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Class D amps that are superior to all or most?

Recently, I have heard about some Class D amps that may be close to the best there is regardless of class. Certainly, this technology has been in development for decades. The main issue has always been the switching power supply. In this regard, I have taken notice of AGD. They have created a whole new power supply that “switches” at a frequency 100 times the normal silicon based MOSFET. The designer uses a gallium nitride based PS. Interesting, it is enclosed in the KT88 glass envelope that sits on top of his amps. I am aware of two more pricey amps that seem to be also at the top- the Solution and the Merrill. There must be others that compete for the title. After my thread, “Is there a SS amp that can satisfy a SET guy?”, I am still on the quest.
Don’t want to spend $50K!
mglik
ieales's avatar
ieales
1,201 posts
 
We've measured no change in bandwidth of our prototypes and Beta units from 20Hz to 20KHz
I don't think I ever mentioned bandwidth. BW is not FR. BW is how far. FR is variation over BW. Some amplifiers drive test loads ruler flat and reactive loads not so well.

fan-boy: "I have a GigantaRama driving BrontoSpheres and it's great."
Frequently, not.
atmasphere's avatar
atmasphere
11,962 posts
 
No, You didn't, here's what you said:
However, the driven device forms part of the output filter and thus effects the frequency response.

In this case its hard to construe the FR being different from the bandwidth because we are talking about the response of the amplifier in its upper range and how its affected by the filter. But no matter: neither are affected if the amplifier is running sufficient feedback.

georgehifi's avatar
georgehifi
10,312 posts
 


Facts are

Everyone likes what good Class-D’s do in the bass on loads that are not too severe, but many hear some thing not quite right with Class-D in the upper mids/highs with many speakers, and this is it’s Achilles heel.
Technics (SE-R1/SU-R1000) claim to get rid of it by making the switching frequency 3 x higher, 1.5mhz, so that then the output filter is also 3 x higher and therefore it has little or no influence down into the upper mids/highs.
Most Class-D’s that have around 600khz switching frequencies, have output filters that have effects down into the upper mids and highs.
And yes throwing a **** load of feedback may fix it, but the best amp "theoretically" would be ones that use no feedback if it can be done without distortions, or very little or local not global.

Cheers George
mike_in_nc
1,162 posts
 
@ricevs -
I have only seen the blah Herb Reichert review of the LKV (says it beats an old class D amp and is somewhat competitive with a $3500 Rogue tube amp). Are there other reviews? 
This is the Herb Reichert who in the latest Stereophile said he likes harmonic distortion in his amplifiers. It's no wonder he didn't like a class D amp -- most have vanishingly small distortion.
georgehifi's avatar
georgehifi
10,312 posts
 
It’s no wonder he didn’t like a class D amp -- most have vanishingly small distortion.

 They have other problems also, like the Ice-Power’s 1200AS2 that has massive phase shift from it’s output filter way down into the mids (red trace) https://ibb.co/J2Hns7s and also (blue trace) a sharp rising output impedance starting at also at the same frequency as the phase shift does. Sure throw maybe a **** load of feedback at it and it could fix it, but to what other detriment.

Cheers George
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