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Class D is just Dandy!

I thought it was time we had a pro- Class D thread. There's plenty of threads about comparisons, or detractors of Class D.

That's fine, you don't have to like Class D amps, and if you don't please go participate on one of those threads.

For those of us who are very happy and excited about having musical, capable amps that we can afford to keep on 24/7 and don't require large spaces to put them in, this thread is for you.

Please share your experiences with class D amps!
erik_squires
guidocorona
4,298 posts
 

@noble100 

Tim, I love your quote from the upcoming issue of Acta Philosophica Refutata (Vol XXVIII, Feb 29th, 2017.... I have not yet received this issue *Grins!*


Jokes aside, it is my understanding that this conjecture -- it is not a theory in the scientific sense of the word -- asserts that switching frequencies of at least 1Mhz are expected to reduce harmonic distortion to 0.005% or better.


It happens that 0.003% has already been achieved for the entire audible frequency band: Mola Mola Kaluga which uses enhanced versions of NCore NC1200 and its matching power supply. ROwland M925 and M825 are also below 0.005% while using stock NC1200 modules.


But let us come down to Earth from the audiophrenic stratosphere above.... The reasonably priced $2500 Merrill Teranis, based on the lower cost NC500 NCore module, declares a THD of 0.005%, thus achieving the preported distortion goal, using a trickled-down version of NCore, with is mainstream switching frequency of about 450 Khz.


G.


erik_squires OP
15,990 posts
 
Hi @guidocorona

The general principles that a higher switching frequency with better transistors yields lower distortion and higher efficiency is not really in question.

I question the audibility of anything measurably better than the current state of the art from ICEPower, nCore or Pascal. I question the importance of 0.03% distortion vs. 0.003% vs. 0.00000001%.  Having a baking scale that measures in femto-grams does not help you bake a better cookie.

If there are audible benefits, I think the answer will be somewhere else. Such as linearity (lack of compression), noise shape or handling difficult to drive speakers (complex impedance curves), etc.

I won’t get excited at all right now over an amp with a high switching frequency, or lower distortion. Especially not at high end prices.

There may be audible differences between the major Class-D technologies, but harping on things I think were solved a decade ago I don’t think will help me find a "better" sounding amp. Maybe a "different" sounding amp though.

Best,

E


guidocorona
4,298 posts
 

Hi Erik, the inability of class D amps to handle difficult loads is one more urban legend....  Most non-trickle down modules that I know have damping factors of 1000 or better, and deliver 30A or better..... NCore NC1200 for one thing drive my difficult to handle Vienna DIe Muzik, with their wild impedance curve, without batting an eye... Even the little Merril Teranis could do it without a sweat, once we raised its gain to 029dB.


In olden days, I heard a ROwland M312 (ICEpower 1000ASP) totally trashing the authority and harmonic resolution of a big Boulder 2000 series monoblock pair driving Die Muzik... Not only my opinion either... there were about 15 people in the room.



Guido

   

erik_squires OP
15,990 posts
 
I'm just saying that I am open to the possibility that different Class D amps, like their linear counterparts, may sound different on different speakers.

But if this IS true, I won't attribute it to Class D vs. linear.

I believe nCore's do have exceptionally low output impedance across the frequency spectrum compared to ICEPower so I'm not surprised. :)

It also depends where your speaker is difficult to drive. With my speakers, there's unlikely to be much difference since they are easy to drive. ESL's however have the hardest trouble at the top end. I would not be surprised if the difference between an nCore and ICEpower module was more measurable/audible with them.

Other speakers, like say Focal's with double woofers, are hardest to drive in the bass, a place where both nCore and ICEPower excel.

Best,

E
guidocorona
4,298 posts
 

 

 

Hi Erik, the big old ICEpower 1000ASP also had an output impedance of 1000… Perhaps that is one of the reasons why it outperformed the authority of the Boulder 2000 series in authority on Die Muzik…. Not sure of the damping factor of less powerful modules though.

 

The audible difference between an old ICEpower 1000ASP and an NCore NC1200 is that simple amps based on the old ASP1000 with little design around them did not sound terribly good, no matter how much they were broken in…. ASP 1000 gave the high current, the raw resolution, the compatibility with difficult speakers, but could sound quite harsh unless the designer created a solid input stage to raise input impedance and attenuate common noise….. The native power supply was somewhat weak in regulation…. The better amps used regulated custom SMPS, and at least in the case of M312 and M301 also an integrated power factor corrected rectifier to avoid any grundge contaminating the signal….. So much so that rowland created an external rectifier called PC-1 which could be used with some of his lower end ICEpower amps like M501, M201, and M102.

 

Here then comes NCore NC1200 with its companion NC1200/700 unregulated supply…. Turns out that a simple implementation of this module inan amp, even without the amp designer doing too much in custom active circuits, usually outperforms any sophisticated class D amps created round the older ICEpower 1000ASP modules. Then, if the designer does apply his more sophisticated input stages, power regulation, power supplies, and rectification to NCore…. Things sore.

Having said the above, I have not tried the latest generation of ICEpower 1000ASP, but I have heard that they are much more musical than the older ones.

 

Guido

 

 

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