Class D amplifier technology, despite initial skepticism and technical challenges, has evolved significantly due to dedicated engineering efforts and component advancements, positioning it as the future of amplification due to its superior efficiency, power, and cost-effectiveness compared to traditional Class A and B amplifiers.
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The second group of questions is
traditionally class D. Is it capable or
not? And here I picked one picture that
in my opinion illustrates these
situations very well. When something new
appears, well, someone invents something
and the crowd shouts which a woman can't
be that beautiful. Such a small woman
can't run that fast. A woman with two
children must be fat. hanger burner.
Jordan Bruno came out with the thesis
that the universe is infinite. He was
burned at the stake. I would have given
up, but he was a tougher guy.
Why does the market in general have such
a negative attitude toward class D?
Because essentially it destroys the
entire established business and the
first stage is denial. I just want to
show you all the drawbacks of class D. I
had a presentation like that back in
2008 when we were working on our first
developments. And let's quickly go
through all the problems. This picture
shows almost all the problems of a class
D amplifier. Class D technology is not
new, but the industry wasn't ready
because it's actually difficult to create.
create.
There were problems with the input
circuits with the modulator and then
there was a serious problem with
operating in the on mode because the
power supply couldn't handle it and
developed specific issues. In this case,
the MOSFETs didn't switch fast enough.
So, you had to make a very large reserve
and then there was a lot of noise
because the MOSFETs weren't ready for
this. There was nonlinearity in the
output filters. There should be
highquality filters there. There was
hystericis and we needed to solve it. So
how should we approach this? We can be
in this crowd and scream class D can't
do it because it has sand on top and
other issues. Or we can see the whole
perspective of this technology and try
to solve it. If we look at a story like
Kodak for example, they had the film
market. I think they had 90% of the
market. They had a lot of money. And
when digital photography appeared, they
couldn't invest in it and keep working.
They said that film is the best. And
where is Kodak now? It's gone. Their
patents were bought up. LG bought their
fourpixel patent. And LG's organic light
emmitting diode TVs are the best. They
have that patent. Nokia's button phones
were everywhere. Nokia was a very good
manufacturer, but they didn't keep up
with smartphones. What happened? Nokia
is gone. It is a niche player now. So
with class D, it's the same thing. We
can pick a side or watch and decide or
say that everything is bad. And indeed,
the tasks that this so-called dead time
is supposed to solve. It can't be that
both MOSFETs are open at the same time.
Yes, such a reserve was needed. The
bigger the reserve, the more distortion.
Today it was decided to use base pumping
when we have what's called a half bridge
in English. I don't even know how to
translate that. When we don't have a
bridge circuit and when we do have a
bridge circuit, let's say when we don't
have a bridge circuit, this problem
exists and [snorts] it can be dealt
with. There's a specific task set for
this because these switches work as
voltage multipliers. But if you have a
fullbridgeidge circuit, everything is
solved without any problems. And chips
like TPA 3,255
have four channels and the best
connection is two channels in a bridge
circuit to get stereo and two channels
even though there are four channels
inside the chip. There was noise with
transistors like this. So they made
specialized transistors and solved it.
And finally, the reason why so many
companies that produced class A and B
amplifiers are no longer working or
can't work in the field of class D is
because it requires completely different
knowledge. We have very powerful pulses.
There are analog circuits. Everything is
on one board. You need different
knowledge. Either you hire these
specialists or you don't have them. And
it turns out that other players like Ice
Power, Hypex, companies that work in the
professional market, these are more
popular ones are the ones who lead.
Regarding transistors, a new standard
has emerged for leadless transistors.
Low noise, good cooling, new casings,
and so on and so on. International
rectifier specialized on it. Then
infinion bought them. Here's the
difference between a simple transistor
and a specialized one in how each
behaves as a pulse. And we're talking
about nightmare currents. About
nightmare currents. Specialized
transistors appeared where they are
paired in one package to have very
precise outputs. Filters have
hystericis. They're bad there. And there
was also a problem that filters could
only be set to one frequency. Today we
have feedback after the filters. It's a
complicated thing, but it's been solved.
