Haible - TAU Phaser mk2

The TAU Phaser MK2 is Random*Source’s latest Eurorack version of Jürgen Haible’s unusual “Pipe” phaser, built around a completely analog, transistor-based 18-pole phase-shifting network. That is a lot of phase shifting: rather than the broad swoosh of a simpler phaser, the TAU produces a much denser pattern of movement through the spectrum, with deep, hollow and increasingly resonant sounds as the feedback comes up. It particularly likes harmonically rich material — pulse and saw waves or noise give the 18-pole network plenty to work with.

There is some nice history behind it. The original Tau was developed by Dennis Colin and Ken McNeill in 1975 and released by Tau Systems around 1980; Colin had previously co-designed the ARP 2600 with Alan R. Pearlman. Jürgen Haible later revisited the Tau, reworking the circuit around more readily available components and adding a number of features and improvements. Random*Source have continued developing his version, and the MK2 brings it into a much shallower, skiff-friendly format while adding two audio inputs and expanded voltage control.

Now, back to the module — PITCH moves the complete phase structure manually, while FEEDBACK takes it from gentle resonance all the way into self-oscillation. At that point the TAU becomes a rather unruly oscillator in its own right: you can move it around with CV and the 1V/oct input, although the latter is better thought of as a way of making musically related shifts than as precision oscillator tracking. Two additional CV inputs have attenuverters, while the internal LFO takes care of classic automatic sweeps. LFO DEPTH is quite useful here, effectively moving between the internal LFO and the PITCH/external CV controls, so the modulation can come entirely from the TAU, entirely from your patch, or somewhere in between.

The NORMAL/COLOR switch inverts the effect signal for a different spectral balance, and the two outputs can be used together for pseudo-stereo patches. The TAU also responds beautifully to being pinged: individual clicks or slow pulses excite the network into short, hollow knocks and plugged-pipe sounds rather than anything resembling a conventional phaser sweep.

Very nice for enormous analog sweeps, resonant drones, odd percussion and those slightly unhinged 70s sci-fi sounds that live somewhere between phasing, filtering, flanging and a resonator.

Features:

• 18-pole, 100% analog transistor-based phase-shifting network
• Based on Jürgen Haible’s redesign of the Tau “The Pipe”
• Revised MK2 Eurorack version by Random*Source
• Two audio inputs with individual attenuators
• Two audio outputs, suitable for pseudo-stereo patches
• Manual Pitch control for the phase network
• Feedback from subtle resonance up to self-oscillation
• Internal LFO with Rate control
• LFO Depth blends between internal LFO and Pitch/external CV control
• Two CV inputs with attenuverters
• 1V/oct input for musically related phase shifts and oscillator-like use
• NORMAL/COLOR switch for an alternative spectral response
• Can be pinged with clicks and sub-audio pulses
• Particularly effective with harmonically rich material such as pulse waves and noise
• MK2 is more shallow & skiff-friendly