WP-20 VCF Stripboard Layout (tested and working)

[Juno60]

Hello @ all!

I finally finished my stripboard layout for Rays simple WP-20 VCF. I built it last weekend and it's working fine. It can be powered by 9V to 12V. Maybe you have to experiment with the value of the resonance pot at 12V 'cause there is still some bleedthrough when the filter is fully closed.
It's not as powerful as a Moog-Ladder-Filter, but it's fun if you need a simple, dirty and quick-to-build low-pass-filter.

Cheers,
Chris

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[Silesius]

Thanks for the layout Juno60!
And one question: does it work with a single power supply? Because I thought the WP-20 used a bipolar power supply.

[Juno60]

The WP-20 uses no bipolar power supply. It's powered by +9V, +18V and 0V. The junction of the two 9V-batteries is just to generate the +18V for the noise-generator. All other modules (VCO, VCF, EG & LFO) are running on +9V & 0V.
Therefore any unipolar power supply from 9V to 12V should work fine with the VCF. I run mine only using the +12V & 0V rails of my power-bus. While testing it I only used a 9V battery and it worked fine.

[Pehr]

Are there any good replacements for the 3900?

[BobTheDog]

Hi Pehr,

TI still do a 3900

http://uk.farnell.com/jsp/search/browse.jsp;jsessionid=IXLMCKGJVQUAECQLCIPZK0Q?N=0&Ntk=gensearch_001&Ntt=lm3900&Ntx=mode+matchallpartial&suggestions=false&ref=globalsearch&_requestid=302906

Cheers

Andy

[Captain Biscuits]

Also a few people selling 3900s on ebay in the UK anywhere from £1.20 to £4.00
Cheers
Ian

[Alienforce]

I built it... but i cant get filter to work..
I am using a 9V battery..
Is it only to connect + and - ?
I dont understand the _|_ in the middle of the + and - .. is that the gnd ?
or shall hook the - on the battery to _|_

[Juno60]

Hi Alienforce,

you need to connect the positive rail (red) of the 9V battery to the "+" on the schematics. The negative rail of the battery is the ground which has to be connected to the ground sign ( _|_ ) on the scheme. The also shown negative connection (-) is not used.

Cheers,
Chris

[Alienforce]

Thanks Chris!
Going to do some testing later today.

[Snaper]

How to add the resosnance pot?
200 k pot maybe, lug 1 to gnd, lug 2 & 3 replace the on-off reso switch?