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Simplest vc BandPass filter ?
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author Simplest vc BandPass filter ?
terrafractyl
Inspired by Adam-V's CGS quad band pass filters, and after at least of year of pining over the Res-4 demos, I really want to try and make something like this.

But i REAlly want voltage control over each band, and I know I could potentially do this with the CGS30's by adding vactrols, but I was thinking there must be a simple voltage controlled filter using OTA's that I can make 4 of instead.

I dont really mind if its SVF, (even though it will probably be more complex and more work) that way I can have BP notch as well. (just like on the res-4)

Anyone got anybright Ideas? I have a bunch of ca3080's lying around so I would be sweet If I could find something that uses those... after looking around on various DIY pages I found a bunch of SVF's that could potentially do the job... maybe something like this?


comes from here... syntiac OB-vcf

but then I started getting swamped in filter schematics and articles about korg p3300 resonators... hmmm.....
any advice or suggestions would be great!
megaohm
I was going to say make a SVF but it looks like you beat me to it. hihi
It's not so complex.
I would urge you to NOT use your 3080 ICs. Use a 13700 or 13600 instead.
A dual for your application is more convenient anyway. If you have a bunch of 3080's sell a handful and that should pay for the all the parts for your whole project. It's a 25 cent chip that has skyrocketed (x10-x20!) since becoming obsolete...er...discontinued. I have a tube of 100 so I'm pretty happy with that development! lol

p.
terrafractyl
Cool thanks I was starting get that impression about the ca3080, old and noisey smile
Sooo many svf filters out there!
Luka
fonik's resonator board is good
i would suggest not including the on-board lfo
Adam-V
You could build the CGS CMOS filter which has bandpass, high pass, low pass and notch capabilites and you get two filters per board.

Just a thought.

Cheers,
Adam-V
Dave Kendall
Hi.

A multi-SVF-based option here;
http://home.comcast.net/~sbernardi/elec/og2/og3_filterbank.html
Has LPF options per band too. Haven't built one, but remember it as something that looked interesting. Could probably be simplified lots.

IMO, +1 on using 13600/13700s instead of 3080s - use them for repairs instead, or for stuff that really needs them where nothing else will do, or even fit! ... smile

cheers,
Dave
terrafractyl
Thanks for the suggestions!

I think foniks resonator boards are sold out...?
and I was literally just then thinking about of the dual cmos filter myself!

Most of the other svf pcb's I've thought of end up getting quite pricey when your ordering 4 of them!

But i'm still considering the idea of trying to find a simple yet effective schematic, breadboarding it and then working from there.
I've only really worked from a premade pcbs before so I think something in me wants the challenge hmmm.....
Luka
just build fonik's on vero
it is pretty simple
terrafractyl
Dave Kendall wrote:
Hi.

A multi-SVF-based option here;
http://home.comcast.net/~sbernardi/elec/og2/og3_filterbank.html
Has LPF options per band too. Haven't built one, but remember it as something that looked interesting. Could probably be simplified lots.

IMO, +1 on using 13600/13700s instead of 3080s - use them for repairs instead, or for stuff that really needs them where nothing else will do, or even fit! ... smile

cheers,
Dave


and bingo!

Thanks a million Dave, this looks like pretty much exactly what I had in mind, even if I dont use this exact build, it will be of great help.
wavehead
Would there be a way to make 4 bandpass filters in a series respond with the same "ring" that the RES-4 has? What is it exactly that makes the RES-4 sound that way?

Really unique and awesome sounding effect, have been wondering whether something similar could be built and expanded upon.
dkcg
wavehead wrote:
Would there be a way to make 4 bandpass filters in a series respond with the same "ring" that the RES-4 has? What is it exactly that makes the RES-4 sound that way?

Really unique and awesome sounding effect, have been wondering whether something similar could be built and expanded upon.


The Res-4 is parallel. You can definately hear/feel them as 4 independant resonators with a common input. You might add the 4 individual outputs as well as the summed output. That was always one of the things I wish it had while I had one. Maybe even a way to invert the channels' phases post filter, something that could be cool that the Res-4 doesn't do.

One more note, it does not self resonate, it needs at least an impulse to ring it. I think that has a lot to do with the sound, otherwise a QMMG would be very close to a Res-4, which it's not.
megaohm
terrafractyl wrote:

But i'm still considering the idea of trying to find a simple yet effective schematic, breadboarding it and then working from there.
I've only really worked from a premade pcbs before so I think something in me wants the challenge hmmm.....


applause

You can learn SOOOOOOOOOOOOOO much more with breadboards and proto board compared to 'painting by numbers' with pcbs.
Takes a hell of a lot longer, though!
Adam-V
terrafractyl wrote:
Dave Kendall wrote:
Hi.

A multi-SVF-based option here;
http://home.comcast.net/~sbernardi/elec/og2/og3_filterbank.html
Has LPF options per band too. Haven't built one, but remember it as something that looked interesting. Could probably be simplified lots.

IMO, +1 on using 13600/13700s instead of 3080s - use them for repairs instead, or for stuff that really needs them where nothing else will do, or even fit! ... smile

cheers,
Dave


and bingo!

Thanks a million Dave, this looks like pretty much exactly what I had in mind, even if I dont use this exact build, it will be of great help.


Brilliant!

Cheers,
Adam-V
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