Topology of car audio amplifiers?

[Jeff Wisnia]

My last kid, now 17 years old, just finished building himself a three
speaker subwoofer enclosure and is driving it with a Kenwood Class D
monaural amp, specifically this one:

http://incolor.inebraska.com/weisinator/components/amplifiers/kenwood/kac-8151d.htm

Another retired EE and I got to wondering what the circuit topology of
that amp is likely to be. While I could probably still draw the
schematic of a Dynaco Mk II or a McIntosh C60 (tube) amp from memory, I
sure haven't kept up with high power audio amplifier technology since
the late 60s. <G>

We understand what Class D operation is, but wonder what system they use
to raise the amp's output voltage to reach the claimed power levels into
those specified speaker impedances.

The specs mention a "Copper-Shielded EE Core Transformer", If that's not
just part of the LC low pass filter after the Class-D stage, could it
possibly be a simple audio output xformer right before the speaker
terminals (Unlikely, as it'd be HUGE at those powers and low
frequencies.) Or, is it part of a dc-dc converter ahead of the Class D
switching? Maybe it's used to step up the chopped signal voltage
*between* the Class-D stage and the LC filter?

Also, do those "non peak" power levels specified by "name" manufacturers
like Kenwood really define continuous survivable rms output power
levels, or is there some industry developed standard for typical musical
"duty cycles" which isn't meantioned?

Inquiring minds want to know.

Thanks guys,

 

[CJT]

My last kid, now 17 years old, just finished building himself a three
speaker subwoofer enclosure and is driving it with a Kenwood Class D
monaural amp, specifically this one:

http://incolor.inebraska.com/weisinator/components/amplifiers/kenwood/kac-8151d.htm


Another retired EE and I got to wondering what the circuit topology of
that amp is likely to be. While I could probably still draw the
schematic of a Dynaco Mk II or a McIntosh C60 (tube) amp from memory, I
sure haven't kept up with high power audio amplifier technology since
the late 60s. <G>

We understand what Class D operation is, but wonder what system they use
to raise the amp's output voltage to reach the claimed power levels into
those specified speaker impedances.

The specs mention a "Copper-Shielded EE Core Transformer", If that's not
just part of the LC low pass filter after the Class-D stage, could it
possibly be a simple audio output xformer right before the speaker
terminals (Unlikely, as it'd be HUGE at those powers and low
frequencies.) Or, is it part of a dc-dc converter ahead of the Class D
switching? Maybe it's used to step up the chopped signal voltage
*between* the Class-D stage and the LC filter?

Also, do those "non peak" power levels specified by "name" manufacturers
like Kenwood really define continuous survivable rms output power
levels, or is there some industry developed standard for typical musical
"duty cycles" which isn't meantioned?

Inquiring minds want to know.

Thanks guys,

FWIW, that 40 amp fuse suggests to me that the continuous power is quite
a bit lower than 1000 watts.

 

[Jeff Wisnia]

FWIW, that 40 amp fuse suggests to me that the continuous power is quite
a bit lower than 1000 watts.

Agreed, the instruction booklet which came with that amp says that's
"peak" power.

I didn't read far enough down the spec sheet it clearly reads "Power
MOSFET Switching Power Supply" which pretty much answers my question.<G>

Jeff