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I went from Class D to Luxman A/AB - And most of what you think is wrong

Hi everyone,

As most of you know, I’m a fan of Class D. I have lived with ICEPower 250AS based amps for a couple of years. Before that I lived with a pair of Parasound A21s (for HT) and now I’m listening to a Luxman 507ux.


I have some thoughts after long term listening:
  • The tropes of Class D having particularly bad, noticeable Class D qualities are all wrong and have been for years.
  • No one has ever heard my Class D amps and gone: "Oh, wow, Class D, that’s why I hate it."
  • The Luxman is a better amp than my ICEPower modules, which are already pretty old.

I found the Class D a touch warm, powerful, noise free. Blindfolded I cannot tell them apart from the Parasound A21s which are completely linear, and run a touch warm due to high Class A operation, and VERY similar in power output.


The Luxman 507 beats them both, but no amp stands out as nasty sounding or lacking in the ability to be musical and involving.


What the Luxman 507 does better is in the midrange and ends of the spectrum. It is less dark, sweeter in the midrange, and sounds more powerful, almost "louder" in the sense of having more treble and bass. It IS a better amplifier than I had before. Imaging is about the same.


There was one significant operational difference, which others have confirmed. I don't know why this is true, but the Class D amps needed 2-4 days to warm up. The Luxman needs no time at all. I have no rational, engineering explanation for this. After leaving the ICEPower amps off for a weekend, they sounded pretty low fi. Took 2 days to come back. I can come home after work and turn the Luxman on and it sounds great from the first moment.


Please keep this in mind when evaluating.


Best,

E
erik_squires
erik_squires OP
16,021 posts
 
At least I’ve given the manufacturers technical reasons behind it, you’ve given zip technical info on why the old technology is as good as GaN Technology.


You are the one who claims there are deficiencies which would be fixed. My point is and always has been:

  1. A measurement is not by itself audible
  2. I have encountered none of the audible claims you ascribe to Class D in general
  3. There’s no consensus on any of the technical items addressed in GaN amps being audible.


You are basing everything on literature, and very little on actual hearing and listening. Yes, I went from an old ICEpower module to Luxman, but hey, I would have gone from a Parasound A21 to a Luxman too. The idea that this proves all Class D are inferior or have a signature to all linear or GaN is just not in evidence. It's in your fandom.
georgehifi's avatar
georgehifi
10,312 posts
 

Keep plugging away Eric, you live with a technology that has been flawed since it’s inception.
GaN technology will finally get rid of these flaws of dead time and switching noise.

No one here knew what GaN was till I posted up about it’s development at EPC years ago, before the Technics SE-R1 was released, I said then it was coming for Class-D and it would finally take Class-D up into the hiend for being for midfi and sub use.
  
I suggest all to wait till this comes about and enjoy your linear amps till then, otherwise you’ll buy into a Class-D technology that will be very hard to sell, once GaN has taken hold in Class-D in an affordable way.
Cheers George
atmasphere's avatar
atmasphere
11,772 posts
 
Uh, George, GaN amps still need deadtime. It *reduces* the need but does not eliminate it.
Deadtime is not a major source of distortion in a class D amp; you can double the amount used above the amount EPC recommends and not be able to hear it. OTOH the accuracy of the encoding scheme plays a much larger role in how much distortion is made.

The reason Technics is switching so fast is not because they don't need any deadtime. Its been done to reduce the residual waveform to a very low level and open up the bandwidth of the amp.

BTW 'switching noise' really isn't a thing unless the switching frequency is really low, in which case the amp won't be suitable for audio. IOW you're simply not able to hear it or any knock-on effects- plain and simple. 

georgehifi's avatar
georgehifi
10,312 posts
 
BTW 'switching noise' really isn't a thing unless the switching frequency is really low,
Which it's artifacts are, even the non technical can see it in any Class-D's 1 or 10khz square wave from on the amps outputs, and in the phase shift the filter produces down to 4khz in many cases.

I know your bringing out your own Class-D amps just like Ricevs is also using off the shelf boards (maybe slightly modded) that's maybe why the negatives toward the GaN Technology, that now even Texas Instruments are behind.
  https://e2e.ti.com/blogs_/b/powerhouse/archive/2018/06/26/the-sound-of-gan    
atmasphere's avatar
atmasphere
11,772 posts
 
Which it's artifacts are, even the non technical can see it in any Class-D's 1 or 10khz square wave from on the amps outputs, and in the phase shift the filter produces down to 4khz in many cases.
You can't see switching noise on any frequency a class D amp can amplify. All that can be seen is a sine wave known as the 'residual'. You've been told this before. That sine wave is at the switching frequency of the amplifier; if you are saying you can hear 250KHz or 1.2MHz sine wave good luck trying convince anyone that you aren't a nutbag.


Regarding phase shift, filters in most class amps are set to 60-80KHz and are usually 12dB per octave; phase shift thus derived is less that you would see with a 6dB slope (with a 6dB slope phase shift can be seen down to about 1/10th the cutoff frequency). So the 4KHz thing in the statement above is just plain false. You might see something at 20KHz though, but it would be slight even on an older class D amp.

I know your [sic] bringing out your own Class-D amps just like Ricevs is also using off the shelf boards (maybe slightly modded) that's maybe why the negatives toward the GaN Technology, that now even Texas Instruments are behind.
We have our own circuit and are not using anyone's boards. We filed for our patent over a year ago and expect the patent soon.

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