class D based on the other OEM boards can do great from midbass to midrange.
In the deep bass, class D amps tend to fail in maintaining current due to insufficient storage capacitance to bridge the 60hz at high current. Maggies being current hogs at low frequencies really show up the class D amp's limitations.
With these observations I have no trouble understanding Wendell's issue with class D. But try to drive your speakers with your current amp first and then line up some class AB candidates to try out to see if you can do better.
Follow Ups:
"In the deep bass, class D amps tend to fail in maintaining current due to insufficient storage capacitance to bridge the 60hz at high current. Maggies being current hogs at low frequencies really show up the class D amp's limitations."
That is a power supply issue, not a Class-D issue. There are numerous Class-D amps (both commercial and DIY) that utilize linear power supplies with large capacitance reservoirs.
You should read up on the switching frequency and type of modulator used in Ncore technology. (The white paper has been available for a few years now.)
https://www.hypex.nl/img/upload/doc/an_wp/WP_Ncore_Technology.pdf
Dave.
There are class D amps with linear supplies that should not have the problem. I have not heard any of them since the HCA2.
I perused the Ncore white papers looking for an attempt to get better resolution. Instead they spoke about the tradeoff between better resolution and power performance and they pushed for the power side. So I dropped the Ncores as uninteresting and spent no more time looking at them and the commercial designs that use them. I follow the occasional review of Ncore or UCD amps but that is as far as it goes. I must say that they get very good reviews.
Since the HCA-2? Maybe it's time for you to revisit this technology? :) It's no wonder you experienced "grain in the top end" with that POS amp as your most recent listening reference.
Regards Hypex, if you became uninterested that was a mistake. The Ncore amplifiers push the bar higher than it's ever been for Class-D performance......both from an objective testing standpoint and from the subjective evaluation side. (IMHO on that second part.)
You seem to have an answer for everything on the PSA. I think you should actually get some experience with these type of amplifiers before offering any further opinions on them.
Dave.
I may be out of date. The technology continues to improve but I have not sampled recent designs. Any suggestions on linear PS class D amps I should seek out?
Yeah. The new Ncore-based ATI amps.
Dave.
There seems to be radio silence on ATI's new NCORE amps. Not much posted out there.
assembler of common parts used most often by the DIY community.
What's new to say? Do they have a really cool box?
A DIY friend of mine who spends a lot of time at the diyaudio forum and has built a number of class D amps, laughed yesterday when I asked him what was so special about the new NCORE amps. He said there was nothing special, at least in his opinion.
My friend's latest project was a low power class A amp, so maybe he has given up on class D - at least for now.
They're newer models. Also, ATI doesn't have the audiophile nose-in-the-air appeal many "high-end" amplifier manufacturers have so they will never garner widespread interest from that niche.
However, there are reviews and usage reports already available.
https://www.soundandvision.com/content/ati-at527nc-and-at524nc-amplifiers-review
Dave.
That was the only review I saw. It was more a home theater review.
ATI apparently owns Theta, so they should have some audiophile chops.
Their AT542NC appears to be 4 Ohm stable, not 2. Would Maggies put them on the edge ?
I don't see any claim for 2 ohm operation with the AT54X series amps. The bridged configuration would yield a 2 ohm load on each amplifier with a 4 ohm speaker.
So, I think probably, the AT52X series would be preferable in this application.
The amplifier I have is an NC500-based unit that doesn't have any problems with my (4 ohm) MMG's.
Dave.
Kessler is a well regarded designer in his own right, and ATI is a big OEM manufacturer. The Theta Ncore Prometheus monos date back to 2013 so they had been at it for a while.
The Theta Ncore Prometheus uses the NC1200 which are supposed to be stable to 2 Ohms and are not running bridged. I would like to hear these.
The reviewer compared it against his reference ML334 amp (ML's entry level stereo amp against Theta's mono-blocks). A more appropriate comparison would have been against the ML335 or ML336 (similar power and price).
ML334:
Rated output power: 125/250/500
Price: $5,900
NC1200:
Rated output power: 400/700/1200
Prometheus Rated output power: 250/500/850
Prometheus Price: $12,000
ML335:
Rated output power: 250/500/1000
Price: $7,900
ML336:
Rated output power: 350/700/1400
Price: $9,500
I have the ML336 in house and think it would be an interesting comparison.
The Maggie 4 ohm load is mostly resistive without dips. If the amp does 4 ohms well then you are just fine.
My Maggies are not on edge.
Do you have some two ohm Maggies?
Dave.
4 Ohms is supposed to be an average, not the exact value across the entire frequency range. Maggies vary less than Stats from what I understand, but they still vary.I always try to buy amps with a safety margin and not run them on edge.
Their AT542NC are also bridged at 4Ohms which would appear to also put them on edge.
Maybe I am being paranoid.
Edits: 07/09/17 07/09/17
4 Ohms is supposed to be an average, not the exact value across the entire frequency range.
While I certainly cannot say that every Magnepan product is like the ones Stereophile tested, the "exact" values seem to not delve into the electrostatic top octave realm.
MG 1.6
MG 3.6
As for me, I find them pretty darn linear in their impedance profile. Apparently, Wendell pulled the plug on reviews afterwards since even JA concedes:
"As I have written before in these pages, measuring physically large speakers with in-room quasi-anechoic techniques is in some ways a fruitless task. The usual assumption, that the measuring microphone is very much farther away than the largest dimension of the speaker being measured, is clearly wrong. "
Some people incorrectly think if an amp can drive smaller Maggies they can also larger Maggies because they are all 4 Ohm and @ 84dB rated.I have empirically found that not to be true. The spec'd ratings don't account for the wider frequency range and larger square footage of drivers to be controlled. What works well on MMG's or 1.6's may not be able to control larger panels in the same fashion.
Edits: 07/13/17
I thought the conversation was about impedance dropping below 4 ohms.
Admittedly, I've only heard large Maggies (20.1/3.6/3.7) using either 200 or 300 watt amps.
E-Stat, Excuse my rambling. FWIW, I have heard them from 100 - 2,000 WPC including passive and active biamping. So far, active vertical biamping appears to be the best that I have heard, but the new *.7(i) series is closing the door to that option. I haven't heard any tri-amping yet.
Edits: 07/15/17
Looking at the impedances of speakers that were used in the test and comparing to Maggie 3.6 which is the last ribbon for which there are measurements. You can see that the maggie load has a very mild curve and its only fault is the current drain due to low sensitivity and high back EMF at low freq./high excursion.
So if there is a solid 4 ohm rating the amp should not hit any snags driving the maggie till it just plain runs out of power.
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