Stereosonic console EQ combined with the RS127 & 135 Brilliance Boxes


phil·ter also phil·tre (fltr)
n. verb transitive
phil·ter also phil·tre
To enchant or bewitch with a philter. .

Now that the PHILTER is integrated in our new, two-channel PHUSION product, the stand-alone PHILTER is only available to special order. Please contact for more details.

PHILTER - Vintage Passive EQ

The Phædrus Audio PHILTER recreates the famous, passive EQ circuits found in the great studios of the 1960s. In addition to low- and high-frequency shelving filters (which were a part of the Stereosonic consoles, the unit incorporates HF peak boost at: 2.5kHz; 3.5kHz; 5kHz; 8kHz; 10kHz; and 12kHz which match the signal frequencies of the RS127 and 135 Brilliance Boxes. Maximum cut/boost is 10dB controlled in steps of 2dB via precision, stepped, rotary attenuators. The EQ is entirely passive and incorporates high-quality inductors and capacitors.

In use...

Using the PHILTER is simple. I/O is via transformer-coupled, line-level XLR connectors on the rear, and the front-panel houses the tone-controls. The Bass and Treble controls are 11-position rotary-switches. Bass frequencies are controllable (boost/cut) by a total of 10dB, in 2dB steps. Treble frequencies are controllable (boost/cut) in the same way. However, treble boost curves are selected via the middle, multi-position rotary-switch. This selects boost centered upon the annotated frequencies: 2.7kHz; 3.5kHz; 5kHz; 8kHz; 10kHz; and 12kHz, or between a high and low shelf response. The response skein for the PHILTER (with the boost-curve selected to 5kHz) is given below. These responses were chosen to emulate famous EQ circuits of the past, and every one is magically "musical".

Abbey Road EQ
Composite response of PHILTER: 5kHz boost

To purchase the Phædrus audio PHILTER contact us at or go to our How to buy page.

The PHILTER User Manual is available here


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