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GaN-based Class D power amps

The use of GaN-based power transistor tech is now emerging for Class D audio power amplifiers. Seems appropriate to devote a forum thread to this topic. At least 3 companies have commercial class D amps in their books:

Merrill Audio, with their model Element 118 ($36k per monoblock, 400 W into 8 ohms, 800W into 4 ohms), Element 116 ($22k per monoblock, 300 W into 8 ohms, 600W into 4 ohms) and Element 114 (coming soon). 
https://merrillaudio.net

Review of Element 118 at this link:
http://www.enjoythemusic.com/superioraudio/equipment/1018/Merrill_Audio_Element_118_Monoblock_Amplif...

ADG Productions, with their Vivace Class D amp ($15k per monoblock pair, 100W into 4 ohms). (The designer emailed me indicating he has another product in the pipeline.)
http://agdproduction.com
Review of the Vivace Class D moniblocks at this link (warning: link might not work (1/11/2019)):
https://positive-feedback.com/reviews/hardware-reviews/agd-production-vivace-gantube-monoblock-ampli...

Technics SE-R1 Class D stereo amp ($17k per stereo amp, 150WPC into 8 ohms, 300WPC into 4 ohms) 
https://www.technics.com/us/products/r1/se-r1.html
Preliminary review of the Technics SE-R1 at this link:
https://www.stereophile.com/content/technics-se-r1-digital-amplifier
Technics also has a lower priced GaN-based class D integrated amp in their catalog:
https://www.technics.com/us/products/grand-class/stereo-integrated-amplifier-su-g700.html

Anyone listened to or own any of these amps?


celander
georgehifi's avatar
georgehifi
4,966 posts
 
We are testing different input impedance values for the best result in all situations. .Once the final number is settled on I’ll let you know..

Testing??? there's nothing to test, once you have a "Output to Input" impedance ratio of 1:10 or more, your fine.
  
We had a large participant demo at our audio society meeting, about 35-40 "golden ear'ed" audiophiles were present. I designed a switchable on the fly input impedance changer on a very good amp that was in a very good system.
  
This impedance changer change the "O/I" impedance ratio in 20 increments of  from 1:100 down to 1:5. It was at 1:5  that only two "super golden ear'ed" audiophiles "thought" they could hear a difference for the worse, but they also both said they probably couldn't pick it in a blind A/B.
All said they heard a difference at 1:3.
AC levels were checked to the mV for all ratios to be the same.

Cheers George        
tweak1
870 posts
 
George, wasn't it you who told me when I had the Hattor XLR passive pre that it was a impedance mismatch with both my Emerald Physics, then later with my Audio Alchemy DPA-1?
klh007
313 posts
 
Mike, Yes many "non doucebags" can appreciate a beautiful chassis, Rowland & Cos spring to mind, on a low rack to avoid ruining the image.
mikepowellaudio's avatar
mikepowellaudio
76 posts
 
LOL< great, because I am a big fan of nice chassis work since it is rather scarce.  Now thats 2 about the rack in the center. Ive got a rack to the ceiling dead center of the front wall.  This is because my rig is also my showroom. So at any given time I have a bunch of different gear different types of circuits or classes of audio so I can demonstrate for people. Personally I would love an empty room with nothing but 2 speakers, everything hidden. I do not like a cluttered look for myself personally. At one point just for the heck of it I will go ahead and move that rack because it's on wheels and if it's not night and day different it's gonna stay there. The thing is speakers are 5 feet in front of the rack so there's nothing in between the speakers furthermore I like my image to come forward from the baffles as well as go back. I do not like the typical audiophile sonic that just only goes back.   
georgehifi's avatar
georgehifi
4,966 posts
 
tweak1
George, wasn’t it you who told me when I had the Hattor XLR passive pre George, wasn’t it you who told me when I had the Hattor XLR passive pre that it was a impedance mismatch with both my Emerald Physics, then later with my Audio Alchemy DPA-1?

With one there was a mismatch and you weren’t getting the best from it, with the other it was fine. And I suggested a buffer stage with the Hattor for the Emerald Phyics


Yes and here is what’s said
georgehifi4,817 posts06-27-2018 9:26am
tweak1 OP
My EP KC IIs sound fantastic

Actually hate to say, your Emerald Phyics EP-100.2SE Class-D amps are not a great match for a passive pre, as their input impedance is "not typical" as they are very low at 19kohm, your passive preamp while working fine would sound even better if it had a unity gain buffer on it’s output.
For a 10kohm passive to work it’s magic the input impedance of an amp/s should be 33kohm or higher.




And this to the other amp.
georgehifi4,817 posts06-28-2018 7:40am
tweak1 OP
I have been keen on getting a Nord Two Stereo amp, but need to sell at least one SE first

This will be great with your Hattor Passive Pre and much better.
As the Nord is double the input impedance of the Emerald Phyics no need for a buffer then. I always say the best buffer is no buffer if possible.



Enough on this impedance subject or celander will get his nickers in a knot, especially Michael Powell for bringing it up..

Cheers George
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