Resonant Frequency: Modular Synth

VCF-1A:

12dB/24dB SVF - Design by Chris MacDonald

This is a very well designed filter from Chris MacDonald. It's a switchable 12dB/24dB state-variable filter with BP and LP outputs. It has an input attenuator and voltage controlled cutoff and resonance. It sounds really nice, not as throaty as the Moog clone, and not as edgy as the MS-20 clone.

VCF-2D:

Moog Transistor Ladder Clone - Design by EFM

Everyone should have at least one Moog ladder filter in their modular. They have deep bass, great sounding resonance and they sound good overdriven. EFM's design has voltage controlled cutoff and resonance, multiple inputs and a built-in envelope generator that can retrigger as an LFO. I no longer have an electronic version of the VCF-2D schematic, but here's a copy of the newer VCF-2E schematic. The design is almost identical, I think he just made a new circuit board layout and corrected some errors.

One "feature" (flaw?) of the Moog filter is a drop-out of bass frequencies with high resonance settings. There is a modification to eliminate this problem. It's also possible to add a HP input. Since I have more than one VCF-2D, I might modify one and leave one stock.

VCF-6C:

EMS Diode Ladder Clone - Design by EFM

vcf6c.jpg (10KB)

The EMS diode ladder works very much like the Moog ladder. The topology is almost the same, except for the use of diodes vs. transistors. VCF-6C is a bit more mellow sounding than the Moog clone. The resonance is not as pronounced, and things tend to sound "smoother" through it. The VCF-6C schematic is available here.

VCF-8E:

Dual Korg MS-20 Sallen-Key Clone - Design by EFM

vcf8e.jpg (16KB)

VCF-8E is a dual MS-20 clone. Each filter is a switchable HP/LP with voltage controlled cutoff and resonance. This filter has a particularly edgy sound... very "electronic" sounding as opposed to the more organic sound of the Moog and EMS units. The resonance is extreme, and the filter sounds amazing when just at the verge of self-oscillation... it's also particularly great when using your VCO for FM. Here's a copy of the VCF-8E schematic.

This filter sounds completely different than any of my other filters... and for this reason, I'd really recommend building it. However, since it's quite harsh, I wouldn't want this as my only filter.