ERIC ARCHER DIY LOWPASS VCF LAYOUT

tokyomatik

I watched the video and sound pretty interesting but to see all that wiring involved is a bit spooky,

take a look:
http://ericarcher.net/devices/diy-lpf/

anybody here made a pcb layout for this or tried to add the optional cv? i would really like to have some opinion before to start a knitting work like that Rolling Eyes

PHOBoS · Posted: Thu Mar 08, 2012 7:14 am Post subject:

hmm , yeah I did build that one on perf and I always design a layout first
so let me look that up for you. (do you need a layout you can print out and
use directly or do you have a program in which you can redraw it ?)

As for the CV, you can use an external voltage instead of the pot but the way
it's designed now it works in the opposite way of how I would like it. You can
solve this with an inverting opamp but you need a single supply, rail-to-rail one.
I think I did actually order one but never gotten around to implement it.

filter sounds nice btw Smile

tokyomatik · Posted: Thu Mar 08, 2012 7:57 am Post subject:

hey mate! thanks for the answer!
yes a layout ready to print would be great, usually i use illustrator or photoshop to reedit images.
i'm not sure i understood this thing of the inverting amp for the optional cv
and powering...do u mean i should power it separately?
could u make me a schematic or diagram??

thanks again for sharing

peace

PHOBoS · Posted: Thu Mar 08, 2012 9:26 am Post subject:

well, you don't have to change anything, it's just a personal preference.
The way it works now is that if the control voltage get's higher it filters more,
and if it get's lower it filters less. I prefer it the other way around so
that's why an extra inverting opamp would be needed.

But you can just add a control voltage to the pot instead of the 9V,
that'll work. Be carefull though, only use a positive CV, it might not
like a negative one. Or maybe add a diode in series.

PHOBoS · Posted: Sun Mar 11, 2012 9:30 am Post subject:

I found the layout, but I'm not sure which file-format you prefer
but here's a gerber file with the layout
(you can use http://www.gerber-viewer.com/ to view and convert it)

and an image which shows the component placements.

I didn't use a TLE2426CLP but made a simple voltage follower with a ua741
(you can use a different opamp for it), I also increased the capacitor size in
the audio path. (from 2.2uF to 4.7uF). the frequency potentiometer is
connected to the pad marked pot (that makes sense I think) and there's an
extra pad for an external control voltage, I also added some protection
diodes (labeled BAT). use some schottky diodes for these like BAT85.

VCF PCB components.JPG

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VCF.zip

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gerber files for eric archer 9V VCF PCB layout by PHOBoS

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tokyomatik · Posted: Sun Mar 11, 2012 8:17 pm Post subject:

hey phobos thanks a lot!
that layout looks is for sure less scary than wiring on perfboard
i'll try to etch a board soon as possible