CEM3328 Low Pass Filter Boards

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

Moderators: Kent, Joe., luketeaford

Post Reply
User avatar
executiveBlaster
Veteran Wiggler
Posts: 523
Joined: Wed Oct 12, 2011 12:59 pm

CEM3328 Low Pass Filter Boards

Post by executiveBlaster »

edit: PCBs have arrived! Built the first one tonight and it kiiccckkss butttt. Pics and samples in the morning!


order list!

synthnut x 2
mono-poly x 2
raisinbag x 1
bjarneroe x 2
krisp14u x 2
dego x 2 & 2 j&p
xpander x 2 & 2 j&p
frozenkore x 1 & 1 j&p
carynrich x 1

if you're not on this list, you and I have made separate arrangements, or I forgot you 8_) I'll update this post when I order the pcbs. Thanks dudes! [/b]

To clarify, the jacks&pots boards are a pcb with footprints for erthenvar jacks and bi-tech pots, with rows of pads on the sides to connect to the main pcb via headers, sandwich style. Together they form a very shallow, 'wireless' module.

Original post:

Hey dudes,

So I have a few (~20) CEM3328 Low Pass Filter ICs, most of which are still safely socketed in my three Ensoniq Mirages. I made these pcbs

Image

which are the filter set up with two cv inputs, one of which is normalled to the output of an AR circuit included on the board (I can't waste opamps...). This chip supports vcresonance, but I didn't include it on the board. It would be a snap to implement with the data sheet (which I'm uploading). Here's a pic of an assembled board connected to another (with the wrong pot footprints :ripbanana: )

Image

I have 7 of those boards left, (and can part with them for cheap!) but what I'm really wondering is if anyone is interested in new pcbs for these chips. It would be a very small run, obviously, unless people wanted the pcbs and could source their own cems (they're out there!) That old layout was fairly random, so a new one could be specifically for skiff-friendly pcbs or whatever format we all agree on.

I'm attaching an audio sample, too, of a diy ota vco through the cem3328, both driven by a diy realtime sequencer (we'll talk about that elsewhere!)[/s]
Attachments
diy vco through cem3328
eb-short.mp3
(419.42 KiB) Downloaded 159 times
c3328pdf.pdf
(220.16 KiB) Downloaded 125 times
Last edited by executiveBlaster on Fri Mar 01, 2013 4:25 pm, edited 9 times in total.
User avatar
xpander
Super Deluxe Wiggler
Posts: 1133
Joined: Tue Dec 30, 2008 6:24 pm
Location: los gatos, california

Post by xpander »

that's pretty cool! how much trouble would it be to do a run with a corrected control board?
User avatar
executiveBlaster
Veteran Wiggler
Posts: 523
Joined: Wed Oct 12, 2011 12:59 pm

Post by executiveBlaster »

None at all, that was the plan!

What format would you want? And would you still want the AR included?
User avatar
dougt
Super Deluxe Wiggler
Posts: 1133
Joined: Thu Apr 30, 2009 3:47 am
Location: Sillycon Valley, CA

Post by dougt »

I have a few CEM3328s at $15/ea if people need any for this...
User avatar
synthnut
Common Wiggler
Posts: 249
Joined: Tue Apr 27, 2010 7:47 am
Location: UK

Post by synthnut »

Hi,

I have a few 3328s king about in a drawer, so would bu up for a couple of boards, especially if you impliment the VC resonance too....
I'd only want the basic board as I'll be doing a MU panel rather than Euro for myself.

TTFN,
Ben

www.bigbluewave.co.uk
www.resynthesis.co.uk
User avatar
mono-poly
Le Cheff
Posts: 5423
Joined: Fri Nov 21, 2008 3:40 pm
Location: Rotterdam, Netherlands

Post by mono-poly »

I'd like a board.
The farad is the captain of my print.

http://www.mono-poly.nl
http://www.noodlebar.org

WTB blue lantern purple vco
User avatar
executiveBlaster
Veteran Wiggler
Posts: 523
Joined: Wed Oct 12, 2011 12:59 pm

Post by executiveBlaster »

Cool! I'll PM you both.
User avatar
Low-Gain
Super Deluxe Wiggler
Posts: 2695
Joined: Thu Apr 22, 2010 12:49 pm
Location: St. Paul, MN
Contact:

Post by Low-Gain »

I have about 3 mirages worth of these chips.. would def be interested! :)
User avatar
xpander
Super Deluxe Wiggler
Posts: 1133
Joined: Tue Dec 30, 2008 6:24 pm
Location: los gatos, california

Post by xpander »

executiveBlaster wrote:None at all, that was the plan!

