A high-voltage combination of venerable classics: a 20-tube powered Fairchild 670 clone (PCB by Drip, original tubes, original tube power supply) compressor/limiter, Distopik EQP-1A program equalizer and a GML/Sontec inspired, surgically accurate Distopik Precision Series Mastering EQ. This bundle is guaranteed to infuse your mixes with both mojo and definition to make them perform their best on all reproduction systems.
Use the Pultec clones to shape the general spectrum balance and control the low end before hitting the Fairchild 670 clone. Experiment with different timing constants and don’t be afraid to push it a bit harder - hardware can usually survive quite a bit more gain reduction then software emulations before it starts “breaking up”. If the audio was already compressed to some extent, try higher ratios and adjust the threshold to barely move the needle. This will add some sweet “tube and iron” presence and depth. Finally, use the Precision EQ to eliminate clogged or resonating frequencies or return some low/high end to the mix, if it had to be adjusted earlier for the Fairchild 670 clone to behave as desired.