I think I know the sound you mean. Depending on what synth you're using you could try playing around with the "unison" setting to detune mulitple copies of the same oscilator. Feeding saws in to this put through a parallel filter network of a low pass at around 150Htz (so you clip harmonics above middle C) and a notch filter centered around the upper high frequencies will typically give you what you're looking for. Adding chorus and a tiny touch of reverb can thicken the sound, but be vrey conservative here. Using your chorus completely wet will make your bassline quite unstable. A note on the reverb used: Don't try to get as smooth a reverb sound as possible i.e. use a diffusion percentage of around 50% or less otherwise things will sound muddy. Exciters can make a differnece too.
Is
this the kind of sound you mean?