Pultec EQP-1A Equalizer

Posted by The Audio Hunt

What is the 'low-end trick' ?

Pultec EQP-1A Equalizer


The Pultec EQP-1A is a single channel, dual-band passive tube equalizer, considered by many engineers as one of the most desirable EQs ever made. It works especially well on vocals, with its signature top end that adds an inimitable air and presence.

Designed and launched by Pulse Techniques in 1951, the EQP-1A uses EEC-82 and EEC-83 valves coupled with a 6x4 rectifying valve in the amplifier. Since this is a passive unit, the incoming signal level is reduced and then restored to its original value – in technical terms, this type of EQ is called a no-loss passive equalizer because the signal level stays constant when the EQ is switched on or off.


Photo: Musictech.net

The Pultec EQP-1A distinguishes itself from most other EQs through its characteristic resonant peak, formed by simultaneously boosting and cutting a center frequency. For example: on the low band, a useful setting which works great on most kick drums is achieved by simultaneously boosting and cutting the 30Hz band, which generates a very musical curve featuring a boost at 80Hz and a dip at around 200Hz. This technique is commonly known as ‘the low end trick’.

Originally embraced by the radio-broadcasting community, the EQP-1A has since found its way into some of the world’s most revered recording studios, where it continues to enhance musicality in records in much the same way it did more than 60s years ago when it was first introduced.



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