My doctor says I need to reduce my stress, so a good laugh is helpful
I'm going to chip in here, not because I have a Master of EE hanging on the wall surrounded by Patents, (which I do)
And not because I can clear a blocked septic, (and yes I have done this, and hats off to all you plumber dudes who do this for a living).
But because I recently used a TDA7056B in a design , these are mono, linear class AB, BTL , 5w output, designed for 12v single supply operation, the neat thing is they have a voltage controlled volume input, just add a capacitor and no start up plops or clicks when the audio is muted. They also have an unbalanced current detection so if the speaker were inadvertently shorted to ground it would shut down. (Annoyingly if the TDA7056A is connected to a microphone, and you tap the microphone , it also shuts down). A bit of searching reveals the chip was originally the TDA7056, then TDA7056A , then TDA7056B , with subtle improvements along the way, you have to wonder whether the earlier versions had magic smoke issues.
The reason for the post is the make the following observation, that seems to have been skirted around by a few:
Normally with a BTL amplifier, each speaker terminal is connected to an amplifier output, but you can't do this with stereo headpones as they share a common ground, so you
do need a decoupling capacitor with headphones. So most of the TDA datasheets will show directly connected speakers , and capacitively connected headphones. So next time when you flick from page to page or datasheet to data sheet and notice the capacitors seem to come and go randomly, have a look and see if the load is a speaker or headphones.
I've just looked in my resistor kit, and lo and behold , in the 13ohm drawer, there are 100 bandoliered resistors: brown-orange-black-gold-brown-red , which is exactly the same quantity as 20 years ago, so just goes to show how useful 13ohm resistors are.
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