GRP Synthesizer Eurorack VCF

The GRP Synthesizer Eurorack VCF is a transistor based low pass filter with four switchable slopes, five audio outputs, two audio inputs and a wealth of CV connectivity options.

GRP are highly regarded for their premium synthesizers designs, prized for their superior sound quality, workmanship and feature sets and their Eurorack modular line up is no different. The range includes two filter designs derived from those found in the A4 and A8.

Their 24dB low pass filter is based around a classic transistor ladder circuit, but with a few mod-cons added. Firstly there’s a distortion circuit which provides everything from subtle enhancement all the way through to outright filth, which beautifully compliments the characteristics of the resonance.

The next addition the automatic gain change, which (as the name suggests) rides the gain of the incoming signal to alleviate any extreme and unwanted behaviour (like bass drop out) that can be caused by high resonance settings, this can of course be switched off if you do want some more aggressive tones.

Conveniently there are two audio inputs, so in smaller systems you can negate the need for a summing mixer, plus there’s a overload LED which illuminates should the connected signals overload the input stage.

In terms of CV connectivity, there’s plenty on offer: a 1 volt per octave input for key tracking the filter to your main pitch CV’s or pitch controlling the filter when in extreme resonance settings. There’s also a dedicated FM input with its own attenuator and a resonance CV input with its own attenuator.

And in true GRP style there are five total audio outputs, one for each of the four poles at 6, 12, 18 and 24dB and a select out which outputs the filter mode selected on the front panel. So with some intelligent mixing you can achieve some great pole sweeping effects and interesting phase artefacts.

This is a classic filter design that’s been relentlessly tweaked to make it the best sounding and most flexible transistor low pass filter possible. Iconic GRP tone for your Eurorack system.

The main features of the GRP Synthesizer Eurorack 24dB Low Pass Filter Include

24dB transistor ladder filter with four selectable slopes
Two audio inputs, channel one has a dedicated attenuator
Three CV inputs, resonance, 1 volt per octave and FM
Four outputs for each pole and one select output
10HP wide