If you’re trying to make your digital master sound more indicative of an analog master, you need to start by considering how analog routing works. Imagine how the signal gets routed in an actual analog system, and consider each step that the signal goes through from start to finish.
Typically an analog master would have begun with the track being stored on a 2 track mix bus tape machine - so we can start with a tape machine plugin.
From there it would be sent to some form of amplifier or transmitter of the signal like a console - so we can use a tube or transformer emulator.
Then we’ll route the signal to an analog eq, and finish with an analog emulated limiter. Finally, the master would end up back on tape, and then to vinyl.
Analog distortion is any form of distortion that’s indicative of classic hardware components and their distortion behavior - this distortion will vary from component to component. When mastering, analog emulated distortion can make the signal sound both classic and warm and as well as full and impressive.
Tube distortion is commonly emulated - typically it creates strong second-order harmonics, resulting in a warm, full sound.
Tape is a bit brighter since it can cause higher-order harmonic distortion.
When mastering, carefully pick which distortion types you introduce, since they heavily correlate with the final timbre of your master. Always, always use oversampling when it’s available - since this will reduce aliasing, a distinctly digital form of distortion.
What makes analog compression different from digital compression is the introduction of nonlinearities in the rate of the compression - these non-linearities include soft-knee settings as well as a ratio that doesn’t remain consistent with amplitude. When mastering, these characteristics can be emulated to create an analog sound.
A lot of digital compressors offer a soft-knee setting which will cause more gradual compression that’s less noticeable - but the compressor will begin to compress at lower amplitudes, resulting in more overall compression when compared to hard-knee settings.
It’s a little harder to find a digital compressor that offers non-linear ratios, but Presswerk by u-he is a good example. If you’ve heard of others definitely let me know.
Analog equalization is unique in that it imparts distinct slopes, Q values, and phase relationships that don’t occur in digital systems unless purposely programmed in. Each analog equalizer utilizes unique curves and phase relations, resulting in the multitude of analog equalizer emulation plugins available today.
If you want to create a more analog sound with your equalization, use something like the curve bender plugin, or similar equalizer plugin. Sometimes a DAW will also offer emulations of a Pultec or API equalizer, which is a good alternative.
If you have the FabFilter Pro Q 3, you can use the natural phase setting, and look up some charts of your favorite analog equalizers to emulate the slopes and curves.
If you already added soft-knee compression and distortion to your master, then you’ve saturated your master - but if you’d like to combine these effects into one, you can use a dedicated saturation plugin. By combining compression and harmonic distortion, you end up with a full and controlled sound.
In the analog domain, saturation occurs when the signal is sent through an electrical component at too high an amplitude to be handled by the component. For example, tape saturation occurs when the particles of the tape have all been re-oriented, yet there’s still a signal to be added.
A gradual non-linear input to output ratio will occur - also known as compression - while harmonics form.
Analog stereo imaging isn’t common, but there are some ways to introduce stereo expansion using analog emulations - this results in expansion that's distinctly analog. Tape crosstalk and tape asperity are 2 technical issues that are useful if you intend to stereo expansion but want to your master to sound analog.
Asperity refers to imperfections on the surface of the tape, which causes noise to exist in the stereo image - resulting in a perceived wider image.
Crosstalk occurs when the left and right channels bleed into one another. This will cause phase cancellation and stereo expansion.
Satin by u-he offers both asperity and crosstalk. Tape by Softube offers just crosstalk.
There are many reasons why you might want to add mild analog noise of distortion to your master - it causes more realistic emulation, can have a pleasing effect and can serve as dithering when converting to lower bit-depths. Analog noise varies greatly from processor to processor.
For example, tape noise will be slightly different than tube noise - furthermore, tape degradation will alter the noise floor and behavior of the noise.
In the case of vinyl emulation, we have a combination of noise types, like hiss and crackle.
What’s interesting is that if you needed dithering, this analog noise will often be louder than the quantization distortion caused in a digital recording, meaning you’ve dithering your master.