A high-end passive stereo equalizer combining the musical character of classic 1950s and 60s designs with SPL’s modern 120V technology.

The SPL PASSEQ brings the concept of the classic passive equalizer into the modern mastering studio. Inspired by the highly musical EQ designs of the 1950s and 60s, it combines a fully passive filter network with SPL’s 120V technology for exceptional headroom, low noise and precise control.

Unlike active equalizers, the PASSEQ uses a passive filter without amplification stages. Boosting a frequency is achieved by attenuating the surrounding spectrum, with a subsequent amplifier stage restoring the overall signal level. As this can require up to 20 dB of gain compensation, SPL’s 120V technology plays an important role in maintaining a clean, low-noise signal path.

All EQ functions are integrated into a single passive filter network built from carefully selected resistors, capacitors and coils. The charging behaviour of the capacitors and saturation characteristics of the coils contribute to the PASSEQ’s distinctive response. Compared with very fast active filter designs, this produces a smoother, more organic character with transparent mids, silky high frequencies and powerful, well-defined lows.

The controls are divided into Low, Mid and High Frequency sections, each providing dedicated Cut and Boost controls. Extensive listening tests and careful component selection were used to develop musical filter curves that capture the qualities associated with classic passive equalizers while offering considerably greater frequency selection and much lower noise than vintage hardware.

A particular highlight is the extended HF+ section, which includes 25 kHz and 35 kHz settings. These ultra-high-frequency options allow broad tonal shaping above the conventional audible range, making them especially useful for adding openness and polish to mixes and masters.

Main Features

* Fully passive equalizer design

* Inspired by classic 1950s and 60s passive EQ circuits

* SPL 120V technology

* Low, Mid and High frequency ranges

* Independent Cut and Boost controls for each frequency range

* Single passive filter network

* Carefully selected resistors, capacitors and coils

* Up to 20 dB of level compensation

* Extended HF+ section

* 25 kHz and 35 kHz HF+ frequency settings

* Low-noise, high-headroom design

* Designed for mixing and mastering applications

PSU works on 100-240V, EU power cord included.

This is our ex demo unit, excellent visual and pristine working condition.

We ship worldwide, feel free to ask for a precise shipping quote.

The listed ex VAT / VAT0% price applies if you have a company with a valid EU VAT number or if you're based outside of EU. Non-EU buyer pays the import duty and tax as regulated by their local customs. Private buyers in EU are a subject to VA