[sdiy] [OT?] Audient iD22 audio interface phantom power issues

Jimmy Moore jamoore84 at gmail.com
Thu Apr 29 19:34:54 CEST 2021

(Less to do with synths, but still in the broader signal chain, so
apologies for being somewhat OT)

I have an Audient iD22 interface that's been great for the 6 years I've
owned it. However, using phantom power (for the first time) only output
38VDC, which eventually climbed up to 44-45VDC, and seems to sit there.
I've had trouble using it to power a cloudlifter.

I don't have schematics for the Audient iD22, but its preamp circuit is
apparently inspired from Douglas Self's Soundcraft preamp
Someone else reverse-engineered a schematic
the P48 source and specific componentry -- it touches a few 47uF Jamicon
caps which might play a role.

Would anyone know why a phantom power circuit (or this circuit?) would
produce such low and variable output?

Audient's power controller -- an LT3439
-- is responsible for generating the various power rails in the device,
which is not without some questionable design choices from an undersized
heatsink and potentially not being properly soldered to the ground plane
to help with heat dissipation (source and more info here

I've written up my own explorations into this
<https://utahjimmy.github.io/projects/8_project-audient/>, but the TL;DR
is: things get really hot on the inside, and perhaps this is all due to
component wear and tear.

I'm only a hobbyist, and not sure if something like this is fixable.
Regardless, I am very curious to hear people's thoughts on what might cause
my output to be low, but slowly increase over time. Does this sound like a
capacitor problem?  A power controller problem?  Both?

Thanks for your time!
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