I'm using a UM-1G USB-MIDI adaptor, taking the MIDI out from my Merge brick and MIDI In to the Zen. The DT-HD1 appears to recognise the Zen as I get the "scores" when i hit correct notes - or miss them - but I can't hear any notes from the Zen or the DT-HD1. Any suggestions?
You do still need a sound source of course. Drum Tutor to the best of my knowledge does not produce any sound. The typical usage of it is to have a Roland sound module (such as the HD-1) plugged into it. Do you own a sound module that has both MIDI IN as well as OUT? If so, the easiest route is probably to plug your zen into the module first, and then plug the module in to the PC.
Alternatively you could use a VST based source (such as your BFD Eco). You might need to fiddle around with port sharing then though. Depends on if either piece of software takes exclusive use of the MIDI port.
And slightly off-topic .... I've also connected the Zen to BFD eco for the first time and while everything appears corectly mapped, I am not really getting any dynamics at all from the program. And the machine-gunning is very noticeable. Are these common phenomena or sould I be getting better dynamics?
You should be getting better dynamics, yes. You might want to play around with your response curve and noise floor settings in the zen. BFD2 also has an 'anti-machine gun' setting, though I do not know if this is available in Eco, and to be honest, I never thought it had *much* effect in BFD2. Best way to combat machine-gunning is to have two snares setup in BFD, each using the same base snare samples, but tuned slightly differently so as to be more distinct. Then assign one to your left hand snare trigger(s) and the other to your right.