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steved
Joined: Oct 07, 2015 Posts: 18 Location: usa
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Posted: Thu Dec 21, 2017 5:13 pm Post subject:
simple sustain circuit Subject description: adding sustain to a gate signal |
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simple circuit to add sustain to a gate signal -
it is easy to add if you only need sustain control and don't want to use up an EG.
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gabbagabi
Joined: Nov 29, 2008 Posts: 651 Location: Berlin by n8
Audio files: 23
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Posted: Sat Dec 23, 2017 11:15 am Post subject:
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Hi steved,
may Iam wrong - but - for me it looks like you add release to the gate signal, so you have an ADSR with
A=0%
D=0f%
S=100%
R= variable
cheers, gabbagbi |
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steved
Joined: Oct 07, 2015 Posts: 18 Location: usa
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Posted: Tue Dec 26, 2017 10:52 am Post subject:
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yes - you are correct- it is trying to be a ADSR with only variable release not sustain.
I am trying to build a TOS type synth and want some control for each note, but really only want a little variable release for each of the gates..experimenting..
i called it sustain because it was inspired by an old Lowrey Organ i found on the road..
they also name the filter attack time 'Symphonic Wow Attack' hahaha
a symphonic holiday |
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gabbagabi
Joined: Nov 29, 2008 Posts: 651 Location: Berlin by n8
Audio files: 23
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steved
Joined: Oct 07, 2015 Posts: 18 Location: usa
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Posted: Sun Dec 31, 2017 11:23 am Post subject:
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Thanks G.Gabba! you rule
hope this is not 2 confusing of a question:
I always get big voltage changes whenever i try to do passive attack and release. I dont have any background in EE so i imagine it is the nature of things- I have played around with all the values of the caps and resistors.
same results from circuits like these:
http://electro-music.com/forum/topic-23960.html&postorder=asc
here is a screen shot to show what i mean:
when i open the attack and release the voltage goes real low as highlighted in yellow.
is this just the way it is if i want to keep this passive? or am i doing it wrong?
Thanks again!!!
Happy new year! |
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gabbagabi
Joined: Nov 29, 2008 Posts: 651 Location: Berlin by n8
Audio files: 23
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steved
Joined: Oct 07, 2015 Posts: 18 Location: usa
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Posted: Sun Jan 07, 2018 1:38 pm Post subject:
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Thanks for your help-
I checked my gate voltage, it drops about .3volts-
my little scope only has one input i used a multi-meter to monitor it..
I have tried a buffered opamp gate, transistor buffer, and direct push button.
leaves me confused .. i wouldn't think .3v would cause the issue...
I also tried other gate sources, one from a old moog satellite synth and get the same results-
so i tried partsim to and see if i could figure out what was up..
Again i am just trying to figure it all out, and am not sure i am using partsim (free online spice sim) correctly, but with this circuit: (r1 and r3 for attack and release pot)
i think i may have a lead on my problem.
i am guessing i am not fully charging the cap-
when i use a 1UF cap the results look like this:
and a 1nf looks like this:
not sure why this circuit gives me so much trouble!
maybe others have the same issues as me-
im going to play with the values until i can get it to act the way i want in the simulator then breadbord it again..
ill get it someday! the race is not for the swift |
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steved
Joined: Oct 07, 2015 Posts: 18 Location: usa
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Posted: Mon Jan 08, 2018 7:56 pm Post subject:
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i dont think it's the cap charge time anymore..
seams like a resistor in there is causing a voltage divider something.
I am going to try different power supplies- so far all tests have been on bi-polar supplies, only using the positive rail and ground..
im lost on what seams so simple.. |
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steved
Joined: Oct 07, 2015 Posts: 18 Location: usa
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Posted: Tue Jan 09, 2018 8:04 am Post subject:
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If anyone is interested or has issues like this:
I think i figured it out -
the usb scope i was using (velleman pcsu01) appears to have an internal voltage divider that gets offset causing the voltage drop.
I dug out my time machine and went back to the 70's to get this scope :
now I can see it all is working-
lesson learned i think
forward to Symphonic Wow Attack !!! |
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JovianPyx
Joined: Nov 20, 2007 Posts: 1988 Location: West Red Spot, Jupiter
Audio files: 224
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Posted: Tue Jan 09, 2018 10:53 am Post subject:
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If manual gate switch is set to 9v and the release pot is at minimum resistance, diode D5 will smoke. You need some small resistance in series with the release pot to prevent that. It can be computed so that 9v via the small resistor does not exceed the diode's forward current rating. _________________ FPGA, dsPIC and Fatman Synth Stuff
Time flies like a banana. Fruit flies when you're having fun. BTW, Do these genes make my ass look fat? corruptio optimi pessima
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gabbagabi
Joined: Nov 29, 2008 Posts: 651 Location: Berlin by n8
Audio files: 23
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Posted: Wed Jan 10, 2018 7:08 am Post subject:
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JovianPyx, you are of course totally right!
There should be an extra resistor.
But that raises the Question of why not using the middle circuit of the thread u mentioned, it has lower partcount.
What a nice piece of engineering u have there! The new ligthweight plastic scopes have there advantages but those things from the past are the real thing!!
Now as you can see the "analog truth", developing can really start off.
cu |
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PHOBoS
Joined: Jan 14, 2010 Posts: 5591 Location: Moon Base
Audio files: 705
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