Atma-Sphere Class D… Amazing

@ghasley 


+1. like a turd in the punch bowl.

So here is a question, @kuribo has gone hard at the aforementioned amplifiers built by Ralph and his fine company, question is have you an opinion (yep regret that now) on the AGD GaN mono blocks? 

@juanmanuelfangioii

If one can get past the aethetics/gimmickry, this is what a reviewer had to say about the $20,000US version:

"output impedance [dashed trace, see Graph, above] rises steeply at HF, as does distortion, while the frequency response varies with speaker load impedance [unloaded/8/4/2/1ohm = grey/black/red/blue/green traces]. Put simply, if the impedance trend of your speakers rises in the treble then the Gran Vivace will likely sound brighter, and vice-versa.."

"a marked increase in THD into loads below 4ohm – typically >0.1% from 1-100W/2ohm versus 0.002-0.08% into 8ohm. Under continuous conditions, distortion increases from 0.004%/1W, 0.005%/10W and 0.09%/100W (all at 1kHz). Distortion also increases with frequency [see Graph 2, below] from 0.005%/1kHz to 0.07%/10kHz and 0.3%/20kHz (all at 10W/8ohm) in line with the response of the reactive output filter network."

The switching frequency is 800Khz, a bit higher than what most using silicon mosfets use (600Khz or so) but not really high enough to take meaningful advantage of the benefits of GaN mosfets. The Techniques GaN, for comparison, switches at 1.5mhz.

Load dependency is a non-starter for me. I wouldn’t call the performance "state of the art".

At $20,000US, for a shiny aluminum box and a fake tube, with performance bettered by amps at 1/20th the price, I can find little to attract me for a listen.

@kuribo 

You are welcome anytime to visit us at the next Audio Show and listen to our amps and then corroborate or revisit your assumptions. However as a matter of curiosity, is there a reason why in your peculiar selective cut&paste exercise you decided to omitt what in the same article the reviewer wrote about the sonic qualities and his personal experience about the sound?

@aw-agd 

However as a matter of curiosity, is there a reason why in your peculiar selective cut&paste exercise you decided to omitt what in the same article the reviewer wrote about the sonic qualities and his personal experience about the sound?

I don't put any value in subjective opinions of third parties of audio equipment, especially when the associated equipment and listening environment are different than my own. In this case, the load dependent frequency response alone tells me that this amp will sound differently depending on the speakers used- all the more reason to disregard the subjective impressions.