The Dåpf’s name might sound at home among the Scots Gaelic‑derived names in the range of Glaswegian developer Instruō, but in fact this is the first time company founder Jason Lim has opted to go for a good old acronym. DAPF: Dual All‑Pass Filter. It’s a noble module, the Dåpf, partly because it’s actually quite difficult to explain to people what an all‑pass filter even is, and even more difficult to get them to understand how they can incorporate it effectively into their patching.
For those in the dark: an all‑pass filter, in short, isn’t actually a filter per se, because, well, it doesn’t filter anything out. Or, as I’ve heard Jason Lim rhetorically ask of the Dåpf: “When is a filter not a filter?” What it does do, though, is rotate the phase of a signal as it sweeps down or up the frequency spectrum. Most recognisably, the sound of this happening in conjunction with one or more other all‑pass filters constitutes a phaser effect. When you see a phaser effect offering more stages, this simply means it can insert more all‑pass filter curves into the signal and increase the complexity of the phase relationships at play. But, as Instruō are keen to point out, that’s not all these mysterious filters are capable of.
As we’ve come to expect from Instruō by now, The Dåpf’s interface really couldn’t cram in any more functionality. Each of its two channels has an input and an output, a slider for adjusting phase position and an attenuvertor. There’s an overall Volt‑per‑octave input — though you’ll need to ensure your patch is eking out enough filter resonance to hear the full benefit of its tracking — and finally a toggle switch for channel 1, which switches between a 6dB/octave (one‑pole) filter response and a 12dB/octave (two‑pole) response. In terms of phase rotation, this is the difference between 180 and 360 degrees.
Initially, patching a signal into one of the Dåpf’s two filters and sweeping it up and down, you’ll hear very little change. Involve both filters, however, and perhaps some modulation, and things start to get more interesting. Even as a ‘basic’ phaser, it sounds deliciously watery and rich. We’ll allow Jason to finish the line above: while all‑pass filters are not a filter, they can also “simultaneously be any kind of filter you could possibly want.” He’s not wrong about that. With a bit of nifty patching the Dåpf opens up even more: it can behave like a low‑pass, high‑pass or notch filter, it can widen sounds in bizarre ways and, of course, act like a good old — highly flexible — phaser.
Since we’re talking about phase relationships, much of this side of the Dåpf is most tangible when its output signal is summed with a dry version of the input signal, so get those mults at the ready. In this context the Pole Toggle switch can mean the difference between a low‑pass filter response and a phasey notch filter sound, and small shifts can make a big difference. The more you patch, the more the Dåpf begins to open up. The normalling here also seeks to squeeze out the most functionality it can. Mono‑to‑mono, mono‑to‑stereo and stereo‑to‑stereo combinations are all possible; a particular highlight is the fact that its two outputs can be used to stereo‑ise a mono signal, and when relative phase rotation comes into the picture things can quickly get very... wavey. Even the simplest oscillator was soon swirling around my studio in three trippy dimensions.
It’s worth pointing out that, being the bare‑bones module that it is, you really do need at least some idea of what’s going on under the hood to get the most out of the Dåpf — and it might take a few steps before results are discernible. In this way, it’s fair to say the Dåpf probably falls into the ‘advanced’ category; more like a classic synth module in that it’s simply a circuit, ready to be manipulated for musical gains and with few preset functions. But once you’ve gotten to grips with that circuit, it’s possible to create some very special sounds. With generous amounts of modulation potential, it can inject a wholly new dimension of movement into your patching.
In this respect, it’s commendable that Instruō have somehow created something simultaneously fresh and classic‑feeling with this little module. The Dåpf has all the makings of a powerful secret weapon, if you’re up to the challenge.
£189
$235