On the mixer it peaks, but records too quiet sound

Hi Everyone!

I was trying to look it up, but was unable as it is pretty specific. However I am pretty sure people had such problem before.

So, I have:

  1. Yamaha MG166CX-USB Mixer
  2. AKAI MPC 1000
  3. Yamaha MM6 Synthesizer
  4. PC with Acid Pro 6
  5. M-Audio BX5a monitors
  • AKAI and Synthesizer connected to the mixer via stereo Analog inputs.
  • Mixer is connected to the PC via USB cable

When computer is not in the “formula” everything sounds great and loud enough (even more than enough), depending on the Monitor/Phones sound regulator.

When I try to record something onto Acid through the mixer directly via USB - the recorded sound is too quiet. I can set it very loud on to the monitors or even through the computer to the monitors, but if I set the channel/main out higher or boost frequencies on the channel which I record to the computer - it starts to peak on the mixer to the red levels which is not good. If I set it right about the peak level, but not at the red levels - it is too quiet…

(USB level knob is set to the HIGHEST!)

Important - I also have Octava microphone connected through the compression channel which records fine with the gain knob leveled up and the channel to which the microphone is connected almost all the way up, but it seems to me it shouldn’t be so much up to be able to record it at a normal sound level, pretty much I can’t really record the voice “too loud”.
Synthesizer is a little better with recording, however same as with the voice - I don’t think it the channel and the main out should be so high to be able to hear it normally
AKAI is peaking the most since I make drums on it and the drum loops I record are completely quiet at barely normal peak levels.

So, as I see it, the problem is with transferring the sound to the computer, the signal is too low. I’ve tried adjusting the channel levels in all the different ways and tried different channels on the mixer to make sure the channel is working fine - but it is still “Peaking” on the mixer and too quiet once recorded on the computer.
Do I need an Audio/USB interface - and then connect the mixer to it to boost the recording signal? Or do I need an amp/pre-amp. I know some stuff about recording, but I always had this problem with quiet signal when recording on the computer…
If not Audio/USB any suggestions/help would be really appreciated!

*** one more thing to add: whatever is recorded if played through the mixer back to the monitors - I can set very loud, but I hear the noice since it was recorded at very high levels of sound… hope it makes sense → so it is definitely a problem with the sound going to the computer via USB