Mytek slams Hypex in Stereophile Amp Review

Not if there's a -50'-60' degree negative phase shift also at 3ohms, then the amp could be looking at nearer 1ohm.

Not exactly how this works, but yes, large phase shifts mean high currents near zero volts. Hard for most amps. Would be nice if we had impedance graphs for the Duntechs. 

Not exactly how this works, but yes, large phase shifts mean high currents near zero volts. Hard for most amps. Would be nice if we had impedance graphs for the Duntechs.

There is a formula for it, on diyAudio somewhere, but as usual it was in my head while I needed it, but soon sieved out of there in a hurry, like rats on a sinking ship.

As for impedance graphs with -phase layovers, Stereophile is the only one to do this, but they never use the EDPR formula to give the real load the amp sees.

Only one I’ve seen do this is Miller Audio Reasearch Test Labs, when they did 3rd party Lab Report testing for HiFi News and Record Review, like they did on the Wilson Alexia, which managed an EPDR of just 0.9ohm!!!! in the bass.
https://www.absolutesounds.com/pdf/main/press/WA%20Alexia%20HFN%200313-4web.pdf

Cheers George

Not if there's a -50'-60' degree negative phase shift also at 3ohms, then the amp could be looking at nearer 1ohm.

Not exactly how this works, but yes, large phase shifts mean high currents near zero volts. Hard for most amps. Would be nice if we had impedance graphs for the Duntechs.

High current at near 0 volts is a lot easier than high current at higher voltages :) This might be why some of our customers had success with the Sovereigns, and we make OTL amplifiers.

Bruno Putzey is one of the top class D designers in the world and the Hypex modules are extremely competent. I highly doubt that they could not drive the Sovereigns. Now the modules need power, and if someone put them in a box that did not give the modules the power they need, that's another thing altogether! I'd be a bit nervous blaming the performance of the amplifier on its modules until I knew more about how well its power supplies worked!

One of the very interesting and best things about Class D is that those modules can be made modified and made proprietary by engineers.

I'm not so sure about it being possible to modify the modules themselves. I believe that they are pretty fixed.

Perhaps the module makers (Hypex, ICE, TI, etc) could tweak the switching frequency for a company like Mytech to impose a house sound, but Class D is high tech and boutique amp makers don't design semi-conductors. 

Where the boutique amp makers get to play and differentiate themselves is with the case, power supply, outputs, and possibly a pre amp.  

Do any readers have specific experience with Hypex amps and big speakers to confirm or deny Mytek’s claims?

My experience is with Rogue’s Hypex-based Sphinx and Pharaoh. Neither could produce the lowest octave of my Monitor Audio Silver 8s (not the most efficient speakers, but certainly not anywhere near the worst). The same applied with my Epos Epic 2s - fairly efficient speakers. My $300 Yamaha embarrassed those amps when it came to bass.