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GaN Systems Amplifier Eval Board Measurements

voodooless

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Even 1% increase in efficiency would be valuable once you factor things like Bluetooth speakers, TVs .etc where you're either limited by power, thermals, or foot print (or even all three).

All of those things are super low budget products for the most part and margins are very low. As it is now, GaN has nothing to offer here.

With the EU remodeling the energy efficiency charts my LG TV (2020 model) gets a big fat D that I'm not happy about, which was 'A' in the previous chart. All of these things can be used as marketing tools.

Isn't it wonderful how that works :facepalm: Now you can even have LED lights with a bad label. Basically, that is a good thing in most cases. They were just fed up adding another + to the already A+++++ label ;)
 

abdo123

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All of those things are super low budget products for the most part and margins are very low.

Not necessarily, I was just making the point that the world wouldn't go any further if we thought something we made 20 years ago is 'good enough'.

we have handheld phones today because we made screens, speakers, microphones, radio transmitters .etc efficient enough at some point in the past to run off a battery.
 

boXem

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It is almost impossible to do an apples to apples comparison here. The power ratings of the Purifi and GaN amps are different, so comparing absolute numbers of watts isn't valid. Efficiency at a given lower power isn't really valid either, as again, the full power capabilities are different and they are at different points on their efficiency curves.
If we would translate the efficiency curve with percentage of max power as X axis, I am wondering if the Purifi would not be better.

It also is not useful to compare efficiency percentages at these high efficiencies. It makes more sense to compare losses. A change from 88% to 90% might be 2.3% in efficiency, but it is a 20% drop in losses. Perspective matters.
Or 16% improvement in losses ;)

Comparing losses at full power is far from the full story. Most amps never run continuous full power. It makes much more sense for actual use conditions to compare amplifiers at some sensible level driven with some reasonable representation of actual use signal. One issue is that there are other losses than switching losses. Comparing at full power tends to skew the importance of switching losses versus total system losses.
Efficiency isn't really the game anyway. Heat dissipation in real use is the important number. Efficiency just looks good on publicity material.
Which is why I am wondering about idle losses, that are a much more important parameter

If GaN lives up to its hype, we might see a halving in switching losses. Other losses will probably remain the same. So how much we win in reality is hard to guess from the numbers available. But halving of losses is the best case. It is going to be continually harder and harder to make real gains.
That's my issue here, I do not see anything up to the hype with this demonstrator.

As noted earlier, the Axgin AX5689 provides a single chip mutli-channel PWM driver solution that takes feedback from after the output filter. There is a good chance a proper implementation using that chip (not the SMSL attempt) is going to stir the pot.
Same comment as John.
And I will add that for a proper implementation of the AX5689, one need competences in control theory to properly program the control loop.
 

boXem

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Even 1% increase in efficiency would be valuable once you factor things like Bluetooth speakers, TVs .etc where you're either limited by power, thermals, or foot print (or even all three).
Well, I am far to be a specialist in silicon manufacturing processes, but I believe that we will not see and integrated chip with GaN inside anytime soon.
 

voodooless

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we have handheld phones today because we made screens, speakers, microphones, radio transmitters .etc efficient enough at some point in the past to run off a battery.

Yes, because we went through many technological revolutions, not evolutions. These things came about because of orders of magnitude improvements. Some things were more gradually for sure, but those were not the big breakthroughs.
 

PeteL

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right, that was just my wild guess, so that makes it currently only suitable for SOTA amps to knock out the extra few db performance! but personally I am pretty open and longing for the day when cost goes down and power amp performance goes like the headphone amp market producing very transparent yet cheap ones for the mass
Headphone amps are cheaper, but they should be cheaper for the simple fact that they do less of what an amp do, produce power. Cost do go down In real money, a 100 W in 1979 was more or less the same price than it is today, but the house you could get a house for 50k then is now 500k. We should really look at dollars per watts, not, it's a piece of electronics so electronics worth 200 bucks. I don't think it's a fair assessment to expect getting 500 watts as a commodity like a a dac or headphone amp.
 

restorer-john

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Headphone amps are cheaper, but they should be cheaper for the simple fact that they do less of what an amp do, produce power.

Headphone 'amplifiers' are a joke. They should be practically free, to be honest.

Seriously, they are either a quiet preamplifier with a low output impedance or basically an opamp with a buffer. Nothing special, and certainly nothing worth the stupid prices that are charged. I remember thinking 20 years ago, you just needed a low power, linear, quiet, class AB power amp, dress it up in a box and sell it to the headphone crowd as something magical. They'd lap it up. And they still do. :facepalm:

Plenty of high quality preamps of yesteryear can quite happily drive any headphone with performance they are only just getting to in 2021. I have preamps from 30+ years ago with <1-10uV (A WTD) residual noise and swings that will drive any set of cans to destruction; off the RCA outputs...

And you get multiple inputs, tone controls, loops, onboard D/A converters etc.
 
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Rottmannash

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Unfortunately I failed to mention to Amir to go ahead and test them in the 2 ohm mode (I run one of them in 2 ohm stereo for my 2 subs [each sub has dual 4 ohm voice coils & is wired as a 2 ohm unit]) and in bridged mono 4 ohm mode (as that is the way I run the other 2, one for the left channel and one for the right channel). There is no shortage of clean power in my system. Perhaps some can hear what noise there is but I cannot.
You're not the only NAD power amp fan here. Have always had them and loved them. Great bang for the buck back in the day. How hot do those run powering the subs @ 2 ohm?
 

orchardaudio

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Where did that come from? Here are the specs from Purifi:

View attachment 135730

It only achieves 94% at max power into 4 ohm. At 50 watts efficiency is 85%. At lowest power levels it seems to sink below 60%. Here is the actual loss:

View attachment 135731

Again, using 4 ohm at 300 watts we are dissipating 25 watts for one channel alone. This is a lot of heat.

