br>There is a long and helpful thread on the filter itself HERE. I'll re-post the critical stuff:
This filter started life as the SVF design (based on the J. Haible discrete 2040 gain cell) which Scott Stites posted over at electro-music in April. I'd been wanting to work with another filter for a while and this one looked interesting, so I started playing with it. I lopped off the audio input section and grafted on the CP3 mixer (moar transistors!) Eventually I made a few other changes - I got it self-oscillating, added a 1v/oct CV input with scale trim, and did some work in the resonance circuit - and the end result of all of that is the filter heard here:
Ignore the photo in the Soundcloud clip, that's a different project using the same circuit. The panel for this one is 14hp, and depth is in the ~40mm range with the two PCBs stacked parallel to the panel. I'll get better photos of the panel and update this post ASAP.
Scott has given his blessing on both a DIY run and a retail release of this filter - so with my deepest thanks to him for the lion's share of this circuit I declare game on. br> br>
br>Prices Eurorack Panel + Bare PCB set: $45/ea
Bare Filter PCB: $20/ea
Shipping: $3/USA, $10/Canada, $15/Overseas
The Paypal address for payment is firstname.lastname@example.org
 A20-25k Pots (lugs) - audio inputs
 B100k Pots (pins) - CV inputs, cutoff frequency
 B10k pot (pins) - notch balance
 B10k Dual-ganged Pot (pins/lugs - BYOC, Banzai, or Small Bear) - resonance
 3.5mm Jack (Erthenvar-style preferred, 16PJ138 in a pinch)
 1900H or clone
 Davies 1913BW
 Davies 1910CS
Surface Mount Parts:
 0.1uF 0805 ceramic, install on back of main PCB
 0.1uF 0805 ceramic, control board
 22pF 0805 ceramic, control board
 47k resistor, 0805, control board
 330R resistor, 0805, control board
 TL072, SOIC, control board
Instructions for trimming
the -6V and null trimpots:
No cables in the module. No inputs, no outputs. Use the test points on the board.
1) The grounded test pad is over by the lower screw hole on the left-hand side of the PCB.
2) Adjust -6V trimpot until the test point "-6V" reads -6.00V. This test point is down by the LM337. Once you set this, for fuck's sake leave that trimpot alone!
3) Measure the test point labelled "-". This incorrectly corresponds to the jack labelled 'mix +' on the front panel. It should read somewhere between 55 and 110mV, give or take. The null trimpot won't effect this measurement, so just note the voltage. It may bounce around a bit. Just... ballpark it.
4) Measure the test point labelled "+". The null trimpot will effect this voltage so you now have two choices:
4a) Recall the voltage from Step 6 and adjust the null trim until the voltage at TP "+" reads the inverse.
4b) Forget Step 6 and adjust the null trim until the voltage at TP "+" is ~0.00V.
5) You're done with the mixer.
PCB v1.2 - note reversed power regulators & resistor lead jumper in bottom left corner. Not necessary on v1.4 PCBs:
Method for connecting the audio input pots - use the same technique for dual-ganged pots with lugs if you're going that route:
Here is a photo guide for the surface-mount section on v1.4 boards:
Here is the pinout diagram for the headers, if you're wiring them up the old-fashioned way:
br>Schematic, sans SMT section:
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br>Full set with panel please. br> br>
br>In for one set! Been waiting eagerly for this one. br> br>
br>One full set, please. br> br>
br>Add me for 1 set + Panel! br> br>
br>One PCB set for me. No panel. br> br>
br>1 full set pcb+panel for me please! br> br>
br>Please put me down for 2 full sets of PCB's + Panels.
thanks! br> br>
Now this is my kind of BOM! br> br>
br>I am interested in a pcb and panel set. br> br>
br>I am interested as well, 2x (pcbs + panel) please! br> br>
br>2 sets: PCBs + Panel, please.
Beautiful work! Thanks!!!! br> br>
br>One PCB set for me. No panel needed. I've been waiting for this one for a while now. br> br>
br>I'm in for one. br> br>
br>Sound great ! And it can do stereo
One full set for me please ! br> br>
br>One full set for me please ... makes my backlog happy br> br>
br>one set for me br> br>
br>Me too, negativspace!
I set (pcb/panel) for me! br> br>
br>I'm in for a pcb & panel set br> br>
br>Take my money already!
- Daniel br> br>
br>1 x pcbs + panel, please. br> br>
1 x pcbs + panel, please.
Finally I can ship your CP3. It's still sitting here with a note "Wait for SVVCF" br> br>