Audio amps

[Cali-Sam]

Dave!!!
Can you dedicate a vblog on audio amplifies, car amps, home theater amps and so on... how they reach the thousands of watts, how watts are calculated. what method of amplification they use..... i love audio amplifiers, but i have so many question marks flying around my head... u can do a tear down if u want... 
i know that you are not a fan of audio amps, and i know that there are info online about the subject, BUT nothing is more informative than your highly educative VBlogs.
thanks for your dedication Dave!!!!!

[nanofrog]

Not sure about a good video for audio amp design, but there are some sites with good information (solid circuits, not Snake Oil, and explain the types of questions you list).

www.diyaudio.com would be a good place to start (people such as Nelson Pass, Bob Cordell, John Curl, and Bob Pease for example have posted there, and links to other useful sites).

[vk6zgo]

The "thousands of watts" for any domestic or car system are mainly what are called "marketing watts".
If the thing doesn't draw 1000watts from the supply,it can't supply 1000watts to the speakers!

The sound systems used at Rock Concerts are another kettle of fish.
They can produce real power in the  multi-kilowatt regions.

The most powerful audio amplifier I ever had anything to do with was a Modulation Amplifier which produced enough audio power to 100% modulate a 55KW AM Broadcast Transmitter.
It was huge,but used the same techniques that lower power amplifiers utilised.

This was in the tube era,but the same can be said for solid state equipment.
Same stuff,but bigger ,or in many cases,"more of",so if you learn about lower power amps,you will be able to understand big ones,too!

[SeanB]

AM transmitters generally have an audio amplifier for the modulator that is the same power as the carrier at that level. As a lot do AM modulation near the final stage the audio amp is pretty big, and has to be both linear with varying loads and have a response that goes to 100kHz or more at full power. It also has to be happy with RF injected into the output at high levels.

[ejeffrey]

Just out of curiosity, why would you do AM modulation on the high power signal rather than modulating a lower power signal and then amplifying it up?  Are the high power RF amplifiers too non-linear?

[SeanB]

AM transmitter amplifiers are very far from linear, to get good efficiency. Typically they run in class C, and this is only to give 80% plus efficiency. Not good to have a 100kW transmitter where you have an input power of 200kW just for the final stage. when you get over 10kW most are hollow state, there are mosfet and bipolar ones, but they use literally thousands of devices to get that power, and are not regarded as reliable enough. The tube ones use one or two tubes at the power, and those are often rebuildable when they wear out, at a big cost saving over new.