GaN Class A amplifier

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#23
Hey mterbekke, i saw your answer weeks later, I answer now 🙂 abit delayed, that JBL 2450 driver looks awesome, do you use it still today ?
I was looking into cirklotrons years ago as you did, forgot its an inefficient amp, is your GAN version more efficient ?
 
#25
Nelson Pass said:
If you review the spec sheets on GaN transistors you will notice that the safe operating area curves (SOA) do not spec operation for more than a few milliseconds. There is no DC curve offered. I discovered this the hard way when I bought a tube of Transphorm GaN fets and blew them up at 20 volts and 1 amp, which of course is 20 watts.

They make great switches for Class D, but at this time I would say Class A is right out, as is Class B and AB.


:snail:
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alexberg said:
I hope some of you are familiar with works of Dr. Ray Ridley, power electronics specialist.
Once a year he posts something audio related on FB /groups/ridleyengineering/
I believe "GaN Class A amplifier" was posted year or two ago. Anyhow he made such a thing and it worked.
So to speak reference design does exist. Sometimes all you have to do is to ask.
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This comment is all I could retrieve:

"The World's First GaN LINEAR Amplifier

Well, this is what we have been working on. Putting GaN into an application for which it was never intended. I think we are probably the first crazy people in the world to try this.

And this is how we managed to blow up a 90 A device with just 50 mA. 30 V drop results in 1.5 W in one of those small packages, and it cannot take the thermal stress without a heatsink on top of the package."

Seems similar to what Mr. Pass found out earlier.

Impressive DIY speakers and TT:
1709980525570.png
 
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#26
Follow-up 😵 🤔
1709984059001.png


"These are biamped. The tweeter is 6 ohms. The cones are paralleled to 1 ohm.

Somebody didn't like my 1 ohm speaker. Why do we have this? Well, it's actually 6 drivers in parallel. Since we are not likely to get the driver makers to up the impedance, we live with what we have.

With modern devices, and designing the amps yourself, 1 ohm is just not really a big deal these days. Keeping the voltages lower actually has some good benefits.

But, each to his own. It's all good."

1709983517856.png


Imho anything below 4 ohm nominal is basically defective, but each to his own (indeed).
 
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#32
Devices made for fast switching generally have low thermal mass and do not tolerate DC operations as well. But will probably work fine within limits. I'd treat it like a device with 1/10 the rating if used at low frequencies and have DC current passing through.
The whole point of the very fast switching devices is the physical layout becomes a paramount part in the circuit. The PCB design must follow the tightest 'design for high speed' rules. This is why very few GAN transistors are available with pins large enough to hand solder anything to. The TO220 package offered with the GAN inside kind of defeats their reason for being with the much too large inductance those leads introduce in the circuit.
Anyhow very interesting if any linear use of GAN has benefits. The very low capacitance is one tempting reason to try them, but the low C also indicates how small the die is and how little thermal mass they possible can posses making them poor for linear service. But derated a lot they probably make intersting devices.
 
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#34
Mark Tillotson said:
GaNFETs are mainly designed for switching, not linear duty. However the secondary breakdown performance looks good - for instance see this paper: https://epc-co.com/epc/Portals/0/epc/documents/product-training/SafeOperatingArea.pdf

Note that there are different manufacturers and the devil is in the details, different devices may be different.

However is it worth it? Class A doesn't require speed, and efficiency and "Class A" don't belong in the same sentence do they?

Surely the whole appeal of GaN is to be able to put a few 100W through a module the size of a postage stamp and not need a fan to cool it, ie better class D performance??
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class a means heat the less heat the better
 
#37
https://exclusive-audio.jp/en/produ...return-power-amplifier?variant=45477341790465

Looking at "Best Music Genre" for GaN I don't think this is for me.........

GaN (Gallium Nitride)​

Sound Quality Features:. GaN-FETs are characterized by ultra-fast switching capability and low power dissipation, resulting in a dynamic and vibrant sound. It has very good transient response, very fast switching capability and efficient power transmission, resulting in a dynamic and powerful sound quality. It is characterized by an energetic and vibrant sound with good sound rise and response.
Ratings:. GaN-FET technology is attracting attention in the audio industry as a next-generation semiconductor material,It is considered to be the most advanced, and is especially favored by users who demand high efficiency and powerful sound. Compared to conventional silicon transistors, GaN-FET technology is considered a step ahead in terms of energy efficiency and sonic accuracy.It is especially appreciated in amplifiers where efficiency and performance are important.
Best Music Genre:. Ideal for genres that require dynamic range and energy, such as rock, electronic music, and pop. It is particularly well suited for contemporary music that demands punchy bass and crisp highs.
 
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#38
Yes, that product description page raises some eyebrows... They also list the silicon carbide option as "SiT" :scratch2:

"In addition, a short delay time of 25ns (nanoseconds) ensures extremely fast signal processing and high speed reproduction." Delay time in a Class A amplifier is revolutionary. :clown:

It would be interesting to see some pics under the hood, but then they wouldn't likely be charging $3-4K for it if we could see inside.
 
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#39
Yes, strange.....
What do the mean by this below (bold and underlined)? ......e.g. the M2X is a PP direct coupled or what do they mean by direct coupled?

Unparalleled driving power due to direct-coupled design​

The greatest feature of the AMP-8510A is that the output semiconductors are directly connected to the speakers without any intermediary connection between them. This design is impossible to achieve with complementary PP (push-pull). The output power is 10W and the bias current is 1.8A, which requires a larger bias current due to the characteristics of a single Class-A amplifier. Due to this direct-coupled design,The direct-coupled design allows the fine nuances of sound that were previously inaudible to be reproduced clearly, even with SATRI-LINK connections using current signal transmission. The benefits of the direct-coupled design bring out the finest details of music even more clearly, enabling an unprecedentedly deep sound experience.
 
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