Low/High Pass filter schematic?

[bradholland]

I'd like to add a 'moog like' filter section to a drum machine project I am working on.
Anyone know any nice schematics kicking around?

 

[etheory]

You can't go wrong with this site: http://www.fantasyjackpalance.com/fjp/sound/synth/synthdata/16-moog-minimoog.html

 

[bradholland]

just realised I double posted about this.
thanks for the link to that moog site, really interesting!

That filter is a bit too overboard for the drum machine I am modding.
I decided that I just need a high pass filter on one of the outputs so that I can fine tune hihats etc.

Do you know of anything a bit simpler??

 

[Jidis]

There's a passive all cap/resistor thing down in the filters forum under "Trident A Range style eq", but I have no earthly idea what it will sound like or if there's any semblance to a Trident HPF. I'm guessing he just tuned it to the same approximate frequencies. I just got some caps to try one yesterday, but a couple are too big for the board I made, so I'll probably etch another one tomorrow or something. It's really simple, and I guess you can use any or all of the three sections to cut it back even further.

Take Care

 

[bradholland]

Hi Jidis,
I thought that when using a passive design that the signal loses a lot of gain?
Perhaps I'm wrong? I'm going to take a look at that. My breadboard is bored!!

 

[Jidis]

I thought that when using a passive design that the signal loses a lot of gain?

Well, I've got one now. 

I've heard it work briefly and it seems to do OK. If I can get some time later and clean up some of this mess, I may try to see what comes off of it (frequency and level-wise). I jotted down the exact tested values of all the parts too. I'm interested to see what LTSpice says it does vs. what it does in real life.

Either way, it is a cool idea if there aren't any serious sonic consequences. I like having so many different combinations to pick from. I may try to do one on a rotary switch later and also play around with some more extreme cutoff values.

Take Care,

George 

 

[guy_4]

Harisson filters :
http://groupdiy.com/index.php?topic=46390.0
Best,
Guy