Allen & Heath Xone:VF1 review

You'll know the basic tone of this skinny yet sexy rackmount filter if you've ever used the basic smooth filters on any of the Allen & Heath DJ mixers. Except this more studio-centric version adds a load of extra features that make it much more useful.

The basics are a 24dB filter with the unit in mono or 12dB in stereo, the only annoyance being that the switch between stereo and mono operation is on the rear, so once it's bolted into your rack it's a proper pain to switch back and forth if you wish to.

We opted for the weightier 24dB mono filtering option most of the time and in a money's-no-object world two of these units working in unison would be the preferred option.

Overview

From left to right the unit has an envelope follower with a switchable slow or fast decay time and a rotary for adding valve overdrive with a switch selecting whether or not the envelope follower is sent to the valve section or not. Selecting this creates a much more modulated overdriven sound.

A switchable Square and Triangle LFO with depth amount allows you to control the sweeping modulation of the filter.

Then there's the two main rotaries controlling the basic cutoff and resonance. Four silent soft-push buttons control hi-pass, band-pass and low-pass filter options plus filter on/off.

These push buttons make filter changes instant and glitchless when punching the filter in or out. Multiple filter types can be selected at the same time by simply pushing more than one 'Pass' button simultaneously, this also allows a 'Notch' and the 'All Pass' function to be enabled, which can result in some surprising tones depending on how hard you push the resonance.

The MIDI capabilities are really useful allowing for control over the unit's filter frequency, filter type, and on/off status. This makes automated sweeps in your chosen sequencer a breeze, with MIDI channel selection easy enough by holding down buttons on the front of the unit (the standard channel is 16).

So far, so good, but there are a few niggles we need to grumble about. There's no tap BPM so quick syncing of LFO Rates isn't possible. Plus, it would have been nice to see MIDI control over the LFO, with possible MIDI syncing options too.

The device really comes into its own when you start getting creative with some of the more in-depth MIDI features such as its three modes.

Mode one allows the filter to be synchronised to the Xone:92 series of DJ mixer, Mode two allows keyboard tracking, which makes the VCF frequency follow the pitch played on a standard MIDI keyboard.

Finally Mode three makes a MIDI keyboard switch the filter on in the last settings used and releasing the key mutes the sound.

The Xone: VF1 unit is really simple to use and for its relatively low price it's great value. It gives extra control and beef to synthesizers and we found it to be a great way to warm up soft synths or add an extra level of control to cheaper analogue synths.

The MIDI side of the filter is really useful but it's a shame some parameters - such as the LFO - couldn't be MIDI controlled.

We found you really have to drive the unit hard to get the classy, rich, filtered tones that most people will recognise, but it can also be used for more subtle duties just as well.

The valve stage is beautiful (and the grill above the valve gets pretty hot) and routing audio through the unit for a slight warming-up is also works well. Basslines sound great either tweaked or untweaked, driven hard or subtly warmed.