Bo Hansen Active DI


I got a couple of these Whirlwind DI boxes really cheap. Their performance is kind of mediocre. But the enclosures are actually nice and sturdy. So, I decided to refit them with Bo Hansén’s active DI circuit.





I took the originals apart and, before throwing the stock circuit boards in the trash, used them as templates to make new circuit boards, to make sure the new boards would fit perfectly.

The components I used are all the same as indicated in the original schematic. But I did make a couple of minor additions.

The Whirlwind originally had a 3-position pad switch (0, -20dB, -40dB) and a 2-position ground lift switch. I elected to keep those switches and use them to add some additional functionality.

I used the 2-position switch for phase inversion, swapping pin2/pin3 on the output XLR jack.

And, I attempted to use the 3-position switch to implement a hi-cut/lo-cut filter with a couple of capacitors. The middle switch position is normal (no cut).

Although I’ve never had occasion to use either, the phase switch does exactly what it should, but the hi/lo cut switch sounds kind of… well, let’s just say that it probably could have been done a little better. Anyway, here’s my circuit layout:


How’s it work/sound?

I’ve used these a number of times at live shows for keyboard and acoustic guitar. Aside from my goofy switches (I just leave them both in norm position), they sound beautiful and they really stand up great to getting kicked around a stage before, during and after shows.