you say you "can hear the sound only through the computer speakers" but "cannot hear any sound through the soundcard" ? aren't the computer speakers physically connected to the soundcard? so, what gives?
otoh. when you play a MIDI file and drive in through a MIDI instrument plugin like Calf Fluidsynth, the thing you get on output is the rendered audio signal produced by the instrument plugin; you only have to connect qtractor's (master) audio output bus to the system soundcard / speakers to get the audible sound into your ears; you don't need to connect any MIDI in or out whatsoever, coz all that is handled internally in sequencer, can you understand?
now it's me who is confused :)
you say you "can hear the sound only through the computer speakers" but "cannot hear any sound through the soundcard" ? aren't the computer speakers physically connected to the soundcard? so, what gives?
otoh. when you play a MIDI file and drive in through a MIDI instrument plugin like Calf Fluidsynth, the thing you get on output is the rendered audio signal produced by the instrument plugin; you only have to connect qtractor's (master) audio output bus to the system soundcard / speakers to get the audible sound into your ears; you don't need to connect any MIDI in or out whatsoever, coz all that is handled internally in sequencer, can you understand?
hope so.
cheers