We have a clear amplitude characteristic
for any load. There was a problem. We
solved it. There were different fite
issues, and you can see how it changes.
Distortion at the output only changes by
selecting the inductor components. But
this was still 2008, and solutions had
already been found. There are different
developers here, but the Japanese were
the first to solve the inductor problem.
It's another level. And here I've picked
out an inductor for you that we were
also developing back then.
It's a good manufacturer. It was one of
the first to offer different solutions.
This is Ferox core. And as you can see,
they cut the magnet, preventing it from
saturating, and solved the hysterosis problem.
problem.
Here, we even wound it by hand and
tested it, but there are none left in stock.
stock.
You see there's a cut here. It's filled
in, but the ferry is cut and it
immediately loses a huge amount of thermobility.
thermobility.
I don't know if that's the right term,
but one needs more of these windings.
But they found some kind of option, but
it was considered cool. We used it in
our own development.
So when your mind tunes into finding
solutions, everything becomes solvable.
Well, here are different types of these
inductors. Some are like this. These are
also wellused, good ones. We see these
kinds. We see fewer of these. They are
present in various developments.
A large air core one basically doesn't
make sense since these ferrets have
already solved the whole problem. We get
distortion through the filters. Three
zeros after the decimal point.
Everything is solved.
Everything is solved. The same applies
to filter components like capacitors.
But that was much easier to solve. And
overall, here's what we get.
Polyropylene capacitors are the best.
Polyester ones are also fine. Basically,
that's not a problem, but you can't use
ceramic ones. If you see ceramic ones,
throw it out. Throw away that board.
I've seen a few. Well, come on. I don't
really know the theory, but they have
different problems. I won't get into
electronics. But the cost of these
capacitors is relatively high if you use
ceramic ones. You might save a euro or
even less, maybe half a euro, but you
absolutely can't cut costs here. That's
the worst thing. And regarding gate
drivers, in 2008 there were about five
of them. Let's see what's there today.
Here we have Infinaon.
It is a German company. They make chips
for the automotive industry and they're
very strategic and good developers. As
you know in cars, microchips have to
work from minus50 to + 70°.
It's a very difficult task. They're a
good manufacturer and they also produce
these gate drivers. All the complexity
we've talked about is already inside the
chip. If you look at their brochure
where they talk about their developments,
developments,
everything is there. There's a small
three-phase strip, there's a solution
for that. There's a bigger one, there's
a solution for that, too. They combine.
They do everything. They give you all
the hints, all their knowledge, offering
you a whole range of gate drivers from
low power to high power. And they're
getting better and better. if there were
about seven back then. Now there are
already several pages more and more.
Voltage is 500 W. That's the range we're
interested in. We're not interested in
anything else. The same goes for field
effect transistors. You can choose any
for any power. Everything is available.
They've even grouped them here by the
loads they can handle, which is mainly
current. There are different options. So
the range we're interested in which is
up to 500 W it's going to get cheaper
and cheaper. Also for less experienced
developers all the key references design
guidelines and reference projects are
provided where everything is done
correctly and properly. Regarding a
circuit board it is a complex thing and
all the grounding component grouping and
so on must be done very properly.
Developers need to know many things on a
theoretical level, especially everything
about grounding high current circuits.
It's not an easy task. It's much more
complicated than just doing A and
B-class amplifier. But if you do
everything properly, then it will be
fine. These hints are given to
developers. If you look at the different
Chinese boards that are produced, they
take the Gerber files as they are, then
tweak them a little, remove some
unnecessary things and might add another
operational amplifier. But overall, they
use these reference designs and quickly
enter the market. Not every developer in
China is highly skilled. There are many
developers who can assemble and
replicate it. To build something like
this from scratch, you need a top tier
developer. They must be extremely
well-trained in theory. And once again,
I want to return to the key developer
behind highquality class D amplifiers
that are now outperforming high-end
systems. That's Bruno putsis. He worked
on it from the very beginnings.
