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 Forum index » DIY Hardware and Software
CEM 3328
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factus10



Joined: Jun 20, 2007
Posts: 158
Location: Buffalo, NY

PostPosted: Sat Mar 15, 2008 2:10 pm    Post subject: CEM 3328 Reply with quote  Mark this post and the followings unread

Anyone have a use for these? I have 8 pulled from a Mirage.
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Danno Gee Ray



Joined: Sep 25, 2005
Posts: 1343
Location: Telford, PA USA

PostPosted: Sat Mar 15, 2008 3:04 pm    Post subject: Reply with quote  Mark this post and the followings unread

They can be made into nice little filter modules can't they?
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Danno Gee Ray



Joined: Sep 25, 2005
Posts: 1343
Location: Telford, PA USA

PostPosted: Sat Mar 15, 2008 3:05 pm    Post subject: Reply with quote  Mark this post and the followings unread

Depending on costs, I might bite.
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factus10



Joined: Jun 20, 2007
Posts: 158
Location: Buffalo, NY

PostPosted: Sat Mar 15, 2008 3:16 pm    Post subject: Reply with quote  Mark this post and the followings unread

I haven't read the data sheet yet but it's a four pole vcf. I was kind of hoping someone could point me in the direction of a schematic or, even better, a pcb Smile
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Danno Gee Ray



Joined: Sep 25, 2005
Posts: 1343
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PostPosted: Sat Mar 15, 2008 3:30 pm    Post subject: Reply with quote  Mark this post and the followings unread

Ah...Ok DUH!

I thought ypou were like trying to get rid of them or something.

try this


cem3328.pdf
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factus10



Joined: Jun 20, 2007
Posts: 158
Location: Buffalo, NY

PostPosted: Sun Mar 16, 2008 8:33 am    Post subject: Reply with quote  Mark this post and the followings unread

Sure, I'm open to that. I only want to keep one for myself and someone has already asked after 4 of them. So that leaves 3.

I have no idea what their value is, so make me an offer. I'm very open to trades.
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goldenechos



Joined: Jun 06, 2007
Posts: 201
Location: Marshall, NC
Audio files: 1

PostPosted: Sun Mar 16, 2008 2:24 pm    Post subject: Reply with quote  Mark this post and the followings unread

The Data Sheet has a schematic for using this chip. The sound is good. the really nice thing about this chip is that the expo. circuit for the Cutoff CV is ON THE CHIP. Therefore, all you have to add is input and output buffers, and CV summing as well as a handful of passives.

The data sheet shows how the 3328 HAS Buffers on the chip, BUT when you consider the rarity/ cost of the chip, I think you will agree that you would be better off to use a Dual Op-amp and buffer the input AND the output.

ADDITIONALLY, you should operate this chip on +/- 12V. If I remember correctly, it has a low maximum supply voltage.

Tony
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Scott Stites
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Joined: Dec 23, 2005
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Location: Mount Hope, KS USA
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PostPosted: Wed Mar 19, 2008 12:15 pm    Post subject: Reply with quote  Mark this post and the followings unread

Jeff Pontius built a filter module with this IC. IIRC, the 3328 can easily be configured so that there is no amplitude loss in the passband at high resonance settings, which he accomplished. I'm not sure if I have his schematic or not - I'm sure he sent it to me at some point.
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factus10



Joined: Jun 20, 2007
Posts: 158
Location: Buffalo, NY

PostPosted: Thu Mar 20, 2008 7:22 am    Post subject: Reply with quote  Mark this post and the followings unread

Hey all,

I have three remaining for trade if anyone is interested.

David
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mono-poly



Joined: Jul 07, 2004
Posts: 935
Location: Rotterdam, Netherlands
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PostPosted: Thu Mar 20, 2008 7:42 am    Post subject: Reply with quote  Mark this post and the followings unread

Yeah i love to see Jeff's design to.
I think this is one of the best CEM lowpass vcf designs.
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Danno Gee Ray



Joined: Sep 25, 2005
Posts: 1343
Location: Telford, PA USA

PostPosted: Thu Mar 20, 2008 3:10 pm    Post subject: Reply with quote  Mark this post and the followings unread

So I guess my trade offer was not up to speed?
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factus10



Joined: Jun 20, 2007
Posts: 158
Location: Buffalo, NY

PostPosted: Thu Mar 20, 2008 3:46 pm    Post subject: Reply with quote  Mark this post and the followings unread

Ack! I'm sorry.... yes, that sounds great. I'll pm you in a second.
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Scott Stites
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Joined: Dec 23, 2005
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PostPosted: Fri Mar 21, 2008 7:31 pm    Post subject: Reply with quote  Mark this post and the followings unread

Here's Jeff's design. I took the time to make sure it was OK with his wife, which of course it was. Jeff sent this to me on 12 June, 2005 with the following text:

Quote:
I attached the latest 3328 filter schematic: (1) I changed the 10K
resistors to 100K on the FM input as the 10K did not provide enough
'sensitivity' to my incoming +-5V input ranges (same thing occurred on the
breadboard, but I suppose it just wasn't prominent enough to capture my
attention), (2) cleaned up a few component misdesignations, and (3) added
a few notes on pot connections and observations. Hope this helps. I'm
sure it is not an 'optimal' design for this filter, but I think it sounds
pretty reasonable and I like the resonance options. And, like we
speculated, the -IN does not interact with the Resonance Level control,
just the +INs.


Somehow he put my name on the schematic, too, though I can't remember contributing all that much to it. I do remember breadboarding it, and it did sound pretty dang good.

Jeff was one in a billion - he knew more about electronic music than anybody I've ever met, and he was an outstanding electronic musician. On top of that, he was just one hell of a human being; certainly one of the kindest and most knowledgable I've ever had the pleasure to have known. I'd say he's also my greatest musical influence, though he'd probably cringe if he caught me saying that Laughing

If you ever run across his "SynthImagery" CD, buy it, you'll not regret it. Powerful stuff.

Not required, but if anyone builds this module, it would be nice to see "Pontius" on the front of it......

Take care,
Scott


Pontius_CEM3328.PNG
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Jeff Pontius' CEM3328 Based Filter
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mrand



Joined: Mar 30, 2014
Posts: 27
Location: Ottawa

PostPosted: Tue Jul 22, 2014 7:16 pm    Post subject: Reply with quote  Mark this post and the followings unread

Old thread here but rather than start a new one I will post here.

Im wondering if anyone is using cem3328s, and if they are having similar experiences as I.

I'm not getting self oscillation until I apply around 7v to the resonance cv pin (pin 10). I'm using a similar layout to the pontius one above, except Ive eliminated the 47uf caps and I'm only dialing in the resonance via a voltage divider, ie no resonance modulation input and no buffers there either.

Datasheet specifies the resonance input should be 0-5v, and that it should self oscillate within that range.

Once it gets into oscillation, increasing the res voltage brings down the cutoff. I haven't noticed any interaction when res is below self oscillation.

Other thing I'm noticing is the output seems a bit quiet, I think.

Thanks for reading!
-C
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