The CGS757 Bi-N-Tic Filter is a strange mixture of a VCO and a switched capacitor filter based on the filter presented by Jan Hall in Electronotes. If you are after something different, this fits the bill. After all, how many filters have a sync input?
A little on how it works:
This filter is based on the original idea by Jan Hall, as presented in Electronotes EN92 P14- 15, which was in turn based on an idea in a 1974 issue of Electronic Design on a Biquart (twice the order) filter.
A VCO drives a pair of analog switches, switching two banks of eight 47nF capacitors across op-amps (effectively creating multiple integrators), and this a multi-passband or comb filter is created at f0, f1, f2 etc.. The overall filter configuration itself should be easily recognized. Two controls are provided within the structure of the filter - damping and bandwidth. Not all combinations of these two are actually valid, some resulting in silence, but none the less, quite an array of variations is possible.
The VCO section uses the well known ASM1-VCO as originally described in Electronotes ENS-76 VCO Option 1. This core was an obvious choice due to the amount of information, lists of suitable substitutes and so on that are available on the web. In this case, a cutdown version is used as its purpose was simply to drive the analog switches. The VCO is connected via a signal processor to the input of a 4024 binary counter. The first three divisions are used to drive the address lines of the 4051 analogue switches.
Specs & Downloads
Specs & Downloads
|Additional Resources||Build Guide Bill of Materials Schematics|
Customer Reviews (2)
- Worth the frustration!Review by Travis
So ok - a couple things to be aware of:
There's 4 different BOM's for this kit out on the web and 2 sets of schematics. Make sure you have the latest versions and you're building the +/- 12v edition. Also be aware that the latest BOM and what's included in the kit don't quite match - I believe there's one trimmer/resistor combo that are off though you should be able to figure it out by process of elimination. Also, make sure you pay attention to the name of the board in the header of the BOM - there's a couple part numbers that repeat themselves on the the ASM board and the main board. Provided you're aware of these things and take your time, the rest should come together fairly easily.
One other thing to be aware of is the jumper that needs it's pads cut and a trace reconnected. While the build guide says this was take care of, mine was only taken care of on one side of the board - when I first powered this module up, it shorted my entire system's power supply. Thankfully everything was restored when I unplugged the module, but it took a good month or so of scouring schematics before I finally decided to take an X-Acto to the pads on the other side of the board. As soon as I did that, everything was good and then some.
Sound-wise, this thing is nuts. I'm not sure exactly how it qualifies as a filter, but it does amazing and horrible things to sound, sometimes simultaneously. While it might not be the most straight-forward build you'll come across, it's definitely worth the challenge. (Posted on 10/12/2016)
- Just weirdReview by Sean
I've been playing with this module for a couple of days and I have to say it's the most bizarre sounding filter I've ever used. When Ken Stone says "If you are after something different, this fits the bill." he's not joking.
I've been approaching it as more of a "effect" than a standard filter. Drums sound awesome through this, and I've managed to create some really bizarre/interesting/vocalish lead and bass sounds with it.
Kit goes together with only minor head scratching. If you've never built one of the Elby Pather kits before the system of carrier boards, columns etc may seem a bit confusing at first, but if you take a look at the BOM and schematic it will all make sense. I was very pleased to see all parts provided and PCBs were of excellent quality. (Posted on 1/3/2016)