electro-music.com   Dedicated to experimental electro-acoustic
and electronic music
 
    Front Page  |  Articles  |  Radio
 |  Media  |  Forum  |  Wiki  |  Links  |  Store
Forum with support of Syndicator RSS
 FAQFAQ   CalendarCalendar   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   LinksLinks
 RegisterRegister   ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in  Chat RoomChat Room 
 Forum index » DIY Hardware and Software
CEM3394 modular schematic
Post new topic   Reply to topic Moderators: jksuperstar, Scott Stites, Uncle Krunkus
Page 2 of 2 [39 Posts]
View unread posts
View new posts in the last week
Mark the topic unread :: View previous topic :: View next topic
Goto page: Previous 1, 2
Author Message
fonik



Joined: Jun 07, 2006
Posts: 3759
Location: Germany
Audio files: 23

PostPosted: Fri Apr 29, 2011 3:41 pm    Post subject: Reply with quote  Mark this post and the followings unread

oops.
alas, i don't even have a 3394 Wink

so you don't want to help because they don't understand the datasheet? or because they ask the wrong questions? advice to RTFM or refering to a products page only doesn't help much IMHO. but thank you for the link anyways.

_________________
Posted Image, might have been reduced in size. Click Image to view fullscreen.
cheers,
matthias
____________
fonitronik at
FlickR (pix) / SoundCloud (sounds) / YouTube (vids) / Vimeo (vids) / facebook (news)
Back to top
View user's profile Send private message Send e-mail Visit poster's website
fonik



Joined: Jun 07, 2006
Posts: 3759
Location: Germany
Audio files: 23

PostPosted: Fri Apr 29, 2011 4:00 pm    Post subject: Reply with quote  Mark this post and the followings unread

again, i don't have a CEM3394. who cares?

i have a question in regards to the VCO section as described in the datasheet (maybe i am just dumb, but i want to learn, so...):
the datasheet states a min/max range of the CV input of -4V to +4V, and the IC is normally powered from +5V / -6.5V. shouldn't the CV input be protected against higher control voltages? all the more as the LM324 is able to swing close to the rails? i don't see this on the cram or ele4music schematic.

_________________
Posted Image, might have been reduced in size. Click Image to view fullscreen.
cheers,
matthias
____________
fonitronik at
FlickR (pix) / SoundCloud (sounds) / YouTube (vids) / Vimeo (vids) / facebook (news)
Back to top
View user's profile Send private message Send e-mail Visit poster's website
bod



Joined: Apr 28, 2009
Posts: 148
Location: Glasgow

PostPosted: Tue Jun 28, 2011 1:50 am    Post subject: Reply with quote  Mark this post and the followings unread

fonik, i've been thinking about this as well as i have a few spare of these chips that i bought to do up an old sixtrak, and fancied doing something with them.

i was just going to make a non patchable keyboard synth with everything running off +5v and -6.5v, but figured it would be nice to include CV sockets for external patching to other things. if we asume that the we are using "standard" +/-5v CV's, then i was thinking an opamp to divide the voltage down to +/-4v would suffice with a zener diode to protect the 3394 from any voltages above the chips supply level of 5v, however i'm not sure how to handle the negative voltages just yet. obviously the opamps would need to be powered from +/-12v or +/-15v in order to handle anything that is pumped into it from an external source.

I havent had chance to poke around in the dark star from doepfer, but they must incorporate something similar with the cv inputs on the unit.
anyway, i'd obviously need to ensure the circuit works and adhere to the specs int he data sheet to make sure i A) dont fry the chip and B) dont fry someones patience from earlier.... Wink
Back to top
View user's profile Send private message
fonik



Joined: Jun 07, 2006
Posts: 3759
Location: Germany
Audio files: 23

PostPosted: Tue Jun 28, 2011 2:16 am    Post subject: Reply with quote  Mark this post and the followings unread

bod wrote:
if we asume that the we are using "standard" +/-5v CV's, then i was thinking an opamp to divide the voltage down to +/-4v would suffice with a zener diode to protect the 3394 from any voltages above the chips supply level of 5v,

1st i would assume keyboard CV's from 0-10V. however, it is all about range anyways. if you have keyboard voltages you would have to turn down your inital freq knob to get the full range, for +/-5V you would have to turn it up (offset).
in tom gamble's schematic you have an additional range trimmer for that IMHO this is redundant (see aaron cram schematic).

