Class S amplification

[gareth]

Hi,

Could anyone explain what the theory is behind Class S amplification?
and if it is worth the time and effort in trying to design this type of amplification?
Any opinions

Gareth

[jony]

I think that class S became today class D amplifier.

[Symon]

actually Class S is more like quad current dumping,
in that it has a small class A amplifier and a powerful class B amplifier linked together.
However at this point the similarity ends, the principals of operation are different. But without looking it up I can't reliably give any more detail.

[gareth]

That sounds pretty good to me Class A input married to Class B output. Do you know if they are a good design? I am asking because you don't seem to see these around anymore.
Also, are Class S difficult designs to realise?

Gareth

[Symon]

I don't know about now but in the mid 1990's Technics were using a Class S like topology in there range of amplifiers. eg SE-A100.

perhaps they still do?

[gareth]

Do you know if there are any reasons why this topology is not used anymore?

Gareth

[sreten]

Hi,

As far as I know the Sandman topology is not called class S.

/sreten.

[Symon]

I've certainly seen it used to mean Sandman topology, but I wouldn't rule out it being used to define some other topology.
I suspect over the years Class S has been used for Sandman and Switching (now known as Class D).

[SpittinLLama]

I don't have a link but back when I was doing research (couple years ago) into different classes Class S was originally defined as what we call Class D today. Class D also was defined but the difference was the LC network on the output. The classes A - H and S were mostly defined nearly 100 years ago. There is a Class E & F but are not very well know (used in communications similar to how Class C is used in radio transmission). In the last 10 years we have seen Class T, I and now XD which are not real classes at all. Class T and I are Class D (Class I being Class BD) and XD being a version of Class AB (or B depending on who you ask). The class of an amplifier is a general description with some having subclasses such as Class D having AD and BD (how the output waveform works) and then tube amplifiers having subclasses based on biasing. Sometimes people get too caught up in trying use a class definition too specifically. But I do hate marketing classes such as T, I and XD.

-SL

[gareth]

Originally posted by SpittinLLama
I don't have a link but back when I was doing research (couple years ago) into different classes Class S was originally defined as what we call Class D today. Class D also was defined but the difference was the LC network on the output. The classes A - H and S were mostly defined nearly 100 years ago. There is a Class E & F but are not very well know (used in communications similar to how Class C is used in radio transmission). In the last 10 years we have seen Class T, I and now XD which are not real classes at all. Class T and I are Class D (Class I being Class BD) and XD being a version of Class AB (or B depending on who you ask). The class of an amplifier is a general description with some having subclasses such as Class D having AD and BD (how the output waveform works) and then tube amplifiers having subclasses based on biasing. Sometimes people get too caught up in trying use a class definition too specifically. But I do hate marketing classes such as T, I and XD.

-SL

Thanks LLama,
I thought that Class D used PWM and Class S was a Class A input feeding a Class B output....do you know if this topology is a good design if implemented properly?

Gareth