I recently picked up both this and the ADDAC604 Dual Filter; it's worth noting that they're completely different from one another (both great, but quite different). While the 604 offers a great straight-forward acidy sort of filter sound (with a stereo option) and not that many features, this is a non-stereo dual filter with a much different character to its sound and a ton of features. It can create different relationships between the two audio inputs and their filtered outputs depending on how you set the switches in the middle. The build quality here is excellent and professional looking, with very stable, secure knobs (in contrast to the wobbly, less satisfying slim-pots of the 604).
For better or worse, this filter is more work than the 604 though (and than many other filters) -- it is complex, and at the time of this review there does not seem to be a proper manual anywhere, so patience/experience and experimentation are key. If you're not willing to really dive in, the stand-alone HP and LP outputs might leave you a bit underwhelmed in basic sweeps -- (although the resonance can be pushed into unique, organic howling territory that the 604 cannot replicate). It is modulation and careful experimentation (especially with the resonance parameters) that can really bring the 702 into its own. Seeming limitations to the spectrum of sound through the separate outputs can be overcome and pushed beyond by CV-ing the cutoffs to their limits and playing with different dual configurations. The unusual flexibility is a great strength of the 702, but it can be a little challenging to wrap your head around and take some experimentation to get pleasing results. There are a lot of interesting features packed into this thing. In addition to CV and manual control over the mix, multiple types of filtered outputs, dual CV inputs for cutoff (per channel), and CV control over resonance -- all of which is a lot by itself -- some of the especially unique offerings here are:
- A limiter for each channel that can be set to 1 of 3 modes; I couldn't claim to understand exactly what they're doing, but they can significantly impact the flavor and intensity and unruliness of the resonance settings;
- A "Raw" or "Smooth" option for each filter (I particularly like this -- "Smooth" seems to add a slew to incoming control voltages that can give modulations a lovely organic feel; "Raw" seems to leave them alone and produces more percussive results);
- A fuzz distortion switch for each filter (these are a bit much for my liking in most patches, as they introduce a pretty massive noise floor, but it's a cool organic sort of tube-y sound that is fun to experiment with);
- Phase switches for both separate filter outputs, as well as for the overall mix out (my technical expertise is lacking here, but in practice, if the output from one or both sides sounds weak or lacking, try flipping the phase switches to bring it back to life);
- A CV inverter switch for the Mix In CV, which can be used to flip your mix modulation upside-down very simply, without external adjustments.
All in all the 702 is one of the more interesting and enjoyable filters I've owned so far in euro, but it's best suited to more experienced patchers or sound experimenters, as opposed to those who just want a straightforward squelchy sort of filter sound.