Quote:
however i'm not sure how to handle the negative voltages just yet. obviously the opamps would need to be powered from +/-12v or +/-15v in order to handle anything that is pumped into it from an external source.

why +/-12v or +/-15v? if i read the datasheet correct, a LM324 can handle +/-16V on its inputs even when powered from +5V/-6.5V. this is actually exactly what aaron cram shows.

anyways, i would have thought that we need some kind of protection for the CEM IC.
opinions?

_________________
Posted Image, might have been reduced in size. Click Image to view fullscreen.
cheers,
matthias
____________
fonitronik at
FlickR (pix) / SoundCloud (sounds) / YouTube (vids) / Vimeo (vids) / facebook (news)
Back to top
View user's profile Send private message Send e-mail Visit poster's website
bod



Joined: Apr 28, 2009
Posts: 148
Location: Glasgow

PostPosted: Tue Jun 28, 2011 3:13 am    Post subject: Reply with quote  Mark this post and the followings unread

the keyboard circuit i have at the moment is an arduino based system i built using a 3 oct keyboard, and the cv out only spans 0-5v. so that should be fine for this purpose.
i wasnt aware the 324 could handle such voltages even when powered from +5 and -6.5V. nifty wee chip! i'm stuck in the MCU thinking of anything over its supply will kill the chip. obviously not with the 324!

so that leaves over voltage protection.... i'm looking through a few articles and data sheets for various things to see what i can come up with....
Back to top
View user's profile Send private message
fonik



Joined: Jun 07, 2006
Posts: 3759
Location: Germany
Audio files: 23

PostPosted: Tue Jun 28, 2011 3:53 am    Post subject: Reply with quote  Mark this post and the followings unread

bod wrote:
i wasnt aware the 324 could handle such voltages even when powered from +5 and -6.5V. nifty wee chip! i'm stuck in the MCU thinking of anything over its supply will kill the chip. obviously not with the 324!

i just read on the national semi site:
Differential input voltage range equal to the power supply voltage

so we would need additional input protection for the opamp as well!?

_________________
Posted Image, might have been reduced in size. Click Image to view fullscreen.
cheers,
matthias
____________
fonitronik at
FlickR (pix) / SoundCloud (sounds) / YouTube (vids) / Vimeo (vids) / facebook (news)
Back to top
View user's profile Send private message Send e-mail Visit poster's website
bod



Joined: Apr 28, 2009
Posts: 148
Location: Glasgow

PostPosted: Tue Jun 28, 2011 5:05 am    Post subject: Reply with quote  Mark this post and the followings unread

ah, well id be tempted to go back to the +/-12v supply for the op amps with over protection on the 3394 inputs then.
having said that, all i can find are the usual diode tricks that only help with positive voltages, and a few exotic solutions from analogue devices that look a little over the top.
Back to top
View user's profile Send private message
Ricko



Joined: Dec 25, 2007
Posts: 154
Location: Sydney, Australia
Audio files: 3

PostPosted: Thu Jun 30, 2011 8:19 am    Post subject: Reply with quote  Mark this post and the followings unread

Couldn't you just put /3 voltage dividers on the CV inputs and then it would fit in happily with voltages produced by +/-15V systems without worrying about over-voltages? (VCO F and VCF F excepting of course)

Same thing with PICs too I suppose.
Back to top
View user's profile Send private message Visit poster's website
bod



Joined: Apr 28, 2009
Posts: 148
Location: Glasgow

PostPosted: Sat Jul 02, 2011 6:23 pm    Post subject: Reply with quote  Mark this post and the followings unread

