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simple sustain circuit
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steved



Joined: Oct 07, 2015
Posts: 18
Location: usa

PostPosted: 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.

Posted Image, might have been reduced in size. Click Image to view fullscreen.
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gabbagabi



Joined: Nov 29, 2008
Posts: 651
Location: Berlin by n8
Audio files: 23

PostPosted: Sat Dec 23, 2017 11:15 am    Post subject: Reply with quote  Mark this post and the followings unread

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

PostPosted: Tue Dec 26, 2017 10:52 am    Post subject: Reply with quote  Mark this post and the followings unread

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..

Posted Image, might have been reduced in size. Click Image to view fullscreen.

they also name the filter attack time 'Symphonic Wow Attack' hahaha

a symphonic holiday Smile
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gabbagabi



Joined: Nov 29, 2008
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PostPosted: Wed Dec 27, 2017 4:52 am    Post subject: Reply with quote  Mark this post and the followings unread

Very Happy
nice street find!

if you want to add a symphonic wow attack to your circuit may consider the attached idea

harmonic symphonic regards,
gabagabi


STEVED AR ENV.png
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steved



Joined: Oct 07, 2015
Posts: 18
Location: usa

PostPosted: Sun Dec 31, 2017 11:23 am    Post subject: Reply with quote  Mark this post and the followings unread

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:
Posted Image, might have been reduced in size. Click Image to view fullscreen.

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
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PostPosted: Mon Jan 01, 2018 4:30 am    Post subject: Reply with quote  Mark this post and the followings unread

you're welcome,
and happy new year.

you're right there is something wrong,
if the gate signal is long enough the envelope should reach always the same level, which is Gate-Voltage minus the voltage drop over the diode (D1) of about 0,6V. Like u an see in the attached pic.

So my first guess is that there is something wrong with ur Gate-signal.
How u generate the Gate-signal? do u had only the scope attached while measuring?
can u make a scope where u see the gate signal together with the envelope, like in the attached pic?

there is nothing wrong with passive circuits if they serve ur needs.

so far,
keep well,
gabbagabi


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steved



Joined: Oct 07, 2015
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Location: usa

PostPosted: Sun Jan 07, 2018 1:38 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks for your help-

I checked my gate voltage, it drops about .3volts-
my little scope only has one input Sad 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)
Posted Image, might have been reduced in size. Click Image to view fullscreen.

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:

Posted Image, might have been reduced in size. Click Image to view fullscreen.

and a 1nf looks like this:

Posted Image, might have been reduced in size. Click Image to view fullscreen.

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
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PostPosted: Mon Jan 08, 2018 7:56 pm    Post subject: Reply with quote  Mark this post and the followings unread

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..

Rolling Eyes Confused Confused Confused

im lost on what seams so simple..
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steved



Joined: Oct 07, 2015
Posts: 18
Location: usa

PostPosted: Tue Jan 09, 2018 8:04 am    Post subject: Reply with quote  Mark this post and the followings unread

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 :

Posted Image, might have been reduced in size. Click Image to view fullscreen.

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
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PostPosted: Tue Jan 09, 2018 10:53 am    Post subject: Reply with quote  Mark this post and the followings unread

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.
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gabbagabi



Joined: Nov 29, 2008
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PostPosted: Wed Jan 10, 2018 7:08 am    Post subject: Reply with quote  Mark this post and the followings unread

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
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PostPosted: Wed Jan 10, 2018 8:02 am    Post subject: Reply with quote  Mark this post and the followings unread

only jumping in to say what a gorgeous scope Shocked

ok a bit more since I am here , I like the passive circuit but maybe a 555 would make things a bit easier, they are great for simple stuff like this.

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