I need BASS!!!

[Timo]

Find a bass patch, literally any bass patch, or pretty much any/all lead patches (with a short attack and short release), too.

Add the sub-osc and whack it up.

The FM feature is my favourite weapon for rich bass on the Virus...

Make sure the Osc2 sync' button is disabled, then use the FM amount knob. - Turn it very slowly (one value at a time) and tune it to the sound you're hearing, while repeatedly holding or hitting a key/note. There's a dozen or so sweet spots on a whole sweep of the FM amount knob, depending on the Osc2 detune value (play around with the detune control - it acts like a "fine-tune" to the FM amount, but it doesn't have to be any way surgically perfect to give nice sonic results - far from it) and the chord structure you're using for the song, and this will add some really nice additional harmonics to underlie and strengthen the bass patch before it goes to be filtered + processed.

After that, use the filter-env control(s) to start with full attack and (moderately quickly) sweep downwards, and then set a filter envelope-amount (depth) of around 64, and add a little resonance (not too much). Lower the cutoff knob until the sound starts with a little higher/mid freqs before sweeping downwards (as specified in the filter env). It'll add a little punch to the forefront of the patch and will control where the resonance will sweep from/to.

Inject a distortion model (start from an actual value of 0 at first to keep it subtle so you can hear the differences between the models, and then when you've found a nice distortion type gently raise it up), and this will bring out the raw-sounding FM harmonics from earlier and give it some real bite. Maybe add a little saturation, but not a lot. Valve emulation stuff isn't all that good for low-EQ's/bass, imho - it makes it woolly and loose. I tend to find valve/saturation is best suited to mid-range sounds.

Finally alter the resonance, the cutoff, filter-env, (etc.) a little to taste, to get everything to balance and flesh out. Add analog-boost and tune it, etc.