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There has been some recent comments on Facebook regarding a "revolutionary" new amplifier from Soundigital out of Brazil. The key to the new amp is apparently the use of GaN FETs. One of the only other applications I have seen on the audio side of things is a couple of systems from Technics. So, any of the DIYMA amp gurus have any feedback?

The specific Soundigital amp in question, the SD300.2D...
Soundigital Amplifiers - Lançamento SD300.2 GaN Power

http://soundigitalusa.com/wp-content/uploads/2016/02/final_final.pdf






More info on GaN (Gallium Nitride) FETs...
Class D Audio

EPC9106 EPC | Programmers, Development Systems | DigiKey

The Panasonic/Technics use of the tech...
Panasonic breathes new life into Technics
 

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Discussion Starter #3
I was hoping for a bit more feedback than this, but yes, the EPC 9106 development board is $1338. If the Soundigital SD300.2D uses the same (or similar) board, it would explain the $1500-$2000 retail pricing that was mentioned on FB.

Among some other benefits stated by the EPC, one of the things that stuck out to me was the switching speed of 400+ kHz. This is on par with what JL is doing with their HD amps and greater than what they have in their XD amps. I have no idea how that compares to other Class D amps, but since we see switching speeds this high in the HDs I don't believe this alone will make GaN FETs a "game changer."

I was really hoping Ricky, Victor, deveds50 and some of the other amp pros around here might be willing to chime in.
 

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Forgive me, but doesn't increased switching speed mean lower efficiency? I always thought you wanted just enough speed, not too much for audio.

Eric
 

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Discussion Starter #5
Forgive me, but doesn't increased switching speed mean lower efficiency? I always thought you wanted just enough speed, not too much for audio.

Eric
I have no idea, but I would guess no. Just based on the claims of 90+% efficiency.
 

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Forgive me, but doesn't increased switching speed mean lower efficiency? I always thought you wanted just enough speed, not too much for audio.

Eric
Not switching frequency, switching speed which is essentially transition time from on to off. Fast switching speed means you don't have the FET in a resistive region for as long.
 

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I can tell you that I will be using them in the near future I knew about these back in Dec and got to see the amp at SBN. So Until I have mine I can't say much, but will definitely be interesting..

I am currently running 2 - soundigital 800.4 and switching out to 2 400.4D and one 800.4, so far, I'm very happy with the power in the small package.. lot less power consumption and having the ability to have my hatch back..
 

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Discussion Starter #8
I can tell you that I will be using them in the near future I knew about these back in Dec and got to see the amp at SBN. So Until I have mine I can't say much, but will definitely be interesting..

I am currently running 2 - soundigital 800.4 and switching out to 2 400.4D and one 800.4, so far, I'm very happy with the power in the small package.. lot less power consumption and having the ability to have my hatch back..
I look forward to seeing your feedback.
 

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I want to know what the middle of the paragraph in the first image is referring to. Something about QRR? QPR? I can't really read it. It says it's related to distortion, and class D amps have low amounts of it, but these new transistors have zero amounts of it. What is that all about?
 

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Discussion Starter #10
I want to know what the middle of the paragraph in the first image is referring to. Something about QRR? QPR? I can't really read it. It says it's related to distortion, and class D amps have low amounts of it, but these new transistors have zero amounts of it. What is that all about?
I know absolutely nothing about this (hence my initial post), but I can use google and "Ctrl+C" and "Ctrl-V" like nobodies business!

EPC eGaN FETs and ICs for Class D Audio Applications said:
The quality of sound reproduced by the audio amplifier, measured by THD (Total Harmonic Distortion), DF (damping factor), and IMD (intermodulation distortion) is influenced by the characteristics of the power transistors used.

eGaN FETs’ near ideal switching performance due to lower propagation delays and faster slew rates (due to their lower gate capacitance) and zero QRR enable very short dead times to provide lower open loop distortion, lowering the THD and overall losses. This reduces feedback, driving down T-IMD and DF to provide a step jump in the sonic quality of Class-D audio amplifiers and lowering overall losses.
http://epc-co.com/epc/Portals/0/epc/documents/briefs/AB003%20eGaN%20FETs%20for%20Class-D%20Audio.pdf

This paper from Infineon might also be worth taking a look at...
http://www.infineon.com/dgdl/Infineon+-+Application+Note+-+Power+MOSFETs+-+OptiMOS+200V+250V.pdf?fileId=db3a304344ae06150144b1d2f8250165
 

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Yeah I saw that FB post and saw Steve's praise of them among a few others, though of course folks balked at the looks of it, which I couldn't care less. I'll be interested in what folks report on the GaN amp's abilities. Appears they'll be doing a 4-channel as well.
 

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Discussion Starter #12
Yeah I saw that FB post and saw Steve's praise of them among a few others, though of course folks balked at the looks of it, which I couldn't care less. I'll be interested in what folks report on the GaN amp's abilities. Appears they'll be doing a 4-channel as well.
I saw the praise as well, but I really have to wonder if these things are really all that special? Or is this just hype?

