Four PCBs ordered!

    

 

    The first time I went to Knobcon (synthesizer convention in Chicago) I met Constantine, who was representing Tip-Top. He was making techno beats with his little modular, which was filled with TipTop modules, obviously, including the wonderful ZDSP reverb and several of those little sample playback ONE modules.

    As Knobcon was winding up, I screwed up my courage and was like "hey wanna go get lunch" and he was like..... okay......... I guess that was a weird American thing to do. But anyway, we had a hamburger in that extremely loud heavy-metal themed restaurant near the hotel, and Constantine (artist name Zvuko) told me about the subtle differences between kick drums, and how best to process them.

    "The 808 kick," said my buddy, "can be tweaked to sound great live. You can adjust the frequency and decay to match the acoustics of the space. The 909 kick," he continued, "will sound great in any room, but won't have the same adjustability." Of course, with mods, the 909 can be just as tweakable as the 808 but I didn't know that at the time.

    "You should put your kick drum signal through a high-pass filter first, then a low-pass filter." What????? I said. 

    So anyway, I went home, thinking about what he'd said, and searched everywhere for a good high-pass filter design. I found one drawn by Ron Folkman for Polyfusion, which was a four-pole filter. I built it point-to-point (using a bit of stiff paper to hold the components as I did back then) and it sounded great, but the cutoff was a bit too steep for my liking.

    I cut the filter in half, studying the schematic carefully, building another example as I went, not as comfortable with the functions of all the components as I am now. Well, when I finished the high-pass filter, and put it in a can, it performed amazingly well, and thus the ZV.HP was born.

    Here's what's going on with that particular signal path: the ZV.HP filter can self-oscillate at very very low frequencies. Probably lower than 10Hz. When you hit a filter that's near self-oscillation, it will "ring" at the cutoff frequency (like I said, down lower than 10Hz if you want!), so you can open a high-pass filter up nearly all the way, so the cutoff is at a frequency that matches the pitch of your kick drum or not (more on that next!) and use the filter as a way to bring even more boom to your kicks.

    Some of the ways I love using my ZV.HP filter: setting the cutoff to a frequency that's really working with my kick drum... so much bass goodness. Tuning the filter slightly higher or lower than the kick frequency will let the kick bounce up or sag down in the decay section of the sound. I'll plug a separate knob into the filter's CV port, and use that to close the filter up when I want to lose some (all!) of the bass frequencies. House and techno producers and DJs use this trick all the time. Many mixers have a bass-cut switch built in. With the separate knob turned up to cut some of the bass, but leaving the cutoff knob on the module alone, you can bring the bass all the way back to your set frequency with a quick flick of the knob.

    All that to say: one of the four PCB projects I just ordered is a 2HP version of that filter. I hope it works because it's a great little filter! Also, my tin-can ZV.HP broke a while ago and I've been using the steep-cutoff Polyfusion one in my kick chain, and it's still okay but not as good.