new GAN amplifier

EPRD isn't a term that's used in engineering circles, even if it's a more valid descriptor than than the invented term  "RMS power".

Any amplifier that relies heavily on NFB to present a low output impedance can be brought undone by a nasty capacitive load, and that includes Bruno's hypex modules, particularly when knowing that the output filter is also within the feedback loop. 

When time permits I'll hook up the sig gen and scope and run some tests to see how well the NC500's perform on a typical square wave test Vs a class AB design. 

Sorry, just a correction there @arty_vandelay it’s EPDR (Equivalent Peak Dissipation Resistance.) for those who want to know the complete title.

Here is a snippet from the measuring labs used by HiFi News and Record Review, also used I believe Absolute Sounds use as well. And Stereophile’s John Atkinson also mentions it from time to time when things get into the hairy load area.
https://ibb.co/qxjtkn7

https://www.stereophile.com/content/heavy-load-how-loudspeakers-torture-amplifiers-page-2

Cheers George

Thanks George, my bad - typo.

Typically, in "eng" speak impedance is expressed as a value with a phase angle (polar form) or real + reactive (rectangular form).

EPDR is obviously a means of expressing power dissipated in the amplifier based on instantaneous values of voltage and current at a specified frequency. In other words, a reverse engineered value. 

Bingo arty_vandelay. However, it is specific to linear amplifiers where that instantaneous voltage represents a large voltage drop across an output device operating in the linear region at a given current and hence high instantaneous power. As the output devices in Class-D are not operated in the linear region, it has little meaning.


What EPDR hits really hard is BJT output stages as BJT devices have secondary breakdown mechanisms impacted by instantaneous power (or accurately power and voltage), even if they can handle the current delivery.

arty_vandelay23 posts11-24-2019 8:43pmEPDR is obviously a means of expressing power dissipated in the amplifier based on instantaneous values of voltage and current at a specified frequency. In other words, a reverse engineered value.

arty_vandelay

Yes, if the Wilson Alexia didn’t have a negative phase shift of -45’ degree in the bass causing an EPDR of 0.9ohm, then it would be an easier load for the amp to drive, but still it would be 1.8ohm and still needing an amp with good current delivery. Definatly not OTL or P/P tube or even most complimentary n & p channel Mosfets, unless they are push pull N channel only, then those can get some current going, like the Solution amps (or similar) I believe.

Cheers George