SPL PASSEQ Mastering Equalizer in Sound & Recording

“I think we always knew: True beauty is analog!”

When developing the PASSEQ Mastering Equalizer, our primary goal was to create a device spezialed for mastering and stereo material – a worthy successor of the legendary original Passeq.

A hardware tool, which demonstrates the advantages of analog hardware while displaying the weaknesses of digital plugins. An equalizer which has that certain kind of magic you can only achieve with an analog passive equalizer. We are very happy that we accomplished this goal and that we are not only pleased with the result, but also received great appreciation from PASSEQ users and product reviews.

In this blog post, we would like to present an extract of a PASSEQ review, published in the edition 01/02 2019 of Sound & Recording magazine:

“It is not rare that in practice the mastering engineer has to try to remove errors of a recording or mix.
In any case, he or she needs the very best tools to do so. And that’s exactly where SPL established their company in the world’s elite with their 120V technology. The passiv SPL PASSEQ was new revised and optimized for these kind of mastering tasks.”

Inner parts:

“… obviously, the developers made every effort to compare various different types of capacitors soundwise. Especially when it comes to passiv filter circuits, it does make a huge difference which kind of dielectric material is used …”

“So hats off to the guys at SPL, because if you take a closer look at the boards, you realize that every single filter setting – individually and probably in interplay – has been optimized in endless listening sessions.”

120 Volt Technology:

“With maximum in and output levels of 32,5 dBu, PASSEQ provides approx. 10 dB more headroom than common studio devices. This is particularly important for the interplay with digital converters: even at maximum levels – which is quiet common when it comes to mastering – the PASSEQ operates clean and in a relaxed manner. There is no D/A converter I know of, that could overdrive this device. There is no noise … and with its huge headroom, the SPL PASSEQ reaches a total dynamic of more than 120 dB. Definitely suitable for mastering!”


“PASSEQ is everything you have ever dreamed of in terms of passive equalisation. No matter the setting, it always sounds natural, never »manipulated«.”

“One may assume that when optimizing the frequencies, a lot of practical experience flowed into this process, from the developers and also from users of the predecessor model.”

“The specific strength of PASSEQ is working out the inner beauty of the sound material. Especially when boosting, the PASSEQ unfolds its magic. The high frequency band in particular sounds incredibly open, airy and soft. Even when boosting the Air-Band to the max it still sounds relaxed and naturally, as if these silky highs have always been there.”
“Thus, the PASSEQ demonstrates the limits of the digital competitors.”


“PASSEQ is the ideal tool for what mastering is all about. Or better what it should be about: finalizing a good mix, put the finishing touches on it, make it shine. Optimizing the frequency weighting, work out this soft shimmer in the high frequencies, this is exactly the talent of PASSEQ. No other equalizer can hold a candle to PASSEQ.”

Find the complete review in the edition (01/02 2019) of the magazine.