Weston Precision Audio - SF1 Dual/Stereo Filter

Weston Precision Audio's SF1 is a dual filter whose main attraction is not just a serial or parallel connection.

Two powerful filters in one - one on the left and one on the right. Both with a full set of pots as you would expect from filters: cutoff, resonance, an input gain (with nice saturation) and an attenuverter for CV control over the filter cutoff. Fairly normal so far...

However, the first thing is a button connecting the two filters. When active, the right filter behaves the same as the left (settings and control voltages). This is good for simple stereo matters. But especially interesting is the different treatment of the two audio signals for right and left.

Furthermore, the middle section stands out: It is used to control the panorama and even has a CV input. With this, it is easy to create great animations and whirlwinds of spacial displacement.

But the most exciting function can be found at the very bottom of the front panel: The different filter behaviors. There are two outputs each for the right and left channels. L1 and R1 output the quite common low-pass, band-pass and high-pass with variable slopes of 12 or 24dB. However, the alternative outputs L2 and R2 provide the somewhat unconventional (especially in a dual/stereo setup) notch, all-pass and phaser.

Finally, the SF1 can of course self-oscillate with V/Oct input and has a CV input for resonance.

Features:

• 9 possible output responses for each filter/channel (HP, LP, and BP both 12dB/oct and 24dB/oct available from L1/R1 out & Notch, All-Pass, and Phaser available from L2/R2 out)
• Attenuverters with a center detent for frequency CV ins
• Audio ins contain overdrive when turned past center
• Self-oscillation capability for use as oscillator(s)
• Voltage-controlled panning output stage which can be modulated into audio frequencies