What format would you want? And would you still want the AR included?
euro. i'd rather have an attenuator on the input than an AR.
User avatar
executiveBlaster
Veteran Wiggler
Posts: 523
Joined: Wed Oct 12, 2011 12:59 pm

Post by executiveBlaster »

Well that's enough interest for me to do a revised run, definitely! If anyone still wants one of these "old" pcbs, let me know and you can still get it, but the revisions will be better. PCBs take 2-3 weeks to get to me, and I can order them first thing monday. Is that an aight wait for you guys?

@xpander totally, this chip really needs attenuated signal in so that you have fine control over how to pluck it (it really loves to be plucked!) If you're the only guy wanting the control board, you and I may have to work out something separate for those (not a prob, though)

What I'm hearing is:

attenuator on the signal input
vc res and attenuator

Do you guys need your platform specific power headers, or are pads ok? Most of my builds aren't hooked up to a euro busboard, so I don't automatically put those footprints on stuff, but I can.

@low-gain so you want 24? :hihi: jk, unless you do!


Bring on the thoughts there
User avatar
Low-Gain
Super Deluxe Wiggler
Posts: 2695
Joined: Thu Apr 22, 2010 12:49 pm
Location: St. Paul, MN
Contact:

Post by Low-Gain »

depending on the price of the board i just might.
can i get a price break? :)
Also, is it the circuit pcb and the control panel pcb?

Maybe you can document a little more clearly as to exactly what this DIY pcb module will have for controls, etc.
User avatar
executiveBlaster
Veteran Wiggler
Posts: 523
Joined: Wed Oct 12, 2011 12:59 pm

Post by executiveBlaster »

@Low-Gain
The initial idea was to just be selling the circuit PCB, the "guts". If there's enough interest (so far it's only ol' xpander up there) I can do a control PCB as well, with bi-tech pots and erthenvar vertical jacks.
And yep, there'll be pricebreaks.

"Guts" PCB features:
Cutoff, Resonance, CV w/ Attenuator, CV without
+Sig w/ Attenuator and resonance scaling (see datasheet attached to first post)
-Sig without attenuator or resonance scaling.
Resonance CV input w/ Attenuator
Output


The panel I'd want to make does not include vc resonance though, as it severely complicates (or just widens) the layout. Checkums


Image



Nowhere for poor vcresonance on that panel. I think this:


Image

is wack. (I also labelled the cv input 'res' and the knob 'q' on accident...)

that being said I'm open to suggestions!

Boards will be $10 each or both for $18, + shipping
(cheaper if we get >50! wonder if there are even 50 chips among us..)
User avatar
Low-Gain
Super Deluxe Wiggler
Posts: 2695
Joined: Thu Apr 22, 2010 12:49 pm
Location: St. Paul, MN
Contact:

Post by Low-Gain »

well like i said. i have 3 mirages worth. and if it is "tricked" out (which having cv res on the front panel would be nice) i'd likely buy up enough to cover all of my chips. Do i need that many? No. i'd likely sell most of them off as completed modules if you're ok with that.. as a basic.. "short run" of a build.
keeping a few for myself. It would put use to the chips i have just sitting around that i would otherwise likely not be able to get rid of for a value of the work i put into getting them.
User avatar
executiveBlaster
Veteran Wiggler
Posts: 523
Joined: Wed Oct 12, 2011 12:59 pm

Post by executiveBlaster »

My thoughts exactly low-gain, and no problem at all. I'm warming up to that second layout, what do you think about it? If vcres makes the difference, it's there!
User avatar
raisinbag
Super Deluxe Wiggler
Posts: 1708
Joined: Thu Aug 18, 2011 11:40 pm

Post by raisinbag »

