[IN STOCK] Eurorack: Discrete State-Variable VCF v1.4

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negativspace
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[IN STOCK] Eurorack: Discrete State-Variable VCF v1.4

Post by negativspace » Wed Apr 16, 2014 6:41 pm

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:

http://soundcloud.com/negativspace/discrete-svf-test-01

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.

Image

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.
Last edited by negativspace on Tue May 26, 2015 11:01 pm, edited 13 times in total.

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negativspace
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Post by negativspace » Wed Apr 16, 2014 6:42 pm

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 jcoates42@gmail.com

BOM
Resistors
[1] 1M R45
[1] 390k R13* (* = change to alter signal level from mixer to filter section. Suggested range is ~270-470k.)
[1] 240k R33
[2] 200k R36,R41
[1] 180k R19
[1] 110k R47
[5] 100k R15,R17,R38,R39,R40
[1] 62k R42
[1] 47k R10
[1] 39k R16
[4] 22k R1,R2,R3,R35
[3] 15k R5,R7,R43
[7] 10k R18,R27,R28,R29,R30,R31,R32
[3] 6.8k R8,R14,R46
[3] 1k R21,R22,R44
[2] 560R R9,R11
[3] 470R R20,R34,R37
[1] 240R R48
[4] 220R R23,R24,R25,R26
[1] 200R R6
[2] 100R R4,R12

Capacitors
[1] 3.3nF Film, C5
[1] 2.7nF Film, C13
[2] 1nF Polystyrene/Polypropylene *main timing caps in VCF
[2] 10-100uF Electrolytic *power decoupling caps, value noncritical
[3] 220pF MLCC, C7,C11,C12
[1] 150pF MLCC, C6
[5] 10uF Electrolytic, Q8,Q9,Q10 = audio path. The other two are for decoupling the +5 and -6V rails.
[2] 0.1uF MLCC

Transistors/Diodes
[11] 2N3904/Other NPN [PN100A] Q1,Q4,Q5,Q8,Q9,Q10,Q11,Q14,Q15,Q16,Q19
[2] 2N3904 Q17,Q18
[6] 2N3906/Other PNP [PN5138] Q2,Q3,Q6,Q7,Q12,Q13
[2] 1N4001

ICs/Sockets
[3] TL072 *or other standard pinout dual opamp.
[1] LM337LZ, TO-92
[1] LM78L05 *silkscreen on v1.2 PCB is reversed; TO-92
[3] 8P DIP socket (optional)

MISC
[1] 20k Trimpot (v/oct)
[1] 2k Trimpot (-6V)
[1] 100r Trimpot (null)
[2] Ferrite Bead
[1] 16P Header (power)
[2] 12P Header + socket (board to board interconnections)
[4] 7/16" Nylon standoff + 3/4" #4-40 screw + hex nut set. (Use 12mm standoff if metric)

Panel Controls
[3] A20-25k Pots (lugs) - audio inputs
[4] B100k Pots (pins) - CV inputs, cutoff frequency
[1] B10k pot (pins) - notch balance
[1] B10k Dual-ganged Pot (pins/lugs - BYOC, Banzai, or Small Bear) - resonance
[12] 3.5mm Jack (Erthenvar-style preferred, 16PJ138 in a pinch)
[6] 1900H or clone
[1] Davies 1913BW
[1] Davies 1910CS

Surface Mount Parts:
[2] 0.1uF 0805 ceramic, install on back of main PCB
[2] 0.1uF 0805 ceramic, control board
[2] 22pF 0805 ceramic, control board
[4] 47k resistor, 0805, control board
[2] 330R resistor, 0805, control board
[1] 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:
Image Image

Method for connecting the audio input pots - use the same technique for dual-ganged pots with lugs if you're going that route:
Image

Image


Here is a photo guide for the surface-mount section on v1.4 boards:

Image


Here is the pinout diagram for the headers, if you're wiring them up the old-fashioned way:

Image
Last edited by negativspace on Mon Apr 11, 2016 4:20 pm, edited 17 times in total.

