The Class TD Amplifiers

[opacheco]

Hi, do someone have any information about how the TD class amplifiers works? I have searching for this topic but I found nothing concrete about them.

Thanks in advance
opacheco

 

[opacheco]

any idea?

opacheco

 

[ccaudle]

any information about how the TD class amplifiers works?

I have never heard that term. Any references to where it is used? Is it a marketing term that one particular company came up with?

 

[opacheco]

I have never heard that term. Any references to where it is used? Is it a marketing term that one particular company came up with?

ccaudle Hello,

The Lab Gruppen company did this Technology reality in its famous Lab Gruppen FP-6400 and the same unit done for L Acoustic LA48, the same amplifier with minors differences; both TD class amplifier using a switching power amp in order to get more efficient amp and get a sound like the B class amplifier….but look like there aren’t more info in the web.

Thanks
opacheco

 

[OneRoomStudio]

I don’t know if “Class TD” is a real thing. Class D certainly is. For while, Tripath (a company that has made a number of nice Class D amplifiers) used the term “Class T” in their marketing, but it was purely marketing - all the “Class T” amps were Class D.

I’m guessing that got further confused and turned into “Class TD” somewhere along the way.

More info here: https://en.wikipedia.org/wiki/Class-T_amplifier

 

[ccaudle]

TD class amplifier using a switching power amp in order to get more efficient amp

OK, I think I see what they are doing.
It is like class H described on this page:
class G and H amplifiers

The power dissipated in the output stage is determined by the current through the output stage, and the voltage across the output devices.
A class D amplifier reduces the product of voltage and current by having the output devices either low impedance, fully on, so the voltage is low, or high impedance/off so the current is low, but the full power supply voltage is across the device.

Class H or TD gets the reduced power dissipation by reducing the power supply voltage when the signal amplitude is low, and raising the power supply voltage as the signal increases, so that the output device always has say 5V across it no matter the output voltage or current.
If the power supply voltage is changed using an analog regulator design, then the entire amplifier dissipation is still high, because now the power supply is dissipating power when the output stage is not.

Lab Gruppen just took the obvious approach of using a variable regulated SMPS for the power supply in a class H design to reduce the total power dissipation, then tasked their marketing department with coming up with something clever to call it.

 

[opacheco]

I don’t know if “Class TD” is a real thing. Class D certainly is. For while, Tripath (a company that has made a number of nice Class D amplifiers) used the term “Class T” in their marketing, but it was purely marketing - all the “Class T” amps were Class D.

I’m guessing that got further confused and turned into “Class TD” somewhere along the way.

More info here: https://en.wikipedia.org/wiki/Class-T_amplifier

Class TD mean Transition D class type, its PSU are continuously variable but no into discrete steps.

opacheco

 

[opacheco]

The only descriptive info that I found about was the Lab Gruppen company:

“Class TD Output Stage
Delivering the High Efficiency of a Class D Design With the Sonic Purity of a Class B Design Amplifier.

The foundation of Lab Gruppen’s prowess in power amplification, Class TD is a breakthrough design that occupied Lab Gruppen’s co-founder Kenneth Andersson for nearly two years. Class TD combines the high efficiency of a digital Class D with the sonic purity of classic Class B designs.

The power supply rails precisely track the audio signal at all times, providing the required voltage plus additional headroom. This process is highly efficient, with only a tiny portion of the supplied voltage emitted as heat in the output stage.

The audio path itself remains entirely in the analog domain. And because the audio path remains outside the switching portion of the circuit, the signal is free from any filtering ripple effects.

Class TD is bridgeable, highly reliable, and maintains a flat response with complex loads as low as 2 ohms nominal. Also, it does not interfere with RF equipment such as wireless (radio) microphones. Though treated separately here, R.SMPS and Class TD were conceived and engineered as an integral design within the amplifier platform. Working together, this new generation of proprietary circuits produces more power from a smaller package while at the same time maintaining Lab Gruppen’s peerless reputation for sonic excellence. The highs stay crisp and transparent. The mids are defined, warm and natural. And the tight low end delivers breathtaking visceral impact.”
(https://www.labgruppen.com/technologies/class-tc-output-stage.html)

Class H designs boost efficiency by modulating the power supply voltage with the input signal, “tracking” the input in order to provide the instantaneous voltage needed for optimum operation of the output devices. However, maximum efficiency with class H is achieved only within a relatively limited dynamic range. The TD stands for “tracking class D,” which means that the power supply tracks the audio signal at all frequencies, supplying the required rail voltage while at the same time reserving additional headroom. The high-speed switching principles of class D are employed as well, though the final output stage remains a proven class AB component. (https://mediadl.musictribe.com/download/webservice/labgruppen/C-Series_Technology_Brief.pdf)

Thanks
opacheco