A little taste of some Kansas home cookin' (VCF)

From circuitbending to homebrew stompboxes & synths, keep the DIY spirit alive!

Moderators: Kent, Joe., analogdigital, infradead, lisa, parasitk, plord, sduck

Post Reply
User avatar
negativspace
Manhattan Analog
Posts: 6571
Joined: Tue Apr 13, 2010 2:50 am
Location: Manhattan, KS, USA
Contact:

A little taste of some Kansas home cookin' (VCF)

Post by negativspace » Wed Jul 10, 2013 11:21 pm

In my scant free time over the last month I've been working on this... it's finally in a state where I feel like sharing. It 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!) and that's what you're hearing in this rather short clip. It's definitely interesting! A very thick, rich-sounding filter with a lot of different personalities depending on how hard you drive the inputs.

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

I've gotten Scott's blessing on a PCB run, if you guys are into this I'll make it happen. I'll offer it with a euro panel as usual but I'm going to keep power connectors and mounting holes onboard for other-format builds.
Last edited by negativspace on Thu Jul 11, 2013 4:53 am, edited 2 times in total.

User avatar
GrantB
Super Deluxe Wiggler
Posts: 1292
Joined: Fri Apr 09, 2010 5:58 pm
Location: Oly

Post by GrantB » Wed Jul 10, 2013 11:35 pm

That sounds great! :yay:

User avatar
appliancide
Super Deluxe Wiggler
Posts: 1458
Joined: Fri Dec 17, 2010 9:51 am
Location: Idiocracy

Re: A little taste of some Kansas home cookin'

Post by appliancide » Thu Jul 11, 2013 12:13 am

negativspace wrote:I've gotten Scott's blessing on a PCB run, if you guys are into this I'll make it happen.
:yay:

I'm way into this! Even before I heard the awesome sample, I wanted it for the synth-nerdiness factor of a discrete SVF.

User avatar
Isaiah
Super Deluxe Wiggler
Posts: 1797
Joined: Wed Jun 02, 2010 6:31 am
Contact:

Post by Isaiah » Thu Jul 11, 2013 12:24 am

Very interesting!
It seems to track 1V/Oct pretty well in your demo. Is there the option to adjust the scaling or add temperature compensation?
Is the VC over Resonance? I remember you saying before that you are fond of VC Resonance. Maybe the design doesn't permit adding that feature.
Any idea of PCB size yet?
Cheers!

User avatar
Dr. Sketch-n-Etch
Super Deluxe Wiggler
Posts: 7584
Joined: Thu Jan 21, 2010 1:46 pm
Location: Vancouver, BC, Canada

Post by Dr. Sketch-n-Etch » Thu Jul 11, 2013 12:36 am

Wow, that filter sounds fantastic. Tonnes of character! :yay:
For every bullshit job, you need a bullshit education -- Brian Eno

User avatar
negativspace
Manhattan Analog
Posts: 6571
Joined: Tue Apr 13, 2010 2:50 am
Location: Manhattan, KS, USA
Contact:

Post by negativspace » Thu Jul 11, 2013 1:09 am

Isaiah wrote:It seems to track 1V/Oct pretty well in your demo. Is there the option to adjust the scaling or add temperature compensation?
It does... I haven't set it up side-by-side with a proper VCO to test the tracking but it handled the CV from the 303 nicely. Regarding scaling or compensation, not as of now but that's something I'd still like to add. It should be pretty straightforward.
Is the VC over Resonance? I remember you saying before that you are fond of VC Resonance. Maybe the design doesn't permit adding that feature.
Your memory is accurate, but this doesn't have that feature. There's no reason it couldn't be added but I don't plan to do so this time.
Any idea of PCB size yet?
I'm going to say 4.25" high by ~12-14hp in width? It depends a bit on the panel design I settle on, I'm going to design this all as one unit with a daughterboard for panel controls and the works. No wires!

User avatar
negativspace
Manhattan Analog
Posts: 6571
Joined: Tue Apr 13, 2010 2:50 am
Location: Manhattan, KS, USA
Contact:

Post by negativspace » Thu Jul 11, 2013 1:13 am

Dr. Sketch-n-Etch wrote:Wow, that filter sounds fantastic. Tonnes of character! :yay:
Thank you! It really does have a lot of character, that sample above is a very narrow display. I'll do a better, deeper one as soon as I get my interface back which should be very soon.

(Tonnes... is that Canadian for "tons"? :hihi: )

User avatar
Piedwagtail
Wiggling with Experience
Posts: 278
Joined: Fri Apr 05, 2013 12:48 pm
Location: within the Shoreditch triangle

Post by Piedwagtail » Thu Jul 11, 2013 1:22 am

Phew! Exemplary work!

Sample: how matched are the transistors?


Robert

User avatar
negativspace
Manhattan Analog
Posts: 6571
Joined: Tue Apr 13, 2010 2:50 am
Location: Manhattan, KS, USA
Contact:

Post by negativspace » Thu Jul 11, 2013 1:33 am

The transistors are "loosely matched." They could be more meticulously selected but they're not just random pulls from the bag. (The board in the clip is my first PCB build so priority was on getting it to work vs. making it perfect.)
Last edited by negativspace on Thu Jul 11, 2013 4:34 am, edited 2 times in total.

