ART DTI

I bought three of these units to connect the balanced inputs and outputs of my Focusrite 18i16 audio interface to the line in and line out of a Kawai DG-30 digital piano (unbalanced TS) and the line in of an Argon Alto A5 hifi active speaker (RCA). My hope was that this would allow me to use longer (5m) balanced cables from the Focusrite to the ART DTI, and then a short unbalanced cable from the DTI to the piano or the speakers. Unfortunately, using the ART DTI devices introduced a very loud mains hum (50 Hz), waaay worse than anything that a cable might have picked up. I tried the DTI in both directions, with the ground lug connected or not, to no avail. Indeed, connecting the ground lug of the DTI to a proper ground made the problem significantly worse, not better. Since I had three devices I could also check if perhaps one was fauly, but they all behaved the same way.

Before I bought the device I saw that some other reviews also mentioned that the DTI made hum worse rather than better, but they seemed isolated incidents; the majority of the reviews seemed very positive. Having now studied the manual more carefully, perhaps this line is crucial: "Grounding: Only connect the unit to equipment with properly
grounded mains power.". Neither the Kawai, not the Argon Alto's are have power supplies that connect to ground; even the Focusrite (USB power adapter) is not connected to ground, unless perhaps through the USB cable to the computer (which _does_ have a ground connection). Perhaps that is my problem (I don't really understand the physics of the situation well enough), but if so, perhaps this should be stated more clearly.

For the record, in the end I went with balanced TRS cable (sssnake SPP2050) straight from the Focusrite into the 18i16, which worked perfectly, no hum at all -- I had previously been using an unbalanced cable, which did pick up a faint but audible hum. For the Argon Alto's, I went with an unbalanced TS to RCA cable (Cordial CFU 6 PC).