Essentially, he solved many, many
problems that already existed in
integrated amplifiers. He's better known
in the amateur environment since this
company grew out of the amateur one. But
he also created the entire Hypex lineup
and now they have a separate engineering
company there working right at the
cutting edge focusing on the last 2% of
quality with a whole group of top
engineers. And I recommend keeping an
eye on them and this company Purify
reading their blogs. Yes, in English it
might be a bit difficult but not too
much. They're popular science so
everything is understandable. And the
second one who we know less about there
are two other developers Patrick
Bostonramm and Lars Press Peterson. Many
developers rely on them. That's Ice
Power, its key developers. And if you
want to keep up with the latest news and
developments there, these two guys are
also top class specialists. They have
whole teams behind them. It's even bigger.
bigger.
But when you read their articles, not
just in the professional world, these
are really, really strong guys. They can
create both chips and specialized
drivers of the future, specialized
drivers for powerful amplifiers. They
work together with Infinine. In general,
they do a lot of work on the amplifier.
This is a class D amplifier, and it's
gradually becoming smaller and smaller
for us. We're interested in a peak power
of 500 W because it can handle any
speaker, even a very demanding one. And
as soon as this is thoroughly worked
out, everything will be fine. We'll have
an excellent amplifier, an excellent
amplifier at a reasonable price. And for
those who shout which, yes, for those
who shout which and are looking for some
kind of reason to say that this
technology is bad, it will come anyway.
It is so far ahead of class B in all key
parameters, especially in terms of
thermal characteristics and so on, that
there are no alternatives. It's about
price, power, and quality. And someone
in the comments wrote that Sukov said
there's hysterosis, but Sukov is a
He was a great engineer who published in
the radio magazine. I also subscribed to
it and looked at these circuits. I was
impressed too. But the philosophy here
is that we are what we are today. What
was in the past? This isn't the Olympic
Games. It's the World Cup. And every
year we start over. In general, Sukov
should be here. He should be dragged to
the gallows. And he should shout that
yes, the class D witness zone has
hysterosis, but I know how to solve it
there. If you cut the ferit, you can
solve it. And then the next hypexex that
comes along will be, I don't know, a
Hypexex amplifier with a Sukov Hoffman
inductor. He is there. And if he's
shouting from the crowd like there's a
witch and she's a redhead and young
people just don't look back, then that's
it. Old grump. He should be able to use
his intellect to solve the challenges of
the future. And for those who are
seriously interested in this topic, I've
selected an article written by Bruno
Putsis. To me, he is a sensei. He has
truly done a great deal for class D
amplifiers and for the future. Here's a
long article. It answers a lot of audio
file questions in a very competent way
and so on.
Everything is there. It's a long
article. It's published and we'll
provide a link when we publish this
video. Here is the author Bruno puts. He
started as a student and look, he's
already a mature specialist
and he did a lot to create those really
cool class D amplifiers.
But the second one who is kind of in the
shadows is Ice Power. I only work with
Ice Power because they produce
industrial-grade units. They are very
well refined and you can buy them at a retailer.
retailer.
They've supplied them to several large
and commercial stores and enthusiasts
can buy them directly as well. Other
companies don't do that. So even with
Hipex, you can't buy the professional
line directly, but you can buy it from
Ice Power. I only work with Ice Power.
But that doesn't mean Hipex is bad.
Hypex is very good. They are the same.
They use the same technology, the same
principles, the same architecture.
So, well, as for me, my focus is 100% on
class D amplifiers as the amplifiers of
the future. I don't want to be like
Nokia saying that button phones are good
and then it's over. Well, that's in some
way my answer to the skeptics of class
D. I think the biggest risk for
amplifiers in the class A and B
amplifier market is the TPA 3255 chip.
The Chinese have mastered it and you can
really build a 250 W clean amplifier at
4 ohms with it. And at 8 ohms, that's
120 W. And that's the niche where class
A and B can compete with the TPA 3255.
But the designs based on this chip are
smaller in size. The Chinese have
mastered it and are now flooding the
market with their developments and
they're getting better and better. And
basically, there are no complaints about
these amplifiers where the power is
higher up to 500 W. There aren't any
good Chinese ones yet. Those tasks are
much more difficult, but up to 100
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