How does the music signal get amplifying current in Class-D ?

[stephend1714]

A totally non-techie guy asks [so keep it simple please] with two other related questions :

!. Any similarity with analog class A or AB ? For class D is there a capacitor storage bank with power reserve ?

2. How is a class D's request for instantaneous current better than the conventional analog amplifier solution ?

 

[nigelwright7557]

Class A is said to be better than AB.
Personally I can never tell the difference. A well designed class AB will sound good anyway.

A class D amp has smoothing capacitors the same as any other type of amp.

 

[rayma]

How is a class D's request for instantaneous current better than the conventional analog amplifier solution ?

The main advantage is efficiency, since the output devices are (almost) always either on (very low voltage drop) or off (no current).
So, when one factor of V(device) * I (device) is low, the product (power) is also low. Thus, low power dissipation in the device.
In practice, the finite device on resistance causes some conduction power loss, and there is also switching loss,
as the device transitions through the active region.

 

[sofaspud]

A) Some people like to describe it as "modulating the DC power supply." For a given impedance, amplify the voltage level and the current must follow.
1) Yes, to the extent that these amp classes are all defined by the time the active device is on and off.
"Capacitor storage bank..." refers to power supplies, not any specific class of amplifier.
2) With class D, the amplifying devices are either on or off. That can be looked at as requesting instantaneous current, but more importantly, it means there is little power wasted as heat in the active devices. Off = infinite resistance. On = zero resistance.