I'd thought about something similar with +/-12v systems but in that situation, a 10v peak to peak lfo becomes 3.3volts peak to peak (if you divide by 3), which limits the range of the sweep and doesn't give you the full effect.
Even though, you can still get a scaled response from the vco and vcf with trimmers on the inputs.
I've got one wired up to an arduino with the cv's coming from the pwm with a low pass filter and a buffer. Despite the low resolution from the pwm, it works a treat! I'll try out some 12 bit dacs i have shortly, however the keyboard controller needs a few tweaks. But, I'm still torn with adding external cv inputs, I just don't want to limit them and/or fry it! Wink
Back to top
View user's profile Send private message
Ricko



Joined: Dec 25, 2007
Posts: 154
Location: Sydney, Australia
Audio files: 3

PostPosted: Mon Jul 04, 2011 9:43 am    Post subject: Reply with quote  Mark this post and the followings unread

well, if you are using 12V put in a 40% voltage divider to get down to 5V.
Back to top
View user's profile Send private message Visit poster's website
Paradigm X



Joined: Feb 15, 2011
Posts: 276
Location: Null and void

PostPosted: Mon Jan 07, 2013 10:05 am    Post subject: Reply with quote  Mark this post and the followings unread

Hullo!

Interesting thread

Did anyone ever get anywhere with this?

Ive picked up an Akai ax73 which i love, but the one parameter editing is a nightmare.

Id love to be able to control at least the vcf and resonance via a pot... any ideas?

I found the data sheet but cant find the ax73 service manual.

This does look promising but i really dont want to break my synth...

Im guessing id need to add the cvs coming from my akai to a fixed cv made by wiring a pot over the PSU but not sure...

Many thanks, Ben


cem3394.JPG
 Description:
 Filesize:  130.35 KB
 Viewed:  105 Time(s)
This image has been reduced to fit the page. Click on it to enlarge.

cem3394.JPG


Back to top
View user's profile Send private message
Paradigm X



Joined: Feb 15, 2011
Posts: 276
Location: Null and void

PostPosted: Wed Feb 05, 2014 8:07 am    Post subject: Reply with quote  Mark this post and the followings unread

richardc64 wrote:
If anyone is interested, I've copypasta a schema together that at least tries to take into account the voltage restrictions.


hey richard.

could you post this if you get a moment?

Nice one Smile

Cheer,s Ben
Back to top
View user's profile Send private message
richardc64



Joined: Jun 01, 2006
Posts: 614
Location: NYC
Audio files: 25

PostPosted: Wed Feb 05, 2014 11:55 am    Post subject: Reply with quote  Mark this post and the followings unread

Can't find mine, which is untested. Having some strange pc and internet problems. Found this one.


philsynth.pdf
 Description:

Download
 Filename:  philsynth.pdf
 Filesize:  37.23 KB
 Downloaded:  105 Time(s)


_________________
"I am endeavoring, ma'am, to create a mnemonic memory circuit... using stone
knives and bearskins." -- Spock to Edith Keeler
Back to top
View user's profile Send private message Visit poster's website
Paradigm X



Joined: Feb 15, 2011
Posts: 276
Location: Null and void

PostPosted: Thu Feb 06, 2014 6:54 am    Post subject: Reply with quote  Mark this post and the followings unread

great, many thanks!
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic Moderators: jksuperstar, Scott Stites, Uncle Krunkus
Page 2 of 2 [39 Posts]
View unread posts
View new posts in the last week
Goto page: Previous 1, 2
Mark the topic unread :: View previous topic :: View next topic
 Forum index » DIY Hardware and Software
Jump to:  

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum
e-m mkii

Please support our site. If you click through and buy from
our affiliate partners, we earn a small commission.


Forum with support of Syndicator RSS
Powered by phpBB © 2001, 2005 phpBB Group
Copyright © 2003 through 2009 by electro-music.com - Conditions Of Use