Class D amps seem poised to take over. Then what?

I said the AGD's sound better than SOME 40-50k amps. It's also not my opinion alone i have had many bring their mega buck amps into my system and most are shocked at the SQ of the AGD's most leave scratching their heads in disbelief.

By your comment you must have heard the AGD's so what's YOUR take on the SQ?

Don’t have to, the AGD is just GaN based Class-D slid into a "bogus" empty tube envelope, which uses (horror) the base pins for all it’s contacts 🤦‍♂️

And there no way the AGD can do what say the Gryphon Antilion can do into the Alexia, Alex, or XLF’s bass, if you do own any of these, they go down to 0.9ohm EPDR (Equivalent peak dissipation resistance). It’s a measurable fact.

Don’t get me wrong, I never said it won’t sound any good, just not the very best for those speakers. And if I had the money for them I’d have the money for the best amp also.

Cheers George

"Then what?"
A: GaN

Keep your Dingos away from him

What does that even mean?
@georgehifi - I read the book written by the Chamberlain's lawyer, and learnt a lot about Dingos, they are most closely related (genetically) to the timber wolf. Highly intelligent is accurate. I've only ever seen them in zoos, never in the wild, even when I drove around Oz.

...yes, but is Class D stable into 2 ohms?

Yes, depending what most meanings of the word 'stable' are. Yes, a class D will not go into oscillation when presented with a 2 ohm load (instability can result in oscillation- so that's one meaning of the word...). Yes, a class D amp can easily double power into 2 ohms or even 1 ohm, since its actual output impedance is probably only a few milliohms (our Beta production amps have an output impedance of about 10 milliohms).


With an output impedance like that, of course an amp can double power. But we also have to be clear about what limitations exist. The limitations are the ability of the heatsinks to get rid of the additional heat, the current available in the power supply and the ability of the output devices to handle that much current. So most class D amps might be able to double power into 2 ohms, but maybe not at full power.


One limitation with GaNFETs is the heatsink- because their appearance has a lot in common with a postage stamp, there's not a lot of methods available to couple them efficiently to a heatsink. And that heatsink has to be very effective at moving heat away from the device. This is (IME) the biggest limitation of GaNFETs; on the case of our design, the heatsink simply isn't fast enough to move all the heat away from the devices if operating at 2 ohms to full power (which would be 800 watts). The output devices are rated for the current, no worries there and its no problem putting in a power transformer that has enough current.


But are they stable? Certainly! For that matter so are any of our tube OTL amplifiers (in that they too will not oscillate when presented with an adverse load) although they certainly won't double power. So what this question really points to is the ability of the amplifier to behave as a voltage source (able to put out the same voltage regardless of load) and so long as you don't ask it to make full power into the load, almost any class D will do that like a walk in the park.


But at the same time its important to know that  **ANY** amplifier driving a low impedance like that will not really be able to strut its stuff. All amplifiers make higher distortion when driving lower impedances; from a high end audio point of view where its all about getting closer to the music, this is the Thing You Don't Do if you want your stereo to sound like real music- the additional distortion will manifest as harshness and brightness with a loss of detail.