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 Forum index » DIY Hardware and Software » YuSynth
VCA and click on gate
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ranioItaly



Joined: Feb 18, 2013
Posts: 13
Location: Italy

PostPosted: Mon Sep 23, 2013 5:14 am    Post subject: VCA and click on gate
Subject description: VCA and click on gate
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hallo, I have finished a VCA, and I made the settings.
It is working, but at every rise gate signal I hear a "click".
Is it correct behavior?
I have put the signal coming from yusynth VCO and a gate signal from a midi to CV converter by Midi-CV_Gate Obsoletetechnology.
Are there any modify?
many thanks
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The Bad Producer



Joined: Mar 08, 2009
Posts: 255
Location: The Manhole

PostPosted: Mon Sep 23, 2013 9:09 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi ranioItaly,

You'd normally use an envelope to open the VCA, triggered by the gate from the MIDI-CV converter. The Gate would open very quick (it's a pulse wave/shape) and this may cause the click where it opens so quickly...

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ranioItaly



Joined: Feb 18, 2013
Posts: 13
Location: Italy

PostPosted: Mon Sep 23, 2013 1:05 pm    Post subject: Reply with quote  Mark this post and the followings unread

thank you "The Bad Producer",
so I can build a yusynth ADSR for cancel this problem and have more new feature.
many thanks for your explanation.
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The Bad Producer



Joined: Mar 08, 2009
Posts: 255
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PostPosted: Tue Sep 24, 2013 2:46 am    Post subject: Reply with quote  Mark this post and the followings unread

Yes, indeed, an ADSR should work here - I believe the click is the very quick 'cut' in the audio when it is turned on by the gate... you could try a passive slew in the meantime (before you have built the envelope) I haven't tried this myself, but it might be interesting. This page here:

http://www.doepfer.de/DIY/a100_diy.htm

Scroll down to '2. Basic circuits' and then see the 'simple lowpass' - using 1uF for C1 and 10k for R1 you obtain about 10 ms slew rate.

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ranioItaly



Joined: Feb 18, 2013
Posts: 13
Location: Italy

PostPosted: Wed Sep 25, 2013 3:19 am    Post subject: Reply with quote  Mark this post and the followings unread

thanks I'll try to build this small circuit in the meantime I will have completed the ADSR. A little circuit could solve a big problem.
I'll let you know if it worked.
many thanks again
Bye
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isak



Joined: Dec 13, 2009
Posts: 696
Location: Israel
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PostPosted: Thu Sep 26, 2013 3:41 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi there.

sorry to interrupt like that, but a lowpass filter will not help you (been there, done that).
i use a gate to open the vca as well, with a switch to choose between gate or env inside my synth.

read my post, it helped me and works like a charm!
(roll down)
http://electro-music.com/forum/topic-58962.html


cheers,
Isak E.

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Benjamin AM



Joined: Nov 04, 2010
Posts: 67
Location: Boise

PostPosted: Thu Sep 26, 2013 5:41 pm    Post subject: Reply with quote  Mark this post and the followings unread

isak wrote:
Hi there.

sorry to interrupt like that, but a lowpass filter will not help you (been there, done that).

.

I have a hard time believing this. In the thread that you quote, you alude to the fact that my proposed circuit add on fixed the key down popping yet the key release pop still remained. I'm just curious if different values were tried. I might suggest a larger value for the resistor connected to ground.
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gdavis



Joined: Feb 27, 2013
Posts: 150
Location: San Diego

PostPosted: Thu Sep 26, 2013 8:13 pm    Post subject: Reply with quote  Mark this post and the followings unread

The "slew limiter" referenced in the thread mentioned above IS a low pass filter. It's a simple RC filter surrounded by buffers. The buffers and pot make it easy to integrate into a variety of circuits and dial in a specific amount of filtering. With proper care, a resistor and capacitor can be made to work in a specific circuit without the extra components. I guess it depends on where you want to put your effort - buying and assembling more components or putting more thought into it.
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isak



Joined: Dec 13, 2009
Posts: 696
Location: Israel
Audio files: 18

PostPosted: Fri Sep 27, 2013 1:56 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi Benjamin AM,

