Nothing does more to define the quality of an analog synthesizer's sound than its filter. Or filters ‹ most of the instruments we looked at have dual filters. In less expensive synths, one of these may be highpass and the other lowpass, allowing you to do bandpass filtering by routing them in series or notch filtering by routing them in parallel. The choice of series and parallel routing is also becoming common. Higher-end instruments may sport dual multimode filters with a built-in distortion/overdrive stage. Another feature to look for: Does each filter in a dual-filter configuration have its own envelope, or do they have to share a single envelope?
The Polymorph's dual filters (lowpass and highpass) are both resonant, and cranking up the resonance on both yields some really meaty distorted sounds ‹ especially when you add the distortion effect, which has its own cutoff and resonance controls. I also liked the fact that each filter has its own envelope and velocity control. For my taste, the Polymorph has unbeatable fatness, due in no small part to the precision with which you can control the distortion.
The filter section on the Q is well designed. Not only can the dual filters be run in series or parallel, you can pan back and forth between the two routings in real time with a knob. Each oscillator can be routed to either or both filters, and the filters' outputs can be panned separately. Filter modes include a comb filter as well as low/high/band/notch with 12 or 24dB rolloff. A dedicated filter drive knob lets you add some gritty edge and thickness to the sound. The Q's distortion effect didn't impress me as much. The more I played the instrument, though, the more convinced I became that it sounds great with no effects at all.
As much as I like the Z1, I can't help feeling it sounds a tiny bit sterile compared to some of the Euro synths. This quality is hard to put your finger on: When I cranked up the resonance and dialed in a distortion effect plus a flanger with tons of feedback, I got some very rude sounds. Then I added a cross-modulation oscillator, and the grunge went clear over the top. But even then, the Z1 sounded . . . um, how shall I put this? It sounded digital. The distortion is a little more brittle, not quite as fat as on some of the other analog-style synths.
That's not to say the Z1's filters aren't excellent. With two multimode filters in series or parallel, the ability to route either oscillator to either or both, and plenty of modulation routings, how could you go wrong?
The Virus's dual filters are both multimode. Not only can they be run in series or parallel, there's also a filter balance (crossfade) knob, with which you can dial up some expressive sweeps that would be tricky to do on other synths. A variable amount of filter saturation can be added if it's beef you're looking for. On the downside, the filters share a single envelope generator.
In this important sonic category, the JP-8080's filters sound a bit thin. It has only one filter per voice, not two. This is a low/band/highpass type, and like many other analog-modeled filters it has switchable 12/24dB-per-octave rolloff. But there's no filter overdrive, and only one type of distortion, which to be honest sounds somewhat digital, in the effects section. As a result, the JP has to rely more heavily on its oscillators (see below) for fat sounds, and on the delay effect for animation.
The Supernova and Nova are also one-filter synths. Their filter overdrive knob adds a very subtle touch of distortion. The filter modulation inputs are more extensive than on some synths, though; there are dedicated routings to modulate both cutoff and resonance from two LFOs, two envelopes, and the mod wheel. And as on the AN1x, the Novation filters have a switchable 12/18/24dB rolloff slope. The AN's filter section rates as more powerful, though, because it has a dedicated highpass filter in addition to the main multimode filter.
The most limited filter section in this month's roundup belongs to the Electribe-A. That's not surprising, considering it's also the most affordable unit in the bunch. Its lowpass filter gives you control over cutoff and resonance. You'll also find an envelope decay knob, a bidirectional envelope amount knob, and a built-in overdrive circuit, but that's pretty much it in the way of tone-shaping.
