18 December 2009

Magic Smoke Electronics TH-201 Mankato Filter

When I ordered something from E-bay recently I was offered a nearly populated PCB by Magic Smoke Electronics. It is a TH-201 Mankato Filter. This filter is designed by Thomas Henry by the way who also designed the drum modules I'm building currently. When I examined what was missing using the bill of components, I found that the guy I bought it from installed all 5% resistors in stead of the 1% resistors that were recommended. So I mailed Magic Smoke Electronics if that was a problem. They stated that it will probably not track on 1V/Oct but should work fine.

Well actually I don't really care about that. So I finished installing the missing components and started wiring it. I got a front panel and pot bracket from Bridechamber for it. Actually I should be on a 4 pot bracket, but I used that already on another module. With a bit of effort I could just fit it on a 3 pot bracket by drilling the holes on the bracket very close to the edge. I also got a tempco from Bridechamber for it, but I didn't bother installing it since it won't track any way. I'm sure I can use it somewhere else in the future where it will matter.

After wiring I started testing it. I first put an input signal on it from my PC Function Generator. It sounded alright, but I found quickly that I wired the input potmeter the wrong way around. And since I used the same system for all potmeters I figured they would be all wrong. And after checking they were indeed. Luckily I anticipated this and left the outer two wires on the potmeters long enough so that I could swamp them. Not really a problem even though some wires were not so easy to reach anymore. After swapping them I found that the filters didn't auto resonate.

Again not a difficult task to fix this. There are two trimpotmeters on the PCB. One for the resonance and one for the 1V/Oct tracking. I didn't bother the last one but set the resonance potmeter so that it starts auto oscillating on 95% of the resonance potmeter. As you can see this filter has lots of outputs. All with different phases. The frequency scope of this filter is also very wide. So you can use it as an LFO or an oscillator too. When used as an LFO the phase shifted outputs are handy. Well after testing everything I put the knobs on and think it is another successful project and nice addition to my modular setup. Here you can find more information on the TH-201 Mankato if you are interested:


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