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General Discussions => The Lab => Topic started by: ilfungo on February 03, 2011, 09:54:19 AM

Title: Vactrol VTL5C4/2 attack and release?
Post by: ilfungo on February 03, 2011, 09:54:19 AM
How it's possible to mod the attack and release time of Vactrol  VTL5C4/2?
Thanks
Title: Re: Vactrol VTL5C4/2 attack and release?
Post by: volker on February 03, 2011, 10:11:28 AM
Take a look at the datasheet (http://www.datasheetcatalog.org/datasheet/perkinelmer/VT500.pdf). Photo cells have an intrinsic time behaviour, you can't mod that. Every cell has specific turn-on and turn-off time constants.

In the end it depends on the usage of cell, its surrounding circuitry and the way it is driven by the sidechain, how fast or slow it will be. If you want to modify anything about it, that's where you start.
Title: Re: Vactrol VTL5C4/2 attack and release?
Post by: ilfungo on February 03, 2011, 10:22:17 AM
thanks volker
I built a DAOC with VTL5C4 /2 and my taste has a fast attack and release ...
On which area of the circuit I can try? (I am a beginner ???)
Thanks
Title: Re: Vactrol VTL5C4/2 attack and release?
Post by: MikeClev on February 03, 2011, 10:29:08 AM
The sidechain!

Do you have a link to the schematic?
Title: Re: Vactrol VTL5C4/2 attack and release?
Post by: ilfungo on February 03, 2011, 10:36:06 AM
This:
http://www.silentarts.de/DIY/D-AOC/D-AOC_Schematic.pdf
Title: Re: Vactrol VTL5C4/2 attack and release?
Post by: MikeClev on February 03, 2011, 10:54:07 AM
I don't have experience with tube circuits but I can't see anything in that circuit that affects the attack and release, I think it just relies on the natural attack and release of the Vactrol itself.

I like this circuit: http://www.forsselltech.com/downloads/schematics/SideChain_B.PDF (http://www.forsselltech.com/downloads/schematics/SideChain_B.PDF)

..as an example of how compression with vactrols can be done. Obviously its not much use if you are going for an all valve circuit, but it lets you see the different stages.

You could in theory take the Forssell sidechain circuit and use it to replace the DAOC sidechain (the V102 tube stage at the lower half of the circuit)...
Title: Re: Vactrol VTL5C4/2 attack and release?
Post by: ilfungo on February 03, 2011, 01:29:05 PM
ok thanks
There is a slower vactrol?
Title: Re: Vactrol VTL5C4/2 attack and release?
Post by: ilfungo on February 04, 2011, 04:11:41 PM
 ??? ??? ???
Title: Re: Vactrol VTL5C4/2 attack and release?
Post by: dmp on February 04, 2011, 05:45:11 PM
You could take a look at the datasheets for the different models... it's a lot to wade through but I don't know the answer off the top of my head.
http://www.alliedelec.com/optoelectronics-lighting/optocouplers-optoisolators/?dsNav=N%3a4294886725-4294965115 (http://www.alliedelec.com/optoelectronics-lighting/optocouplers-optoisolators/?dsNav=N%3a4294886725-4294965115)
For instance, VTL5C4/2 is spec'd for 6.0ms on, 1.5sec off. Different models have different specs.
Basically, if you want to slow down the attack or release, on most compressors you can do so with adding / changing passive components. Speeding up is a different story since it would be limited by the speed of the vactrol.
The DAOC is a bit of an odd beast because the sidechain does not have components to rectify the signal to a DC value, instead, it seems the sidechain buffers the audio signal and applies that directly to the vactrol -presumably the vactrol is kind of a reservoir that rectifies the signal, in a sense. I'm not sure it would change the result the way you want,  but you could try putting in release / attack components like in the Forrsell schematic, resistors / capacitors that create reservoirs to slow down the voltage getting through to the vactrol.
Title: Re: Vactrol VTL5C4/2 attack and release?
Post by: ilfungo on February 05, 2011, 06:44:10 AM
Thanks dmp
I understand the problem ...
ask for help from a friend, unfortunately I am a beginner in electronics and I do not know where to start ...
can you give me some help?
Thanks
Title: Re: Vactrol VTL5C4/2 attack and release?
Post by: [silent:arts] on February 05, 2011, 06:47:56 AM
there is no way to mod the attack and release times in the D-AOC.
it is like the LA2A.
you like the timing - or not
Title: Re: Vactrol VTL5C4/2 attack and release?
Post by: MikeClev on February 05, 2011, 05:02:12 PM
there is no way to mod the attack and release times in the D-AOC.