I did exactly what you told me to do.
Don't know why it's hard to believe?
I have no reason to say faulty things, specially when your only trying to help.
Sorry if you were ofended, but it's true.
After using the scheme you attached and this click/pop didn't went away I was trying to find an answer my self after you didn't replayed, the scheme I attached worked.
I only post my finding, nothing else.
BTW...I didnt tried other values resistors to ground, maybe it will work, like you say.
BTW2...if you don't believe me there is a sound clip I posted in the post where you tried to help, after making your scheme you can hear the click/pop when I realese my finger from the keyboard key.

gdavis,
I didn't knew that the scheme I posted is a lowpass filter.
I dont care about the extra components as long as this scheme fixed the click/pop thing, this what matters to me.
I'm sure there are more cheaper ways to do it but Im not experienced enough to even think about them.
Hope one day I will Smile

Cheers.

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Benjamin AM



Joined: Nov 04, 2010
Posts: 67
Location: Boise

PostPosted: Fri Sep 27, 2013 6:22 pm    Post subject: Reply with quote  Mark this post and the followings unread

isak wrote:
Hi Benjamin AM,
Sorry if you were ofended, but it's true.
After using the scheme you attached and this click/pop didn't went away I was trying to find an answer my self after you didn't replayed, the scheme I attached worked.

I'm not offended at all. I just want to make the point that a LPF will work. The values of from my previous attachment removed most of the sound from the sudden opening and closing of the VCA. They were suggested values and the end result is all a matter of preference. Don't be afraid of experimenting. I just spent 10 minutes with some alligator clips(bread board would work better) and found that the following values gave very smooth results. The control input resistors(R19 or R20) should be adjusted accordingly due to the loss of signal from the circuit.


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isak



Joined: Dec 13, 2009
Posts: 696
Location: Israel
Audio files: 18

PostPosted: Fri Sep 27, 2013 7:17 pm    Post subject: Reply with quote  Mark this post and the followings unread

Next time I will explore Smile
Thank you for your findings!

Cheers.

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ranioItaly



Joined: Feb 18, 2013
Posts: 13
Location: Italy

PostPosted: Sun Oct 20, 2013 2:12 am    Post subject: Reply with quote  Mark this post and the followings unread

hi to all,
I 've fixed the problem with the simple circuit suggested by The Bad Producer, and no more click is heard when play the keyboard.
It's a alternative for a simple use. I've also built an ADSR for a more complex use.
Thank you
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-minus-



Joined: Oct 26, 2008
Posts: 761

Audio files: 13

PostPosted: Sat Oct 26, 2013 1:12 am    Post subject: Reply with quote  Mark this post and the followings unread

I'm having a similar problem. I built four YuSynth VCAs. I tested them some time ago with a triangle to the CV and an audio triangle to the signal input, and all seemed good.

I have now breadboarded the Thomas Henry Superseque. I'm using the step CV's to feed an oscillator. I am using a trigger out on the sequencer to trigger a MFOS AR EG which is sending the envelope to the CV input of the YuSynth VCA. The oscillator is going through the signal input of the VCA.

What is happening is this. If the attack of the envelope is too steep or set on its most counter clockwise rotation, I get a distinctive click. This is evident even on steps where there is zero CV going from the sequencer to the oscillator. If I disconnect the sequencer to the oscillator and still trigger the envelope going to the VCA, I can still hear the click. It is as if the CV input of the VCA is bleeding through the audio output of the VCA. If I adjust the envelope so it has a slight attack, the click goes.

Is this something to be expected from analog circuits? Is it normal behaviour for sudden attacks or releases to cause popping? Also, is it unrealistic to expect zero bleed through of the CV through to the audio output?

I do need to trim these VCAs with a dual trace scope. I only have a single trace. Any suggestions here?

Thanks!
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isak



Joined: Dec 13, 2009
Posts: 696
Location: Israel
Audio files: 18

PostPosted: Sat Oct 26, 2013 1:23 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi minus.

usually when i send EG to VCA or VCF i always keep the release pot a bit open, if not i get a click (depending on the VCA and the EG behavior).

hope it helps.

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