Led indicator in solid state amps

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Led indicator in solid state amps

Postby phase396 » 06 Mar 2019, 20:34

Hello everyone. I have a pretty simple question. After looking at a lot of schematics, I've noticed that some placed the inicator led between the +/- power rails and some place it between the + rail and ground. Why? Is one way better than the other? I've built a solid state amp that has a tda7294 chip amp in the output and uses a split rail (+/-) supply. Any help would be apreciated.
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Re: Led indicator in solid state amps

Postby thetragichero » 07 Mar 2019, 00:47

it shouldn't make much difference as long as you have a proper current limiting resistor in there (sometimes I can forget that a +/-15V supply is a 30V supply kinda thing)
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Re: Led indicator in solid state amps

Postby deltafred » 08 Mar 2019, 10:18

The advantage to putting it across the +/- supplies is that it acts as a monitor so if it fails to light or is dim then you know something is wrong with the supply rails. If it is across the + only then the - rail can be faulty and it will still light normally.

The slight disadvantage is that more power is dissipated in the current limiting resistor.
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