Vcres is nice. I have on an evenfall filter and it is a nice option to have.
User avatar
xpander
Super Deluxe Wiggler
Posts: 1133
Joined: Tue Dec 30, 2008 6:24 pm
Location: los gatos, california

Post by xpander »

raisinbag wrote:Vcres is nice. I have on an evenfall filter and it is a nice option to have.
+1

i'm down for 2 sets of main pcb / control pcb / euro faceplates. i definitely think the limiting factor on this module will be the paucity of 3328's.
User avatar
Dego
Veteran Wiggler
Posts: 748
Joined: Thu Jan 29, 2009 9:22 am
Location: Sweden

Post by Dego »

xpander wrote:
raisinbag wrote:Vcres is nice. I have on an evenfall filter and it is a nice option to have.
+1

i'm down for 2 sets of main pcb / control pcb / euro faceplates. i definitely think the limiting factor on this module will be the paucity of 3328's.
I want the same. I really want a panel as well.
User avatar
Low-Gain
Super Deluxe Wiggler
Posts: 2695
Joined: Thu Apr 22, 2010 12:49 pm
Location: St. Paul, MN
Contact:

Post by Low-Gain »

It makes a lot of sense to have.. But i'd probably put the cv res pot in the middle of the 4 pots..
take a look at panasonic snap in pots too.. I really like them. 50k linears work nicely..

http://www.mouser.com/ProductDetail/Pan ... U1tQ%3d%3d

http://www.digikey.com/product-detail/e ... -ND/243639
User avatar
raisinbag
Super Deluxe Wiggler
Posts: 1708
Joined: Thu Aug 18, 2011 11:40 pm

Post by raisinbag »

Nice! Blacet-mania! Ya those panasonics are nice. I have only used them on Johns boards, since that is what comes with the kit OR is what the pcb/ bom calls for, they are slick.
User avatar
executiveBlaster
Veteran Wiggler
Posts: 523
Joined: Wed Oct 12, 2011 12:59 pm

Post by executiveBlaster »

I'm pretty sure those pots will fit with the footprint I was planning on.

http://www.mouser.com/Search/ProductDet ... EC15BR100K

These are what I use. The footprint is called EVUF in diptrace, leading me to believe it's some kind of standard (EVUF is in the part number for your pots, too)

@Low-Gain you mean like this ?

Image

I'm not crazy about 5 pots in a box like that, visually or spacially, but it might be aight, and I DO love the symmetry.
User avatar
executiveBlaster
Veteran Wiggler
Posts: 523
Joined: Wed Oct 12, 2011 12:59 pm

Post by executiveBlaster »

This chip also sports "Custom Tailoring of Volume vs Resonance", meaning that the output signal stays more or less the same volume as you turn up the resonance. It's so handy, as you can crank up into wet squelch without having to adjust anything else.

Here

www.soundcloud.com/executiveblaster

are some examples of what it sounds like. Every song on there uses this filter.
User avatar
krisp14u
Oakley4All!
Posts: 1181
Joined: Fri Jan 25, 2008 4:19 pm
Location: UK
Contact:

Post by krisp14u »

Put my name down for a 2 PCB's :hyper:
Cheers :guinness:

Paul
www.krisp1.com/store/
Fine Modular systems Built in Yorkshire UK EU Planet Earth
User avatar
Low-Gain
Super Deluxe Wiggler
Posts: 2695
Joined: Thu Apr 22, 2010 12:49 pm
Location: St. Paul, MN
Contact:

Post by Low-Gain »

executiveBlaster wrote: @Low-Gain you mean like this ?

Image

I'm not crazy about 5 pots in a box like that, visually or spacially, but it might be aight, and I DO love the symmetry.
I dig it! :)
User avatar
frozenkore
Super Deluxe Wiggler
Posts: 1098
Joined: Thu Oct 08, 2009 4:19 pm
Location: Highland, IN

Post by frozenkore »

Please put me down for one set (both PCBs and a panel, if offered).
Cheers!
Brian
User avatar
carynrich
Wiggling with Experience
Posts: 456
Joined: Sat Dec 19, 2009 8:00 am
Location: Chicago

Post by carynrich »

i'll take one circuit pcb, thanks.
Post Reply

Return to “Music Tech DIY”