[quote name='discreet' timestamp='1453127682' post='2956588']
They are very useful indeed but should be used with discretion, especially the VPF and especially live. The VLE (Vintage Loudspeaker Emulator) gradually rolls off a wider and wider range of top-end for a more old-skool sound, while the VPF (Variable Pre-Shape Filter) will progressively Boost lows and highs, in effect giving you a mid-scooped sound. Though this makes the amp sound very nice when playing solo or at home, you definitely don't want to be scooping your mids in a live situation as you will not be heard.
It's important to note that both controls are only in the 'OFF' position when fully LEFT, and not at 12 o'clock.
They are a major selling point of Markbass amps. When I had a Markbass, I set the EQ controls flat and got all the sounds I needed using only the VLE and VPF filters. You can get an amazing combination of tones just by using the filters and nothing else.
[/quote]This. I do exactly the same on my Markbass amps.