Purifi Class D: Junk?

You only need the current you need. It does not matter if an amp doubles its current/power down to 2 ohms. All that matters is that it have enough current at 2 ohms to drive a 2 ohm speaker to the volume required. The IceEdge 1200 module puts out 700 watts into 8 ohms, 1200 into 4 ohms and I measured 1000 watts into 2 ohms......so what? Michael Fremer used this amp module on his 2 ohm Wilson Alexx speaker and said it was great in the bass. Of course, if he had a larger room and played way louder then maybe 1000 watts would not be enough......I mean, how many speakers are 2 ohm......not many. Let’s see......Alexx speaker is 91db sensitivity.....and say you are 10 feet back....so that would be around 82db with one watt......10 watts gives 92db and 100 watts gives 102db.....and 1000 watts gives 112db.......I doubt many listen this loud. This is why 500 watts into 2 ohms is plenty for most people and most speakers (most speakers don’t go near 2 ohms).

The Merrill class D amps all double their power down to 2 ohms.....all of them. Most class D amps don’t do this because it costs more money for larger supplies and it is generally not needed. Did you know that the big Parasound Jc1+ amp does not double all the way down to 2 ohms? Stereophile measured 500 watts into 8, 830 into 4 and 1200 into 2 ohms. I guess they should make an even bigger amp to satisfy those that need number doubling.......$16K and no power doubling.....too bad.  The 60 thousand dollar Gryphon amp doubles to 2 ohm....but it only does 700 watts at 2 ohms.....so my $2K IceEdge amp I sold last year will probably play louder than the $60K Gryphon.......doubling does not matter.....only the power you need matters.

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doubling does not matter.....only the power you need matters

Tell that to a pair of ML-2 monoblocks 20w only at 8ohm and can double all the way to 1ohm, one of the most magnificent amps you’ll ever hear.
http://www.hifido.co.jp/photo/05/504/50446/c.jpg

You just shot yourself in the foot, listening to you all you need then is one of these Class-D 3000w for only $399aud, that just $313usd!!! get two and bridge them.
https://www.bavasmusic.com.au/behringer-nx3000-power-amplifier-with-smartsense?gclid=EAIaIQobChMIqIa...

If you like or need volume, that "pathetic" 20W amp sound quite anemic. So it doubles to 1 ohm. If I have inefficient mainly 8 ohm speakers it will still be anemic. There is no magic in a 160W into 1 ohm amp that halves in power all the way to 8 ohms. 


You shot yourself in the foot with this really idiotic argument. I expect most people are shaking their heads reading it.

Show us just one that’s not, and can almost double it’s rms measured wattage from 4ohm to 2ohm. The true indication of not current limiting, like many good A/B bjt amp.

George, seriously, you would do yourself well to educate yourself on how amps work, at a basic level.


Your metric seems to be "at full power". That is actually causing you to have confusion; its a misleading and lousy metric. What is important is that the amp behave as a voltage source, and by that I mean that it will make constant voltage regardless of the load impedance, at music power levels. If you exceed the power the amp makes into whatever impedance, it will clip (overload). I'm stating stuff that should be obvious but because you trot this trope so often, I have to assume that everything I'm telling you here is new for you.

With any amplifier the designer is faced with limitations; often verses cost. For example, our module has GaN output devices that are rated at 35 amps. This means that we should not exceed 17 amps in the field if we want the output section to survive; employing 50% margins is a good idea with any kind of semiconductor!


In addition the heatsink has to be effective, and yes you do need them for GaNFETs if you plan to run the amp at higher power levels, and especially if that involves lower impedances. So far all traditional solid state amps all have this factor in common too.

Finally you have to look at how much you want to spend on the power supply. Given you know the limitations of the output devices there's an argument for setting the power supply current to a certain maximum so that current will not be exceeded.


So really what this comes down to is what I've been harping to you all along: the current capacity of the output section, its heatsinks and the current available to support the output power of the amp are the variables and these are no different than traditional solid state.


What **is** different is that the output impedance of any class D amp employing GaNFETs is several times lower than any traditional solid state amp. That is why they can act as a voltage source to a much lower impedance than traditional amplifiers. So your metric of 2 ohms is not harder to attain than it is for traditional solid state should the designer feel its important. 

It must be getting close to the release of the your new Class-D to respond like that with such verve and virgor with doubling of wattage v halving of impedance loading.

Take it up with the likes of D’Agostino, Curl, ect ect manufacturers of the greatest amps that are recognized as being able to drive speakers with loadings that make Class-D’s run for the hills, they will tell you the same thing.

Like I said "if" all that matters is wattage with Class-D, and what you and your mate say is anywhere near true, then all anyone needs is this $300 3000w Class-D
https://www.bavasmusic.com.au/behringer-nx3000-power-amplifier-with-smartsense?gclid=EAIaIQobChMIqIa...

As much as I like my NC500 monoblocks on my easy to drive secondary speakers, they can’t compete in an A/B against my friends Gryphon Antillion on his Wilson Alexia MkII’s, and the Gryphon is less than half the wattage of the NC500’s