The Pultec Trick - How To Achieve Tight Low End
Our Tube-Tech PE 1C, used to acheive the pultec trick.
What Is the “Pultec Trick”?
Unlike digital parametric EQ’s, Pultec units (as well as their clones) function via the utilization of large boost and attenuation knobs, and, while you can select the frequencies and (to an extent) the bandwidth you wish to alter, they’re less meant for surgical and more intended for “broad” correction.
Analog equipment is imperfect, and that’s a part of what gives each piece a unique character and tone. In the original Pultec manuals, users were advised against boosting and cutting the same frequency, which, due to the imperfections of analog gear produced “strange” results. Turns out, audio engineers started falling in love with said strange results.
Boosting and attenuating the exact same frequency produces unique and, oftentimes, desirable EQ curves - most famously utilized to tighten up low-end.
What’s Going On Under the Hood?
Cutting and boosting the same frequency utilizing a precise software parametric EQ is a zero-sum operation. The boost and cut would cancel out and result in nothing. This, however, is far from the truth with Pultec-style EQs.
Pultec and Pultec-style analog EQs rely on capacitors, transistors and tubes to shape signals. Being that these passive elements result in a signal reduction, Pultec EQs contain a tube amplifier to return the signal to it’s original and desired level. These elements impart harmonic saturation on whatever is passed through the unit, imparting a musical and interesting tone otherwise unachievable with digital emulation models. See our blog post on analog saturation for more info on the “hows and whys” of analog sound.
The Pultec EQ, in all of its imperfect glory, boasts different curves for its low-frequency boost and attenuation controls. This means that, the boost and cut curves are not the exact same shape, meaning that, unlike perfect parametric EQ work, these adjustments cannot cancel each other off.
The boost control applies a broad and soft shelving curve starting below the selected frequency, which puts some extra focus on the fundamental frequencies.
The attenuation curve applies a narrower curve, and begins slightly above the selected frequency.
By boosting and cutting at a single frequency (let’s say 60Hz) - a complex EQ curve is created which boosts the desirable low-end frequencies while simultaneously reducing mud and excessive unwanted buildup.
Thus, boosting and cutting a kick drum at 60 Hz with a Pultec style EQ should reinforce the desirable fundamental thump while reducing often problematic buildup and boxiness, AND also introduce desirable second and third harmonics via analog saturation due to tried and true hardware musicality. Enhance the good stuff, clean up the bad, and add analog richness, all with literally 2 knob twists. Sounds like a win-win-win!
One more secret ingredient is how analog Pultec style EQs handle phase. All Pultec EQs introduce tiny time delays between the signals passing through the analog circuitry - and yet again, what was once deemed a limitation of analog equipment has since become a desirable source of sound processing. This phase difference creates a natural-to-the-ear rounding/softening of the low end, while reinforcing the desired boost in a manner that digital emulations have thus far fallen flat at recreating.
History of the Pultec EQ
The Pultec EQ is an industry staple. Designed in the 1950s, it is an equalization unit built and designed by Gene Shenk and Ollie Summerland. The invention of the Pultec provided engineers with a level of sonic shaping previously unheard of in the post-production industry, marking the first-ever passive equalizer, and has since achieved a status of fame for its beautiful, coloured tone. The Pultecs flavour is notable to the point that engineers have a history of running tracks through it without applying any EQ whatsoever.
In 1961, the EQP-1A was introduced - further pushing the envelope of sonic shaping capabilities via updated frequency selections, including a boost at 16 kHz, a 20 Hz boost and attenuation, and 5, 10 and 20 kHz attenuation. Although Pultec formally closed it’s doors in 1980, Pultec EQ’s have continud to gain notoriety for their “Pultec magic”, earning the original Pultec EQP-1 induction into the TECnology Hall of Fame in 2005.
Modern recreations have, due to the rarity of the original units, come extremely close to replicating the magic of the original Pultecs, nearly matching the units 1:1, developing characters of their own - and carrying the torch and continuing the tradition of the magic Pultecs have imparted on records for ages. Units range from low tier recreations like the Warm Audio EQP-WA to high-quality, hand-built models such as the the Tube-Tech PE 1C.