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Synthcube am4023 VCF
MUFF WIGGLER Forum Index -> Fractional Rack Modules  
Author Synthcube am4023 VCF
I recently ordered one of Synthcube's am4023 VCF kits. This is a kit version of Rob Keeble's PCB that he did some time ago, which is based on the Odyssey 12db 2 pole VCF circuit. The kit is available in 1U & 2U versions, in both minijack and banana. I got the 1U minijack kit.

I don't have any 'stock' frac filters in my rig - I have a MMM VCF that I built from their kit and a LPG, which can act as a filter. So I jumped at the chance to get a 1U wide filter, as that's the only space I have left.

My kit showed up yesterday. Wow, it's certainly an impressively put together kit. All the parts are packed in separate boxes, grouped by type:

The kit contains lots of resistors - the values that only have 1 or 2 resistors are nicely identified in their own packet, which saves a lot of time:

This makes a nice change from the Blacet kits where everything is lumped together in a bag and you have to spend a while identifying everything. This is not a criticism of Blacet by the way - if I had to pack the amount of kits they do, I'm sure I'd do it that way eek!

A number of the wires are supplied with connecting headers already made up:

The documentation is a nice ring bound document that contains all the instructions and schematics. My only criticism of it was the parts list was sometimes hard to read as the font is quite small. But I am getting old...

The PCB was easy to put together. It started to get a bit fiddly when it came to mounting the sockets, pots and PCB to the panel - there isn't much room at all behind the panel. This bit would be easier on the 2U wide panel I would guess. I haven't come across the sockets that are used before, they look nice and have a nice feel to them. But I lack the right tool to tighten the washer - it is a circular type with 2 small slots. The instructions didn't mention which lugs were which (signal, ground), but a quick test with the meter soon sorted that out.

Here's the completed module:

The knobs go right to the edge of the panel, and the pots stick out a bit at the side, but it doesn't seem to interfere when racking up the module. The layout of the controls seems a bit unconventional, I expect freq/res at the top on a VCF, but they are in the middle on this one.

I can't say how it compares to any of the Blacet filters, as I've never heard one. But this is a really nice sounding filter. I haven't properly calibrated it yet, but it has a really nice sounding sine wave when self oscillating. Unusually there is a fine tune control so you can really tune in the sine wave to the desired pitch. I can see myself using this as the basis for some BD patches. It's hard to describe filters sometimes, but this one sits on the 'smooth' side rather than 'wild' or 'harsh' (like a MS20 for example). Just feeding it a single sawtooth I was also able to get some fairly 'acid' type tones out of it.

Considering the effort that has gone into this kit, the price is very good value - just under $100, which for me worked out at about £65 plus shipping. The good news for me was customs didn't get their grubby hands on it!

Sorry for the long post, but it's not often we get a new Frac filter 8_)
That kit looks gourmet!

Very tempting. Anything that comes with a panel is tempting really - I'm over making my own and I'm too cheap to order proper ones. At least, that's my excuse for my ever-growing DIY backlog...
holy christ!!

woah that packaging.
it's true we don't often get a new filter around these parts..any chance of an audio sample?
werock, thanks for the feedback. comments noted for future kits!
would love to hear the audio demo when you get the filter dialed in

this is a quick, rough sample demo we did during prototyping... there's a second demo, too
chamomileshark wrote:
it's true we don't often get a new filter around these parts..any chance of an audio sample?

Ok, here's a couple of quick samples.

The first is some general wiggling of the frequency and res controls, ending up in bass drum like oscillation.

The second has an lfo modulatng the frequency, while gradually upping the resonance.

Stay tuned for another couple of new modules in frac.... Barton Dual Quantizer , and j3rk Dual 258j Oscillator

More news midweek

Synthcube, I can't find these (2u only) on you website.
Will these be restocked?
Here's the link to the 2u version... We have 1u versions also in stock, and both 1u and 2u versions in frac banana Am4023&product_id=144
I see.

Want I'm looking for is the 1u minijack version, same as Werock's.

That one I can't find on the website.
here's the link to to the 1U minijack version: 4023&product_id=146

hope this helps
Just about to start a build for the AM4023 pcb I bought from you about a month ago.
Going to stick it behind a Eurorack panel.
I checked the synthcube site but struggled to find any hires picks of a completed dotcom/MU module.

Do you have any I could see for a visual guide before I drill the panel?

cheers! smile
if you go to and search '4023' you should see the MOTM, dotcom/MU and Frac panel versions, in 1U and 2U wide- lots of options for you!
Good luck with it... keep us posted
Yeah, I've seen all those pics, cheers.
Was wondering if there were any more, especially hi res pics
of the wiring!

This is my first DIY panel. Drilled the holes myself!
Slightly off but I don't care. smile
Panel design by my daughter Catherine with a permanent marker.

But apart from that, what I could use a bit of help with would be how to
make this a 12v unit on the pcb as I'm a Eurorack whore!

Any advice as to what to do during the build to make this adjustment
would be a learning experience and most appreciated!

I've been getting loads of help from Frequency Central's Rick Holt
and have successfully built a System X VCO and Moog Vogue filter,
but now it's getting scary! smile
Most importantly, that is an AWESOME panel!

I will take some pictures of the PCBs and get them to you. It's a really straightforward build..

There are no adjustments required for euro/12v.. In fact the circuit was designed for use in a euro system originally . The only change will need to be an adaptor to connect the euro power cable to the 4pin power header, or you can directly solder to the PCB holes.
This is simply wonderful news!
I've only just joined this modular 'subculture' and
it's time's like these that make me realize how fucking
cool you all are!

More advise on the power 'adapter' or direct soldering
would be greatly appreciated. smile
The only thing holding me back from getting started is the farrite inductors.
Not sure which specific rating to use.
Plus adapting it for 12v operation in my Eurorack format.

Any advice would be greatly appreciated.

Mouser carries some of these: CHAGAIN=Y#select:freq1

Mostly I see the 4/5mm long ones being used.
Cheers mate. Sourced some on ebay for pretty cheap. smile
All that's left is sorting out the ribbon from my Eurorack case
to the PCB!
Acid Mitch
What does the 2u version have that the 1u doesn't ?
The synthcube site keeps giving me errors when trying o get info on it.

Any one patching 2 of these in series for some 24 db action ?
Acid Mitch wrote:
What does the 2u version have that the 1u doesn't ?
The synthcube site keeps giving me errors when trying o get info on it.

Any one patching 2 of these in series for some 24 db action ?

The 2u has a second CV in with attenuator and three inputs (one direct, two with attenuators). I plan on building a second one soon, mainly because I'd like to use one for kick drums and one as a VCF.
Acid Mitch wrote:
What does the 2u version have that the 1u doesn't ?
The synthcube site keeps giving me errors when trying o get info on it.

Any one patching 2 of these in series for some 24 db action ?

Would you please send us an email with your browser version so we can check the issue with the site? Apologies for any inconvenience.
Acid Mitch
Hey Synthcube,
I just tried your contact page and after typing my message and hitting send got told " Oops! Google Chrome could not connect to

Access a cached copy of www.­synthcube.­com/­contact ", very frustrating hihi hihi

What's your email address ?

@monstrinho - thanks for answering. I'll have a few follow up questions shortly smile_
Sorry about that
Seems to be an issue with the main page contact form
You can use the contact form at, or email is: info at synthcube dot com.
Acid Mitch
Emailed you.
I got one of these filters in the mail today, and I really like it. The resonance sounds great!
Is this filter sounding good? Not that many 12dB Odyssey filter around in MU format.
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