Interesting chips - CEM 3328

[mlabbee]

There's a small lot for sale on Ebay - Has anyone seen these before?  It's a 4 pole, lowpass VCF in a chip.  Looks like you could do interesting things with a small parts count.  Has anyone used these before?  It looks like this company made a few different ICs for synths that could make for some interesting stompboxes . . .

[puretube]

Curtis chips - well known in the (DIY) synth scene...
they been kinda competition products to the SSM ICs way back
before being discontinued.

[mlabbee]

I've started digging around a bit and am starting to see that - very interesting little chip. I've been playing around a bit with filters recently, but have been kind of scared off from breadboarding them due to the large part count for most of the schems I've found - something like this could be very usefult for a stompbox (although you'd probably have to stick with a wall wart.  I'm thinking a couple of simple LFOs or an envelope follower and you could get some very cool sounds . . .

Very pricey chips, though - I better not fry them

[puretube]

there was a whole series of CEM chips (VCO/VCF/VCA/ADSR...) to build compact (polyphonic) synths.
correct me if I`m wrong, but iirc, some Oberheims had them in there (Matrix1000 ?) before they switched to SSM products...

P.S.: they`ve always been "pricey"

[Vsat]

Have tried them - nice sounding chip. CEM3328 arrived on the scene fairly late - have only seen a few synths where it was used. Crumar Bit-01 and Bit-99 used them, also the original Ensonique sampling keyboard (Mirage?)

Works quite well on +/-5V... +/- 15V gave latch-up problems(!!) Has V.C. regen built in, which is handy, and an interesting feature of the chip is provision to set the amount of passband loss at high regen settings with a fixed resistor (to overcome the classic volume drop when regen is cranked up, as seen in the Moog and most other 4-pole filters). Another thing to watch out for - this chip has the wimpiest built-in op amp buffer that I have ever seen - it will oscillate at around 2 MHz just from having 10 inches of wire connected to the output. A series 100 ohm resistor cured this.
Cheers, Mike

[Mark Hammer]

Hi Mike,

Spring has sprung, and the gas prices between Quebec and Ontario hopscotch daily.

CEM chips seem to vary in their reputation with respect to sound quality, particularly as one started to get into the later multifunction ones.  Is it reasonable to suggest that, despite whatever later ones may lack in comparison to their predecessors or certain discrete circuits, that they are still worth exploring for guitar effect purposes?  Or do they have limitations which place them squarely in the realm of synth-only?

regards,
Mark

[Vsat]

Mark,
CEM3328 is the only CEM I have had hands-on wiring experience with, the other CEM's I've listened to have been in various commercial synths. There is lots of discussion  about the relative merits of CEM vs SSM, Moog vs SSM, Moog vs ARP and so on... there are differences, some may prefer one to another, but the bottom line is they all sound good. AFAIK all these chips are capable of being operated at lower supply voltages than +/- 15V, and some could probably be set up to operate with a single 9V supply or 12V supply, if that is a consideration.
Cheerio, Mike

[Paul Perry (Frostwave)]

No reason why you cant build guitar FX with CEM chips, but, seeing the scarcity of them & the expense, it is hardly worth bothering with them (in my opinion).
It's bad enough when you are trying to fix an existing unit that relies on obsolete chips, but designing something to use them... that's asking for trouble..

[puretube]

http://www.synthtech.com/cems.html

[R.G.]

No reason why you cant build guitar FX with CEM chips, but, seeing the scarcity of them & the expense, it is hardly worth bothering with them (in my opinion).
It's bad enough when you are trying to fix an existing unit that relies on obsolete chips, but designing something to use them... that's asking for trouble..

Dang it, Paul. Do you just have to keep making good sense?

[puretube]

http://www.till.com/articles/arp/patents.html

[puretube]

http://www.digisound80.co.uk/digisound/modules/80-2/80-2.htm