new GAN amplifier

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

georgehifi,
EPDR does not define "difficulty" to drive the load per-se, even though it was defined that way in consumer audio media. It is illustrative of the thermal stress that is put on the amplifier output devices instantaneously. The peak current at the worst case EPDR is not the peak current of the amplifier.

Good current delivery with complimentary P-Channel is certainly possible, but better performance these days can be done with N-channel so that is normally the preferred architecture.

Note that MOSFETs don't have secondary break-down effects, hence EPDR is not nearly as critical for FET output stages. They don't mind high instantaneous power.

It's probably worth making the point that a person who owns a pair of Alexia's is probably driving them with a decent amplifier. Most, if not all high-end class A-AB designs are usually very over-engineered to avoid device failures and to be able to drive the sorts of difficult loads that will inevitably be presented with ease. Also, when the difficult load is isolated to a relatively narrow bandwidth as is typically the case it's really not a significant issue.    

Like the Halcro Eclipse  with its incredible specs; 110kg/250 pounds, 135,000$ 😉