Yamaha DTXpress/DTXplorer/DTXtreme

Hello and thanks in advance for any help. I'm recording direct to my 
Tascam 388 and although I have both the internal and knob volume 
maxed out I'm still not getting a strong signal. I get a stronger 
signal (still not good enough) going from the module headphone jack 
out to the board. I have to put the faders on my Tascam all the way 
up and still the meters barely register the kit. Now, I've been going 
through a compressor which has boosted the signal enough, but still I 
should not have to go through a compressor, there should be plenty of 
signal going direct from the outs of the module. Any ideas?

Thanks,
Eddie