plug the guitar into the HD300...plug the XLR into the DT25...fire it all up...put the HD300 in LIVE mode...Pull up a patch and turn off all of the FX...navigate to the PRE models and start tweaking...don't even bother with any FX at all until you get something decent...no need to worry about the mic models as they are disabled in LIVE...when you pick an amp to tinker with...try starting the tone stack flattened out (noon)...run through the cab models and find the one that gets you close, then use the tone stack...try NO CAB also...There are over 400 combinations there and the cab models in LIVE mode are not the same as STUDIO...They are LIVE cab models...and a lot of them work pretty well...you might also try stack power amp and combo power amp modes in the soft menu...That setting only affects the LIVE mode (DUAL also, but you don't want that mode with a DT)...pick what gets you closer to the target...it takes a little time to get under it...A lot of options in that setup...then after you get some tone going, start adding some FX...bottom up approach...best way to get to know it...

What do you mean by "live mode"? I've had a HD500 since release and have never heard of this, and the internet doesn't seem to be of any assistance. How do you specifically set this mode? Also *why*? The HD series should automatically configure itself properly when connecting to a DT series amp.

EDIT: Whoops, I guess Live Mode is something the HD500 doesn't have. Why is that?