Of all the classic hardware equalisers of yesteryear, the Pultec stands alone as the only revered unit not to belong in a console or mixing board. Neve, Harrison and SSL EQs all have their place in the canon, but the Pultec with its legendary simultaneous boost/cut frequency adjustments makes it a mainstay in the recording process.

Whether in plug-in software form, cheap clone or lovingly handmade replica - producers and sound engineers are still tweaking knobs on that famous blue facade. While particularly useful in beefing up bass-heavy sources (Bass guitar, kick drum), the Pultec is not a one-trick pony, often finding a home on the master bus or across a main vocal track. Rumour has it that Frank Sinatra’s vocals in the Capital years had its smoothness provided with the EQP-1A’s high frequency shelf roll-off.

Motown engineers would use the attenuator to carve-out frequencies on backing tracks to make room for the main vocal to ‘sit’ in the mix.

Based on a 1940s passive filter design licensed from Western Electric, the original Pultec was launched in 1951 in New Jersey by Pulse Technologies (PulTec for short). An all-valve unit designed by Ollie Summerland and Gene Shank for the broadcast and recording industries, it provided two-band passive equalisation with flexible high-shelving and low-shelving options. A push-pull amp after the EQ stage restored the signal to its original level, eliminating the gain insertion losses typical of passive filters.

This make-up stage and traditional ECC-82 & ECC-83 valves ensure that even passing a signal through the unit without EQing with improve the sound.

The low-frequency section of the EQP-1A is a shelving EQ, providing four selectable frequency bands at 20, 30, 60 and 100Hz. These frequencies can be boosted to a maximum of 13.5dB and attenuated (cut) by 17.5dB. 

This is where the Pultec’s ‘mojo’ lies - boosting and cutting identical low-end frequencies creates a very satisfying low end ‘bump’ in the signal due to the Boost control having a  slightly higher gain than the Attenuation control has cut, and the frequencies they affect being slightly different. This is sometimes known as the ‘low-end trick’

Effectively, you can add weight to the bass region while also notching a bit above the cutoff point. Example: boosting 30Hz on a kick drum while simultaneously cutting the same frequency creates a curved with a boost at 80Hz with a dip at around 200Hz. See the graph below representing a boost and cut at 100Hz - think electric bass here!

 

Interestingly, the original Pultec manual recommends against this behaviour:

“…The ‘Low Frequency’ selector switch determines the curve on which the left hand ‘Boost’ and ‘Atten’ controls are effective. EITHER the boost control OR the attenuate control should be operated as required. Do not attempt to boost and attenuate simultaneously on the low frequencies.”

On the high-shelf side you can set separate ranges for the boost and attenuation.

Seven centre frequencies – at 3, 4, 5, 8, 10, 12 and 16kHz – can be boosted by up to 18dB, while a Bandwidth control alters the Q of the equalisation curve from sharp to broad.

High frequencies can also be cut at 5, 10 and 20kHz. This is a shelf-cut with up to 16dB of attenuation available.
This interaction of the bell-style boost and shelf-style cut sets the high-end tone shaping part from the simultaneous boost/cut of the low end filter section.
Boosting at 12kHz and cutting at 5k might will add ‘air’ to a track without increasing presence.

Another high-end example is the Greg Wells "Punch’n’Shine" - Get a Pultec EQP-1A across your master bus and boost at 20Hz and and then attenuate (cut) 1 db less than you’re boosting. Push 2 db at 8k and attenuate 10k by 1 db with a broad bandwidth. This will give your mix more ‘punch’ down low and ‘shine’ up top.

Attenuating at 20kHz can also smooth out and ‘warm up’ a vocal track when placed last in the effects chain.

The musicality of these unique EQ filters have made the Pultec a studio mainstay whether on vocals, bass guitar, drums, or the mix bus - you name it.

For boosting low end without the mud, getting some roll-off warmth back in the top end, or just applying broad EQ strokes to your mix, the Pultec EQP-1A Equaliser is a go-to in any engineer’s toolkit. 

 

Here at Federal Audio we have a number of options if you’d like to get some classic Pultec mojo EQ on your tracks.

The Bettermaker 502P is a fully-analog Pultec-style Equaliser in a double-wide 500 series format. All the frequency modifiers are there from the EQP-1A, plus the option for stereo and mid-side processing. Best of all you can control the 502P via software within your DAW and recall all settings, presets and user patches. Bettermaker offer this device as a ‘Remote’ unit that is fully controlled via software (its still 100% analog in it signal processing).

 

 

 

Lindell Audio offer Pultec-style EQ in two of their units - the 6X-500 VIN (a Mic Preamp with two band Pultec-Style EQ) and the PEX-500 VIN (a dedicated Pultec-style boost/cut EQ). Both units are fully discrete, analog and come in the handy API 500 series format and feature vintage op-amps for added colour.

If you’re working fully ‘in-the-box’ there is a Pultec plug-in option from just about every software company in the pro audio world.

 

Our Pultec-of-choice in this world is Acustica Audio’s Purple Bundle. Comprised of an emulated EQP-1A and the mid-range MEQ-5, the Acustica plugs stand head and shoulders above the competitors due to their dynamic convolution processing. This technology provides an insane amount of realism to the plug-in - blurring the line between software and hardware. This comes at a cost to your CPU and RAM of course, and the heavy calculations needed to create the ultra-real mojo can cause a degree of latency in older computers, but the results are amazing.