PM Resonator™

3 Channel Formant Filter

The PM Resonator is a recreation of the formant filter section of a Polymoog™ synthesizer in a standard MU double-width modular panel. Each of the three filter channels has a control for frequency, signal gain, and emphasis or resonance.

 A rotary switch selects the type of filter mode for each of the three channels. The modes are low pass, bandpass, band notch, and high pass.

The MU version is housed in a 2MU (4.25 inch wide by 8.75 inch high) panel with DOTCOM compatible power connector.


Technical Specifications

Low Frequency Range
Normal 60Hz - 300Hz:
 Extended 180Hz - 900Hz

Medium Frequency Range
Normal 300Hz - 1.5KHz;
 Extended 600Hz - 3KHz

High Frequency Range
1.5KHz - 7.5KHz

Typical Input Impedance
100K Ohms

Typical Output Impedance
1K Ohms (short circuit protection)

Module Power
+15 Volts 45 mA.
-15 Volts 25 mA.
+5 Volts 0 mA.

Module Size
Panel height - 8.75 inches (222 mm) 
Panel width - 4.25 inches (108 mm)
Depth (behind panel) 2.1 inches (53 mm)



We produce electronic synthesizer modules in the two most popular formats, MU (Moog compatible 5U) and EU (Eurorack compatible 3U). A wide range of voltage controlled modules including oscillators, amplifiers, mixers, envelope generators, special effects units, wave generators, filters, power systems and cases allow users complete freedom to configure any desired electronic music instrument.


Grove Audio builds microphones, preamplifiers, equalizers, compressors and other professional audio equipment for performance and studio use. We build units in popular formats such as 19 inch rack mount and 500 series 3U modules. We can also produce custom designs on request. Contact us for a consultation.


You can explore all of our products, download spec sheets, and purchase our products in the Grove Audio Synth Store. You can also learn about our periodic specials and new product introductions. Click the button below to go directly to the store.

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Grove Audio has been manufacturing professional recording and modularized electronics for musicians and performers since 1995.