new GAN amplifier

Not sure what all this has to do with a new GAN amplifier, but the Wilson Alexia, at least the current model does not seem that hard to drive. Even the older ones only drop to 2ohms.


Can you put some more details into your hypothesis that being able to double power into 2 ohms is a guarantee of "quality". I can see reasons why it could be, but not a guarantee, just as the way I can see why power limitations at 2 ohm are not a guarantee of a lack of quality.

Back to Class-D, there is of course no inherent reason why a Class-D can't work at 2 ohms, or less. If you want best operation with low impedance loads, you would want to optimize for that, but then that is true for a linear amplifier as well.



https://www.stereophile.com/content/wilson-audio-specialties-alexia-series-2-loudspeaker-measurement...

https://www.stereophile.com/content/wilson-audio-specialties-alexia-loudspeaker-measurements

Not sure what all this has to do with a new GAN amplifier, but the Wilson Alexia

BJT's and their ability to drive into these kinds of loads, and the BS statement that OTL can do it too🤣

Absolute Sounds test report Quote:
With the combined EPDR of impedance and - phase angle the Wilson Alexia presents a scary 0.9ohm load to the amp 

https://www.absolutesounds.com/pdf/main/press/WA%20Alexia%20HFN%200313-4web.pdf

georghifi,

You appear to be misinterpreting what EPDR means. An EPDR of 0.9 ohms does not mean the amplifier sees an 0.9ohm load, it means that the power dissipation in the amplifier is equivalent to what it would see with a 0.9 ohm load. It sounds the same, but it is much different. When the load and current are in phase, the output transistor has the lowest drop across it (rail to load) when the current it at a maximum, hence power in the device at this voltage is not high. When the current is out of sync, you can have a maximum current when the voltage drop across the transistor is higher, hence the peak power across the transistor is much worse. Again, this is not "load" impedance, this is a mathematical formula to generate a convenient number to represent dissipation in a linear amplifier.


Here is the kicker. This problem is much worse for BJT transistors because BJT transistors experience secondary breakdown at high voltage and current, especially at high temperature. So in addition to taking into account the additional heat dissipation, you need to take into account secondary breakdown mechanism, which may mean doubling up devices, where one would normally be okay. MOSFETs don't experience secondary breakdown and don't mind that peak power, as long as average power is taken into account.

Here is the 2nd kicker, this problem does not exist at all for Class-D amplifiers.

Post removed Nov 20, 2019

I agree, not worth the effort, what a Class-D w****r.

Cheers George