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 Forum index » DIY Hardware and Software » The layout factory
ERIC ARCHER DIY LOWPASS VCF LAYOUT
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tokyomatik



Joined: Jan 20, 2011
Posts: 123
Location: berlin
Audio files: 6

PostPosted: Wed Mar 07, 2012 6:54 pm    Post subject: ERIC ARCHER DIY LOWPASS VCF LAYOUT Reply with quote  Mark this post and the followings unread

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
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PHOBoS



Joined: Jan 14, 2010
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PostPosted: Thu Mar 08, 2012 7:14 am    Post subject: Reply with quote  Mark this post and the followings unread

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

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tokyomatik



Joined: Jan 20, 2011
Posts: 123
Location: berlin
Audio files: 6

PostPosted: Thu Mar 08, 2012 7:57 am    Post subject: Reply with quote  Mark this post and the followings unread

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
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PHOBoS



Joined: Jan 14, 2010
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PostPosted: Thu Mar 08, 2012 9:26 am    Post subject: Reply with quote  Mark this post and the followings unread

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.

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PHOBoS



Joined: Jan 14, 2010
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PostPosted: Sun Mar 11, 2012 9:30 am    Post subject: Reply with quote  Mark this post and the followings unread

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 PCB components.JPG



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

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tokyomatik



Joined: Jan 20, 2011
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PostPosted: Sun Mar 11, 2012 8:17 pm    Post subject: Reply with quote  Mark this post and the followings unread

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
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milooz



Joined: Nov 06, 2013
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Location: France

PostPosted: Wed Nov 06, 2013 4:17 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi Everybody it's my first post here Wink

I'm waiting for an etched board based on the gerber file from Phobos

I have few questions about the frequency pot: what's the value of the pot? how to wire the pot on the board? I've seen the pad marked "pot" but i don't know which pin of the pot goes to the pad on the board and if i have to solder other pins of the pot somewhere on the board (to ground ?)

I must receive the board and components this week and i hope to start soldering during the week-end...This is my second DIY project (first was a WSG from MFOS)

Thanks for the help

Cheers from France
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PHOBoS



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PostPosted: Wed Nov 06, 2013 6:53 am    Post subject: Reply with quote  Mark this post and the followings unread

welcome party!

milooz wrote:
I have few questions about the frequency pot: what's the value of the pot? how to wire the pot on the board? I've seen the pad marked "pot" but i don't know which pin of the pot goes to the pad on the board and if i have to solder other pins of the pot somewhere on the board (to ground ?)

According to Eric Archer's schematic it's a 10K (lin) pot. The wiper is connected to the pad marked pot and the two outer lugs are conected to
GND/+9V but I didn't add any extra pads for these connections. If I build a synth there are usually several pots that need to be connected between
+ and GND (or -) and then I connect those all together and straight to the supply. But you can connect it to where the power is connected to the board.

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milooz



Joined: Nov 06, 2013
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PostPosted: Wed Nov 06, 2013 7:01 am    Post subject:   Reply with quote  Mark this post and the followings unread

Hi Phobos,

Thank you very much for your help, i will let you know how the filter works when it's finish.
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milooz



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PostPosted: Sun Nov 17, 2013 11:14 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks to PHOBos,

I've etched his board layout (pcb made by techiguitare in France) and finished the soldering... first test and the filter works really well.

15€ for the board etching + 15€ for the components and you've got the best 30€ VCF out here Wink
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PHOBoS



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PostPosted: Sun Nov 17, 2013 4:14 pm    Post subject: Reply with quote  Mark this post and the followings unread

great to hear it's working Very Happy
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milooz



Joined: Nov 06, 2013
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PostPosted: Sun Nov 17, 2013 4:31 pm    Post subject: Reply with quote  Mark this post and the followings unread

For now i didn't solder the "CV in" and im not sure how to do this?
I think i have to solder a wire from the pad "CV" to the tip of a jack but i don't know if i have to solder the ring of the jack to ground?

If i'm right the filter only accept positive CV, what kind of device can send positive CV?
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PHOBoS



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PostPosted: Sun Nov 17, 2013 5:38 pm    Post subject: Reply with quote  Mark this post and the followings unread

milooz wrote:
I,..don't know if i have to solder the ring of the jack to ground?

yep that's correct.

Quote:
If i'm right the filter only accept positive CV, what kind of device can send positive CV?

a baby 10 sequencer would be something that gives out a positive CV, ADSR's often have a positive output too. It's also pretty easy to make a single supply LFO with square, triangle and saw output. I did add some protection against negative voltages so you could add a signal that's both positive and negative but it will only react to the positive part.

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milooz



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PostPosted: Wed Jan 01, 2014 12:59 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi PHOBos,

My filter is now in box (pedal format) with cv input working great with home build sequencer Wink

But, i've noticed a significant volume decrease when the effect is engaged. Do you think it's normal with this kind of circuit and can i make some mods to resolve the problem?
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PHOBoS



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PostPosted: Wed Jan 01, 2014 1:42 pm    Post subject: Reply with quote  Mark this post and the followings unread

hmm, well if you use a filter the ouput signal will be somewhat less then what it was, but that also depends on the source signal you use. I mean if it has a
lot of low frequencies than a LPF will have less of an effect then when it has a lot of high frequencies. However if the output is just generally lower you
could try to boost it by increasing the gain resister at the output stage (R21 = 100K).

I have build that filter myself so maybe I can do a test to see what the output level is compared to the input. (probably in the weekend)

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milooz



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PostPosted: Wed Jan 01, 2014 3:08 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks for the reply!
Which one is R21 on your pcb? I will try some higher values for this resistor but can't find the location for R21
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PHOBoS



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PostPosted: Wed Jan 01, 2014 4:00 pm    Post subject: Reply with quote  Mark this post and the followings unread

It looks like I changed some values on my version. I usually do that if I find a circuit, breadboard it and then make adjustments to my liking. But had
forgotten that I did that with this circuit too. Embarassed I guess you build it with the values on the PCB.

R21 is the 470K resistor on my version, but I shall make a list to see what I replaced. (I wouldn't advice making that one larger btw).

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milooz



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PostPosted: Wed Jan 01, 2014 4:13 pm    Post subject: Reply with quote  Mark this post and the followings unread

Yes of course i've used all the values and components specified on the pcb Cool! Just to clear, i have to replace the 470k resistor with a higher value or smaller value if i want more volume from the output?
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PHOBoS



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PostPosted: Wed Jan 01, 2014 4:43 pm    Post subject: Reply with quote  Mark this post and the followings unread

you would have to make it larger but 470K is allready pretty large, it's possible though. (if you make it very large it will be more sensitive to noise)

I just took a look and the only values I changed are from the output mixer:
Code:
Rx    org.    mod.
-------------------
R17 =  33k ->  47k
R18 =  10K -> 220k
R19 =  33K ->  47K
R20 =  10K -> 100K
R21 = 100K -> 470k

MIXPOT = 10k -> 50k

(I also added a 100K resistor to GND on the output to prevent pops when plugging in a cable)

So you could make R18 and R20 smaller. (you can find all those resistors between the 4.7uf capacitors)

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