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

Mike Bryant mbryant at futurehorizons.com
Thu Apr 29 21:19:52 CEST 2021

Hmm this guy seems a bit biased.  Nothing wrong with Jamecon caps or XMOS USB.  More expensive solutions aren’t going to sound any better.

I’d put a multimeter on the power rail feeding R7 with a load attached and see what it does.  Possible the supply is flaky and turning on slowly.  Conversely it could have been engineered to come on slowly.  Note that 44V is inside the phantom power spec so if it gets there eventually it’s not actually non-compliant.

From: Jimmy Moore [mailto:jamoore84 at gmail.com]
Sent: 29 April 2021 20:06
To: Mike Bryant
Cc: synth-diy at synth-diy.org
Subject: Re: [sdiy] [OT?] Audient iD22 audio interface phantom power issues

Hi Mike,

I've tried the other device (A Cloudlifter CL-1) on a separate mixer and it works as expected.   I should have spent more time looking at that schematic -- the 24V on the phantom power switch doesn't make sense to me, either.

I'm just piggybacking on what others have compiled.  A lot of the sleuthing goes to Khron:


Plus a great deal of general griping on gearspace


On Thu, Apr 29, 2021 at 12:57 PM Mike Bryant <mbryant at futurehorizons.com<mailto:mbryant at futurehorizons.com>> wrote:

Definitely not based on the Douglas Self preamp – his has balanced feedback whereas this has unbalanced feedback and is a bit of a mish-mash of other designs.

Have you checked whatever you are plugging in using the phantom power on another device ?   Sounds like it may have a large input capacitor and is taking far more current than the 6k8 resistors can supply.   The phantom power arrangement shown is the one used on all but the highest end devices.  That said R7 is only connected to 24V on your schematic.  This must be wrong if it gets to 44V eventually, but one wonders if there is more circuitry than shown.

From: Synth-diy [mailto:synth-diy-bounces at synth-diy.org<mailto:synth-diy-bounces at synth-diy.org>] On Behalf Of Jimmy Moore via Synth-diy
Sent: 29 April 2021 18:35
To: synth-diy mailing list
Subject: [sdiy] [OT?] Audient iD22 audio interface phantom power issues

(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<https://patentimages.storage.googleapis.com/52/76/46/8792fb86ea4215/GB2242089A.pdf>.  Someone else reverse-engineered a schematic<https://1.bp.blogspot.com/-1twYw6xYHS0/YBh0OBol7sI/AAAAAAAAELs/VR6cPIPxRtAQULgTOpiTylR9FPWWshplgCLcBGAsYHQ/s1751/PreampSchematic.png> indicating 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<https://www.analog.com/media/en/technical-documentation/data-sheets/3439fs.pdf> -- 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<https://1.bp.blogspot.com/-bNr19B8hntQ/YBmtQyRfP5I/AAAAAAAAEMI/QdWLMuHWTdUoV9MWjmX_zIxosI2PVEhowCLcBGAsYHQ/s2048/IMG_1292.jpg> to help with heat dissipation (source and more info here<https://khronscave.blogspot.com/2021/02/67-audient-id22-part-2-repair.html?m=1>)

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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