Lo-fi processing can be easily achieved with the use of some older technology. Run your tracks through tape machines (such as more affordable two-track Revox A77), cassette decks, and VHS players to get a lo-fi vibe. One of the greatest advantages of using retro technology is its sonic uniqueness which can change the aesthetic of a boring synth line, or a dull beat and add life to a mix.
Old Skool Samplers
Sampling drum machines into various, old school samplers can be a great way to create unique-sounding tracks. Run your drum machine into some classic kit like the Akai S-range of samplers, and using the editing features, begin filtering, pitch shifting and so forth. This will create one-of-a-kind drum hits and samples. Older samplers can be picked up on eBay for affordable prices and despite their sometimes-clunky interfaces, can yield very unique results.
Bit by Bitrate
Certain DAWs allow the option of exporting sounds at lower sample rates and bit depths. These features can usually be found during the bounce/export stage. For example if you have a drum track that can use the lo-fi sound, try exporting it at 8-bit and 22.050k, which is a great starting point for getting that hazy sound. Another option for producers who stay in the in-the-box is a bit-crushing plugin such as the d16 Decimort, which was recently updated to version 2. You can try the same settings as above with the luxury of more precise values.
Out of the Box
Record your tracks through guitar pedals, into your DAW to shape your samples. Vintage pedals can particularly deliver gritty/saturated sounds found in so many lo-fi tracks. If you are running VSTs, try recording the outgoing signal into your pedals, then back into your DAW. Not only does it give the sound some ‘life’ but pedals can be picked up for very little expenditure second-hand – even the cheaper Behringer and Boss models can do wonders for a sound.
Struggling to get beats and synths sounding dirty in the box? Try sampling old tape vinyl sounds as well as static from hardware and radio transmission. Mixing this in with the original source can help add a great nostalgic lo-fi feel.