I agree with the above. A fine introduction or quick refresher.
Analogue effects are often best done with real equipment. But software can do a job, such as freebie
Ferox for saturation. But the more proficient you get the less you can rely on things like these. Tape saturation is kind-of like a fabric softener for sound. If you want real warmth, then a valve unit or VST should also be used.
If you've access to a good tape deck then that's likely the best option of all. Even the UAD card emulators apparently can't give you the full deal.
For warmth, AMT Max Warm enhances in compression. Hardware emulations like the Terratec
Phase 88 Rack or Focusrite
Platinum Penta can provide a boost with their harmonic distortion. Behringer's
Ultragain Pro and
Tube Ultra-Q both use valves but for different effects. With a flick of the knobs and switches, Ultragain can either warm a track or give it a crisp, dry airy sound with a slightly-warmer by-product.
The Ultra-Q is an equaliser with valve stage. This can wetten and sweeten a very dry sound and add presence to the track, even if you don't bother with the actual EQ.
Even a retro organ can be used to flavour a guitar input, preferably bass. I do this myself.
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