Can one use a transformer to isolate ground at the output, to act as a ground lift?

It came up for a specific project, but I'm also asking in a general sense as someone who needs to learn more about transformers

For context, the effort is a (bass) eq/preamp, including an active DI out. I would like to have the option to accept phantom power through the DI jack, and including a ground lift with phantom power seems tricky.

I ALSO have an EBTECH 'hum eliminator,' which is passive and seems to just be a transformer and a few resistors, and I'm assuming its isolating the ground

So.. I don't know if I sound like a doofus here, but it seems feasible that I could utilize these transformers, isolate the ground on the 1/4" out (to amp).. I'm assuming that's the easier move?

Any meat on these bones? Am I a big dummy? Is that rhetorical?

I'm trying to find some info on the transformers, they say NX817 LF3 , as well as EBTECH101 WE-MIDCOM, but I'm not finding much to elucidate me as to its characteristics.. me dumdum brain me think it probably 1:1, but I'm clueless as to if that would even be appropriate

 

Sure you can, just look at the schematic of any DI box.

Quote from: Eddododo on January 25, 2025, 01:11:54 AMincluding a ground lift with phantom power seems tricky

Why? Might it have something to do with "DI jack"? P48 is typically for XLR but jacks (TRS) can be balanced too.

Quote from: Eddododo on January 25, 2025, 01:11:54 AMI would like to have the option to accept phantom power through the DI jack, and including a ground lift with phantom power seems tricky.

Do you mean you want to power the unit from phantom power via the Di output? You can do that, and yes it will effectively break the ground connection, though the transformer won't be truly floating, but it doesn't need to be.

QuoteI'm trying to find some info on the transformers, they say NX817 LF3 , as well as EBTECH101 WE-MIDCOM

Those are Wurth transformers. If you post a pic we may be able to identify them.

OK, I read a DI box review in Sound on Sound today, and here is what that manufacturer did.  Warning, it's a bit complex. You need the ground pin on the balanced output to always be connected as it is part of the phantom power.  Disconnect that ground pin and the phantom dies.  Essentially they use the phantom power to run a power supply that has a small power transformer driven from a high frequency oscillator.  Then there is the traditional full wave rectifier, filter caps etc.  That setup means that the unit power supply ground is isolated from the power supply for the audio circuit.  The ground lift switch can disconnect the audio ground from the balanced out ground, without disconnecting the balanced out ground from the power supply, and you essentially have a ground lift.   

This is the beasty in question with a better description and photos of the board  https://www.soundonsound.com/reviews/grace-design-m303

+1! I should have clarified that if you have a transformer output then you don't need a ground lift, it would do nothing since the ground is no longer part of the signal current path (but it is needed for phantom power current return).