Over the last couple months, I've been ever so fortunate as to have been a beta tester for the TipTop Audio Z-DSP voltage controlled digital signal processor. It was an extremely exciting prospect when I first heard about it; processing any modular signal, AC or DC, with a DSP and extending that with external voltage control. It basically meant that almost anything would be possible with this module, even if in the beginning, we would only get a taste. And what a sweet taste it was.
Our beta units came supplied with the Dragonfly Delay algorithm cartridge, which consists of 8 different delay algorithms; some mono-mono, mono-stereo, time-ratio'ed multi-tap, etc, each of which having their own unique set of 3 controls which can be controlled with the manual controls and CV inputs. But it's just the algorithm that makes the Z-DSP special. If the DSP where the engine, the rest of module would be the drive train, chassis, steering wheel, etc.
The Z-DSP, in addition to any done in the algo, has a stereo, patchable, analog feedback path, with independent CV control over the feedback amount for each channel. This allows you to patch any external processing in the feedback path of the processing, in place of, or in addition to any feedback done in the algo. It also allows you have a CV controlled input, if you can sacrifice the use of the feedback loop (rather than use the normal inputs, patch your signal to the feedback in inputs and use the feedback CV as an 'input VCA'). Or, use it as a 2nd set of stereo inputs (again, sacrificing the use of the external feedback). The Z-DSP also has CV selection, as well as directional sequencing of the algorithms stored on a cartridge. With a simple pulse, you can sequence forward through the algos. With a simple pulse and gate, you can sequence forward and backward. And with any arbitrary CV you can scan through the algos. The sounds that can result from this may be subtle and intentional, or wild and chaotic. A very unique approach to signal processing. Equally, if not more, unique is the fact that the Z-DSP offers the ability to inject your own clock for the DSP and override its own. Almost everyone these days is familiar with sample rate reduction, and bit-depth reduction, but actually reducing/varying the processor clock is an entirely different sonic result. Not only can it achieve aliasing and "crunchiness" similar to that of sample rate/bit-depth reduction, but it can lead to insanely glitched out and wild digital instability. Hell, it's possible to crash the DSP (of course, no damage is done in this case).
One might be able to argue "but I can do all this stuff with my computer, why would I want this in a module?". Well, I know that one of the main reasons I enjoy modulars (and the Z-DSP) is because I have real-time, no latency, tactile control over the processing. A physical, "real" interface to play with; wether it's manually twiddling knobs, or using control voltages to replace my hands, having that "real" interface allows me to sculpt what I want sonically much more easily. I'm finding that, even with just the delay (which I use a lot in my compositions) I'm able to get a much better sense of what my final composition will sound like because I'm playing with the delay in real time, and not adding it later as an after though. In this way, the delay becomes part of the composition, not just an effect. For example, the following piece was written after a week with the Z-DSP. It's not exactly a great demo of the Z-DSP per se because it's not really doing anything extreme; no algo sequencing, heavy CV (there is a little CV of the feedback loop amount), or crazy clock mangling, but, without the Z-DSP, this patch sounded lifeless and dull.
I am head over heels for the Z-DSP. And I've only ever experienced the Drangonfly Delay cart. I'm eagerly anticipating not only the Bat Filter cart, but also the various other magic that is being cooked up down at TipTop Audio.