Garageband/USB Mixer volume issue

My track input volume when I record is at its maximum when I record, as is the mixer output volume because I just cannot get much sound of the playback from GB. When I import a song from my itunes, however, the volume is nice and loud. It is also notable, that when I play my guitar through the mixer, I have to crank the volume all the way to make it register on the LED/clip light indicator. This is reflected when I go to my Mac's system preferences for sound, and the input level for the mixer only registers when the input and output volumes are maxed out. Could this a defective preamp issue? Or is it most likely a mixer setup issue?

The USB interface is connected to the mixer by RCA cables that are plugged into the mixer's tape/CD out and connect to the interface's corresponding in jacks. There is another set of RCA's connected from the mixers tape/CD in to the interface's out jacks that the manual recommends so you can monitor through headphone jack on the mixer what is being recorded.

I have tried both mono channels as well as the stereo channel, all resulting in a very low volume play back of instrument recording on GB. It is also worth noting that when I click on the track info on GB, not matter what channel I am using, I cannot adjust the volume of the monitor.

I also played around with Audacity, and had the same problem as GB.

When I record, the meter for my real instrument track will not go beyond 20 unless I crank up the volume all the way on the corresponding track, the main mix, as well as turning up the trim. When these adjustments are made, the signal will reach about 4 on the upper half of the meter, however I have yet to make it max out. It seems odd that I should have to turn everything up to get a substantial signal. When I record on to garage band, I can get it to record some what loudly (still not adequate volume) however, when I play it back it is basically a whisper.

The USB interface has no control panel of its own, it is a very simple design. It literally is a small box with two sets of RCA jacks, one input and one output. It has not external volume control or any other dials. It is also has no settings accessible through the audio system preferences, input selection screen.

My set up includes a guitar plugged into the line in 1 jack. I usually press the "main" button next to the slider that controls the volume for this track so it can be heard in the main mix and be dually controlled by the main mix slider. The USB interface is connected to the mixer through its CD/input out RCA jacks and connects to the interface's in jacks. This connection is done from mixer RCA output to interface input to guarantee the ability to monitor computer recording through the headphone jack on the mixer. When recording I press the main and Cd/Tape "source" buttons in order to select, well a source for the recording.The "CD/tape to main mix" button is pressed during play back to in order to make what was recording audible from the mixer.