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negativspace
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Post by negativspace » Wed Apr 16, 2014 6:42 pm

Schematic, sans SMT section:

Image[/quote]
Last edited by negativspace on Fri Oct 23, 2015 5:13 pm, edited 141 times in total.

sammy123
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Post by sammy123 » Wed Apr 16, 2014 9:09 pm

Full set with panel please.
Last edited by sammy123 on Thu Apr 17, 2014 7:53 am, edited 1 time in total.

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lintfresh
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Post by lintfresh » Wed Apr 16, 2014 9:12 pm

In for one set! Been waiting eagerly for this one.

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spneca
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Post by spneca » Wed Apr 16, 2014 9:13 pm

One full set, please.
Last edited by spneca on Thu Apr 17, 2014 5:36 pm, edited 1 time in total.

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qp
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Post by qp » Wed Apr 16, 2014 9:47 pm

Add me for 1 set + Panel!
Last edited by qp on Thu Apr 17, 2014 7:04 am, edited 1 time in total.

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dropmotif
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Post by dropmotif » Wed Apr 16, 2014 9:48 pm

One PCB set for me. No panel.

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rosch
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Post by rosch » Wed Apr 16, 2014 9:54 pm

1 full set pcb+panel for me please!

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Post by 3M-10 » Wed Apr 16, 2014 9:58 pm

Please put me down for 2 full sets of PCB's + Panels.

thanks!

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sduck
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Post by sduck » Wed Apr 16, 2014 9:59 pm

negativspace wrote:BOM

Resistors:
[0] 100k
******
Now this is my kind of BOM!

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skyshaver
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Post by skyshaver » Wed Apr 16, 2014 10:02 pm

I am interested in a pcb and panel set.

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lodsb
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Post by lodsb » Wed Apr 16, 2014 10:19 pm

I am interested as well, 2x (pcbs + panel) please!

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thetwlo
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Post by thetwlo » Wed Apr 16, 2014 10:23 pm

2 sets: PCBs + Panel, please.

Beautiful work! Thanks!!!!
Last edited by thetwlo on Fri Apr 18, 2014 2:49 pm, edited 2 times in total.

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Barcode
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Post by Barcode » Wed Apr 16, 2014 11:05 pm

One PCB set for me. No panel needed. I've been waiting for this one for a while now. :tu:

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mikecameron
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Post by mikecameron » Wed Apr 16, 2014 11:09 pm

I'm in for one.

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Post by mDang » Wed Apr 16, 2014 11:47 pm

Sound great ! And it can do stereo :)
One full set for me please !
Analogeeks

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Rigo
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Post by Rigo » Wed Apr 16, 2014 11:54 pm

One full set for me please ... makes my backlog happy :hihi:

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regenbot
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Post by regenbot » Wed Apr 16, 2014 11:59 pm

one set for me :tu:

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qfactor
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Post by qfactor » Thu Apr 17, 2014 12:31 am

Me too, negativspace!
I set (pcb/panel) for me!

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mcop
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Post by mcop » Thu Apr 17, 2014 12:32 am

I'm in for a pcb & panel set

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apophis93
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Post by apophis93 » Thu Apr 17, 2014 12:34 am

Take my money already! :hyper:

one set.

- Daniel

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mxmxmx
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Post by mxmxmx » Thu Apr 17, 2014 12:42 am

1 x pcbs + panel, please.

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negativspace
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Post by negativspace » Thu Apr 17, 2014 12:49 am

mxmxmx wrote:1 x pcbs + panel, please.
Finally I can ship your CP3. It's still sitting here with a note "Wait for SVVCF" :hihi: :deadbanana:

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Monobass
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Post by Monobass » Thu Apr 17, 2014 12:50 am

1 PCB + panel please
Thonk - CLICK HERE - Modular Synth DIY + Eurorack Accessories Store

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