Are leds noisy ?

LEDs can be used for bias in quite low-level signal circuitry, I understand. Never done it myself, though.

However, I suspect the OP is asking about panel LED indicators or merely cosmetic LEDs. Perhaps he has read of the significant interference generated by LED lighting? In that case the problem is the SMPS circuitry used to power the LED from the mains supply. The LED itself generates no noise or interference to speak of.

If you can use an LED in the circuit without harm, then putting one on the front panel will do even less harm to the sound.
 
LED's are not designed as voltage references. Other than for economy reasons, I can't see why they are used for that purpose. The TL431 isn't that expensive...

Except that the average LED is at least 50dB quieter everywhere... with single-figure dynamic impedance if run at optimal current; and is a passive, therefore utterly well-behaved part. And is dirty-cheap!
 

FoMoCo

Member
2012-12-04 10:04 pm
Except that the average LED is at least 50dB quieter everywhere... with single-figure dynamic impedance if run at optimal current; and is a passive, therefore utterly well-behaved part. And is dirty-cheap!
Possibly true, depending on the LED. However, the 431 is more consistent across different current ranges. When bypassed properly, you'll never know the difference. And... You don't have to worry about selecting the optimal part.