Bo Hansen Active DI

Hi all,

New to electronics and to CL. I'm looking at Bo Hansen's Active DI ( as my first build and thought it would be interesting to throw the schematic up on CL. I thought it would help me understand how it works, as well as provide useful information for test purposes when I actually build it.

I think I have the components drawn correctly, but I'm struggling with the inputs/outputs/power supply. I'd appreciate any thoughts or suggestion. Bo kindly took a look and offered his comments here:

I'm not sure how to incorporate his suggestions into this simulation and am hoping that someone here with experience using CL with audio electronics can help.

Here's a link to my circuit:

Thanks, Brian

by bds2020
January 13, 2014


Welcome to CL.

Just so that everyone understands what you're talking about I have assumed by "DI" you mean one of these:

Here's a copy of your circuit tidied up a bit for clarity and with a form of 48V phantom power supply added:

I'm not sure what load there should be at the console end but at the value of 100R that you have used, the gain of the circuit is significantly reduced below unity due to the transformer winding resistances.


by signality
January 14, 2014


Thank you. This is very helpful. I need to spend some time now playing with it.

The one thing that jumped out at me is that the top voltage rail is simulating a higher voltage and amperage (+32v, 4.5 mA) than indicated in the original schematic (+24v, 3.5mA).

Thanks again, Brian

by bds2020
January 14, 2014

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