User avatar
cleaninglady
Super Deluxe Wiggler
Posts: 1259
Joined: Mon Aug 24, 2009 8:04 pm
Location: creeping up behind you

Post by cleaninglady » Thu Jul 11, 2013 2:55 am

If it happens , i would very much like to get one. :guinness:

User avatar
diablojoy
Super Deluxe Wiggler
Posts: 1615
Joined: Fri Jan 22, 2010 9:03 pm
Location: melbourne

Post by diablojoy » Thu Jul 11, 2013 3:29 am

:lol: you beat me to it
I have the schematic sitting in front of my computer
it was next in line for a layout.
oh well i shall sit back and watch this with interest now
I may still end up doing some for myself anyway as i dont build in euro.
It probably wont happen today but if it does it definitely wont go smoothly.

User avatar
Paradigm X
Super Deluxe Wiggler
Posts: 1979
Joined: Tue Nov 02, 2010 5:43 am

Post by Paradigm X » Thu Jul 11, 2013 3:58 am

this is Stite's 2040-a-like jobby?

Yeah, id started a version with the THAT chips... and didnt get very far.

Would love a pcb or two.

User avatar
keninverse
Ultra Wiggler
Posts: 996
Joined: Mon Jul 26, 2010 4:12 pm
Location: mission control htx

Post by keninverse » Thu Jul 11, 2013 4:38 am

I'm with some of the others...
If this is Scott's discrete 2040 I'm so in, especially if there's a run of panels...in euro and buchla.

User avatar
negativspace
Manhattan Analog
Posts: 6571
Joined: Tue Apr 13, 2010 2:50 am
Location: Manhattan, KS, USA
Contact:

Post by negativspace » Thu Jul 11, 2013 4:40 am

Yeah, it's the one you're thinking. I changed the OP to clarify a bit. :tu:

User avatar
woodster
Super Deluxe Wiggler
Posts: 1295
Joined: Mon Mar 05, 2012 9:36 am
Location: UK

Post by woodster » Thu Jul 11, 2013 5:01 am

Well tasty, and even better that it's going to be DIY!
I'd definitely be interested in building one if made available.

User avatar
Paradigm X
Super Deluxe Wiggler
Posts: 1979
Joined: Tue Nov 02, 2010 5:43 am

Post by Paradigm X » Thu Jul 11, 2013 6:09 am

Cool, so youve gone for the transistor version rather than the THAT matched pairs version?

This thing did sound great when i heard it.

Nice one

User avatar
Synthsense
Common Wiggler
Posts: 217
Joined: Sun Nov 04, 2012 12:40 pm
Location: VCAlona

RSF Kobol?

Post by Synthsense » Thu Jul 11, 2013 6:37 am

Excuse my ignorance but.....Is this one the VCF (made of discrete components) You can find in the RSF Kobol? It sounds nice, thanks for this new project!

User avatar
joshuagoran
Wiggling with Experience
Posts: 363
Joined: Tue Apr 09, 2013 9:28 am
Location: NE Ohio, USA

Post by joshuagoran » Thu Jul 11, 2013 9:02 am

Awesome! Interested to see this come along. I've not had a SVF and this one sounds great and I dislike wiring panels :P

User avatar
mcop
Wiggling with Experience
Posts: 441
Joined: Fri Apr 27, 2012 7:39 am
Location: Bristol UK

Post by mcop » Thu Jul 11, 2013 11:48 am

Very nice, interested to see where this goes. I'd seen Scott's thread over at EM and had this earmarked to try at some point so if you do a board I could well be interested.

Norman_Phay

Post by Norman_Phay » Thu Jul 11, 2013 12:08 pm

I'd be interested in a couple of boards for this, for sure. Demo clip sounds nice!

Norman_Phay

Post by Norman_Phay » Thu Jul 11, 2013 12:13 pm

I'd be interested in a couple of boards for this, for sure. Demo clip sounds nice!

User avatar
rosch
roadkill
Posts: 790
Joined: Thu Dec 23, 2010 12:44 pm
Location: doucheland

Post by rosch » Thu Jul 11, 2013 12:16 pm

2 for me please!
i like the discrete nature, in a very indiscrete anti-wiring package :sb:

User avatar
logicgate
Super Deluxe Wiggler
Posts: 1465
Joined: Wed May 30, 2012 11:43 am
Location: Fillory

Post by logicgate » Thu Jul 11, 2013 1:40 pm

1 for me!! And I back the "anti wiring" plea, lol

User avatar
VCOscillator
Common Wiggler
Posts: 195
Joined: Mon Jan 14, 2013 9:30 am
Location: UK

Post by VCOscillator » Thu Jul 11, 2013 2:54 pm

Excellent work, the samples sound great! Count me in also for 1 please :tu:
Chain Reacting

User avatar
vtl5c3
Common Wiggler
Posts: 149
Joined: Fri Jan 16, 2009 5:49 pm

Post by vtl5c3 » Thu Jul 11, 2013 4:45 pm

Two for me, plz.

Post Reply

Return to “Music Tech DIY”