How many LEDs you see on the VU meter when you send signal to your BOUM ? 5 to 6 should be a good start
Did you set the IN GAIN parameter to position 2 or more ?
With VU meter at 5-6 LEDs (near 0dB), IN GAIN at 0dB, DISTO in BOOST mode, COMPRESSOR at min position, you should get a clean sound when the DRIVE pot is at its min position. Raising DRIVE pot will add a soft distortion before mid position, then a more drastic one.
If it’s not the case, maybe your BOUM is faulty (contact us via support email).
If you look at the diagram (p. 6 of the User Manual), you can see that the compressor is placed before the distortion generator. After the compressor, you have an amplifier set by the DRIVE pot, followed by the distortion generator (4 modes).
If you want a “clean” compressor sound, select IN GAIN 0 dB, BOOST mode, fast or slow attack, mid to long release, DRIVE under 9 o’clock.