new GAN amplifier

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$ 😉

atdavid516 posts11-25-2019 11:00amNote 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.

When did you last look at a MOSFET SoA plot? Its true that going back 30 years or more they generally didn't have secondary breakdown issues but these days its rare to find an SoA plot which is purely thermally limited.