Julian Posted February 15, 2006 Report Share Posted February 15, 2006 finally my holliday started, so its soldering time again.next project is the AOUT_LC and my CEM VCF.I had a nice idea, to build a Box like this:So there are 2 Audio In2 CV In for controlling the CEM with other analog gear2 CV Out to controll other analog gear with the midibox1 Audio Outfurther 2 Depth knobs controlling the depth of the midibox and external CV2 Filter Knobs controlling the CEM manually1 Master Vol1 Switch to select between MIDIBOX or external CVbut since im quite a noob in designing my own circuits maybe someone can have a look on this layout I made, if it'll work.I tried to limit the CV voltage for the CEM to 5V using a ZENER diode. I hope in this way the ZENER will cut off any voltage above 5V?! (for example when the manual CutOff pot delivers already 5V and the AOUT delivers also some Volts) don't know if i made that right.further i'm not sure about the CV out (red box) is it the right way to go to buffer the output with an OpAmp?I know it's a flaky design, but it's like i said... me <- n00b ;Dso long, Julian Quote Link to comment Share on other sites More sharing options...
stryd_one Posted February 16, 2006 Report Share Posted February 16, 2006 Nice one mate, keep it coming :)I'd love to see a multi-channel version!PS.. .Do I know you from IRC as Monome? Quote Link to comment Share on other sites More sharing options...
Julian Posted February 16, 2006 Author Report Share Posted February 16, 2006 another question...Is it possible to drive the TL072 on the AOUT_LC with +/- 5V isntead of 12V?since the CEM doesnt need more than 5V CV anyway...so long,julianPS: no, i'm quite seldom on the IRC... Quote Link to comment Share on other sites More sharing options...
raphael Posted February 16, 2006 Report Share Posted February 16, 2006 Is it possible to drive the TL072 on the AOUT_LC with +/- 5V isntead of 12V?since the CEM doesnt need more than 5V CV anyway...No, the TL072 is a OPAMP. The input voltage of such amps must never exceed the supply voltage! The D/A ladder will deliver up to 5V which would be the absolute maximum allowed.You will at least get heavy distortion on the outputs.Raphael Quote Link to comment Share on other sites More sharing options...
TK. Posted February 16, 2006 Report Share Posted February 16, 2006 On the other hand: the full +/-5V range is not required for the CEM3378 anyhow, and I'm also not sure, if a buffer OPAMP is really usefulI remember, that during my experiments some weeks ago I added an additional pot as voltage divider between the AOUT_LC outputs, and the resonance/CutOff input of the filter in order to reduce the control range.This remembers me, that I wanted to determine the best fitting divider values for my own final board (which will be a quad-filter) - so, i can give you more infos soonBest Regards, Thorsten. Quote Link to comment Share on other sites More sharing options...
Jaicen Posted February 17, 2006 Report Share Posted February 17, 2006 The TL07x family will happily run up to +24v (+\- 12v) so you should be fine. It'll give slightly more headroom than +9-12v as well, good for transients. That said, i'd probably just use a Mosfet buffer/gain stage as it'll draw less current and take up less space. I'm looking forward to seeing how this one turns out ;) Quote Link to comment Share on other sites More sharing options...
moebius Posted February 17, 2006 Report Share Posted February 17, 2006 another question...Is it possible to drive the TL072 on the AOUT_LC with +/- 5V isntead of 12V?No. It's unity gain stable, but NOT an rail-to-rail opamp. Better to use bigger margins for opamp supply. (You can find rail-to-rail, unity gain stable opamps but it will cost ya) (By the way, the circuit is averaging not an adder) It's hard to hit the rails this way without CV inputs being over the rails. And hitting the rails with opamp isn't LETHAL :DMoebius Quote Link to comment Share on other sites More sharing options...
kk74 Posted February 28, 2006 Report Share Posted February 28, 2006 On the other hand: the full +/-5V range is not required for the CEM3378 anyhow, and I'm also not sure, if a buffer OPAMP is really usefulI remember, that during my experiments some weeks ago I added an additional pot as voltage divider between the AOUT_LC outputs, and the resonance/CutOff input of the filter in order to reduce the control range.This remembers me, that I wanted to determine the best fitting divider values for my own final board (which will be a quad-filter) - so, i can give you more infos soonBest Regards, Thorsten.I'm really looking forward to hearing more about your quad-filter! I have 4 CEM3378 here that's only waiting to be put into good use (that is, connected to the quad SID i'm planning to build) Quote Link to comment Share on other sites More sharing options...
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