First of all, My new Direct Injection box works perfectly! I bought an Art - DPDB which is a dual DI box and it works so good I have just ordered another one (from Juno records) so I will have all of my synths going into these boxes and then onto my soundcard.
I have just done some extensive testing using balanced & unbalanced cables and comparing going direct into my soundcard and also monitored with sennheiser HD25 headphones and visually with Ozone 5 advanced. With Ozones EQ I can take a snapshot of the noise and compare different cables and synths noise.
My findings are of course only for my system but a lot should be applicable to many other situations.
First of all I had a massive hum & digital noise from my moog slim phatty, this was the biggest problem and was clearly audible. Running the slim phatty into the DI box and lifting the ground (switch on DI box) completely removed the noise!
I also tested using an unbalanced cable and a balanced cable from the slim phatty to the DI box and although the slim phatty output is unbalanced I got the best result (least noise) from a balanced cable, maybe because it's newer & better quality?
Next my DSI Tetra. This has stereo (2) unbalanced outputs that gave me that nasty digital noise. The Tetra midi is connected via USB and this is where the noise seems to come from. If I unplug USB cable while listening the digital noise disappears. So I added the DI box inline and BINGO! the noise vanishes.
I also tested balanced and unbalanced cables again like with the slim phatty but conversely it is the unbalanced cables (the older and mis-matched cables) that offer less noise than balanced!
So finally I come to the Microbrute. It was the least of my noise problems and still benefitted from the DI box and the little bit of digital noise I could detect was gone with a flick of the ground lift switch!
Like the Slim Phatty, the micro brute worked fine with a balanced cable from the unbalanced output to the unbalanced input of the DI box.
I hope this little test will help other people as I had no idea what a DI box was and the nasty digital noise was everywhere.
<---- My EDM record label.