The closest thing out there in terms of similar power and class D is probably the Mosconi D2 150.2. From what I have seen those D2 amps are well received. I would imagine that the limited edition Soundigital GaN at $1500-$2000 would be a pretty significant premium over the D2 (not sure what retail is). Is there enough difference in this new amp tech to make it worth it? I'll maintain a healthy dose of skepticism until I see some independent reviews/tests/commentary.
 

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Yep. Truth but verify. Agreed.


Sent from iPhone using Tapatalk
 

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I read some of the information about GaN on Texas Instrument's site. I agree, these seem really interesting, but I'm skeptical as to whether or not they'll offer a practical improvement, as opposed to a theoretical one. Current class D amps are kicking ass fullrange, they offer great FR and low distortion. These chips may be better on paper, but I wonder if in the real world their advantages are going to matter.
 

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Not an amp pro, but I know just enough about electronics to be dangerous.

GaN FETs have a lower on-resistance and switch off faster and harder than silicon. For Class D amps, this has a bunch of benefits.

First, power losses are reduced (i.e. efficiency goes up). So you need less heat sink. And because the GaN FETs conduct electricity so much better than Si, the devices themselves are smaller. This means smaller amps that run cooler at the same or higher power levels.

GaN FETs switch much faster than Si. So you can increase switching frequency without losing too much efficiency. This in turn allows smaller inductors in the power supply, EMI, and output filters. It also allows the feedback loop and output filter to reduce their effect on the audio band, for better transient response and slew rate.

GaN is harder to manufacture than Si, but it uses a lot of the same techniques and equipment. Because the conductivity per unit area is so much better than Si, devices are smaller, and you can put more of them on a wafer. This should bring costs down pretty quickly as the chip factories gain experience. EPC is already offering (or claiming) GaN devices cheaper than the equivalent Si FETs.

GaN doesn't require a new design approach in the same way that MOSFETs did over bipolar transistors, or bipolars over tubes. But GaN makes radically better power switching MOSFETs than silicon. The only real drawbacks are unfamiliarity and device prices, and the device costs are coming down pretty quickly.

I think in 15 years we'll be saying "Remember silicon MOSFETS?".
 

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Discussion Starter #17
Thanks for the response chucko. A lot of what you're stating is what I was picking up looking at EPC's website and videos.

I guess the question for today is, do they warrant the significantly higher price tag over traditional MOSFET Class D amps? Either through a recognizable audible difference, increased efficiency, smaller footprint (via reduced heatink), etc.

It would be interesting to see how the Soundigital amp fared in a Richard Clark or similar bling listening test.
 

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I guess the question for today is, do they warrant the significantly higher price tag over traditional MOSFET Class D amps? Either through a recognizable audible difference, increased efficiency, smaller footprint (via reduced heatink), etc.
My opinion? Not today. The audible differences would be slight; maybe some golden-eared folks might find them worth the money.

The EPC amp is a demo piece. It's intended for electrical engineers, not for audioheads. A mass-produced board would be cheaper, even using current parts.

I think as GaN sees wider adoption in other areas (e.g. power supplies, where efficiency and power density in space and weight are big deals), mass production will bring device prices down, and we'll start to see some radically powerful and tiny amps at a modest premium or even a discount to current silicon Class D.
 

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I have no idea, but I would guess no. Just based on the claims of 90+% efficiency.
I developed and in the process of patent 1.2GHz switcher and it shows 96% efficiency.
i don`t have comment on soundsdigital amplifier. So far it seems nothing more than creative marketing.
 

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Not an amp pro, but I know just enough about electronics to be dangerous.

GaN FETs have a lower on-resistance and switch off faster and harder than silicon. For Class D amps, this has a bunch of benefits.

First, power losses are reduced (i.e. efficiency goes up). So you need less heat sink. And because the GaN FETs conduct electricity so much better than Si, the devices themselves are smaller. This means smaller amps that run cooler at the same or higher power levels.

GaN FETs switch much faster than Si. So you can increase switching frequency without losing too much efficiency. This in turn allows smaller inductors in the power supply, EMI, and output filters. It also allows the feedback loop and output filter to reduce their effect on the audio band, for better transient response and slew rate.

GaN is harder to manufacture than Si, but it uses a lot of the same techniques and equipment. Because the conductivity per unit area is so much better than Si, devices are smaller, and you can put more of them on a wafer. This should bring costs down pretty quickly as the chip factories gain experience. EPC is already offering (or claiming) GaN devices cheaper than the equivalent Si FETs.

GaN doesn't require a new design approach in the same way that MOSFETs did over bipolar transistors, or bipolars over tubes. But GaN makes radically better power switching MOSFETs than silicon. The only real drawbacks are unfamiliarity and device prices, and the device costs are coming down pretty quickly.

I think in 15 years we'll be saying "Remember silicon MOSFETS?".
:rolleyes:

what about GaAs or SiGe?
what about organic developments?
Si mosfets are here to stay.
And BTW unfamiliarity is a not a problem as supporting circultry is more similar than you it seems think.
 
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