I screwed up a setting yesterday. I hooked up a sound devices mix pre d to a house mixer aux send to record some vows. I didnt release i was on 48V at the mix pre d input. Amazingly, I still got distortion free audio! Can some pros enlighten me how was that possible? I have always set it to line level.

Some audio equipment is well enough designed so that feeding 48V phantom power back into an output will have no effect. Especially equipment with proper output transformers will be completely impervious to phantom voltage. You did not identify the house mixer, so we are left to speculate what it might have been.

But, as you seem to suspect, is is NEVER a good idea to feed phantom power to anything except a microphone that needs it.

I am a bit surprised that your SD mixer even allows applying phantom power when set for line-level. How do you know you were really feeding phantom?

Hi Richard, It was an operator error. Due to limited time to setup, i had accidentally left the SD input switch at 48V and hooked it to the house mixer. I am sure the house mixer was a LINE level. On reviewing the audio it is fine but it lacks bass. I think that is the side effect but I'm still glad it was distorted!

When switched to line-level, Phantom Power is disabled by default on 'most' mixer's input, if you used mic level, you were lucky everything was wired accordingly and no damage occurred.

I screwed up a setting yesterday. I hooked up a sound devices mix pre d to a house mixer aux send to record some vows. I didnt release i was on 48V at the mix pre d input. Amazingly, I still got distortion free audio! Can some pros enlighten me how was that possible? I have always set it to line level.

If you're Mix pre was set to line level, phantom power was probably switched out. It's not typical for an mic/line input to present phantom power when switched to line level.

Regards,

Ty Ford