Let me correct that for you:

"there is no easy way to mod the attack and release times in the D-AOC."

I suggested a way... its not easy, like changing a capacitor or resistor, but its a way!
Title: Re: Vactrol VTL5C4/2 attack and release?
Post by: [silent:arts] on February 06, 2011, 02:57:13 AM
there is no way to mod the attack and release times in the D-AOC.

Let me correct that for you:
"there is no easy way to mod the attack and release times in the D-AOC."
I suggested a way... its not easy, like changing a capacitor or resistor, but its a way!

I couldn't disagree more :o

for sure it is possible to exchange the complete sidechane,
but I wouldn't call it D-AOC anymore :D
Title: Re: Vactrol VTL5C4/2 attack and release?
Post by: Tekay on February 06, 2011, 06:31:26 AM
Think this is the background to the Forssell opto sidechain? I have used it together with VTL5C4/2, only had to change the input resistor (before opto). http://www.silonex.com/audiohm/pdf/compressor.pdf. More applications at http://www.silonex.com.
Title: Re: Vactrol VTL5C4/2 attack and release?
Post by: ilfungo on February 06, 2011, 11:00:15 AM
thank you all for your suggestions
Perhaps the changes are too complicated for me
I was hoping just change a few component
thanks
Title: Re: Vactrol VTL5C4/2 attack and release?
Post by: tommypiper on February 06, 2011, 01:38:03 PM
ilfungo, what is it about the character of the compression that you don't like in the DAOC?  Is it too fast, too slow, too soft, too hard....?

Have you tried an LA-2?  Do you like the LA-2?

I'm wondering if your DAOC is working correctly, since everyone else seems to love them. 

I'm still planning to build one so I am curious about your reaction to the compression.
Title: Re: Vactrol VTL5C4/2 attack and release?
Post by: ilfungo on February 06, 2011, 01:46:42 PM
Hello Tommy
I've already built a LA2A and
I love its compression.
DAOC is (for me) too nervous compression
attack and release (for me) too fast.
Title: Re: Vactrol VTL5C4/2 attack and release?
Post by: tommypiper on February 06, 2011, 02:20:10 PM
ilfungo, I see.  Thanks.  

Have other DAOC builders confirmed that their units are also faster than an LA-2?  If yes, then maybe it's a taste issue (for you).  If no, then your unit may be working differently than others.   :-\

I appreciate your continued questions and experiments, on behalf of all those interested in the DAOC.
Title: Re: Vactrol VTL5C4/2 attack and release?
Post by: ilfungo on February 06, 2011, 05:58:46 PM
I do not know if the other is like me,
but the thing is I do not understand how others can use this compressor for mastering.
Vactrol = 25% of tolerance
then link the two channels do not work well ...
Surely it is a matter of personal taste
but I built:
6 x 1176
6 x LA4
1 x LA2A
1 x GSSL + turbo + Supersidechain
I use every day
but reluctantly I have trouble using the DAOC.
I'm sure you do not have a problem because everything works and all voltages are correct.
This is just my opinion
I hope not to offend anyone
Title: Re: Vactrol VTL5C4/2 attack and release?
Post by: zayance on February 06, 2011, 07:20:09 PM
I don't think that this one was ever intended to be used as "Mastering", but lot of people use lot of things for "Mastering" so go figure.
But most would like a fast attack and release for that purpose, but lacking the control is a major loss for if you want to use it as mastering.
If you already have a LA2A, well then this one is a nice addition to it, one comp with slow attack and release, and another one with fast attack and fast release.
Taste and colors etc... as always....
I'm slowly finishing mine, and what you say you don't like, i actually like without having heard of it yet  :D :D