The original EQP-1 was launched in 1951 by Pulse Techniques, a company formed by Ollie Summerland and Gene Shank in Teaneck, New Jersey, USA.Summerland and Shank hand-built the first units and, following a very early modification to the design, the original Pultec EQP-1A remained in production for the best part of 30 years.
The Pultec is a 3U all-valve design that makes use of EEC-82 and EEC-83 valves alongside a 6×4 rectifying valve in the onboard push-pull amplifier. The amplifier restores the signal level that is reduced when an audio signal is fed into the unit, making the EQP-1A a no-loss passive equalizer. This means that the signal level remains the same regardless of whether EQ is switched in or out, which is very useful when comparing a flat signal to an equalized one.
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. Sound engineers long ago discovered that interesting (and useful) equalization curves could be achieved by simultaneously boosting and cutting at the same time, as the boost and cut frequencies overlap.
This has become known as the ‘low-end trick’. On a bass drum, for example, if 30Hz is simultaneously boosted and cut, the curve created gives a boost at 80Hz with a dip at around 200Hz – a very pleasing curve on some bass drums. The sound can be further sweetened using the high-frequency controls.
The Pultec’s high-frequency section features a boost-peaking EQ and offers seven centre frequencies – at 3, 4, 5, 8, 10, 12 and 16kHz – which can be boosted by up to 18dB, while a Bandwidth control alters the Q of the equalization curve from sharp to broad. The high frequencies can also be cut at 5, 10 and 20kHz. This is a shelf-cut with up to 16dB of attenuation available.
