What are all the ADSR's out there to build?

LetterBeacon · Joined: Mar 18, 2008 Posts: 454 Location: London, UK

I'd definitely be up for a board if there was a run. With the Cliff sockets where they are too.

nicolas3141 · Posted: Wed Feb 18, 2009 3:04 pm Post subject:

rjd2 · Joined: Sep 02, 2007 Posts: 236 Location: philly

fonik · Posted: Wed Feb 18, 2009 3:44 pm Post subject:

okay, i am actually knee deep in the TH SCm sale and the PS3100 docu has to be finished. nevertheless i hope i will have the time to breadboard it the next days. i don't think i would do a PCB run, though. so anyone?

widdly · Posted: Wed Feb 18, 2009 8:18 pm Post subject:

Has anyone tried the 324 envelope on +/-15v?

I'm not getting much joy from it. The release seems to work as an attack and release and it needs a lot of voltage to trigger. I'd be interested if I've made a mistake in my layout or if I need to modify for this voltage.

numbertalk · Posted: Wed Feb 18, 2009 8:20 pm Post subject:

Would you be willing to post your ready-to-etch PCB image online with a BOM (if that's okay with Nicolas as well)?

fonik · Posted: Wed Feb 18, 2009 11:49 pm Post subject:

LetterBeacon · Joined: Mar 18, 2008 Posts: 454 Location: London, UK

fonik · Posted: Thu Feb 19, 2009 9:16 am Post subject:

nicolas, i wonder what the blue LED is for? i would have added a NPN and resistor as LED driver...

numbertalk · Posted: Thu Feb 19, 2009 10:22 am Post subject:

Thanks!

fonik · Posted: Thu Feb 19, 2009 4:16 pm Post subject:

tonight i breadboarded the circuit and powered it with +/-15VA. that's what i came up with:

i lowered the 33ka resistor in the voltage divider at the neg in of the first OpAmp (comparator) to 10k. this gave me a trigger threshold of approx. 1.5V. Smile

i lowered the 1M resistor in the feedbackpath of the 3rd OpAmp (junction 10nF, diode, 1M to GND...) to 390k, just because this was what i had on hand. it gave me a peak of approx. 9V. Very Happy

i added a NPN and a 1k resistor as driver for a LED (Collector to +V, Base to output of last OpAmp, Emitter to 1K to LED to GND). Wink

a 500ka pot for release gave me a better control. Smile

i normalled the input socket to a 10k/10k voltage divider to allow the LFO mode to work. Smile

i found the LFO mode a little bit strange: sustain pot has to be fully ccw. when release pot is fully ccw the LFO would be gateble, which is very cool. Cool

as soon as the release pot is not ccw the LFO is always on. as soon as i turned up the sustain potentiometer the LFO stopped. Confused

i did not get the external retrigger input to work. Crying or Very sad

experiences, insights or explanations anyone?

nicolas3141 · Posted: Thu Feb 19, 2009 4:20 pm Post subject:

nicolas3141 · Posted: Thu Feb 19, 2009 4:26 pm Post subject:

nicolas3141 · Posted: Thu Feb 19, 2009 4:46 pm Post subject:

fonik · Posted: Fri Feb 20, 2009 12:41 am Post subject:

yusynth · Joined: Nov 24, 2005 Posts: 1314 Location: France

Hi Matthias

I reckon Q2 is there to drive a LED, isn't it ?

fonik · Posted: Fri Feb 20, 2009 2:49 am Post subject:

nicolas3141 · Posted: Fri Feb 20, 2009 3:15 am Post subject:

A hot soldering iron will help keep you warm Smile

I don't think a more complex switch would add much. If you wanted to be able to mess about with the DC offset you could, as you suggest, follow this with a DC mixer like Ken Stone's CGS04 - using the invertable inputs would be best. My philosophy is to have lots of very simple modules so I would rather keep the mixer separate in my setup, but everyone has their own approach to this sort of thing.

Cheers,
Nicolas

yusynth · Joined: Nov 24, 2005 Posts: 1314 Location: France

Another point is that it would be more accurate to use a FET-OPA for U1D. Therefore I'd suggest to replace the LM324 by a TL074.

nicolas3141 · Posted: Fri Feb 20, 2009 3:40 am Post subject:

nicolas3141 · Posted: Fri Feb 20, 2009 3:46 am Post subject:

Thanks for uploading the redrawn schematic matthias, it makes it so much easier to discuss when we have a drawing with refdeses. I must do better drawings myself.

fonik · Posted: Fri Feb 20, 2009 4:51 am Post subject:

fluxmonkey · Joined: Jun 24, 2005 Posts: 708 Location: cleve

nicolas3141 · Posted: Fri Feb 20, 2009 2:25 pm Post subject:

nicolas3141 · Posted: Fri Feb 20, 2009 2:39 pm Post subject:

I think one of the things that makes the DX7 so amazing is not the FM so much as the envelopes. Separate complex envelopes available for modulating just about everything. Even though this ADSR is not as sophisticated, it is simple enough that you can easily have several of them in your synth. But then the cost of the pots starts to add up and if you are mostly using them in LFO mode, two of the pots are not really getting used. So here is a variation that gives you an ASR envelope. It is still 4 stage, but the decay and release rates are controlled by the same pot. I think there was a commercial synth with envelopes like this, but I can't remember which one. This version is also good if you are short of front panel real estate. If your pots aren't PCB mounted, the same PCB can do both versions because the difference in the circuit is so small (circled in red).

Cheers,
Nicolas

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