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Foxtrot Quad Multimode, Multi-Topology Filter

Sound Examples

Linking three Foxtrot Korg-style band pass filters produce a formant like sound. An Alpha Pro is used as a simple VCA with CV from an envelope generator. An LFO feeding the pan CV provides a little auto-pan and finally there's a little pitch shift reverb. The notes are random!
Nothing more than a couple of saw tooth signals into a single Moog style Foxtrot channel. An LFO controls cut off frequency and another is used into the Aux CV to vary the response from band pass, through low pass to high pass. The LFOs are unsynchronised so the rhythm evolves slowly.
Foxtrot is a quad, multimode filter with three different classic filter types.

Each of the four filter channels can be:

1) A ladder filter, based on the classic MOOG designs from the '60 and '70s
2) A Sallen-and-Key filter based on the Korg 35 module used in the MS-20
3) A State Variable filter as used in the Oberheim SEM

Each filter type produces Low Pass, Band Pass and High Pass responses which can be morphed between using the front panel control or CV.

In addition, any or all of the filter channels can be linked together internally producing a parallel filter bank controlled by a single cut-off control or CV. Check out some of the examples for how amazing this sounds.

The AUX CV input can be switched to allow CV control of the filter response, resonance or pan of each filter channel's dual outputs.

Finally, each filter can be overdriven to accentuate the unique sound of each filter type.

Foxtrot is available now at £399.00 (inc VAT).

Specifications:

Width: 38HP
Depth: 22mm excl. power cable. Approx 32mm inc. shrouded power cable
Power Requirements:
+12v: 250mA
-12v: 100mA
+5v: 0mA
Inputs:
Signal (Zero attenuation): ±5v nominal, ±12v max
Cut-off CV (Zero attenuation): 0-5v nominal
AUX CV (Zero attenuation): ±5v nominal
Outputs:
Dual Outputs: ±5v nominal, ±10v max

Documentation

Alpha Pro Quad VCA and Mixer

Sound Examples

A very quick demo of some of the overdrive sounds available from Alpha Pro.
OK – so this is getting silly, but this is an interesting patch – a combination of Foxtrot and Alpha Pro. In the first section we just use an SK low pass with a linked band pass (to emphasis a few frequencies) then Mode 2 distortion from Alpha Pro.

The second section is similar, but the pitch CV is fed to the Foxtrot's Aux CV input (set to control Q) which pushes the filter into self-oscillation on the higher notes (it needs a bit of careful tuning, of course).
At its heart, Alpha Pro is four identical VCAs, each with overdrive and stereo outputs. However, it’s also possible to link any of the VCAs together to form a voltage controlled mixer. This flexibility allows Alpha Pro to replace a bank of VCAs, sub-mixers and even your output mixer.

Each VCA has two Signal inputs and a summing mixer with individual attenuators.

There are two mix buses, allowing each VCA to act stand-alone or as part of the mix. So you can configure two separate sub-mixes, with any of the VCAs contributing to the mix, or use all channels to make an 8 input, stereo output main mix.

The VCA gain is controlled by the Initial Gain knob, and two Gain CVs – again mixed together, each with an attenuator. Having two Gain CV inputs allows for more complex modulation possibilities without needing another CV sub-mixer.

Gain response can be set to exponential or linear.

The XING switch enables zero crossing detection to prevent clicks on very fast CV inputs.

Two drive modes are available, a soft clip and a harder fuzz, with the DRIVE control increasing the gain into the overdrive circuit to increase the effect.

The VCA output is stereo, with manual and CV control of pan – again, with an attenuator.

Alpha Pro is available now as a 'founders edition' at the special launch price of £399.00 (inc VAT). The founders edition also includes the Alpha Switch as standard.

Specifications:

Width: 38HP
Depth: 22mm excl. power cable. Approx 32mm inc. shrouded power cable
Power Requirements:
+12v: 250mA
-12v: 100mA
+5v: 0mA
Inputs:
Signal (Zero attenuation): ±5v nominal, ±12v max
Gain CV (Zero attenuation): 0-5v nominal
Pan CV (Zero attenuation): ±5v nominal
Outputs:
Stereo: ±5v nominal, ±10v max
With Drive Modes 1&2 outputs are normalised to around ±5v max

Documentation

Alpha Switch

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The Alpha Switch is a 2HP expander to the Alpha Pro VCA.

It breaks out the function links on the back of the Alpha Pro to four switches:

1) Signal Inputs: DC or AC coupled
2) Pan CV: No zero crossing detection, or zero crossing follows XING switch
3) Overdrive Position: With the system set to mono mix, this switch sets whether the overdrive circuit comes pre or post the mix buses
4) Stereo Mix Bus: Controls whether the mix buses are stereo (post pan) or mono (pre pan)

Due to ongoing improvement and development, the appearance and specifications of all products are likely to change.