Quad VCF for Casio SK samplers!

[Silesius]

Hi everybody,
I have build this filter for my Sk-5 (thanks Gmeredith and Tim Escobedo!), but I think I need just one of them, not the four. But I would like to trigger it from the cv outs. Instead of have one filter per voice, I want just one filter but triggered everytime a play a note. I imagine I just need to mix together the four outputs with diodes (as said above), but I'm very noob and I'm not sure. And if so, what diodes could do the job?

Also, I would like to try the attack/decay mod shown here, but I don't have the 4pdt switch. What I have is a 4 pole 3 position rotary switch (which is also recommended). I understand the way it works with the 4pdt switch (each of the 4 points goes to ground through a capacitor), but I can't figure out how to connect the rotary switch. I imagine every output from the sk goes to one of the poles, but then what? One capacitor to ground for each position? I repeat I'm learning and not very good, but this is not the same as with the 4pdt switch. Anybody knows how to do that. Any ideas will be highly appreciated.
Thanks!

[Silesius]

Ok, the filter works perfectly, but I tried to trigger it with the SK-5 CV outs and it does not seem to do anything. The CV in of the filter works, because I can modulate it with a 40106 square LFO, but the CV outs from the Casio doesn't seem to affect the filter. I've tried the four outs mixed with diodes, and just one output with one voice output, and nothing happens. I've followed step by step the guide posted above, but I don't know what happens. I thought that if I could build a working filter (I'm not very good), the rest would be easy, but now I'm not sure of that.

Also, I'm having lots of problems with the slow attack mod too This one seemed to be very easy, but is not working properly for me. Once I discovered how to use the 4pole 3position rotary switch, I made a board with 220 and 47uf caps and connected it to the points shown in the guide. In the beginning it seemed to work, but when you press the keys fast (not very fast, just a little fast) the slow envelope does not respond and the notes sound with the normal envelope. Why? I've checked all I could check, but with no luck. I made again the connections in the breadboard, checked the points one million times, but it does not work as expected. It's supposed to work this way? You can only play very slow?

I've been working day and night for five days with this mods, and I'm thinking on giving up. Has anybody made this mods? I can't understand why they don't work, specially the slow attack mod (it's very simple). Is there anybody with similar problems?

Thanks

[Top Top]

[Silesius]

Thanks for your reply Tip Top! I have used 1n4148; I have also 1n914 at home, but I think they are equivalent. I think I have another ones at home. Which one do you think would be the best option?
Anyway, I'm afraid this is not the problem, because I tried to test the filter using just one cv out and one voice out, with no mixing, as shown in the pdf guide, but the filter behaves the same, it does not open and close with the sk envelopes.

[Top Top]

I don't know off hand, but both of those have forward voltages over 4v I think...

When you tried just one, did you use a diode in the path?

[andrewF]

1n4148 & 1n914 are basically the same, it won't change anything swapping them over.

forward voltage drop is 0.6 to 0.7V

if you could post some close-up photos of your circuit and connections it would be good

[Danno Gee Ray]

Anyone know where I can find the original circuits and schematics from Tim Escobedo? The Geo-Cities links are all down now. I'd really like to check this circuit out.

Anyone out there that can help me?

Thanks.

[Danno Gee Ray]

I found a Mirror...

http://www.jiggawoo.eclipse.co.uk/guitarhq/Circuitsnippets/snippets.html