The design goal is not efficiency, that is secondary. The #1 design goal for all these modules is audio performance. Efficiency can be further improved at the sacrifice of audio performance. Here are some efficiency and dissipation numbers for my amp's power stage.

1623786340906.png


1623786545638.png
 

spacevector

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Efficiency can be further improved at the sacrifice of audio performance.
Does the trade-off mostly come down to Fsw? Higher switching frequency may help with audio performance but will lead to lower efficiency?
 

orchardaudio

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Does the trade-off mostly come down to Fsw? Higher switching frequency may help with audio performance but will lead to lower efficiency?
Yes switching frequency, also dead-time. You want to have as small a dead time as possible for best performance.

One great thing about GaN fets is that the reverse recovery charge (Qrr) is zero (0). This eliminates a loss element completely that is present in non-GaN devices.
 

Tks

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hah, feedback loop arrangement is a much more intellectual and effective thing than just using the new MOSFETs. B. Putzeys class D amps will win that evaluation board for THD+N, SNR, and other audio-related specs even being implemented on 1990x MOSFETs ;) Only the efficiency get some profit, is anyone feels that silicon class D amps are too hot?

Try touching the back metal on some of the powered speakers out there. Straight up skin scorching. (Granted audio companies are neglegent or just dumb with how awful thermal solutions are in this industry).

Efficiency inrpovements are basically at the basis for basically gating performance gains in any feild. Computing especially if one hasnt noticed. As compute demand constantly grows it would never make sense to keep efficiecy stagnant. Likewise power demands are increasing simply in virtue of a growing global market and population.

Euphemeralization is the name of the game.
 

Vini darko

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Try touching the back metal on some of the powered speakers out there. Straight up skin scorching. (Granted audio companies are neglegent or just dumb with how awful thermal solutions are in this industry).

Efficiency inrpovements are basically at the basis for basically gating performance gains in any feild. Computing especially if one hasnt noticed. As compute demand constantly grows it would never make sense to keep efficiecy stagnant. Likewise power demands are increasing simply in virtue of a growing global market and population.

Euphemeralization is the name of the game.
I had to look that word up (Euphemeralization) doing more with less. Still not sure how to pronounce it though :facepalm:
 

EJ3

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You're not the only NAD power amp fan here. Have always had them and loved them. Great bang for the buck back in the day. How hot do those run powering the subs @ 2 ohm?
That amp is on the bottom of my stack, I have it raised 1/2"for a bit more airflow (I also have the 2 NADs above it raised 1/2" for the same reason) and there is at least 6" of free space per side of the amp stack. It is on a shelf under a coffee table which has a 3" high drawer underneath the table top. The room is a large but somewhat convoluted with 1/2 walls, a staircase, a bay window, a set of sliding glass doors, a fire place and large openings to other rooms. The subs ([home built from the larger Radio Shack Cabs with 93 db [Pioneer's spec] efficient at 1 watt RMS 12' Pioneer that spec 20 Hz to 80 Hz) seem to run at around 10 watts according to RMS averaging meters at moderately loud levels. They are slightly warm to the touch while running, just slightly more than at idle. I am sure that the leading edge of a Tympani drum has much more power, but it is the average and the ability to dissipate heat that we are talking about. The L&R channels for the mains (speakers: 1 watt= 89 db manufacturers spec) run slightly cooler when not in the stack & slightly warmer when in the stack. Even running things harder than I would stay in the room to listen to (for about 45 minutes) doesn't make any of the amps too hot to hold your hand on. Perhaps this is because the power is divided among 3 amps. My average annual power use is about the same as when I had CFL's (and no stereo equipment hooked up) before I got LED's and hooked up the stereo. Due to a quirk in this 1965 home, the stereo is idling when it is not in use. That is something that will change as I go through things. I don't see any point in letting the system idle (even though it does SEEM to sound better when it has been on 15-30 minutes).
 

EJ3

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I had to look that word up (Euphemeralization) doing more with less. Still not sure how to pronounce it though :facepalm:
You know that you have it when you can use it with others in a sentence that makes sense during your lunch or dinner (even though you may have to explain the word).
 

tomchris

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Plenty of high quality preamps of yesteryear can quite happily drive any headphone with performance they are only just getting to in 2021. I have preamps from 30+ years ago with <1-10uV (A WTD) residual noise and swings that will drive any set of cans to destruction; off the RCA outputs...

Can you recommend a couple off the top of your head?
 

fordiebianco

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The counterpoint is that large amounts of metal are easy low tech answers, .

Don't underestimate the aesthetic value of large amounts of metal (for some, cough).
 

Spinitch

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Panasonic, Technics: SU-R1000 put GaN in their flagship amp. Along with other tech for a fairly heft $8K, compliments their turntable with phono . The power devices employ high-speed, low-resistant GaN (gallium nitride) which – due to their ultra-short switching rates – contribute to a highly dynamic sound image with ultimate time correctness.
 

paulraphael

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A couple of TL;DR questions ...

Are there disadvantages to GaN besides price?
And how much added cost might there be with a powerful class-d amp (say, 1000W/channel)?
 
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